Loading...
The URL can be used to link to this page
Your browser does not support the video tag.
Home
My WebLink
About
ASRPC20200225 4.1
PLANNING COMMISSION STAFF REPORT 4.1 TO: Chair and Planning Commission February 25, 2020 SUBJECT: Resolution No. 2020-03, approving Minor Subdivision request SUB18- 0002 and Tree Removal request TR20-0003 allowing the subdivision of an existing 2.06 acre property located at 775 Kirkcrest Road into two single family residential parcels and the removal of six Town-protected trees EVALUATION/ DISCUSSION Conformance with General Plan and Zoning District The site has a General Plan Land Use Designation of Residential – Country Estates, which requires a one-acre lot size minimum. The site is zoned R-40; Single Family Residential District, requiring a minimum parcel size of 40,000 square feet. The proposed parcels, at 44,008 and 40,045 square feet (net), exceed the minimum density and lot size requirements. Soils and Geology The subject property is located at the bottom area of the hillside on the west side of Danville, and are relatively steep sloping. In order to determine the suitability, of residential development on proposed Parcel B, a Geotechnical Engineering Report was prepared by Terracon Associates (Attachment D). The report concludes that the site is suitable for residential development. An additional, more detailed report will be required as part of any building permit submittal for development of the parcel. Hillside Development The applicant was required to prepare a schematic preliminary grading plan to demonstrate how proposed Parcel B could be developed (Attachment E, Sheet 2). While specifically not part of this approval, the plan demonstrates how a residence could be built on the parcel, utilizing a split pad design, and meeting all the development standards contained within Town codes. The actual development of the parcel would be subject to approval of a separate Development Plan application. Tree Removal In order to construct the project improvements, including the new driveway for proposed Parcel B, and the bio-retention facility, six Town-protected oak trees would need to be removed (Attachment C). The trees range in size from 10 to 14 inches in diameter. Several 775 Kirkcrest Road 2 February 25, 2020 large specimen oak trees are located at the upper portion of the site, and would be preserved. Since there is a creek with significant vegetation and tree cove across the driveway to the east, the proposed tree removal would not have a significant impact on privacy between the proposed new parcel and existing residences to the east. Storm Water Runoff This development would be subject to the County’s Storm Water Control Plan guidelines and regulations. As a result, all runoff from new, and existing, impervious surfaces would be required to be collected and conveyed to new bio-retention facilities that would be required to be constructed as part of this project. The Town has reviewed and approved the preliminary Storm Water Control Plan that has been prepared for this project (Attachment E, Sheet 5). ENVIRONMENTAL REVIEW The project has been found to be Categorically Exempt from the requirements of the California Environmental Quality Act (CEQA) Section 15315, Class 15 (Minor Land Division). PUBLIC CONTACT Public notice of the February 25, 2020 hearing was mailed to property owners within 750 feet and posted online. A total of 98 notices were mailed to surrounding property owners. RECOMMENDATION Adopt Resolution No. 2020-03, approving Minor Subdivision request SUB18-0002 and Tree Removal request TR20-0003 allowing the subdivision of an existing 2.06 acre property located at 775 Kirkcrest Road into two single family residential parcels and the removal of six Town-protected trees. Prepared by: David Crompton Principal Planner Attachments: A - Resolution No. 2020-03 B - Public Notification, Notification Map & Notification List C - Tree Survey (ORR Design Office) D - Geotechnical Engineering Report E - Vesting Tentative Map RESOLUTION NO. 2020-03 APPROVING MINOR SUBDIVISION REQUEST SUB18-0002 AND TREE REMOVAL REQUEST TR20-0003 ALLOWING THE SUBDIVIISON OF AN EXISTING 2.06 ACRE PARCEL LOCATED 775 KIRKCREST ROAD INTO TWO SINGLE FAMILY RESIDENTIAL PARCELS AND THE REMOVAL OF SIX TOWN-PROTECTED TREES (APN: 201-240-023) WHEREAS, KAREN AND PHILIP BURKHART (Owners) DEBOLT CIVIL ENGINEERING (applicant) have requested approval of Minor Subdivision application SUB2018-0002 to subdivide an existing 2.06 +/- acre parcel into two single family residential parcels, resulting in one additional single-family residential parcel; and WHEREAS, the Tree Removal request would allow for the removal of six Town- protected Oak trees with diameters of 10-14 inches; and WHEREAS, the subject site is located at 775 Kirkcrest Road and is further identified as Assessor’s Parcel Number 201-240-023; and WHEREAS, the Town of Danville Subdivision Ordinance requires Planning Commission approval of a tentative parcel map prior to recordation of a final map; and WHEREAS, the Town’s Tree Preservation Ordinance requires approval of a Tree Removal application prior to the removal of any Town-protected tree; and WHEREAS, the project is Categorically Exempt from the requirements of the California Environmental Quality Act (CEQA), Section 15315, Class 15, Minor Land Divisions; and WHEREAS, the Planning Commission did review the project at a noticed public hearing on February 25, 2020; and WHEREAS, the public notice of this action was given in all respects as required by law; and WHEREAS, the Planning Commission did hear and consider all reports, recommendations, and testimony submitted in writing and presented at the hearing; now, therefore, be it RESOLVED that the Planning Commission approves Minor Subdivision request SUB18- 0002 and Tree Removal request TR20-0003, subject to the conditions contained herein, and ATTACHMENT A PAGE 2 OF RESOLUTION NO. 2020-03 make the following findings in support of this action: Minor Subdivision: 1.The proposed subdivision is in substantial conformance with the goals and policies of the 2030 General Plan. 2.The design of the proposed subdivision is in substantial conformance with the applicable zoning regulations. 3.The design of the subdivision and the type of associated improvements will not likely cause serious public health problems because water and sanitary facilities services will be available to the new parcel. 4.The design of the proposed subdivision and improvements are not likely to cause substantial environmental damage or subsequently injure fish or wildlife or their habitat since this property is in an area where residential development has previously occurred. 5.The design of the proposed subdivision and proposed improvements will not conflict with easements, acquired by the public at large, for access through or use of, property within the proposed subdivision. Tree Removal: 1.Necessity. The primary reason for removal of the Town-protected trees is that they are located in the only feasible location for a new driveway and the reasonable development of the property. 2.Erosion/surface water flow. Removal of the Town-protected trees will not cause significant soil erosion or cause a significant diversion or increase in the flow of surface water. 3.Visual effects. With respect to other trees in the area, the project site and surrounding neighborhood contains a significant number of additional trees not effected by the development. Specifically there is a creek area to the east with significant vegetation and tree cover that will continue to provide a barrier and privacy screen between the subject property and the existing properties and residences to the east. PAGE 3 OF RESOLUTION NO. 2020-03 CONDITIONS OF APPROVAL Conditions of approval with an asterisk ("*") in the left-hand column are standard project conditions of approval. Unless otherwise specified, the following conditions shall be complied with prior to the approval of the final map for the project. Each item is subject to review and approval by the Planning Division unless otherwise specified. A. GENERAL 1.This approval is for a Minor Subdivision application SUB18-0002 and Tree Removal request TR20-0003 to subdivide an existing 2.06 acre into two single family residential parcels and to allow the removal of six Town-protected trees. Development shall be substantially as shown on the project drawings as follows, except as may be modified by conditions contained herein; a.Vesting Tentative Parcel Map titled “775 Kirkcrest Road,” as prepared by DeBolt Civil Engineering, consisting of five sheets, dated October 24, 2019. b.Tree Survey prepared by Orr Design Office Traverso Tree Service, dated June 29, 2019. c.Stormwater Control Plan for Small Land Development Projects prepared by DeBolt Civil Engineering, dated May 20, 2019. 2.All Town and other related fees that the property may be subject to shall be paid by the applicant. These fees shall be based on the current fee schedule in effect at the time the relevant permits are secured, and shall be paid prior to issuance of said permit and prior to any Town Council final approval action. The following fees are due at final map approval for the project: 1.Base Map Revision Fee ...............................................$ 188.00 2.Parcel Map Plan Check Fee ....................................$ 2,954.00 3.Improvement Plan Check Fee ............... 3% of cost estimate 4.Engineering Inspection Fee ................... 5% of cost estimate 5.Excavation Mitigation Fee (Flood Control) ..........$ 1,300.00 6.Park Land in Lieu Fee (1 unit) ..............................$ 11,462.00 The following fees are due at building permit issuance for the project: 1.Finish Grading Inspection Fee ............................... $ 84/unit 2.Stormwater Pollution Program Fee ....................... $ 56/unit PAGE 4 OF RESOLUTION NO. 2020-03 3.SCC Regional Fee (1 unit) .......................................$ 1,465.00 4.SCC Sub-Regional Fee (1 unit) ...............................$ 4,042.00 5.Residential TIP Fee (1 unit) .....................................$ 2,000.00 6.Tri-Valley Transportation Fee (1 unit) ..................$ 4,613.65 3.Prior to issuance of building permit the applicant shall reimburse the Town for notifying surrounding residents. The fee shall be $201.00 ($120 plus 98 notices x $0.83 per notice x two notices). * 4. Prior to the issuance of grading or building permits, the applicant shall submit written documentation that all requirements of the San Ramon Valley Fire Protection District (SRVFPD) and the San Ramon Valley Unified School District have been, or will be, met to the satisfaction of these respective agencies. * 5. In the event that subsurface archeological remains are discovered during any construction or pre-construction activities on the site, all land alteration work within 100 feet of the find shall be halted, the Town Planning Division notified, and a professional archeologist, certified by the Society of California Archeology and/or the Society of Professional Archeology, shall be notified. Site work in this area shall not occur until the archeologist has had an opportunity to evaluate the significance of the find and to outline appropriate mitigation measures, if they are deemed necessary. If prehistoric archaeological deposits are discovered during development of the site, local Native American organizations shall be consulted and involved in making resource management decisions. * 6. Construction activity shall be restricted to the period between the weekday hours of 7:30 a.m. to 5:30 p.m. (Monday through Friday), unless otherwise approved in writing by the City Engineer for general construction activity and the Chief Building Official for building construction activity. Prior to any construction work on the site, including grading, the property owner shall install a minimum 3’ x 3’ sign at the project entry which specifies the allowable construction work days and hours, and lists the name and contact person for the overall project manager and all contractors and sub- contractors working on the job. * 7. The applicant shall provide security fencing, to the satisfaction of the City Engineer and/or the Chief Building Official, around the site during construction of the project. * 8. The applicant shall require their contractors and subcontractors to fit all PAGE 5 OF RESOLUTION NO. 2020-03 internal combustion engines with mufflers which are in good condition, and to locate stationary noise-generating equipment as far away from existing residences as feasible. * 9. A watering program which incorporates the use of a dust suppressant, and which complies with Regulation 2 of the Bay Area Air Quality Management District shall be established and implemented for all on and off-site construction activities. Equipment and human resources for watering all exposed or disturbed soil surfaces shall be supplied on weekends and holidays as well as work days. Dust-producing activities shall be discontinued during high wind periods. * 10. As part of the initial submittal for the final map, plan check review process, the applicant shall submit a written Compliance Report detailing how the conditions of approval for this project has been complied with. This report shall list each condition of approval followed by a description of what the property owner has provided as evidence of compliance with that condition. The report must be signed by the applicant. The report is subject to review and approval by the City Engineer and/or Chief of Planning and/or Chief Building Official, and may be rejected by the Town if it is not comprehensive with respect to the applicable conditions of approval. * 11. Planning Division sign-off is required prior to final Building Inspection sign- off. 12.Prior to the issuance of grading or building permits, the applicant shall retain a specialist to assess rodent control impacts anticipated to be associated with grading activity and installation of subdivision improvements. As deemed necessary, following the Planning Division’s review of the specialist’s assessment, the applicant shall develop and implement the corresponding rodent control plan to reduce impacts to surrounding properties to the extent reasonably possible for the time periods of heavy construction activity. The report shall include a schedule for regular rodent inspections and mitigation based on the development schedule for the project. This rodent control plan is subject to review and approval by the Planning Division. B. SITE PLANNING * 1. All exterior lighting installed as part of a development shall be compliant with the following dark sky criteria: lights shall be shielded on the top and sides so that light does not go up to the sky, and; except where needed for safety, lights shall utilize motion detectors so that they are only used when needed and shall utilize the minimum wattage necessary. PAGE 6 OF RESOLUTION NO. 2020-03 * 2. The location of any pad mounted electrical transformers shall be subject to review and approval by the Planning Division prior to the issuance of a building permit. To the extent feasible, such transformers shall not be located between any street and the front of a building. * 3. Any on-site wells and septic systems shall be destroyed in accordance with Contra Costa County Health Services Department - Environmental Health Division regulations. Environmental Health Division permits and inspections for this work shall be obtained. The maintenance of existing on-site wells shall be allowed for landscape irrigation purposes subject to review and approval by the Contra Costa County Health Services Department – Environmental Health Division. 4.The development and use of the parcels created by this subdivision shall comply with all requirements of the Town’s R-40; Single Family Residential District Ordinance. C. LANDSCAPING 1.Project approval authorizes the removal of six Town protected Oak trees as identified on the project tree survey. The applicant shall mitigate the removal of the Town-protected trees by providing for the planting of new trees of a number equal to the diameter(s) of the tree to be removed. The trees shall be a minimum of 15-gallon trees. The location of mitigation trees associated with this approval shall be subject to Town review and approval, and may be deferred until the subsequent approval of a Development Plan for the development of Parcel B. 3.A security deposit, in the amount of the assessed value of the Town- protected tree(s) for which grading is proposed to occur within the dripline (calculated pursuant to the Town’s Tree Protection Ordinance), shall be posted with the Town prior to the issuance of a grading permit or building permit to maximize the probability that the affected trees will be retained in good health. The applicant shall be required to secure an appraisal of the condition and value of all affected trees. The appraisal shall be done in accordance with the current edition of the “Guide for Establishing Values of Trees and Other Plants,” by the Council of Tree and Landscape Appraisers under the auspices of the International Society of Arboriculture. The appraisal shall be performed by a Certified Arborist, and shall be subject to review and approval by the Chief of Planning. A tree preservation agreement shall be prepared that outlines the intended and allowed use of funds posted PAGE 7 OF RESOLUTION NO. 2020-03 as a tree preservation security deposit. That portion of the security deposit still held by the Town two full growing seasons after project completion shall be returned upon verification that the trees covered by the deposit are as healthy as can be provided for under the terms of the tree preservation agreement. All grading or construction work in proximity to Town-protected trees shall be supervised by a Certified Arborist. D. ARCHITECTURE * 1. All ducts, meters, air conditioning and/or any other mechanical equipment whether on the structure or on the ground shall be effectively screened from view with landscaping or materials architecturally compatible with the main structures. * 2. The street numbers for each structure in the project shall be posted so as to be easily seen from the street at all times, day and night. 3.The development of Parcel B, including associated landscaping, shall be subject to the review and approval by the Town and Design Review Board under a separate Development Plan application. E. GRADING * 1. Development shall be completed in compliance with a detailed soils report and the construction grading plans prepared for this project. The engineering recommendations outlined in the project specific soils report shall be incorporated into the design of this project. The report shall include specific recommendations for foundation design of the proposed buildings and shall be subject to review and approval by the Town’s Engineering and Planning Divisions. * 2. Where soils or geologic conditions encountered in grading operations are different from that anticipated in the soil report, a revised soils report shall be submitted for review and approval by the City Engineer. It shall be accompanied by an engineering and geological opinion as to the safety of the site from settlement and seismic activity. * 3. All development shall take place in compliance with the Town Erosion Control Ordinance (Ord19-4). Restrictions include limiting construction primarily to the dry months of the year (May through October) and, if construction does occur during the rainy season, the developer shall submit an Erosion Control Plan to the City Engineer for review and approval. This PAGE 8 OF RESOLUTION NO. 2020-03 plan shall incorporate erosion control devices such as, the use of sediment traps, silt fencing, pad berming and other techniques to minimize erosion. * 4. All new development shall be consistent with modern design for resistance to seismic forces. All new development shall be in accordance with the Uniform Building Code and Town of Danville Ordinances. * 5. Stockpiles of debris, soil, sand or other materials that can be blown by the wind shall be covered. * 6. If toxic or contaminated soil is encountered during construction, all construction activity in that area shall cease until the appropriate action is determined and implemented. The concentrations, extent of the contamination and mitigation shall be determined by the Contra Costa County Health Department. Suitable disposal and/or treatment of any contaminated soil shall meet all federal state and local regulations. If deemed appropriate by the Health Department, the property owner shall make provisions for immediate containment of the materials. * 7. Runoff from any contaminated soil shall not be allowed to enter any drainage facility, inlet or creek. * 8. All grading activity shall address National Pollutant Discharge Elimination system (NPDES) concerns. Specific measures to control sediment runoff, construction pollution and other potential construction contamination shall be addressed through the Erosion control Plan (ECP) and Storm Water Pollution Prevention Plan (SWPPP). The SWPPP shall supplement the Erosion Control Plan and project improvement plans. These documents shall also be kept on-site while the project is under construction. A NPDES construction permit may be required, as determined by the City Engineer. 9.The applicant shall create a construction staging plan that addresses the ingress and egress location for all construction vehicles, parking and material storage area. All staging of construction materials and equipment shall occur on-site. This plan shall be subject to review and approval by the Town prior to the issuance of a grading permit. F. STREETS * 1. The applicant shall obtain an encroachment permit from the Engineering Division prior to commencing any construction activities within any public right-of-way or easement. PAGE 9 OF RESOLUTION NO. 2020-03 * 2. All mud or dirt carried off the construction site onto adjacent streets shall be swept each day. Water flushing of site debris or sediment or concrete washing is expressly prohibited. * 3. All improvements within the public right-of-way, including curb, gutter, sidewalks, driveways, paving and utilities, shall be constructed in accordance with approved standards and/or plans and shall comply with the standard plans and specifications of the Development Services Department and Chapters XII and XXXI of the Town Code. At the time project improvement plans are submitted, the applicant shall supply to the City Engineer an up-to-date title report for the subject property. 4.The new private driveway serving Parcel B shall meet all requirements of the San Ramon Valley Fire Protection District. 5.As may be determined necessary by the Town, a satisfactory private road and private storm drain maintenance agreement for Parcels A and B shall be submitted for review and approval by the Town. G. INFRASTRUCTURE * 1. The new residence shall be required to connect to public water and sewer facilities, subject to all permitting requirements and conditions imposed by EBMUD and CCCSD. * 2. Drainage facilities and easements shall be provided to the satisfaction of the City Engineer and/or the Chief Engineer of the Contra Costa County Flood Control & Water Conservation District (CCCFC & WCD). * 3. All runoff from impervious surfaces shall be intercepted at the project boundary and shall be collected and conducted via an approved drainage method through the project to an approved storm drainage facility, as determined by the City Engineer. Development which proposes to contribute additional water to existing drainage systems shall be required to complete a hydraulic study and make improvements to the system as required to handle the expected ultimate peak water flow and to stabilize erosive banks that could be impacted by additional storm water flow. * 4. Roof drainage from structures shall be collected via a closed pipe and conveyed to an approved storm drainage facility in the street curb. No concentrated drainage shall be permitted to surface flow across sidewalks. PAGE 10 OF RESOLUTION NO. 2020-03 * 5. Any portion of the drainage system that conveys runoff from public streets shall be installed within a dedicated drainage easement, or public street. * 6. If a storm drain must cross a lot, or be in an easement between lots, the easement shall be equal to or at least double the depth of the storm drain. * 7. The applicant shall furnish proof to the City Engineer of the acquisition of all necessary rights of entry, permits and/or easements for the construction of off-site temporary or permanent road and drainage improvements. * 8. Electrical, gas, telephone, and cable TV services, shall be provided underground in accordance with the Town policies and existing ordinances. All utilities shall be located and provided within public utility easements, sited to meet utility company standards, or in public streets. * 9. All new utilities required to serve the development shall be installed underground. * 10. All street, drainage or grading improvement plans shall be prepared by a licensed civil engineer. H. MISCELLANEOUS * 1. The project shall be constructed as approved. Minor modifications in the design, but not the use, may be approved by staff. Any other change will require Planning Commission approval through the Development Plan review process. * 2. Pursuant to Government Code section 66474.9, the applicant (including the applicant or any agent thereof) shall defend, indemnify, and hold harmless the Town of Danville and its agents, officers, and employees from any claim, action, or proceeding against the Town or its agents, officers, or employees to attack, set aside, void, or annul, the Town's approval concerning this Minor Subdivision application, which action is brought within the time period provided for in Section 66499.37. The Town will promptly notify the applicant of any such claim, action, or proceeding and cooperate fully in the defense. * 3. Use of a private gated entrance for more than one house is expressly prohibited. PAGE 11 OF RESOLUTION NO. 2020-03 * 4. As a part of the issuance of a demolition permit and/or building permit for the project, the developer shall submit a recycling plan for building and construction materials and the disposition of green waste generated from land clearing on the site. Prior to obtaining framing inspection approval for the project, the applicant/owner shall provide the Planning Division with written documentation (e.g. receipts or records) indicating that waste materials created from the demolition of existing buildings and the construction of new buildings were/are being recycled according to their recycling plan, or in an equivalent manner. * 5. The proposed project shall conform to the Town’s Stormwater Management and Discharge Control Ordinance (Ord. No. 2004-06) and all applicable construction Best Management Practices (BMPs) for the site. For example, construction BMPs may include, but are not limited to: the storage and handling of construction materials, street cleaning, proper disposal of wastes and debris, painting, concrete operations, dewatering operations, pavement operations, vehicle/equipment cleaning, maintenance and fueling and stabilization of construction entrances. Training of contractors on BMPs for construction activities is a requirement of this permit. At the discretion of the City Engineer, a Storm Water Pollution Prevention Plan (SWPPP) may be required for projects under five acres. * 6. The project shall conform to the Regional Water Quality Control Board post- construction C.3 regulations which shall be designed and engineered to integrate into the project’s overall site, architectural, landscaping and improvement plans. These requirements are contained in the project’s Stormwater Control Plan and are to be implemented as follows: ▪Prior to issuance of permits for building, site improvements, or landscaping, the permit application shall be consistent with the applicant’s approved Stormwater Control Plan for a Small Land Development Project and shall include drawings and specifications necessary to implement all measures in the approved plan. The permit application shall include a completed Stormwater Control Plan for a Small Land Development Project as published by the Contra Costa Clean Water Program. * 7. The applicant shall conduct a boundary survey to verify the exact location of all property lines prior to recordation of the final map. APPROVED by the Danville Planning Commission at a regular meeting on February 25, PAGE 12 OF RESOLUTION NO. 2020-03 2020, by the following vote: AYES: NOES: ABSTAINED: ABSENT: _____________________________ CHAIR APPROVED AS TO FORM: _______________________________ ______________________________ CITY ATTORNEY CHIEF OF PLANNING il()ÏrcET0 suRR()ulrDllr0 BY "S m ø l l Tow n Atm osp h e re." Outstdnding Qualiv oÍ LiÍe" NOTICE OF A PUBLIC HEARING Danville Planning Commission Meeting Tuesday, February 25,2020 at7:30 PM I Town Meeting Hall,20L Front Street All interested persons are encouraged to attend and be heard at the scheduled public hearing at7:30 p.m., Tuesday, February 25, 2020 at the Town Meeting HalI, 201 Front Skeet, Danville, CA. For additional information regarding the projecf please contact the staff representative as referenced above. NOTE: If you challenge the Towrls decision on this matter in court, you may be limited to raising only those issues you or someone else raised at the public hearing described in this notice, or in written correspondence delivered to the Town af or prior, to the public hearing. In compliønce with tlrc Americans with Disabilities Act, the Town of Danaille witt prouide speciøI assistance for disabted citizens. If you need speciøl assistance to participate in tlds meeting, please contact the City Clerk (925) 314-3388. Notificøtion 48 hours prior to the meeting will enøble the Town to make reasonable arrøngements to ensure øccessibility to tlds meeting. [28CFR 35.1.02-35.104 ADA Title II] Project Name:775 Kirkcrest Road -- Burkart Case File Nos.:MS13-0035 Location:775 Kirkcrest Road I APN: 201-240-023 Description:Minor Subdivision request to subdivide an existing 2.06 acre parcel into two single family residential parcels. Property Owner: Applicant: Philip and Karen Burkart 775 Kirkrest Road Danville, C1-94526 DeBolt Civil Engineering 811 San Ramon Valley Boulevard Danville, CA94526 Staff Contact:David Cromptorç Principal Planner |(925) 31,4-3349 |dcrompton@danville.ca.gov ATTACHMENT B Vicinity Map Site Plan: 775 Kirkcrest ::1. PROJECT SITE a, i K¡RfiCNBT, totlÞ...... I ¿ 'I t I If-- t_r Ì It*-aF*q.Ú 1 i FANCEL 'ÁT:-Cæ{tS+tÈr....r*¡æ¡ r - J;t/ !á- - A B C D E 1 APN NAME JAMES MICHAEL GLEN TRE KEOGAN KEVIN P TRE HARTNETT DONALD F & CAROLTRE POURSOHI FAZLOLAH & FARIBA TRE POTTER RANDALL G & NATALIE M BENTSEN DONALD R & MURIEL TRE DOYLE TERENCE & KIMBERLEY TRE RIEDEL FREDERICK & JUDITH TRE READY REALTY INVST FUND INC SMITH BRENT E & SANDRA S TRE BOSWELLJOYCE M TRE CORLEY BRIAN & ZEPHRA SPENCE BRIAN R TRE HEATHORN EDWARD W & WENDY TRE FRANDSEN MICHAEL LYLE TRE RUE KITTY TRE SCOTT LAWRENCE & CYBILLE TRE GRANVELLE GORDON C & MOLLY TRE MONTANA DEBIE A & WILLIAM A SILLA RICHARD L TRE CREVEY JOHN R TRE GIORGI LOUIS J JR & JOANNE TRE LESCURE NORMAN & KATHRYN TRE WILLIAMS RICHARD G & KATHY H ASHFORD-NG CAROLA HILARY TRE DU WEIDONG DEBELLIS JOAN M TRE KARPENKO MARK VICTOR CORDES JANET TRE TALBOT JOHN D TRE WILLIAMSON JOHN B HARTMAN CHARLES W WIJESINGHE MANIK TRE DOYLE MICHAEL J & JOE ANNE TRE HUMPHREY JONATHAN & CLAIRE TRE RYBURN WALLACE W & BARBARA A WANDERER BONNIE LTRE RANEY JEROME S & LAURA E TRE JOHANNESSEN PATRICIA M TRE BARNES THOMAS E TRE YOO DANIEL SUNGWOONG TRE HARRINGTON JOHN R & DIANE TRE PICKERING DAVID J MOORES MELISSA K TRE KLOOS WILLIAM A & VERNA M TRE MILLER GREGORY E TRE NAVONE ERIK J & HILARY F TRE FOSTER JAMES W & SUSAN G TRE BETTY GREG & WENDY ADDRESS PO BOX r.25 PO BOX 3s7 PO BOX 624 1. ROBERTS CT 1OO7 KIRKCREST LN 11 SHADOW OAK RD 12 SHADOW OAK RD 120 KUSS RD 1232 KENILWORTH RD 125 KUSS RD ]-25 NAUTILUS DR 140 WAYNE AVE 1415 HOLIDAY HILL RD 15 SHADOW OAK RD 150 KUSS RD 151 KUSS RD 18 SHADOW OAK RD 186 KUSS RD 201 KUSS RD 2l WINDWARD RD 22 GARY WAY 22 WINDWARD RD 222 KUSS RD 223 KUSS RD 225 SAN FRANCISCO BLVD 228 KUSS RD 231 KUSS RD 234 KUSS RD 239 KUSS RD 247 KUSS RD 250 KUSS RD 268 WAYNE AVE 3 ROBERTS CT 30 HARMONY CT 30 WINDWARD RD 3OO OAK VIEW TER 33 WINDWARD RD 332 HARTFORD RD 333 HARTFORD RD 340 HARTFORD RD 341 HARTFORD RD 348 HARTFORD RD 349 HARTFORD RD 352 HARPER LN 357 CORDELL DR 358 CORDELL DR 360 HARPER LN 363 CORDELL DR 364 CORDELL DR CITY STATE ZIP DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA. 94526 DANVILLE CA 94526 DANVILLE CA 94507 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 HILLSBOROUGH CA 94010 DANVILLE CA 94526 VALLEJO CA 94591 ALAMO CA 94507 GOLETA CA 93TT7 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 ALAMO CA 94507 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 SAN ANSELMO CA 94960 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 ALAMO CA 94507 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 2012400L4 2011200I4 199060021 201.L20027 201110013 199060017 L99060014 20L2400t6 20r_11_0009 201240001 2072600t5 201131007 201250018 199060016 201240006 20]-260022 199060015 20L240022 20r.260005 199060022 20t!2oo;o4 199060018 201250012 201260010 20LL37021 20L2500lt 20L26002L 20L2500].6 20t2600L3 2012600L] 201250024 2012500L7 207].20020 201230012 199060019 1990s0009 199060020 20Lr3LOO4 201131010 20113L005 201131009 2011"31006 201r_31008 201230013 20L230006 201_L3101_8 20L2300L7 201230005 20L13tO28 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 A B C D E 51 199060026 201230004 20LL3LO27 201230t22 201230003 20L220003 20LL3L020 20L230002 20L230024 201230001 201t3t026 201230038 201.12001.8 201230016 207].31025 201240003 20L220022 20L240012 207240013 20L2400L7 199060011 20L240021 199060010 201230040 199060009 207240020 201260076 199060004 201240018 20L260008 199383013 199060027 20L120019 20L220023 20L2400LO 201230039 201230032 201220004 201230041 207240023 201240007 201120003 20LL20006 201110010 201_120008 20L092001 20L720007 201110011 201.7tOOL2 JORDAN JANICE K TRE ROULETTE EDWIN & MARIANNE TRE MORRISON MARILYN LTRE BLY ALEXANDER L TRE SCHREMP BERNICE M TRE DODD WILLIAM HOLDRUM JR & KEVA DRISCOLL BRIAN & PATRICIA TRE HOPKINS HARVEY S & PAM S RILEY RICHARD P & NANCY G STEWART MICHAEL A & SHARON TRE TINGEY TANNER G TRE AGENO BARBARAJ TRE GOWENRALPHL&ROBINJP DOYLE JOHN F & MARGARET M TRE CALIFORNIA PACIFIC TITLE CO DECHENE ROBERT A & ELIZABETH PUGH STEVEN W TRE HOFFMANN STEPHAN & STACIE RADO MARTIN & ADRIENNE TRE SOUZATHOMASA&AMYHTRE YEOH MATTHEWÏZE YUN EBERHARDT CLYDE S & MARILYN CHUNG GUYFAR HUTCHESON WILLIAM E TRE GOLDSTEIN JOSHUA L & KATHRYN N JAMES MICHAEL G TRE BOLLINGER JOHN J & TIFFANY LAMBERT ROBERT R & SHARON TRE GIRVAN GARRETTJ & CATHYATRE MONTALBO DAVID K WENDT MATTHEW & JACQUELINE TRE STORM GARY & MICHELLE FISET RICHARD F & JUDY M TRE WILKINSON RICHARD A & CYNTHIA KARPENKO LYDIA TRE BLESSING JASON & HOLLY TRE MOAL STEPHEN W & THERESA M TRE ESFORMES JACK H & MELONIE E HUTCHESON TERESA R BURKART PHILIP & KAREN TRE SHUNAY RICHARD & SARAH STEPHENS JEFFREY S & TAMRA J PASICHUKE JAMES & JILL TRE HARPER THOMAS R & CAROLYN A TYLER JOHN JR & JOAN C TRE KIVEL SARAH HO PAULETTE A AGENO MICHAEL TRE THOMAS THOMAS L & LISA W TRE 370 DEL AMIGO RD 371 CORDELL DR 372 CORDELL DR 372 HARPER LN 379 CORDELL DR 379 HARPER LN 380 CORDELL DR 387 CORDELL DR 394 HARPER LN 395 CORDELL DR 396 CORDELL DR 398 HARPER LN 4 ROBERTS CT 40 HARMONY CT 41 SUTTER ST 410 CLIPPER HILL RD 42 GENTLE CREEK PL 422 CLIPPER HILL RD 444 CLIPPER HILL RD 450 CLIPPER HILL RD 481 CLIPPER HILL RD 481.HARPER LN 485 CLIPPER HILL RD 488 HARPER LN 489 CLIPPER HILL RD 489 HARPER LN 490 CLIPPER HILL RD 5OO OAK VIEW TER 505 HARPER LN 528 CLIPPER HILL RD 592 BRADFORD PL 595 BRADFORD PL 6 ROBERTS CT 608 BRADFORD PL 613 BRADFORD PL 625 BRADFORD PL 640 BRADFORD PL 699 TERRY tN 750 KIRKCREST RD 775 KIRKCREST RD 787 KIRKCREST RD 799 KIRKCREST RD 845 KIRKCREST RD 865 KIRKCREST RD 9 ROBERTS CT 9OO KIRKCREST RD 946 STOCKTON ST APT 188 987 KIRKCREST LN 997 KIRKCREST LN DANVILLE CA 94526 DANVILLE CA 9.4526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 SAN FRANCISCO CA 94104 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94526 DANVILLE CA 94507 ALAMO CA 94507 DANVILLE CA 94526 ALAMO CA 94507 SAN FRANCISCO CA94108 DANVILLE CA 94507 DANV¡LLE CA 94507 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 4080 Cabrilho Drive Martinez, CA 94553 Telephone (925) 930-7901 Fax (925) 723-2442 January 23, 2019 Philip & Karen Burkhartc/o Garry Orr gary@orrdesign.com Re: Tree Assessment for 775 Kirkcrest Road, Danville Dear Philip & Karen, This report is an assessment of trees located on the undeveloped portion of the property at 775Kirkcrest Road. Per Gary Orr’s request, the scope of work includes tagging, measuring, and assessing health & structure of all trees > 6” in diameter. I also identified the trees under or in the easement affected areas by referencing his notes. Assumptions & Limitations This report is based on my site visit on 1/23/19, and the tree removal plan provided by OrrDesign Office dated 7/6/18. It was assumed that existing features and trees were accurately surveyed. Several trees were not surveyed, so I added them to my tree location plan. I did not note whether the non-surveyed trees were within utility easements as their boundaries areunclear. The health and structure of the trees were assessed visually from ground level. No drilling, rootexcavation, or aerial inspections were performed. Internal or non-detectable defects may exist and could lead to part or whole tree failures. Due to the dynamic nature of trees and their environment, it is not possible for arborists to guarantee that trees will not fail in the future. Tree Inventory & Assessment Table#s: Each tree was given a numerical tag from #1-37 (off-site trees are given a number but werenot physically tagged.) Their locations are given in the tree protection plan. DBH (Diameter at Breast Height): Trunk diameters in inches were calculated from the circumference measured at 4.5’ above average grade. Health & Structural Condition Rating Dead: Dead or declining past chance of recovery. Poor (P): Stunted or declining canopy, poor foliar color, possible disease or insect issues. Severe structural defects that may or may not be correctable. Usually not a reliable specimenfor preservation. Fair (F): Fair to moderate vigor. Minor structural defects that can be corrected. More susceptible to construction impacts than a tree in good condition. Good (G): Good vigor and color, with no obvious problems or defects. Generally more resilient to impacts. Age Young (Y): Within the first 20% of expected life span. High resiliency to encroachment. Mature (M): Between 20% - 80% of expected life span. Moderate resiliency to encroachment. Overmature (OM): In >80% of expected life span. Low resiliency to encroachment. ATTACHMENT C Tree Assessment, 775 Kirkcrest Road January 23, 2019 Jennifer Tso, Certified Arborist 2 Easement (per Gary Orr’s plan, if trees are located within a utility easement) PLE: Overhead Power Line (PG&E) Easement UGE: Underground Utility Easement ?: Likely to be in an easement, but details unknown # Species DBH Health Structure Age Easement Comments 1 California bay(Umbellularia californica) 13 G G-F M DBH estimated. In fenced yard area ~10’ from fence. Tag attached to corner fencepost. 2 Coast live oak(Quercus agrifolia) 15 P F M PLE Under power lines. Sparse canopy.Circling root on down slope side. 3 Valley oak(Quercus lobata)8 F-P F Y PLE Under power lines. Stunted growth withepicormic sprouts. 4 Coast live oak 14, 8.5 G-F G-F M PLE Topped for power line. Larger stem has closing wound on lower 7’ of inner side; cause unknown. 5 Coast live oak 12.5 F F M UGE Under power lines. Sparse canopy. Minor sycamore borer damage. Co-dominant stems with included bark at 4.5’. 6 Coast live oak 7.5, 12 G G M 7 Coast live oak 7.5 G-F F Y UGE Phototropic lean away from adjacent oak.Neighbor house drops through canopy. 8 Coast live oak 17.5 F F M UGE Minor sycamore borer. Co-dominant stems at 5’ with included bark. Sparse canopy. Under power lines. 9 Coast live oak 7 F G Y Sparse canopy. 10 Coast live oak 8 F-P G-F Y Dominated by thorny vine. 11 Coast live oak 8 G-F G-F Y Lowest 1' of trunk parallels ground beforeresuming vertical growth. 12 Coast live oak 6 G G Y 13 Coast live oak 6.5 G-F G-F Y 14 California bay 6, 6, 6 G G-F M PLE 15 Coast live oak 7 F-P F Y Topped. Sparse canopy. 16 Coast live oak 9.5 F G-F M PLE Minor sycamore borer damage. Sparse canopy. 17 Coast live oak 9 F-P G-F M PLE Sparse canopy. Moderate sycamoreborer. Termites under bark on lower trunk. Stained/bleeding lower trunk with Hypoxylon-like growth. 18 Coast live oak 6.5 G G Y PLE 19 Coast live oak 7.5, 13 G-F F M PLE Moderate sycamore borer damage. Smaller stem attached at 3’ with included bark. 20 Coast live oak 8 G G Y PLE Power lines above. 21 Coast live oak 6 G-F G Y ? Tree Assessment, 775 Kirkcrest Road January 23, 2019 Jennifer Tso, Certified Arborist 3 # Species DBH Health Structure Age Easement Comments 22 Coast live oak 7 G-F F Y ? No live foliage in lower 2/3 of canopy. 23 Coast live oak 7.5 F F-P Y ? All live foliage in top 1/5 – 1/6 of tree. Girdling root. 24 Coast live oak 6 G-F F Y At base of #25. 25 Valley oak 21.5 F G M Root crown buried. Stunted growth. 26 Valley oak 21 F G M Buried root crown. Lower growth stunted, epicormic sprouts not vigorous. 27 Coast live oak 6.5 G F Y 28 Valley oak 16, 16 F G M Co-dominant stems at 2' with wide attachment. Stunted growth. 29 Valley oak 30 G-F G M Neighbor’s tree, no tag, DBH estimated. Epicormic sprouts not vigorous. 30 Coast live oak 6.5 G G Y Neighbor’s tree, no tag, DBH estimated. Trunk engulfing stake ties. 31 Deodar cedar (Cedrus deodara) 7 G F Y Neighbor’s tree, no tag, DBH estimated. Trunk girdled by guy wires at 3’. 32 Coast live oak 8 G G Y Neighbor’s tree, no tag, DBH estimated. Co-dominant stems at 7’ above grade. 33 Coast live oak 11 G G-F M Neighbor’s tree, no tag, DBH estimated. Multiple stems at 8’ (may have been topped). 34 Valley oak 31 G-F G-F M Closed trunk cankers on lower 4' of trunk. Multiple stems at 6’ with wide attachment. Buried root crown. 35 Valley oak 24.5 G-F G-F M Circular tag #29. 36 Valley oak 18 G-F G-F M Buried root crown. 37 Valley oak 19 G-F G-F M Buried root crown. Circular tag #31. Thank you for the opportunity to provide this report, and please do not hesitate to contact me if there are any questions or concerns. Sincerely, Jennifer Tso Certified Arborist #WE-10270A Tree Risk Assessor Qualified Geotechnical Engineering Report Burkhart Residence Improvements Danville, California July 17, 2015 Terracon Project No. ND145059 Prepared for: Philip & Karen Burkhart Danville, California Prepared by: Neil O. Anderson and Associates A Terracon Company Concord, California ATTACHMENT D Terracon Consultants, Inc. 5075 Commercial Circle, Suite E Concord, CA 94520 P [925] 609 7224 F [925] 609 6324 terracon.com July 17, 2015 Philip and Karen Burkhart 775 Kirkcrest Road Danville, CA 94526 Phone [925] 362-9751 pab@latitudewines.com Re: Geotechnical Engineering Report Burkhart Residence Improvements Danville, California Terracon Project Number: ND145059 Dear Mr. and Mrs. Burkhart: Neil O. Anderson & Associates, A Terracon Company (Terracon) has completed the geotechnical engineering services for the above referenced project. This study was performed in general accordance with our proposal dated November 26, 2014 and accepted November 11, 2015. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction for the proposed development of your parcel. We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us. Sincerely, Terracon Consultants, Inc. Cindy A. Wright, G.I.T. Patrick C. Dell, Senior Associate Project Geologist Geotechnical Engineer Enclosures cc: 5 – Client (Hardcopy) 1 – File TABLE OF CONTENTS Responsive ■ Resourceful ■ Reliable Page EXECUTIVE SUMMARY ............................................................................................................... i 1.0 INTRODUCTION ............................................................................................................... 1 2.0 PROJECT INFORMATION ............................................................................................... 1 2.1 Project Description ................................................................................................ 1 2.2 Site Location and Description ................................................................................ 2 3.0 SUBSURFACE CONDITIONS .......................................................................................... 4 3.1 Geology ................................................................................................................. 4 3.2 Landslides and Debris Flow .................................................................................. 5 3.2.1 Site Specific Aerial Photograph Review .................................................... 6 3.2.2 Photographic Review ................................................................................. 6 3.2.3 Site Reconnaissance ................................................................................. 7 3.3 Typical Profile ........................................................................................................ 8 3.4 Groundwater .......................................................................................................... 9 3.5 Slope Stability Analysis ....................................................................................... 10 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION ..................................... 11 4.1 Geotechnical Considerations............................................................................... 11 4.2 Earthwork ............................................................................................................ 12 4.2.1 Site Preparation ....................................................................................... 12 4.2.2 Engineered Fill Requirements ................................................................. 13 4.2.3 Compaction Requirements ...................................................................... 14 4.2.4 Grading and Drainage ............................................................................. 15 4.2.5 Earthwork Construction Considerations .................................................... 17 4.2.6 Utility Trench Backfill ............................................................................... 17 4.3 Foundations ......................................................................................................... 18 4.3.1 Foundation Design Recommendations ..................................................... 18 4.3.2 Foundation Construction Considerations .................................................. 19 4.3.3 Additional Pool Considerations ................................................................ 21 4.3.4 Seismic Considerations ........................................................................... 22 4.4 Retaining Walls ................................................................................................... 23 4.5 Pavements .......................................................................................................... 25 4.5.1 Subgrade Preparation.............................................................................. 25 4.5.2 Design Considerations............................................................................. 26 4.5.3 Estimates of Minimum Pavement Thickness ........................................... 26 4.5.4 Pavement Drainage ................................................................................. 27 4.5.5 Pavement Maintenance ........................................................................... 27 4.6 Exterior Hardscapes ............................................................................................ 28 4.7 Testing, Inspections, and Review ........................................................................ 28 5.0 GENERAL COMMENTS ................................................................................................. 29 TABLE OF CONTENTS (continued) Responsive ■ Resourceful ■ Reliable APPENDIX A – FIELD EXPLORATION Exhibit A-1 Site Location Exhibit A-2 Boring Location Plan Exhibit A-3 Site Geology & Landslide Hazard Maps Exhibit A-4 Field Exploration Description Exhibit A-5 to A-10 Boring Logs Exhibit A-11 Test Pit – Cross Sections APPENDIX B – LABORATORY TESTING & SLOPE STABILITY ANALYSIS Exhibit B-1 Laboratory Testing Description Exhibit B-2 Atterberg Limits Results Exhibit B-3 Grain Size Distribution Exhibit B-4 & B-5 Triaxial Unconsolidated-Undrained Exhibit B-6 Slope Stability Cross Section Location Exhibit B-7 Slope Stability Cross Section Exhibit B-8 Slope Stability Slope/W Results APPENDIX C – SUPPORTING DOCUMENTS Exhibit C-1 General Notes Exhibit C-2 Unified Soil Classification System Exhibit C-3 Description of Rock Properties Exhibit C-4 Benched Fill Detail Exhibit C-5 Dissipater Detail Exhibit C-6 Earth Retaining Wall Drain Detail Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable i EXECUTIVE SUMMARY A geotechnical investigation has been performed for a proposed development of an adjacent proposed parcel for the Burkhart residence located at 775 Kirkcrest Road in Danville, California. Five borings were drilled to approximate depths ranging from 21½ to 51 feet below the ground surface (bgs). In addition, three test pits were excavated with a backhoe to depths of between 11 and 17½ feet bgs. Based on the information obtained from our subsurface exploration, the site can be developed for the proposed project. The following geotechnical considerations were identified: The upper surface materials encountered at the site are highly plastic sandy fat clays. Depth to highly weathered bedrock varied across the site from 7½ to 10½ feet bgs. The bedrock encountered was mainly moderately to highly weathered sandstone. No groundwater was encountered. Due to the varying depths of proposed cut/fill and the potential for settlement of the fill, expansive nature of the near surface clays, and the potential for slope movement, the pool, retaining walls, building foundations, and critical structural foundations should be supported by drilled piers that derive their support from the underlying highly weathered bedrock. Other ancillary structures, such as low height seating walls and planters, may be supported on shallow spread foundations bearing on firm, undisturbed native soil, engineered fill or weathered bedrock for support. A slope stability analysis indicated that the calculated minimum factor of safety did not meet the minimum required factor of safety during a short term seismic event during saturated conditions. We recommend that a relatively shallow slide area identified within the proposed house building pad be remediated prior to construction of the improvements at this site. Once the shallow slide area is remediated, then the recommendations for design and construction of the improvements contained in this report can be used. Good surface drainage should be constructed to provide rapid removal of runoff away from the new improvements. Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support. We therefore recommend that Terracon be retained to monitor this portion of the work. This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations. Responsive ■ Resourceful ■ Reliable 1 GEOTECHNICAL ENGINEERING REPORT BURKHART RESIDENCE IMPROVEMENTS DANVILLE, CALIFORNIA Terracon Project No. ND145059 July 17, 2015 1.0 INTRODUCTION This report presents the results of our geotechnical engineering services performed for the proposed developments at the lot adjacent to the Burkhart residence located at 775 Kirkcrest Road in Danville, California. Logs of the borings and test pits along with a site location map and boring location plan are included in Appendix A of this report. The purpose of these services is to provide information and geotechnical engineering recommendations relative to: subsurface soil conditions foundation design and construction groundwater conditions seismic considerations earthwork slope stability infiltration testing pool shell and retaining wall design and construction 2.0 PROJECT INFORMATION 2.1 Project Description Item Description Site Layout See Appendix A, Exhibit A-2: Boring Location Plan Project Overview A preliminary grading plan dated February 25, 2015 was provided to our office by Orr Design Office. The project consists of subdividing the existing parcel and developing the southern parcel (Parcel B) with a new single-family residence. The northern parcel (Parcel A) contains the existing single-family house. We understand that the development of Parcel B will consist of the construction of a new approximately 3,000 square foot house, 2+ car garage, driveway, retaining walls, a swimming pool and spa, and associated outdoor patios and hardscapes. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 2 Item Description Proposed Construction The building pad will be cut into the hillside and will either be graded flat on the hillside or the house will be supported by piers above grade. The driveway is anticipated to begin at the northeast corner of the parcel and will be graded into the ascending slope to access the house. The proposed locations of the pool/spa and outdoor patios are unknown at this time, but will likely be located in the southwest corner of the property. Retaining walls up to 10 feet in height will also be constructed. Grading Based on the conceptual site plan provided by Orr Design Office we understand that cuts of up to about 12 feet and fills of about 8 feet will be required for construction of the proposed development. However, we understand most of the fill areas will be placed behind retaining walls. Cut and fill slopes 3H:1V (Horizontal to Vertical) max Retaining walls Based on the conceptual site plan provided by Orr Design Office we understand that retaining walls will be utilized across the project site to create level areas for the building pads, a pathway along the creek, and landscaped areas. Retaining walls will range in height from 1 foot to 10 feet. We have anticipated retaining walls will consist of concrete stem construction. 2.2 Site Location and Description Item Description Location The project is located at 775 Kirkcrest Road in Danville, CA. Existing improvements The current parcel is approximately 2.06 acres and is proposed to be split into an approximately 1.1 acre northern parcel, Parcel A, and an approximately 0.96 acre southern acre, Parcel B. Parcel A contains the existing single family house, garage, pool and spa, and hardscapes. Parcel B, which is the focus of this investigation, is not developed except for a pier supported solar panel array located along the northern edge. The solar panels will be removed as part of this project. Current ground cover Parcel B is covered in overgrown grass, mature oak trees, and smaller trees and bushes near the creek and bottom of the slope. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 3 Item Description Existing topography The project site is located near the eastern base of the Las Trampas Ridge which is a northwest to southeast trending ridge. A creek is located along the eastern portion of this site. The general slope of the property exceeds 2H:1V in some areas, but is as low as 4H:1V in the flatter portions of the site. General topographic changes across the site exceed 80 feet in elevation, with the portions near the creek being roughly 400 to 405 feet above mean sea level (amsl) and the top portions of the slope being roughly 480 to 485 feet amsl. Surrounding Development North: Parcel A with the existing Burkhart residence, Kirkcrest Road South: Adjacent residential house, Harper Lane East: Creek and residential house, slope flattens significantly on the other side of the creek. West: Adjacent residence located upslope. Erosion was not observed on the subject property; however, a slide was observed on the site. An illustration of the approximate area of the slide is shown below as Figure 1. The approximate location of the slide is also shown on Exhibit B-6. The observed slide showed signs of historic movement, including a small scarp. Excavation of test pits confirmed the location and depth of the slide. This is discussed in greater detail in Section 3.2.3 - Site Reconnaissance. Figure 1. Site image showing approximate area of observed surficial slide. North is to the right in the figure. Aerial image from Google Earth. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 4 3.0 SUBSURFACE CONDITIONS 3.1 Geology The site is located in the foothills area of the Las Trampas Ridge. This area has the potential to experience very high susceptibility to landslides and high seismic ground motions. The area is mapped by Dibblee (1980)1 as older alluvial deposits and landslide debris. Crane (1995)2 mapped the site to be within the lower limits of a large landslide. Portions of the site are underlain by the Rodeo Shale and Briones Formations, which is in general agreement with our field investigation findings (test pits and soils borings performed on-site). Within the area near the site, overturned beds have been mapped by Dibblee. With the complicated overturned anticlinal folding, and relatively close proximity to the Calaveras Fault (<0.25 miles from the site), the potential for ongoing motion and sliding is significant. Most of the bedding tends to dip back into the slope at angles of 55 to 70 degrees. This may assist in counteracting some of the natural tendency for daylight/slope failures. As mentioned above the Calaveras Fault is located very near to the site. An earthquake forecast for the State of California called the Uniform California Earthquake Rupture Forecast (UCERF3) was compiled by the United States Geological Survey (USGS), the Southern California Earthquake Center (SCEC), and the California Geological Survey (CGS), with support from the California Earthquake Authority. It updated the greater San Francisco Bay Area earthquake forecast of 2002. This report included probabilities for earthquakes of magnitude 6.7 or greater in the next 30 years. The overall probability of a magnitude 6.7 or greater earthquake in the Greater Bay Area is 63 percent, about 2 out of 3, which is very close to the probability of 62 percent obtained by the original 2002 working group. The earthquake probability is highest for the Hayward-Rodgers Creek Fault system, 31 percent, or nearly 1 out of 3. The last damaging earthquake on the Hayward Fault was in 1868. The 140 years since 1868 is the same length of time as the average interval between the past 5 large earthquakes on the southern Hayward Fault. The probability of a large earthquake on the San Andreas Fault in the next 30 years is about 21 percent, or about 1 out of 5. This fault was responsible for the magnitude 7.8 1906 San Francisco earthquake and the magnitude 6.9 1989 Loma Prieta earthquake. The Calaveras Fault in the East Bay, and the San Gregorio Fault along the San Francisco Peninsula Coast have probabilities of 7 percent and 6 percent, respectively, of producing a magnitude 6.7 or greater earthquake in the next 30 years. In the East Bay, near the Central Valley, the Greenville Fault, the Mt. Diablo Thrust, and the Concord- 1 Dibblee, T.W., 1980, Preliminary geologic map of the Las Trampas Ridge quadrangle, Contra Costa And Alameda Counties, California, United States Geological Survey (USGS), Open File Report 80-545 2 Crane, R., 1995, Geologic Map of the Las Trampas Ridge 7.5' Quadrangle, Unpublished, California Geological Survey (CGS) 3 SCEC, 2015, Third Uniform California Earthquake Rupture Forecast (UCERF3), http://www.scec.org/ucerf/ Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 5 Green Valley Fault were assigned probabilities of 3 percent or less of producing a magnitude 6.7 or greater earthquake in the next 30 years. The general seismicity for the overall greater project area is therefore greater than other areas around the country and needs to be considered for evaluations for hazards of geologic significance. The Calaveras is also an active fault. The recent West Napa Fault earthquake is evidence of this. This fault is believed to be an extension of the Calaveras. Due to historic slope movements near and on the site, the on-site rock type characteristics (Briones Formation – Sandstone and Siltstone that weather and break down to saturated low strength clays and silt soils), the relatively steep topographic relief on-site, and the potential for relatively large magnitude seismic motion, the potential for future slope movements would be considered high for this site. Because of this high potential we have included a slope stability analysis as part of this investigation and used its results as part of our construction recommendations. The slope stability analysis further assesses the likelihood of failure due to both shallow and deep seated landslides in association with the proposed construction. A stability analysis is part of this report and is discussed in greater detail in Section 3.5. 3.2 Landslides and Debris Flow Landslides and debris flows can pose a serious hazard to property in the hilly terrain of the San Francisco Bay region. Slope movement occurs on sloping sites when surficial soils are saturated, increasing the weight and decreasing the shear strength of the soils. Generally, movement of the slope due to such conditions occurs within the upper near surface unstable clayey soils which are known to exist in the area. Soil movement also occurs when the upper portion of the slope is excessively loaded or the bottom portion of the slope is undercut causing the driving force to exceed the resisting force. Slope movement can also be triggered by strong ground shaking from a seismic event due to the lack of lateral confinement. According to the Landslide Hazard maps reviewed4, the site is located within a large historic landslide. The slide depicted appears to be regionally underlying a large number of local structures. The creek (and in some places potentially the Calaveras Fault) seem to border the base of the slide. We observed in a test pit and in a surface expression a smaller landslide approximately 65 by 40 feet in area, and roughly 10 to 12 feet deep at the middle. The approximate location of this small slide is shown on Exhibit B-6. Based on our review and interpretation larger, deep seated landslide motion is relatively rare, and is likely controlled by large seismic events, creek and hillside toe dynamics, and over-saturated conditions. In our opinion, shallow earth flows and/or surficial creep of the expansive clay soils would be the most likely mechanism for slope movement at this site. 4 Nilsen, 1975, Las Trampas Ridge Quadrangle, Open-File Report 75-277-24 Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 6 3.2.1 Site Specific Aerial Photograph Review Our firm reviewed multiple aerial photographs (both single and stereo pair), and satellite imagery to determine the potential slides that may exist on the site. The areas of potential landslide concern were compared against existing site data (work and maps performed by others). Aerial Photographs Reviewed Year Number Source Photo Type 1939 (07-26-39) BUU-281-90 USGS Non-Stereo Pair 1946 (07-26-46) GS-CP 1-5 & 1-6 USGS Stereo Pair 1972 (05-24-72) AV-1056-01-17 &-18 USGS Stereo Pair 1973 (05-02-73) CC 3526-3-30 & -31 USGS Stereo Pair 1973 (04-21-73) 1-21-25 & -26 USGS Stereo Pair 1980 (01-28-80) CS-VEZR 1-210 &1-211 USGS Stereo Pair 1948, 1991, 1993, 2002, 2008, 2009, 2011, 2012 Various Dates Google Earth Non-Stereo Pair All of the photographs were reviewed in detail. Ultimately, the best quality shots were more heavily reviewed to determine the impact to the site from historic landslides. Overall, we have mapped one small-sized depression/landslide on-site. A larger slide encompasses the entire area as indicated by Nilsen and Others in previous reports. The smaller slide is within the proposed building envelope and we recommend that it be remediated prior to construction. Recommendations for remediation are provided in Section 3.5 Slope Stability Analysis. 3.2.2 Photographic Review A variety of photographs were retrieved and reviewed from the USGS in Menlo Park. 1939 through 1980 Photo Review – In this photo set we were able to detect the overall large slide area as mapped by Nilsen and others. The smaller depression noted during our field work is also evident. It is apparent from the review of these photographs that the site is impacted by the slides mentioned. Of particular note, the smaller slide is within the building envelope and we recommend that it be remediated prior to construction. 2014 Photo Review - Various photographs were reviewed in Google Earth, and an apparent depression exists as mapped during our field reconnaissance and shown within this report. In- field review confirms the size to be roughly 65 by 40 feet in area, and roughly 10 to 12 feet deep at the middle. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 7 3.2.3 Site Reconnaissance The reviewing Certified Engineering Geologist (CEG) for the project (Daniel E. Kramer, Petralogix Engineering, Inc.) visited the site for a final review of the observed features on April 14th, 2015. Various notes and photographs were taken, and observations about the shallow slide were made and reviewed. The general bedding for the area and dip of the beds observed appeared to be into the hillside within Test Pits 1 and 2. In these test pits, no evidence of a landslide or slope movement was observed or noted. However, in Test Pit 3 a zone of apparent slide material was observed which had elevated moisture content and exhibited mixed and mottled soil conditions. The zone began around 10 feet below ground surface (bgs) and extended to at least 12½ feet bgs. In this area the slope direction changed and for this reason fracture patterns began to daylight. As mentioned, general bedding is into the hillside. However, the overturned beds noted by Dibblee and Others may be causing axial folding and fracture patterns in this area which are conjugate to the observed bedding plane. These conjugate shear and fractures could potentially daylight along this slope face and be the cause of this slide mass development. Regardless of the kinematic and historic mechanisms for failure, the slide exists and is an apparent feature within the proposed building zone. Rock outcrops were not available and/or observed for verification of any deeper sliding. Based on general geometry of the slope and the mapped and observed larger regional slide mass, we recommended that a deeper boring be excavated within the proposed building zone area. This deep boring was used to investigate the potential impact of the larger slide mass, and also the potential interaction between the larger and smaller slide masses. A fifty-one foot deep boring was performed using continuous core methods. A review of the logs and field cores was performed to assess the samples obtained for laboratory analysis. A slide material was encountered at depth (30 to 35 feet bgs). At this depth the recovery of the soil core was only 1½ feet out of 5 feet of core length. The sample was highly saturated, had a low density, was ductile and plastic, and deformed very easily. No slide plane was observed, but based on the mentioned characteristics and the reviewed geology, this was taken to be the lower extent of the larger slide mass. In this area the slide would naturally daylight near the slope toe, which is the natural creek line. Data from the lab samples, the field observations, the slope geometry, and the probable seismic conditions were utilized by Terracon in the overall stability analyses. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 8 3.3 Typical Profile Exhibit A-2 in Appendix A presents the locations of the five borings and three test pits that were excavated on the project site. Based on the results of the borings, subsurface conditions at the project site can be generalized as follows: Stratum Approximate Location of Stratum (bgs) Material Description Consistency/ Density 1 Surface to 1½ ft to 10½ ft Sandy Fat Clay Soft to Stiff 2 1½ ft to 10 ft Completely Weathered Bedrock – Sandy Lean Clay, tan to brown Stiff to Very Stiff 31 From 7½ ft or 10½ ft to Undetermined Sedimentary Bedrock – Sandstone with clayey matrix, highly weathered, tan, extremely fractured, very weak as a rock mass with strong subangular rock fragments Medium Dense to Dense 42 From 47 ft to Undetermined Sedimentary Bedrock – Greywacke: bluish gray, medium strong to strong rock 1.Borings 2 through 5 and all the test pits were terminated within Stratum 3. 2.Only observed in Boring 1 One soil sample and two samples of the weathered bedrock were submitted to our lab for index testing. In addition, two soil samples from the infiltration tests were also tested for index testing. The results are presented in the following table: Sample Location Depth (feet) Liquid Limit (%) Plastic Limit (%) Plasticity Index (%) Percent Fines (%) Boring 2 3½ 46 21 25 51 Boring 2 16 33 20 13 51 Boring 3 8½53 24 29 75 Infiltration 12” 1 34 20 14 77 Infiltration 24” 2 52 26 26 88 The soil sample from Boring 3 classified as sandy fat clay (CH) which was of high plasticity. The bedrock samples from Boring B-2 were in such a weathered state that soil index tests could be performed and the rock material from both samples classified as sandy lean clay (CL). The soil samples from the infiltration tests classified as lean clay (CL) for the 12-inch deep sample and fat clay (CH) for the 24-inch deep sample. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 9 The soil samples from each boring were similar consisting of dark brown, moist, highly plastic fat clay with varying amounts of fine-grained sand. The transition from clay soils to bedrock was marked by the change in color from dark brown clay soils to the tan with grey and rust mottling colored bedrock. Soil conditions and stratification encountered in the test pits were similar to the borings. One exception was in Test Pit 3 where a zone of slide material was present from approximately 10 feet to 12½ ft bgs. Conditions encountered at each boring and test pit location are indicated on the individual boring logs and test pit cross sections. Stratification boundaries on the logs and cross sections represent the approximate location of changes in soil types; in situ, the transition between materials may be gradual. Details for each of the borings and test pits can be found in Appendix A of this report. 3.4 Groundwater Groundwater was not encountered in any of the borings or test pits at the time of our field explorations. No groundwater data was available for the ridge on which this site is located. Based on local groundwater mapping5 the closest groundwater data is approximately 1 mile away in downtown Danville, with a median groundwater depth of 7 to 19 feet bgs. We assume groundwater depths in the area of the subject site are greater than those encountered within the adjacent valleys provided no perched water tables are present on the site. The boreholes were observed while drilling and after completion for the presence and level of groundwater. Groundwater was not observed in the borings while drilling, or for the short duration that the borings were allowed to remain open. However, this does not necessarily mean the borings terminated above groundwater. Due to the low permeability of the soils encountered in the borings, a relatively long period of time may be necessary for a groundwater level to develop and stabilize in a borehole in these materials. Long term observations in piezometers or observation wells sealed from the influence of surface water are often required to define groundwater levels in materials of this type. Groundwater level fluctuations occur due to seasonal variations in the amount of rainfall, runoff and other factors not evident at the time the borings were excavated. Therefore, groundwater levels during construction or at other times in the life of the structures may be higher or lower than the levels indicated on the boring logs. The possibility of groundwater level fluctuations should be considered when developing the design and construction plans for the project. 5 California State Water Resources Control Board, “GeoTracker GAMA”, 2014, Former Unocal (T0604147099), http://geotracker.waterboards.ca.gov/gama/ Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 10 3.5 Slope Stability Analysis As mentioned previously both large scale and small scale slope movements have been mapped on the site. To further evaluate the stability of the slopes at their current and proposed loading configurations a slope stability analysis was performed using the SLOPE/W6 software package developed by GEO-SLOPE International, Ltd. A cross sectional profile was created using the preliminary grading plan provided to us by Orr Design Office. This profile is presented in Appendix B. Based on the field and laboratory test results, subsurface soil conditions, and our experience in with similar soils, the following total stress soil parameters were utilized in the slope stability analysis. Soil Description Unit Weight (pcf) Cohesion, C (psf) Friction Angle, Ø (degrees) Surficial Soils – Fat Clay (CH) 105 500 0 Lean Clay (CL) and Completely Weathered Sandstone Bedrock 121 600 0 Highly Weathered Sandstone Bedrock 117 0 34 Bedrock Impenetrable Results of the analysis are presented in Appendix B, Stability Analysis. The proposed slope profile was loaded with a surcharge of 100 pounds per square foot to simulate the weight of the house. (Since we are recommending that the house be supported on drilled piers we realize that the weight of the house should not impart any loading to the slope. We added the surcharge weight to be conservative in our analysis.) The slope was first analyzed for the static condition. The slope was then analyzed in a seismic condition utilizing a pseudo-static coefficient of 0.20. SLOPE/W evaluates the most likely failure plane given the slope configuration and soil strength. For this site the estimated failure plane corresponds to a relatively shallow earth flow where the surficial soils would move along the boundary with the completely weathered bedrock below. This failure plane is illustrated in Exhibit B-8. The results of our static and seismic slope stability analyses produced calculated factors of safety of 1.83 and 1.10 which satisfies the recommended factor of safety of 1.5 for long term static loading but not the factor of safety of 1.15 for short term (seismic) loading as recommended by CGS Special Publication 1177. Because of this we recommend that remedial measures should be implemented before construction. 6 SLOPE/W, A limited equilibrium slope stability analysis program for personal computers, Copyright © 1995-2015 GEO-SLOPE International Ltd. All Rights Reserved. 7 California Division of Mines and Geology 1997, Guidelines for Evaluating and Mitigating Seismic Hazards in California, Special Publication 117. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 11 The area identified previously in Figure 1 and in Exhibit B-6 should be excavated down to the weathered bedrock and then backfilled with engineered fill compacted to a minimum of 90 percent of the maximum dry density obtained in the ASTM 1557 test method. The backfill should be constructed and placed as shown on Exhibit C-4, Benched Fill Detail. Care should be taken to protect any slopes as specified in Section 4.2.4, Grading and Drainage, of this report. The areas above the slopes shall be well drained to carry runoff away from any slopes to limit saturation of the soil. V-ditches and properly graded slopes can be used to move surface runoff quickly from the slopes. We also recommend that irrigation not be used on slopes or be kept to a minimum and properly maintained. If low areas or settlement occur in the slope which creates areas where ponding of water can occur; these areas should be filled and re-graded immediately to reduce the potential for water to saturate the slope. Ponding of water or irrigation on the slope can saturate the clay soils, increasing the risk of slope movement or failure. Even with the remediation of the of the identified slide area described above, the possibility of soil creep due to the wetting and drying cycles of the surficial, expansive clay layer still exists throughout the site. Again, proper grading and drainage are important to reduce the potential effects of the creep. The geotechnical recommendations provided in this report are for the stated post-grading conditions. As indicated it is impractical and not economically feasible to design and expect the limited improvements necessary for the proposed construction to also provide resistance against geologic conditions and/or global slope movement. The homeowner should be aware that if global movement of the surrounding terrain were to occur, the proposed improvements could shift, settle, and/or crack. Development of this site will involve re-grading of the existing slopes. The homeowner, architect, and engineer should be aware that re-grading of the slopes may affect the stability of the slopes and may also affect the adjacent properties. 4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION 4.1 Geotechnical Considerations From a soil engineering standpoint, our office concludes that the site is suitable for construction of the proposed improvements; however, all of the conclusions and recommendations presented in this report should be incorporated into the design and construction to help reduce the potential for soil and foundation related problems. The main items of consideration for construction of the improvements are the presence of highly plastic surficial clay, the moderate amount of cut/fill being placed at varying depths, and the potential for slope movement. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 12 The highly plastic surficial clay soils encountered in our test borings are expansive and subject to volume changes with variations in moisture content. Special measures should be taken to protect hardscapes from the swelling pressures of the clay as indicated. Fill placed for the improvements should be compacted properly as specified in Section 4.2. It should be noted that engineered fills will experience some type of settlement over time. In addition, the site is susceptible to shallow slope movement that should be considered during the design and construction of the proposed improvements. Swimming pools are rigid structures and are not tolerant of differential movement. Differential movement can stress and crack a pool. The functionality and design of a swimming pool is dependent on the pool shell being free of structural cracks. Due to the varying depths of proposed cut/fill and the potential for settlement of the fill, expansive nature of the near surface clays, and the potential for slope movement, the building, pool, and retaining wall foundations should extend through the surficial clay soils and completely weathered bedrock and rely on the underlying highly weathered bedrock for support. This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. However, even if these procedures are followed, some movement and at least minor cracking in the improvements could still occur. The severity of cracking and other cosmetic damage such as uneven slabs will probably increase if modification of the site results in excessive wetting or drying of the expansive soils. Eliminating the risk of movement and cosmetic distress may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. We would be pleased to discuss other construction alternatives with you upon request. We recommend the exposed subgrade be thoroughly evaluated after stripping of topsoil and creation of cut areas, but prior to the start of structural fill operations. We recommend that the geotechnical engineer be retained to evaluate the bearing material for the foundations and slab subgrade soils. Subsurface conditions, as identified by the field and laboratory testing programs, have been reviewed and evaluated with respect to the proposed improvement plans known to us at this time. If any changes are made to these plans, we should be contacted to review the changes and determine if any modifications or revisions to our recommendations are warranted. 4.2 Earthwork 4.2.1 Site Preparation Prior to placing any fill, all vegetation, topsoil, all debris, and any otherwise unsuitable material should be completely removed from the construction areas. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 13 Where fill is placed on existing slopes steeper than 5H:1V, including behind retaining walls, benches should be cut into the existing slopes prior to fill placement. The benches should have a minimum vertical face height of 1 foot and a maximum vertical face height of 3 feet and should be cut wide enough to accommodate the compaction equipment. This benching will help provide a positive bond between the fill and natural soils and reduce the possibility of failure along the fill/natural soil interface. Furthermore, we recommend that fill slopes be over filled and then cut back to develop an adequately compacted slope face. A detail for a typical benched fill slope is provided on Exhibit C-4. Once cuts have been made and prior to placing any engineered fill, the subgrade soil should be scarified and compacted. The depth of scarification of subgrade soils and moisture conditioning of the subgrade is highly dependent upon the time of year of construction and the site conditions that exist immediately prior to construction. If construction occurs during the winter or spring, when the subgrade soils are typically already in a moist condition, scarification and compaction may only be 8 inches. If construction occurs during the summer or fall when the subgrade soils have been allowed to dry out deeper, the depth of scarification and moisture conditioning may be as much as 18 to 24 inches. A representative of our office should be present to observe the exposed subgrade and specify the depth of scarification and moisture conditioning required. As indicated previously, the surficial clay soils are underlain by completely weathered and then highly weathered sandstone bedrock at the site. The depth of bedrock noted in our boring logs shall not be construed as a maximum or minimum. Depths to bedrock may vary across the site. Our data along with local experience shall be used to come up with the most effective way to excavate foundations into bedrock. If additional information is desired on the hardness of the bedrock, we are experienced in providing seismic refraction soundings which provide primary wave velocity which is then used by us to provide input on what equipment or method may be suitable for the excavation of bedrock. If it is desired to retain our office to perform such a study we can be contacted to discuss in more detail. The contractor should plan his work accordingly. 4.2.2 Engineered Fill Requirements After moisture conditioning and compaction of native subgrade soils is complete, the approved engineered fills may be placed and compacted according to the following recommendations. Engineered fill materials (on-site or import) shall consist of sandy silts, sands, or sands and gravels. Engineered fill material shall not contain rocks greater than 3 inches in greatest dimension and should be non-expansive in nature with a plasticity index less than 12. The on-site clay soils may be used as fill in the landscaping, however, they are not suitable for use as engineered fill. At least seven days prior to the placement of any engineered fill, the engineer shall be notified of the source of materials. Samples of the proposed fill shall be obtained to determine the suitability of the materials for use as engineered fill. A representative Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 14 from our office should be present during grading to provide construction observation and compaction testing. Fill materials shall be spread in layers and shall have a uniform moisture content that will provide the specified dry density after compaction. If necessary to obtain uniform distribution of moisture, water shall be added to each layer by sprinkling and the soil disked, harrowed, or otherwise manipulated after the water is added. The layers of the fill material shall not exceed 8 inches in thickness and each layer shall be compacted with suitable compaction equipment to provide the specified dry densities. No fill shall be placed during weather conditions which will alter the moisture content of the fill materials sufficiently to make adequate compaction impossible. After placing operations have been stopped because of adverse weather conditions, no additional fill material shall be placed until the last layer compacted has been checked and found to be compacted to the specified densities. Engineered fill should extend a minimum of 5 feet beyond proposed improvements or under any exterior concrete flatwork. 4.2.3 Compaction Requirements Recommended compaction and moisture content criteria for materials are as follows: Material Type and Location Per the Modified Proctor Test (ASTM D 1557) Minimum Compaction Requirement (%) Minimum Moisture Content for Compaction Above Optimum (%) Subgrade (On-site Soils): Scarify to a Min. Depth of 8 inches 90 3 Engineered Fill Place in lifts not to exceed 8 inches 90 2 Caltrans Class II Aggregate Base or Permeable Material Place in lifts not to exceed 6 inches 95 2 The density of the upper 8 inches of subgrade and of each layer of fill shall be checked by the engineer after each layer has been compacted. Field density tests shall be used to check the compaction of the fill materials. Sufficient tests shall be performed by the engineer on each layer to determine that compaction of the entire area is in general compliance with the compaction specifications. If the dry densities are not satisfactory, the contractor will be Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 15 required to increase the weight of the roller, the number of passes of the roller, or manipulate the moisture content as required to produce the specified densities. 4.2.4 Grading and Drainage Development of this site will involve grading of the existing slopes. The homeowner, architect, and engineer should be aware that grading of the slopes may affect the stability of the slopes and may also affect the adjacent properties. It is our understanding no grading is planned on the adjacent slopes. If grading will occur on the adjacent slopes our office should be contacted to provide additional grading recommendations. Special care should be taken to ensure adequate drainage is provided throughout the life of the proposed improvements. Properly designed and constructed foundations can be seriously damaged by neglecting to install and regularly verify performance of recommended drainage systems. Surface drainage should be designed to provide rapid runoff of surface water away from the proposed improvements. The ground surface surrounding the exterior of the improvements shall be sloped to drain away from the improvements in all directions. Drains should be provided at the top of all slopes where the contributing drainage area to the slope has a flow path longer than 30 feet measured horizontally. Runoff water should not be allowed to run over the slopes. Runoff over the existing slope can cause erosion and instability of the slope. Surface drainage should be collected and discharged to an existing drainage system. Implementation of adequate drainage for this project can affect the surrounding developments. Consequently, in addition to designing and constructing drainage for this project, the effects of site drainage should be taken into consideration for the existing structures on this lot, the undeveloped portions of this lot, and surrounding sites. 4.2.4.1 Infiltration Testing We understand that surface runoff from the driveway, roof, and other hardscapes will be collected, filtered through a bio-retention vault system, and finally discharged into the creek or storm drain. From conceptual plans we received from Orr Design Office the bio-retention vault system will be located beneath 70 linear-feet of the walking trail located next to the creek. The surficial stratum of clay soils can prevent surface water from infiltrating into soils. Additionally, silt and clay sized soil particles can migrate into and clog filter drainage systems if they are not properly designed or maintained. Consequently, special care should be taken in the design of the drainage plan for the site. Infiltration tests were performed near the current walkway at depths of 12 inches and 24 inches below the ground surface. Soil samples were taken at both of these depths and sent back to our lab for grain size analysis. At 12 inches the soil was classified as lean clay with sand (CL) with 77% silt/clay particles and the soil at 24 Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 16 inches classified as fat clay (CH) with 88% silt/clay particles. Gradation curves are located on Exhibit B-3. Because of the risk of slope movement at this site, we do not recommend any drainage systems that will store water at the toe of the slope that could potentially saturate the adjacent soils. Runoff will need to be processed quickly and moved away from the slope. The on-site clay soils do not allow for water to quickly move through them and should not be used as an infiltration pathway. From the conceptual drawings, the filter material within the drainage system will be clean gravel material. An impenetrable barrier should be used to provide a barrier between to the filter material and native material to prevent saturation of the surrounding soils. We recommend using an enclosed concrete vault system. Additionally, all outlets from the drainage system should use a dissipater with additional erosion control methods such as rip rap especially if the runoff will be discharged on the creek slope. A typical dissipater detail is shown on Exhibit C-5. The infiltration tests were performed as part of the scope of services and the test results are presented below. These results are being presented for information only to show that unfavorable conditions are present regarding an infiltration system. These results are not for design purposes. The infiltration tests were performed in general accordance with ASTM D3385; using a 12-inch diameter and 24-inch diameter double-ring infiltrometer. Once the rings were placed, the soils were pre-soaked prior to running the tests. Depths of water level were measured in each of the rings at regular intervals, and if needed, water was added to the rings to manually replenish the lost water. Readings were made over a period of two hours. The test results are summarized in the following table. Sample Location Depth of Test (inches) Average Infiltration Rate1 (in/hr) Average Infiltration Rate1 (cm/hr) Soil Type, USCS Infiltration 1 12 3.0 7.5 Lean Clay with Sand (CL) Infiltration 2 24 0.01 0.04 Fat Clay (CH) 1.No safety factor applied Since our tests were performed using clean water, the storm water runoff will likely contain materials such as silt, leaves, oil residues, and other matter that may reduce the infiltration characteristics of the soils. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 17 4.2.5 Earthwork Construction Considerations Although the exposed subgrade is anticipated to be relatively stable upon initial exposure, unstable subgrade conditions could develop during general construction operations, particularly if the soils are wetted and/or subjected to repetitive construction traffic. The use of light construction equipment would aid in reducing subgrade disturbance. The use of remotely operated equipment, such as a backhoe, would be beneficial to perform cuts and reduce subgrade disturbance. Should unstable subgrade conditions develop, measures will need to be employed to stabilize the site. If this condition occurs, we are experienced in providing recommendations to stabilize unstable soil conditions. Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of foundations and concrete patio slabs. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations. If the subgrade should become desiccated, saturated, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and recompacted prior to foundation and concrete patio slab construction. Trees or other vegetation whose root systems have the ability to remove excessive moisture from the subgrade and foundation soils should not be planted next to the improvements. Trees and shrubbery should be kept away from the exterior edges of the improvements a distance at least equal to 1.5 times their expected mature height. As a minimum, all temporary excavations should be sloped or braced as required by Occupational Health and Safety Administration (OSHA) regulations to provide stability and safe working conditions. Temporary excavations will probably be required during grading operations. The grading contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required, to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current OSHA Excavation and Trench Safety Standards. The geotechnical engineer should be retained during the construction phase of the project to observe earthwork and to perform necessary tests and observations during subgrade preparation; proof-rolling; placement and compaction of controlled compacted fills; backfilling of excavations into the completed subgrade, and just prior to construction of slabs. 4.2.6 Utility Trench Backfill All trench excavations should be made with sufficient working space to permit construction including backfill placement and compaction. Utility trenches are a common source of water Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 18 infiltration and migration. If utility trenches are backfilled with relatively clean granular material, they should be capped with at least 18 inches of cohesive fill in non-pavement areas to reduce the infiltration and conveyance of surface water through the trench backfill. 4.3 Foundations In our opinion the house, pool, retaining walls, and other critical structures should be supported by drilled piers that derive their support from the underlying weathered bedrock. The foundations for other backyard improvements, such as low height seating walls and planters, may consist of spread footings provided they bear a minimum 12 inches into firm, undisturbed native soil, engineered fill or weathered bedrock for support. Our office should be retained to review ancillary structures to be founded on spread footings to evaluate their suitability for spread footings and not piers. Design recommendations for foundations for the proposed structures are presented in the following paragraphs. 4.3.1 Foundation Design Recommendations Description Spread Footing Drilled Friction Piers Net allowable bearing pressure 1 Stiff to hard native sandy clay Compacted engineered fill Weathered bedrock 1,500 psf 2,500 psf 2,500 psf - - 500 psf (skin friction) Minimum dimensions 12 inches - width 18 inches - diameter Minimum embedment below finished grade 24 inches & bear 12 inches into suitable subgrade 5 feet into bedrock Approximate total settlement2 <1 inch <1/2 inch Estimated differential settlement2 <1/2 inch across the width of the improvements <1/2 inch Allowable passive pressure 3 Stiff to hard native clay Compacted engineered fill Weathered Bedrock 350 pcf 350 pcf 400 pcf 350 pcf 350 pcf 450 pcf4 Ultimate coefficient of sliding friction 3 Stiff to hard native clay Compacted engineered fill Weathered Bedrock 0.3 0.3 0.4 - - - 1.The recommended net allowable bearing pressure is the pressure in excess of the minimum surrounding overburden pressure at the footing base elevation. Assumes any unsuitable fill or soft soils, if encountered, will be undercut and replaced with engineered fill. Bearing capacity may be increased by 1/3 for temporary wind and seismic loads. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 19 2.The foundation settlement will depend upon the variations within the subsurface soil profile, the structural loading conditions, the embedment depth of the footings, the thickness of compacted fill, and the quality of the earthwork operations. 3. The sides of the excavation for the spread footing foundation must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid. If the loaded side is sloped or benched, and then backfilled, the allowable passive pressure will be significantly reduced. Passive resistance in the upper 3 feet of the soil profile should be neglected. Passive and frictional resistance may be combined. However, the passive resistance shall be reduced by 50 percent where the supportive soil is firm native soil or engineered fill. 4. Lateral loads to piers can be resisted by computing a passive pressure fluid pressure acting against the projected area equal to 1.5 times the pier diameter. The upper portion of the pier above weathered bedrock should be neglected for lateral support. Due to the potential for slope creep, piers should be designed for a creep load of 40 pcf acting against the upper 5 feet of the piers and against a projected area equal to 2 pier diameters. 4.3.2 Foundation Construction Considerations 4.3.2.1 Spread Footings Spread footings should be placed a minimum of 24 inches below finished grade and bear a minimum 12 inches into firm, undisturbed native soil, engineered fill, or the weathered sandstone bedrock. A 15-foot horizontal offset should be maintained from the bottom of the footing excavations to any adjacent slope/cut face. If achieving the required embedment into suitable material is not feasible and/or the horizontal offset cannot be maintained or is not feasible, the drilled pier foundation option should be utilized. Foundations types should not be mixed within a structure. The base of all foundation excavations should be free of water and loose soil and rock prior to placing concrete. Concrete should be placed soon after excavating to reduce bearing soil disturbance. Care shall be taken to ensure the bottom of all footings is in a moist condition prior to casting footings. If the soils at bearing level become excessively dry, disturbed or saturated, the affected soil should be removed prior to placing concrete. It is recommended that the geotechnical engineer be retained to observe and test the soil foundation bearing materials. If unsuitable bearing soils are encountered in footing excavations, the excavations should be extended deeper to suitable soils and the footings could bear directly on these soils at the lower level or on lean concrete backfill placed in the excavations. The footings could also bear on properly compacted backfill extending down to the suitable soils. Overexcavation for compacted backfill placement below footings should extend laterally beyond all edges of the footings at least 8 inches per foot of overexcavation depth below footing base elevation. The overexcavation should then be backfilled up to the footing base elevation with engineered fill placed in lifts of 9 inches or less in loose thickness and compacted to at least 90 percent of the Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 20 material's maximum dry density as determined by the ASTM D 1557 test method. The overexcavation and backfill procedures are illustrated in the figures below. 4.3.2.2 Drilled Pier Foundations The piers shall be designed and constructed in accordance with the following criteria. These criteria were developed from analysis of field data, laboratory data, and our experience. Drilled piers should be designed as friction piers that derive their support from the underlying weathered bedrock. The pier foundation shall be designed to distribute the weight of the structure solely on the piers. Piers should extend a minimum 5 feet into highly weathered bedrock. Highly weathered bedrock was encountered at 7½, 10, and 10½ feet below the existing ground surface in our borings. The depth of bedrock noted in our boring logs shall not be construed as a maximum or minimum. Depths to bedrock may vary across the site. All piers should have a minimum spacing of at least 3 pier diameters unless our office provides reduction values for group action of piers. All piers should be connected with continuous grade beams or a thickened floor slab which rely on the piers for full support. Grade beam and thickened floor reinforcement should be designed by the structural engineer so as to distribute the structural loads to the piers. Grade beams should extend a minimum of 18 inches below the lowest surrounding grade. In order to protect the thickened floor and/or continuous grade beams from the swelling pressure of the clay soils and clay present in weathered bedrock, they should be underlain by a 4-inch thick void form. Concrete should be placed immediately after the holes are drilled, cleaned and inspected utilizing a "drill and pour" procedure to reduce the potential for possible contamination of the open pier holes. Groundwater was not encountered during this investigation. Groundwater levels can and will fluctuate seasonally. If groundwater, caving conditions, or gravel are encountered during drilling, it may be necessary to adjust pier lengths. Concrete should not be placed in pier holes containing more than 4 inches of water unless the tremie method is used. If Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 21 drilling problems occur, we should be contacted to discuss alternatives with the structural engineer. Formation of mushrooms or enlargements at the tops of piers should be avoided during pier drilling. If mushrooms develop at the tops of the piers during drilling, sono-tubes should be placed at the pier tops to help isolate the piers. Pier excavation operations shall be continuously observed by a staff engineer/geologist of our office to verify that suitable depth and bearing material have been encountered. 4.3.3 Additional Pool Considerations The swimming pool should be supported by drilled piers designed and constructed in accordance with the criteria presented in Sections 4.3.1 and 4.3.2.2. Pool walls should be designed to resist an active earth pressure of 45 pounds per cubic foot (pcf) equivalent fluid pressure for walls with flat backfill and 65 pcf equivalent fluid pressure for walls retaining a slope between 4:1 to 2:1 (H:V) grade. Downhill pool walls should be designed for an outward hydrostatic pressure of 63 pcf. If raised bond beams are planned for pool construction, drainage should be installed behind any raised bond beams. Drainage shall consist of either composite drain such as Miradrain 6200, Mirafi G100W, or Amerdrain Totaldrain or a 12-inch thick free draining gravel blanket. Free draining gravel shall consist of CalTrans Class II permeable material or 3/4 inch clean gravel wrapped in Mirafi 140N filter fabric or equivalent. The drainage should extend from pool water level to within 12 inches of the top of the raised bond beam. A 4-inch diameter perforated Schedule 40 PVC or ABS drain pipe should be installed at the base of the raised bond beam. The drain pipe should be sloped to a positive gravity outlet at a 2 percent minimum slope. In order to protect the pool from the swell pressures of the clay soils and weathered sandstone bedrock, the pool floor should be underlain by a 4-inch thick void form. The pool and void forms should be underlain by a 6-inch thick layer of 3/4 inch clean gravel underlain by Visqueen or a similar impermeable material. A 4-inch diameter perforated Schedule 40 PVC or ABS pipe should be installed in the gravel at the deepest point of the pool. The perforated pipe should slope at a 2 percent minimum grade to a tight line at the edge of the pool that carries the drainage to an existing drainage system or to a positive gravity outlet with a dissipater. A typical dissipater detail is shown on Exhibit C-5. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 22 4.3.4 Seismic Considerations Code Used Site Classification 2013 California Building Code (CBC)1 C 2 Site Latitude 37.82245° N Site Longitude 121.92891° W Ss Spectral Acceleration for a Short Period 2.307g S1 Spectral Acceleration for a 1-Second Period 0.730g Fa Site Coefficient 1.0 Fv Site Coefficient 1.3 Sms MCE Spectral Response Acceleration Value Short Period 2.307g Sm1 MCE Spectral Response Acceleration Value 1-Second Period 0.949g SDs Design Spectral Response Acceleration Value Short Period 1.538g SD1 Design Spectral Response Acceleration Value 1-Second Period 0.633g 1.In general accordance with the 2013 California Building Code, Table 1613.5.2. 2.The 2013 California Building Code requires a site soil profile determination extending a depth of 100 feet for seismic site classification. The current scope requested does not include the required 100 foot soil profile determination. Borings for this report extended to a maximum depth of approximately 51 feet and this seismic site class assignment considers that very dense soil and soft rock continues below the maximum depth of the subsurface exploration. Additional exploration to greater depths could be considered to confirm the conditions below the current depth of exploration. Alternatively, a geophysical exploration could be utilized in order to attempt to justify a more favorable seismic site class. A liquefaction analysis for the subject site was not requested or intended and is beyond the limited scope of this investigation. Based on review of available liquefaction hazard mapping8, the higher elevation portion of the project site is in an area mapped as very low for liquefaction susceptibility, while the lower portion adjacent to the creek is identified as having moderate liquefaction susceptibility. Sites with loose granular soils below groundwater elevation are most susceptible to liquefaction. Because the soils we encountered in our borings were moderately plastic clay soils and bedrock, the probability of liquefaction is low based on observed site conditions. If desired, our office is qualified to perform a liquefaction analysis for the site. Based on our review of San Francisco Bay Area Alquist-Priolo Fault Zones (http://gis.abag.ca.gov/website/FaultZones/index.html) published by the Association of Bay Area Governments (ABAG), the site is not located within a mapped Alquist-Priolo earthquake zone. 8 U.S. Geological Survey, 2000, Map of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, Open file report Open File Report 2006-1037 Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 23 4.4 Retaining Walls The lateral earth pressure recommendations given in the following paragraphs are applicable to the design of rigid retaining walls subject to slight rotation, such as cantilever or gravity type concrete walls. These recommendations are not applicable to the design of modular block - geogrid reinforced backfill walls. Recommendations covering these types of wall systems are beyond the scope of services for this assignment. However, we would be pleased to develop recommendations for the design of such wall systems upon request. Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Backfill must meet the requirements for engineered fill in Section 4.2.2. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls. Earth Pressure Coefficients Earth Pressure Conditions Coefficient for Backfill Type Equivalent Fluid Density (pcf) Surcharge Pressure, p1 (psf) Earth Pressure, p2 (psf) Active (Ka) Engineered Fill- 0.38 On-Site Clay - 0.49 45 60 (0.38)S (0.49)S (45)H (60)H At-Rest (Ko) Engineered Fill - 0.55 On-Site Clay - 0.66 66 80 (0.55)S (0.66)S (66)H (80)H Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 24 Earth Pressure Conditions Coefficient for Backfill Type Equivalent Fluid Density (pcf) Surcharge Pressure, p1 (psf) Earth Pressure, p2 (psf) Active (Ka) Engineered Fill- 0.38 On-Site Clay - 0.49 45 60 (0.38)S (0.49)S (45)H (60)H At-Rest (Ko) Engineered Fill - 0.55 On-Site Clay - 0.66 66 80 (0.55)S (0.66)S (66)H (80)H Passive (Kp) Engineered Fill – 2.7 On-Site Clay - 2.0 320 245 --- --- --- --- Applicable conditions to the above include: If seismic design is required, a lateral load (pounds per foot) equivalent to 9H2 (H = height of retaining wall in feet and load in pounds per foot) should be applied at 0.6H from the bottom of the wall stem. For active earth pressure, wall must rotate about base, with top lateral movements of about 0.002 H to 0.004 H, where H is wall height For passive earth pressure to develop, wall must move horizontally to mobilize resistance Uniform surcharge, where S is surcharge pressure In-situ soil backfill weight a maximum of 120 pcf Horizontal backfill, compacted between 95 and 98 percent of standard Proctor maximum dry density Loading from heavy compaction equipment not included No hydrostatic pressures acting on wall No dynamic loading No safety factor included Backfill placed against structures should meet the requirements for engineered fill in Section 4.2.2. For the engineered fill values to be valid, the engineered backfill must extend out and up from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively. To control hydrostatic pressure behind the wall we recommend that a drain be installed at the foundation wall with a collection pipe leading to a reliable discharge. A 12-inch-thick gravel drainage behind the walls that extend from the bottom of the walls to within 12 inches of the top of the wall should be used. The drain should be capped with 12 inches of compacted clay to help prevent surface runoff from entering the drain. The gravel should consist of Class II permeable material or ¾ inch crushed rock wrapped in Mirafi 140N or equivalent filter fabric. A 4-inch diameter perforated drain pipe should be installed at the base of all retaining walls. The drain pipe should slope at a minimum 2 percent slope to an existing drainage system. Geosynthetic drainage composite such as Miradrain 6200, Mirafi G100W or Amerdrain Totaldrain may be used in lieu of the 12-inch thick gravel drainage. A typical retaining wall drain detail is shown on Exhibit C-6. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 25 These pressures do not include the influence of surcharge, equipment or loading, which should be added. Heavy equipment should not operate within a distance closer than the exposed height of retaining walls to prevent lateral pressures more than those provided. 4.5 Pavements 4.5.1 Subgrade Preparation For recommendation purposes we have assumed that the driveway and parking areas will be constructed using standard paving methods with an asphalt concrete pavement. If pavers are to be used, then recommendations from Sections 4.6 can be used. Pavers, however, are not recommended on slopes. We would be pleased to discuss other driveway surfacing options with you upon request. On most project sites, the site grading is accomplished relatively early in the construction phase. Fills are placed and compacted in a uniform manner. However, as construction proceeds, excavations are made into these areas, rainfall and surface water saturates some areas, heavy traffic from concrete trucks and other delivery vehicles disturb the subgrade and many surface irregularities are filled in with loose soils to improve trafficability temporarily. As a result, the pavement subgrades, initially prepared early in the project, should be carefully evaluated as the time for pavement construction approaches. We recommend the moisture content and density of the top 8 inches of the subgrade be evaluated and the pavement subgrades be proofrolled within two days prior to commencement of actual paving operations. Areas not in compliance with the required ranges of moisture or density should be moisture conditioned and recompacted. Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by removing and replacing the materials with properly compacted fills. After proofrolling and repairing deep subgrade deficiencies, the entire subgrade should be scarified and developed as recommended in Section 4.2 of the Earthwork section this report to provide a uniform subgrade for pavement construction. Areas that appear severely desiccated following site stripping may require further undercutting and moisture conditioning. If a significant precipitation event occurs after the evaluation or if the surface becomes disturbed, the subgrade should be reviewed by qualified personnel immediately prior to paving. The subgrade should be in its finished form at the time of the final review. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 26 4.5.2 Design Considerations We anticipate that traffic loads will be produced primarily by automobile traffic and occasional delivery trucks. Pavement design methods are intended to provide structural sections with adequate thickness over a particular subgrade such that wheel loads are reduced to a level the subgrade can support. The support characteristics of the subgrade for pavement design do not account for shrink/swell movements of an expansive clayey subgrade such as the soils encountered on this project. Thus, the pavement may be adequate from a structural standpoint, yet still experience cracking and deformation due to shrink/swell related movement of the subgrade. Eliminating the risk of shrink/swell related movement in the subgrade may not be feasible, but it may be possible to further reduce the risk of movement if significantly more expensive measures are used during construction. We would be pleased to discuss other construction alternatives with you upon request. Pavement performance is affected by its surroundings. In addition to providing preventive maintenance, the civil engineer should consider the following recommendations in the design and layout of pavements: Final grade adjacent to the driveway and parking area should slope down from pavement edges at a minimum 2 percent; The subgrade and the pavement surface should have a minimum ¼ inch per foot slope to promote proper surface drainage; Install joint sealant and seal cracks immediately; Seal all landscaped areas in, or adjacent to pavements with curbs extending a minimum of 6 inches into the underlying clayey subgrade to reduce moisture migration to subgrade soils; Place compacted, low permeability backfill against the exterior side of curb and gutter; and, Extend curbs, and/or gutters a minimum of 6 inches into clayey sand subgrade soils rather than on unbound granular base course materials. 4.5.3 Estimates of Minimum Pavement Thickness Typical Minimum Pavement Section (inches) Traffic Area Subgrade R-Value1 Traffic Index Asphalt Concrete Aggregate Base Course 2 Total Thickness Driveway 5 4 3 6 9 1.Assumed - typical value for similar native material. 2.Paving materials must conform to the requirements of the State of California, Department of Transportation, Standard Specifications, Latest Edition. Type B Asphalt Concrete and Class 2 Aggregate Base should be used. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 27 The minimum pavement sections outlined above were determined based on the laboratory test results and post-construction traffic loading conditions for this type of development. These pavement sections do not account for heavy construction traffic during the early stages of the development. A partially constructed structural section may be subjected to heavy construction traffic that can result in pavement deterioration and premature failure. Our experience indicates that this pavement construction practice can result in pavements that will not perform as intended. Considering this information, several alternatives are available to mitigate the impact of heavy construction traffic on the pavement construction. These include using thicker sections to account for the construction traffic, using some method of soil stabilization to improve the support characteristics of the pavement subgrade, or by routing heavy construction traffic around paved streets. We are available to discuss these alternatives with you. 4.5.4 Pavement Drainage Proper grading and drainage is essential for serviceability of the pavements throughout the design lifetime. The pavement sections provided above assume that the subgrade soils will not experience significant increases in moisture content. Paved areas should be sloped to provide rapid drainage of surface water and to drain water away from the pavement edges. Water should not be allowed to accumulate on or adjacent to the pavement, since this could saturate and soften the subgrade soils and subsequently accelerate pavement deterioration. Periodic maintenance of the pavements will be required. Cracks should be sealed, and areas exhibiting distress should be repaired promptly to help prevent further deterioration. Even with periodic maintenance, some movement and related cracking may still occur and repairs may be required. Water that infiltrates through the pavements often collects in the underlying granular base materials. Accumulation of water in the granular base can soften the subgrade which can be detrimental to pavements. Installation of drains beneath the pavement would reduce the potential for these effects. 4.5.5 Pavement Maintenance The driveway pavement section provided in this report represents minimum recommended thicknesses and, as such, periodic maintenance should be anticipated. Therefore preventive maintenance should be planned and provided for through an on-going pavement management program. Maintenance activities are intended to slow the rate of pavement deterioration, and to preserve the pavement investment. Maintenance consists of both localized maintenance (e.g., crack and joint sealing and patching) and global maintenance (e.g., surface sealing). Preventive maintenance is usually the first priority when implementing a pavement maintenance program. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 28 Even with periodic maintenance, some movements and related cracking may still occur and repairs may be required. 4.6 Exterior Hardscapes Hardscapes or decking should not be constructed within 15 feet of the crest of a descending slope. The near surface clay soils are susceptible to shifting due to seasonal moisture fluctuations which can lift and crack concrete decking. If shifting and cracking of hardscapes or deck are not desired, all subgrade should be over-excavated, moisture conditioned, and compacted as specified in Section 4.2 and then backfilled with engineered fill up to within 18 inches of grade. The surface 18 inches shall consist of Caltrans Class II aggregate base. Concrete pavers should be considered for hardscapes and decks since they are not as susceptible to cracking. If the homeowner is willing to accept more risk of shifting and cracking in concrete patios as a result of soil heave, the surficial clay soils may be scarified, moisture conditioned, and compacted to a depth of 18 inches and overlain by 4 inches of 3/4 inch clean crushed rock, Caltrans Class II permeable material, or Caltrans Class II aggregate base. Concrete patio slabs should be a minimum 5 inches thick and be reinforced with minimum No. 4 bars spaced at 12 inches on center in each way. The subgrade soils and backfill material should be moisture conditioned and compacted as specified in Section 4.2. 4.7 Testing, Inspections, and Review Our office shall be retained to review the completed house, swimming pool and grading/drainage plans to verify that our recommendations have been properly interpreted and incorporated. Unless our office is allowed this opportunity, we disavow any responsibility from problems arising from failure to follow geotechnical recommendations or improper interpretation and implementation of our recommendations. Our office shall be retained to perform the recommended pier excavation inspections, compaction testing, and grading control. Unless we have been retained to provide these services, our office cannot be held responsible for problems arising during or after construction that could have been avoided had these services been performed. The fees for these review and inspection services are in addition to that associated with this report. Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable 29 5.0 GENERAL COMMENTS Terracon should be retained to review the final design plans and specifications so comments can be made regarding interpretation and implementation of our geotechnical recommendations in the design and specifications. Terracon also should be retained to provide observation and testing services during grading, excavation, foundation construction and other earth-related construction phases of the project. The analysis and recommendations presented in this report are based upon the data obtained from the borings and test pits performed at the indicated locations and from other information discussed in this report. This report does not reflect variations that may occur between borings or test pits, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until during or after construction. If variations appear, we should be immediately notified so that further evaluation and supplemental recommendations can be provided. The scope of services for this project does not include either specifically or by implication any environmental or biological (e.g., mold, fungi, bacteria) assessment of the site or identification or prevention of pollutants, hazardous materials or conditions. If the owner is concerned about the potential for such contamination or pollution, other studies should be undertaken. This report has been prepared for the exclusive use of our client for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices. No warranties, either express or implied, are intended or made. Site safety, excavation support, and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless Terracon reviews the changes and either verifies or modifies the conclusions of this report in writing. This report should not be used after 3 years. Responsive ■ Resourceful ■ Reliable 8 APPENDIX A FIELD EXPLORATION TO P O G R A P H I C M A P I M A G E C O U R T E S Y O F TH E U . S . G E O L O G I C A L S U R V E Y QU A D R A N G L E S I N C L U D E : L A S T R A M P A S RI D G E , C A ( 1 / 1 / 1 9 9 5 ) a n d D I A B L O , C A (1 / 1 / 1 9 8 0 ) . SI T E L O C A T I O N Bu r k h a r t R e s i d e n c e 77 5 K i r k c r e s t R o a d Da n v i l l e , C A 50 7 5 C o m m e r c i a l C i r . S t e . E Co n c o r d , C A 9 4 5 2 0 ND 1 4 5 0 5 9 DI A G R A M I S F O R G E N E R A L L O C A T I O N O N L Y , AN D I S N O T I N T E N D E D F O R C O N S T R U C T I O N PU R P O S E S Pr o j e c t M a n a g e r : Dr a w n b y : Ch e c k e d b y : Ap p r o v e d b y : CA W CS R CS R CS R .D W G Ju n e 2 0 1 5 Pr o j e c t N o . Fil e N a m e : Da t e : A-1Exhibit 1” = 2 4 , 0 0 0 S F Sc a l e : B-1 (50') Infil. 2 (24") Infil. 1 (12") TP-3 B-5 (20') B-4 (20') TP-2Prev. Boring B-3 (20')TP-1 B-2 (20') DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Boring Location Plan Contra Costa County California 2 3 CAWright CAWright CRStock As Shown April 24, 2015 ND145059 site.dwg Exhibit A-2 775 Kirkcrest Road, Danville N Aerial Dated June 9, 2014; Excerpted From Google Earth DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Site Geology & Landslide Hazard Maps Contra Costa County California 3 3 CAWright CAWright CRStock As Shown May 5, 2015 ND145059 site.dwg Exhibit A-3 775 Kirkcrest Road, Danville Relative Landslide Susceptibility Map, Site Shown in Red Landslides and Related Features Map, Site Shown in Red Geology, Site Shown in Red Landslide Hazards in the Las Trampas Ridge Quadrangle and Parts of the Diablo Quadrangle Alameda and Contra Costa Counties, California Landslide Hazard Identification Map No. 38 by Hasmukhrai H. Majmundar Geologist 1996 Geologic Map of the Las Trampas Ridge Quadrangle, Alameda and Contra Costa Counties, California Dibblee Foundation Map DF-161,Map Scale 1:24,000 Dibblee, T.W., and Minch, J.A. 2005 Landslide Hazards in the Las Trampas Ridge Quadrangle and Parts of the Diablo Quadrangle Alameda and Contra Costa Counties, California Landslide Hazard Identification Map No. 38 by Hasmukhrai H. Majmundar Geologist 1996 Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable Exhibit A-4 Field Exploration Description The proposed boring and test pit locations were laid out in the field by a Terracon representative using a scaled site plan provided by the client and measuring from known points. Ground surface elevations indicated on the boring logs were interpolated from preliminary grading plans and Google Earth elevations. The locations and elevations of the borings should be considered accurate only to the degree implied by the means and methods used to define them. The test pits were excavated using a rubber tire backhoe and were backfilled with the excavated material. The borings were drilled with a CME-55 tracked rig using 4-inch diameter, continuous flight, solid-stem augers to advance the boreholes. Samples of the soil encountered in the borings were obtained using the split-barrel sampling procedures. In boring B-1, the 4-inch solid stem augers were used down to a depth of 10½ feet bgs then a mud rotary method was used to advance the borehole through the weathered bedrock for the remainder of the boring. NQ sized core samplers were used to continuously sample the weathered bedrock in 5-foot core lengths. The cores were then wrapped in plastic to maintain their natural moisture content, photographed, and finally placed within core boxes for transport and storage. Sampling of soil encountered in the rest of borings was performed at various depths using a California Modified (CM) 2.5-inch o.d. split spoon sampler with stainless steel tube liners. The CM sampler was driven by a with a 140-pound automatic hammer falling 30 inches. Blow counts required to drive the CM sampler every 6 inches for a total of 18 inches were recorded. The samples were tagged for identification, sealed to reduce moisture loss, and taken to our laboratory for further examination, testing, and classification. Information provided on the boring logs attached to this report includes soil descriptions, consistency evaluations, boring depths, sampling intervals, and groundwater conditions. The borings were backfilled with cement- bentonite grout prior to the drill crew leaving the site. A field log of each boring was prepared by the field engineer. These logs included visual classifications of the materials encountered during drilling as well as the driller’s interpretation of the subsurface conditions between samples. Final boring logs included with this report represent the engineer's interpretation of the field logs and include modifications based on laboratory observation and tests of the samples. 10.5 21.0 SANDY FAT CLAY (CH), dark brown, stiff to very stiff,moist, organic rich near surface increase in plasticity from moderate to high coarse grain sand size rock fragments, sample moist to dry SEDIMENTARY BEDROCK - SANDSTONE, light brownto tan, fine-grained, extremely fractured, highly weathered, extremely weak, clay matrix SEDIMENTARY BEDROCK - SANDSTONE, brown to tan, coarse-grained, highly weathered, very weak, claymatrix, hard sub-angular sandstone fragments 1/2" to 2" 1/2" dark brown angular rock fragments little to no matrix, possible shear zone 6" thick 5-7-7 4-4-8 11-16-19 6-11-20 2.8(HP) 2.0(HP) +4.5 (HP) +4.5(HP) 2525 1920 923 7476 8887 9679 416.5+/- 406+/- 5.4 5.4 4.5 Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.825621° Longitude: -122.020213° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 1 of 2 Advancement Method:4" S.S. Auger then Mud Rotary with NQ Wireline CoreBarrel Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/21/2015 BORING LOG NO. B-1 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/21/2015 Exhibit:A-5 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 427 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 5 10 15 20 25 RE C O V E R Y ( F t . ) Water level not determined WATER LEVEL OBSERVATIONS 31.0 47.0 51.0 SEDIMENTARY BEDROCK - SANDSTONE, brown totan, coarse-grained, highly weathered, very weak, claymatrix, hard sub-angular sandstone fragments 1/2" to 2" (continued) SEDIMENTARY BEDROCK - SANDSTONE, dark brown to bluish-gray, highly weathered, very weakalmost all clay matrix between 31' and 32' <1" thick layer of shear zone with little to no matrix poor recovery between 36 feet and 41 feet SEDIMENTARY BEDROCK - SANDSTONE, dark brown to bluish-gray, highly weathered, medium strong,alternating layers of bluish-gray Greywacke, Claystone, anddark brown Sandstone Coring Terminated at 51 Feet 396+/- 380+/- 376+/- 4.75 4.3 1.5 5 5.4 Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.825621° Longitude: -122.020213° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 2 of 2 Advancement Method:4" S.S. Auger then Mud Rotary with NQ Wireline CoreBarrel Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/21/2015 BORING LOG NO. B-1 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/21/2015 Exhibit:A-6 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 427 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 30 35 40 45 50 RE C O V E R Y ( F t . ) Water level not determined WATER LEVEL OBSERVATIONS 3.0 7.5 21.5 SANDY FAT CLAY (CH), dark brown, moist, organic richtop soil COMPLETELY WEATHERED BEDROCK - SANDY LEAN CLAY (CL), tan with gray mottling, stiff to very stiff,fine-grained, moist dry, trace medium strong <1/2" subangular rusted sandstone rock fragments SEDIMENTARY BEDROCK - SANDSTONE, tan with gray mottling, medium dense to dense, weak cementation,fine-grained, extremely fractured, highly weathered, veryweak, dry, clay matrix dry, moderately weathered with clay matrix, with strongrock fragments <1/2", tan, rust, and gray color dry, same as above but with only dark brown and rustcolored rock fragments and matrix Boring Terminated at 21.5 Feet 7-8-13 6-11-14 10-18-20 10-18-29 15-27-37 14-24-22 +4.5(HP) +4.5(HP) +4.5 (HP) +4.5 (HP) +4.5(HP) +4.5 (HP) 51 51 22 15 1628 1727 1512 12 11 1014 85 89 8285 7689 9281 94 104 101100 46-21-25 33-20-13 447+/- 442.5+/- 428.5+/- Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.825193° Longitude: -122.020377° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 1 of 1 Advancement Method:4" Solid Stem Auger Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/21/2015 BORING LOG NO. B-2 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/21/2015 Exhibit:A-7 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 450 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 5 10 15 20 RE C O V E R Y ( F t . ) Groundwater not encountered WATER LEVEL OBSERVATIONS 1.5 7.5 21.5 SANDY FAT CLAY (CH), dark brown, moist, organic richtop soil COMPLETELY WEATHERED BEDROCK - SANDYLEAN CLAY (CL), tan to brown, stiff, fine-grained, moist SEDIMENTARY BEDROCK - SANDSTONE, tan with rust mottling, medium dense to dense, fine-grained, extremelyfractured, highly weathered, very weak, moist to dry, claymatrix, with 1/2" to 1" subangular medium strong rock fragmentsdry, 1/2" to 1 1/2" subangular strong rock fragments Boring Terminated at 21.5 Feet 5-6-6 6-5-7 8-14-19 13-21-30 11-26-37 18-33-50/5" +4.5(HP) +4.5(HP) 3.8 (HP)+4.5(HP) +4.5 (HP) +4.5(HP) +4.5 (HP) 75 19 17 1717 2125 87 11 9 911 78 89 9097 8783 9096 89 98 101104 53-24-29 448.5+/- 442.5+/- 428.5+/- Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.825427° Longitude: -122.020408° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 1 of 1 Advancement Method:4" Solid Stem Auger Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/21/2015 BORING LOG NO. B-3 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/21/2015 Exhibit:A-8 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 450 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 5 10 15 20 RE C O V E R Y ( F t . ) Groundwater not encountered WATER LEVEL OBSERVATIONS 1.5 10.0 21.5 SANDY FAT CLAY (CH), dark brown, moist, organic richtop soil COMPLETELY WEATHERED BEDROCK - SANDYLEAN CLAY (CL), brown with rust mottling, stiff to very stiff, fine-grained, moist trace 1/2" to 1" subangular strong sandstone rockfragments moist to dry SEDIMENTARY BEDROCK - SANDSTONE, brown withrust mottling, dense, weak cementation, fine-grained,extremely fractured, highly weathered, very weak, clay matrix dry, tan with rust and gray mottling, 1" to 2" rock fragmentsmore gray in color Boring Terminated at 21.5 Feet 7-6-5 5-6-7 6-7-14 8-12-17 10-22-34 13-21-27 4.0 (HP) 3.0(HP) 2.8(HP) +4.5 (HP)4.5(HP) 4.3 (HP)+4.5 (HP) +4.5(HP) +4.5 (HP) 23 2322 1313 1615 12 14 88 86 8588 9394 9194 101 98 102101 452.5+/- 444+/- 432.5+/- Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.825581° Longitude: -122.020456° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 1 of 1 Advancement Method:4" Solid Stem Auger Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/21/2015 BORING LOG NO. B-4 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/21/2015 Exhibit:A-9 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 454 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 5 10 15 20 RE C O V E R Y ( F t . ) Groundwater not encountered WATER LEVEL OBSERVATIONS 3.5 5.0 10.0 21.5 SANDY FAT CLAY (CH), dark brown, moist, organic richtop soil SANDY LEAN CLAY (CL), brown, stiff, moist COMPLETELY WEATHERED BEDROCK - SANDY LEAN CLAY (CL), brown, stiff to very stiff, fine-grained,moist, clay matrix with coarse sand sized angular rockfragments SEDIMENTARY BEDROCK - SANDSTONE, tan with rustand gray mottling, medium dense to dense, weakcementation, fine-grained, extremely fractured, highly weathered, very weak, moist to dry, sandy clay matrix,trace >1/2" rock fragments dry, with 1" to 1 1/2" medium strong rock fragments moderately to slightly weathered strong rock with only atrace of matrix, most competent rock found in all borings Boring Terminated at 21.5 Feet 5-6-8 5-7-10 9-16-26 11-26-30 10-19-23 18-30-50/5" +4.5 (HP) 3.8(HP) 2.8(HP) +4.5 (HP) +4.5 (HP) +4.5(HP) +4.5 (HP) 24 2125 1717 1615 11 10 1211 80 8587 9393 9392 91 95 103104 436.5+/- 435+/- 430+/- 418.5+/- Hammer Type: 140# Automatic SPT HammerStratification lines are approximate. In-situ, the transition may be gradual. LOCATION DEPTH Latitude: 37.82569° Longitude: -122.02029° GR A P H I C L O G See Exhibit A-2 TH I S B O R I N G L O G I S N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G E O S M A R T L O G - N O W E L L N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 7 / 1 5 / 1 5 775 Kirkcrest Road Danville, CA SITE: Page 1 of 1 Advancement Method:4" Solid Stem Auger Abandonment Method:Borings backfilled with cement-bentonite grout uponcompletion. 5075 Commercial Circle, Suite EConcord, California Notes: Project No.: ND145059 Drill Rig: CME-55 track Boring Started: 4/22/2015 BORING LOG NO. B-5 Philip and Karen BurkhartCLIENT: Driller: Taber Boring Completed: 4/22/2015 Exhibit:A-10 See Exhibit A-3 for description of fieldprocedures. See Appendix B for description of laboratoryprocedures and additional data (if any). See Appendix C for explanation of symbols and abbreviations.Elevations were interpolated from a topographicsite plan. PROJECT: Burkhart Residence FI E L D T E S T RE S U L T S LA B O R A T O R Y TO R V A N E / H P ( t s f ) PE R C E N T F I N E S WA T E R CO N T E N T ( % ) DR Y U N I T WE I G H T ( p c f ) ATTERBERGLIMITS LL-PL-PI Approximate Surface Elev: 440 (Ft.) +/- ELEVATION (Ft.)SA M P L E T Y P E WA T E R L E V E L OB S E R V A T I O N S DE P T H ( F t . ) 5 10 15 20 RE C O V E R Y ( F t . ) Groundwater not encountered WATER LEVEL OBSERVATIONS 0 ft -10 ft -15 ft -20 ft 10 ft 20 ft 30 ft -5 ft 5 ft 25 ft15 ft 0 ft -5 ft -10 ft -15 ft -20 ft 5 ft 10 ft 15 ft 0 ft -10 ft 20 ft 25 ft 10 ft 30 ft 20 ft 25 ft -5 ft -15 ft -20 ft 15 ft5 ft 30 ft CL-CH, Clay with Sand, Dark Brown, Moist, Medium Plasticity Test Pit - 1, Bearing E/W , Slope N12E Test Pit - 2, Bearing N8E, Slope N15W Test Pit - 3, Bearing N20E, Slope N15W Completely Weathered Sandstone with Soil Support as Matrix, Brown to Light Brown, Dry to Moist Small Feature, Clay with Sand, Dark Brown, Moist Highly Weathered Sandstone, Close to Very Close Fracturing, Rock Fragments 0.25" to 4.0", Angular, Irregular Breaks, Light Brown, Fine to Medium Grain, Dry, with Clay in Matrix CL-CH, Sandy Clay, Dark Brown, Moist, Contains Sandstone Rock Fragments, No Structure Siltstone Transition, White, Dry to Moist, 0.25" Fractures Test Pits Excavated on April 10, 2015 DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Test Pit - Cross Sections Contra Costa County California 11 11 CAWright CAWright CRStock As Shown May 5, 2015 ND145059 site.dwg Exhibit A-11 775 Kirkcrest Road, Danville Responsive ■ Resourceful ■ Reliable 1 APPENDIX B LABORATORY TESTING Geotechnical Engineering Report Burkhart Residence ■ Danville, California July 17, 2015 ■ Terracon Project No. ND145059 Responsive ■ Resourceful ■ Reliable Exhibit B-1 Laboratory Testing Samples retrieved during the field exploration were taken to the laboratory for further observation by the project geotechnical engineer and were classified in accordance with the Unified Soil Classification System (USCS) described in Appendix C. At that time, the field descriptions were confirmed or modified as necessary and an applicable laboratory testing program was formulated to determine engineering properties of the subsurface materials. Laboratory tests were conducted on selected soil samples and the test results are presented on the logs of the borings or in the body of the report. The laboratory test results were used for the geotechnical engineering analyses, and the development of engineering, earthwork, and construction recommendations. Laboratory tests were performed in general accordance with the applicable ASTM, local, or other accepted standards. Selected soil samples obtained from the site were tested for the following engineering properties: In-situ Water Content Percent Passing the No. 200 Sieve Unit Weight Sieve Analysis Triaxial Testing Atterberg Limits 0 10 20 30 40 50 60 0 20 40 60 80 100 CH o r O H CL o r O L ML or OL MH or OH PL PI Description SANDY LEAN CLAY SANDY LEAN CLAY FAT CLAY with SAND LEAN CLAY with SAND FAT CLAY CL CL CH CL CH Fines P LAS TIC IT Y I NDE X LIQUID LIMIT "U" L i n e "A" L i n e 46 33 53 34 52 21 20 24 20 26 25 13 29 14 26 51 51 75 77 88 LL USCS B-2 B-2 B-3 Infiltration 12" Infiltration 24" ATTERBERG LIMITS RESULTS ASTM D4318 3.5 16.0 8.5 1.0 2.0 Boring ID Depth (Ft) 5075 Commercial Circle, Suite E Concord, California PROJECT NUMBER: ND145059PROJECT: Burkhart Residence SITE: 775 Kirkcrest Road Danville, CA CLIENT: Philip and Karen Burkhart EXHIBIT: B-2 LA B O R A T O R Y T E S T S A R E N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . A T T E R B E R G L I M I T S N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 5 / 1 5 / 1 5 CL-ML 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 0.0010.010.1110100 % FINES % CLAY USCS Infiltration 12" Infiltration 24" 0.0 0.0 0.5 0.0 22.6 11.9 GRAIN SIZE LEAN CLAY with SAND(CL) FAT CLAY(CH) 16 20 100 90 80 70 60 50 40 30 20 10 0 REMARKS SILT OR CLAYCOBBLESGRAVELSAND medium 76.9 88.1 GRAIN SIZE IN MILLIMETERS PERCENT FINER 3/4 1/23/8 SIEVE (size) D60 30 403 60 HYDROMETERU.S. SIEVE OPENING IN INCHES U.S. SIEVE NUMBERS 44 100632 fine coarse SOIL DESCRIPTION CU SAMPLE ID 10 14 506 2001.5 81 140 coarse fine COEFFICIENTS % COBBLES % GRAVEL % SAND D30 D10 CC PE R C E N T F I N E R B Y W E I G H T P E R C E N T C O A R S E R B Y W E I G H T % SILT GRAIN SIZE DISTRIBUTION ASTM D422 CL CH 1 1/2"1"3/4"1/2"3/8"#4 #10 #20#40#60#100#200 DEPTH (Ft) 1.0 2.0 5075 Commercial Circle, Suite E Concord, California PROJECT NUMBER: ND145059PROJECT: Burkhart Residence SITE: 775 Kirkcrest Road Danville, CA CLIENT: Philip and Karen Burkhart EXHIBIT: B-3 LA B O R A T O R Y T E S T S A R E N O T V A L I D I F S E P A R A T E D F R O M O R I G I N A L R E P O R T . G R A I N S I Z E : U S C S 1 N D 1 4 5 5 0 5 9 B U R K H A R T . G P J T E R R A C O N 2 0 1 2 . G D T 6 / 2 / 1 5 Triaxial Unconsolidated-Undrained (ASTM D2850m) Sample: 1 2 3 4 MC, %24.0 #DIV/0! #DIV/0! #DIV/0! Dry Dens, pcf 98.1 #DIV/0! #DIV/0! #DIV/0! Sat. %90.3 #DIV/0! #DIV/0! #DIV/0! Void Ratio 0.718 #DIV/0! #DIV/0! #DIV/0! Diameter in 1.90 0.00 0.00 0.00 Height, in 4.01 0.00 0.00 0.00 MC, %28.1 #DIV/0! #DIV/0! #DIV/0! Dry Dens, pcf 95.8 #DIV/0! #DIV/0! #DIV/0! Sat. %100.0 #DIV/0! #DIV/0! #DIV/0! Void Ratio 0.759 #DIV/0! #DIV/0! #DIV/0! Diameter, in 1.92 #DIV/0! #DIV/0! #DIV/0! Height, in 4.02 0.00 0.00 0.00 Cell, psi 73.5 0.0 0.0 0.0 BP, psi 68.5 #N/A #N/A #N/A Job No.:843-002 Date:6/22/2015 Strain, %5.0 5.0 5.0 5.0 Client:BY:MD/DC Deviator ksf 1.392 #N/A #N/A #N/A Project:Excess PP 0.000 #N/A #N/A #N/A Sample 1)B5 @ 5.0'Sigma 1 2.112 #N/A #N/A #N/A Sample 2)Sigma 3 0.720 #N/A #N/A #N/A Sample 3)P, ksf 1.416 #N/A #N/A #N/A Sample 4)Q, ksf 0.696 #N/A #N/A #N/A Stress Ratio 2.933 #N/A #N/A #N/A Rate in/min 0.0401 #DIV/0! #DIV/0! #DIV/0! Total C N/A ksf Total Phi N/A Degrees Eff. C N/A ksf Eff. Phi N/A Degrees Yellowish Brown Clayey SAND/ Sandy CLAY REMARKS: Strengths picked at 5% strain. *Sample was back-pressure saturated prior to shear. Final Effective Stresses At: NO145059 Neil O Anderson 0.0 1.0 2.0 0.0 1.0 2.0 3.0 4.0 Sh e a r S t r e s s , k s f Normal Stress, ksf Total Stress Effective Stress Total Best Fit Effective Best Fit 0 500 1000 1500 2000 2500 0 5 10 15 20 25 De v i a t o r S t r e s s , p s f Strain, % Stress-Strain Response Sample 1 Sample 2 Sample 3 Sample 4 Triaxial Unconsolidated-Undrained (ASTM D2850m) Sample: 1 2 3 4 MC, %9.5 #DIV/0! #DIV/0! #DIV/0! Dry Dens, pcf 107.1 #DIV/0! #DIV/0! #DIV/0! Sat. %44.8 #DIV/0! #DIV/0! #DIV/0! Void Ratio 0.574 #DIV/0! #DIV/0! #DIV/0! Diameter in 2.40 0.00 0.00 0.00 Height, in 5.31 0.00 0.00 0.00 MC, %18.8 #DIV/0! #DIV/0! #DIV/0! Dry Dens, pcf 111.8 #DIV/0! #DIV/0! #DIV/0! Sat. %100.0 #DIV/0! #DIV/0! #DIV/0! Void Ratio 0.508 #DIV/0! #DIV/0! #DIV/0! Diameter, in 2.35 #DIV/0! #DIV/0! #DIV/0! Height, in 5.31 0.00 0.00 0.00 Cell, psi 78.9 0.0 0.0 0.0 BP, psi 68.5 #N/A #N/A #N/A Job No.:843-002 Date:6/19/2015 Strain, %5.0 5.0 5.0 5.0 Client:BY:MD/DC Deviator ksf 4.646 #N/A #N/A #N/A Project:Excess PP 0.000 #N/A #N/A #N/A Sample 1)B-1 @ 14.5-15.5'Sigma 1 6.144 #N/A #N/A #N/A Sample 2)Sigma 3 1.498 #N/A #N/A #N/A Sample 3)P, ksf 3.821 #N/A #N/A #N/A Sample 4)Q, ksf 2.323 #N/A #N/A #N/A Stress Ratio 4.103 #N/A #N/A #N/A Rate in/min 0.0493 #DIV/0! #DIV/0! #DIV/0! Total C N/A ksf Total Phi N/A Degrees Eff. C N/A ksf Eff. Phi N/A Degrees Yellowish Brown Clayey SAND w/ Gravel (Weathered Rock) REMARKS: Strengths picked at 5% strain. *Sample was back-pressure saturated prior to shear. Final Effective Stresses At: NO145059 Neil O Anderson 0.0 2.0 4.0 0.0 2.0 4.0 6.0 8.0 Sh e a r S t r e s s , k s f Normal Stress, ksf Total Stress Effective Stress Total Best Fit Effective Best Fit 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0 2 4 6 8 101214161820 De v i a t o r S t r e s s , p s f Strain, % Stress-Strain Response Sample 1 Sample 2 Sample 3 Sample 4 B-4 (20') TP-3 B-5 (20') B-1 (50') Cross Section Profile Location Solar Approx. Observed Slide Area DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Slope Stability Cross Section Location Contra Costa County California 1 3 CAWright CAWright CRStock As Shown May 5, 2015 ND145059 site.dwg Exhibit B-6 775 Kirkcrest Road, Danville 380 390 400 410 420 430 440 450 460 470 0 50 100 150 200 B-4 B-5 House Pad 440' Elev. TP-3 B-1 Existing Tree Proposed Driveway Proposed Walking PathBrown, Moist, Completely Weathered Bedrock Clay Topsoil - Dark Brown Tan, Dry, Highly Bedrock Possible Slide Zone Greywacke Bedrock Distance (feet) Red Profile is Proposed Ground Surface 36 - 41 ft bgs 46 ft bgs 10 ft bgs 6 ft bgs 1.5 ft bgs 15 ft bgs 7.5 ft bgs 5 ft bgs Profiles from Orr Design Office, Preliminary Grading Plan, Dated Feb, 25,2015 El e v a t i o n ( f e e t ) Black Profile is Current Ground Surface Creek DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Slope Stability Cross Section Contra Costa County California 2 3 CAWright CAWright CRStock As Shown May 5, 2015 ND145059 site.dwg Exhibit B-7 775 Kirkcrest Road, Danville DESIGNED BY: SCALE: APPVD. BY: DRAWN BY: DATE: SHEET NO.: JOB NO. OF BY DESCRIPTIONDATEREV. FILE NAME:2110 Overland Avenue, Suite 124 Billings, MT 59102 FAX. (406) 656-3578PH. (406) 656-3072 Consulting Engineers and Scientists Burkhart Residence Slope Stability SlopeW Analysis Contra Costa County California 3 3 CAWright CAWright CRStock As Shown May 5, 2015 ND145059 site.dwg Exhibit B-8 775 Kirkcrest Road, Danville APPENDIX C SUPPORTING DOCUMENTS Trace WithModifier Water Level After a Specified Period of Time GRAIN SIZE TERMINOLOGYRELATIVE PROPORTIONS OF SAND AND GRAVEL TraceWithModifier Standard Penetration orN-ValueBlows/Ft. Descriptive Term (Consistency) Loose Very Stiff Exhibit C-1 Standard Penetration orN-ValueBlows/Ft. Ring Sampler Blows/Ft. Ring Sampler Blows/Ft. Medium Dense Dense Very Dense 0 - 1 < 3 4 - 9 2 - 4 3 - 4 Medium-Stiff 5 - 9 30 - 50 WA T E R L E V E L Auger Shelby Tube Split Spoon RockCore 8 - 15 PLASTICITY DESCRIPTION Term < 15 15 - 29> 30 Descriptive Term(s) of other constituents Water InitiallyEncountered Water Level After aSpecified Period of Time Major Component of SamplePercent ofDry Weight (More than 50% retained on No. 200 sieve.)Density determined by Standard Penetration ResistanceIncludes gravels, sands and silts. Hard Very Loose 0 - 3 0 - 6 Very Soft 7 - 18 Soft 10 - 29 19 - 58 59 - 98 Stiff less than 500 500 to 1,000 1,000 to 2,000 MacroCore 2,000 to 4,000 4,000 to 8,000> 99 LOCATION AND ELEVATION NOTES SA M P L I N G FI E L D T E S T S DESCRIPTION OF SYMBOLS AND ABBREVIATIONS Descriptive Term (Density) Non-plasticLow MediumHigh Boulders CobblesGravelSand Silt or Clay 10 - 18 > 50 15 - 30 19 - 42 > 30 > 42 _ CONSISTENCY OF FINE-GRAINED SOILS Hand Penetrometer Torvane Standard PenetrationTest (blows per foot) N value Photo-Ionization Detector Organic Vapor Analyzer (HP) (T) (b/f) N (PID) (OVA) (50% or more passing the No. 200 sieve.) Consistency determined by laboratory shear strength testing, field visual-manual procedures or standard penetration resistance DESCRIPTIVE SOIL CLASSIFICATION > 8,000 Unless otherwise noted, Latitude and Longitude are approximately determined using a hand-held GPS device. The accuracyof such devices is variable. Surface elevation data annotated with +/- indicates that no actual topographical survey was conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic maps of the area. Soil classification is based on the Unified Soil Classification System. Coarse Grained Soils have more than 50% of their dryweight retained on a #200 sieve; their principal descriptors are: boulders, cobbles, gravel or sand. Fine Grained Soils haveless than 50% of their dry weight retained on a #200 sieve; they are principally described as clays if they are plastic, and silts if they are slightly plastic or non-plastic. Major constituents may be added as modifiers and minor constituents may be added according to the relative proportions based on grain size. In addition to gradation, coarse-grained soils are definedon the basis of their in-place relative density and fine-grained soils on the basis of their consistency. Plasticity Index 01 - 10 11 - 30> 30 RELATIVE PROPORTIONS OF FINES Descriptive Term(s)of other constituents Percent ofDry Weight < 55 - 12> 12 RELATIVE DENSITY OF COARSE-GRAINED SOILS Particle Size Over 12 in. (300 mm) 12 in. to 3 in. (300mm to 75mm)3 in. to #4 sieve (75mm to 4.75 mm)#4 to #200 sieve (4.75mm to 0.075mm Passing #200 sieve (0.075mm) ST R E N G T H T E R M S Unconfined Compressive Strength, Qu, psf 4 - 8 GENERAL NOTES ModifiedCaliforniaRing Sampler Grab Sample Modified Dames & Moore Ring Sampler No Recovery Water levels indicated on the soil boring logs are the levels measured in theborehole at the times indicated. Groundwater level variations will occur over time. In low permeability soils,accurate determination of groundwater levels is not possible with short term water level observations. Exhibit C-2 UNIFIED SOIL CLASSIFICATION SYSTEM Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A Soil Classification Group Symbol Group Name B Coarse Grained Soils: More than 50% retained on No. 200 sieve Gravels: More than 50% of coarse fraction retained on No. 4 sieve Clean Gravels: Less than 5% fines C Cu 4 and 1 Cc 3 E GW Well-graded gravel F Cu 4 and/or 1 Cc 3 E GP Poorly graded gravel F Gravels with Fines: More than 12% fines C Fines classify as ML or MH GM Silty gravel F,G,H Fines classify as CL or CH GC Clayey gravelF,G,H Sands: 50% or more of coarse fraction passes No. 4 sieve Clean Sands: Less than 5% fines D Cu 6 and 1 Cc 3 E SW Well-graded sandI Cu 6 and/or 1 Cc 3 E SP Poorly graded sandI Sands with Fines: More than 12% fines D Fines classify as ML or MH SM Silty sandG,H,I Fines classify as CL or CH SC Clayey sand G,H,I Fine-Grained Soils: 50% or more passes the No. 200 sieve Silts and Clays: Liquid limit less than 50 Inorganic: PI 7 and plots on or above “A” line J CL Lean clayK,L,M PI 4 or plots below “A” line J ML SiltK,L,M Organic: Liquid limit - oven dried 0.75 OL Organic clayK,L,M,N Liquid limit - not dried Organic silt K,L,M,O Silts and Clays: Liquid limit 50 or more Inorganic: PI plots on or above “A” line CH Fat clay K,L,M PI plots below “A” line MH Elastic Silt K,L,M Organic: Liquid limit - oven dried 0.75 OH Organic clayK,L,M,P Liquid limit - not dried Organic silt K,L,M,Q Highly organic soils: Primarily organic matter, dark in color, and organic odor PT Peat A Based on the material passing the 3-inch (75-mm) sieve B If field sample contained cobbles or boulders, or both, add “with cobbles or boulders, or both” to group name. C Gravels with 5 to 12% fines require dual symbols: GW-GM well-graded gravel with silt, GW-GC well-graded gravel with clay, GP-GM poorly graded gravel with silt, GP-GC poorly graded gravel with clay. D Sands with 5 to 12% fines require dual symbols: SW-SM well-graded sand with silt, SW-SC well-graded sand with clay, SP-SM poorly graded sand with silt, SP-SC poorly graded sand with clay E Cu = D60/D10 Cc = 6010 2 30 DxD )(D F If soil contains 15% sand, add “with sand” to group name. G If fines classify as CL-ML, use dual symbol GC-GM, or SC-SM. H If fines are organic, add “with organic fines” to group name. I If soil contains 15% gravel, add “with gravel” to group name. J If Atterberg limits plot in shaded area, soil is a CL-ML, silty clay. K If soil contains 15 to 29% plus No. 200, add “with sand” or “with gravel,” whichever is predominant. L If soil contains 30% plus No. 200 predominantly sand, add “sandy” to group name. M If soil contains 30% plus No. 200, predominantly gravel, add “gravelly” to group name. N PI 4 and plots on or above “A” line. O PI 4 or plots below “A” line. P PI plots on or above “A” line. Q PI plots below “A” line. Exhibit C-3 DESCRIPTION OF ROCK PROPERTIES WEATHERING Term Description Unweathered No visible sign of rock material weathering, perhaps slight discoloration on major discontinuity surfaces. Slightly weathered Discoloration indicates weathering of rock material and discontinuity surfaces. All the rock material may be discolored by weathering and may be somewhat weaker externally than in its fresh condition. Moderately weathered Less than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a continuous framework or as corestones. Highly weathered More than half of the rock material is decomposed and/or disintegrated to a soil. Fresh or discolored rock is present either as a discontinuous framework or as corestones. Completely weathered All rock material is decomposed and/or disintegrated to soil. The original mass structure is still largely intact. Residual soil All rock material is converted to soil. The mass structure and material fabric are destroyed. There is a large change in volume, but the soil has not been significantly transported. STRENGTH OR HARDNESS Description Field Identification Uniaxial Compressive Strength, PSI (MPa) Extremely weak Indented by thumbnail 40-150 (0.3-1) Very weak Crumbles under firm blows with point of geological hammer, can be peeled by a pocket knife 150-700 (1-5) Weak rock Can be peeled by a pocket knife with difficulty, shallow indentations made by firm blow with point of geological hammer 700-4,000 (5-30) Medium strong Cannot be scraped or peeled with a pocket knife, specimen can be fractured with single firm blow of geological hammer 4,000-7,000 (30-50) Strong rock Specimen requires more than one blow of geological hammer to fracture it 7,000-15,000 (50-100) Very strong Specimen requires many blows of geological hammer to fracture it 15,000-36,000 (100-250) Extremely strong Specimen can only be chipped with geological hammer >36,000 (>250) DISCONTINUITY DESCRIPTION Fracture Spacing (Joints, Faults, Other Fractures) Bedding Spacing (May Include Foliation or Banding) Description Spacing Description Spacing Extremely close < ¾ in (<19 mm) Laminated < ½ in (<12 mm) Very close ¾ in – 2-1/2 in (19 - 60 mm) Very thin ½ in – 2 in (12 – 50 mm) Close 2-1/2 in – 8 in (60 – 200 mm) Thin 2 in – 1 ft (50 – 300 mm) Moderate 8 in – 2 ft (200 – 600 mm) Medium 1 ft – 3 ft (300 – 900 mm) Wide 2 ft – 6 ft (600 mm – 2.0 m) Thick 3 ft – 10 ft (900 mm – 3 m) Very Wide 6 ft – 20 ft (2.0 – 6 m) Massive > 10 ft (3 m) Discontinuity Orientation (Angle): Measure the angle of discontinuity relative to a plane perpendicular to the longitudinal axis of the core. (For most cases, the core axis is vertical; therefore, the plane perpendicular to the core axis is horizontal.) For example, a horizontal bedding plane would have a 0 degree angle. ROCK QUALITY DESIGNATION (RQD*) Description RQD Value (%) Very Poor 0 - 25 Poor 25 – 50 Fair 50 – 75 Good 75 – 90 Excellent 90 - 100 *The combined length of all sound and intact core segments equal to or greater than 4 inches in length, expressed as a percentage of the total core run length. Reference: U.S. Department of Transportation, Federal Highway Administration, Publication No FHWA-NHI-10-034, December 2009 Technical Manual for Design and Construction of Road Tunnels – Civil Elements NOTES: 1) DIMENSIONS SHOWN ARE FOR ESTIMATING PURPOSES. ACTUAL DIMENSIONS AND EXTENT OF KEYWAYS, BENCHES, AND SUBDRAINS WILL BE DETERMINED IN THE FIELD BY THE SOIL ENGINEER. 2) NATURAL SLOPES OF 6:1 (H:V) OR STEEPER ARE TO BE BENCHED PRIOR TO FILL PLACEMENT. 3) SLOPE BENCHES INTO HILLSIDE AT 4± PERCENT. 4) BENCHES AND KEYS TO BE EXCAVATED INTO BEDROCK. 5) FILL SLOPES SHOULD BE COVERED WITH SOME TYPE OF EROSION CONTROL MEASURE. (I.e. EROSION RESISTANT VEGETATION, JUTE NETTING, OR GEOTEXTILE EROSION CONTROL MAT) 6) FILL SLOPES SHOULD BE OVERBUILT AND TRIMMED BACK TO FIRM, COMPACTED FILL. 3 1 MAXIMUM SLOPE 2 TO 6 1 NATURAL GROUND SURFACE COMPACTED ENGINEERED FILL 4±% 4' TO 10' 5' MAX SHEAR KEY DEPTH - 4' MIN. INTO BEDROCK,U.N.O. WIDTH - 8' OR 1/3 SLOPE HEIGHT MIN. BEDROCK MIRADRAIN 6200 OR EQUIV. AT EACH CUT FACE TYP 4" PERFORATED SCH 40 PVC PIPE AT BASE OF CUTS. SLOPE TO EXISTING SITE DRAINAGE OR TO A MUNICIPAL STORM DRAIN AT 2% MIN SLOPE. TYP 4% 2±% 5075 COMMERCIAL CIRCLE, UNIT E CONCORD, CA 94520 FAX. (925) 609-6324PH. (925) 609-7224 Project Mngr: Approved By: Checked By: Drawn By: Project No. Scale: Date: File No.Consulting Engineers and Scientists EXHIBIT PROJECT NAME PROJECT ADDRESS 1 PROJECT ADDRESS 2 BENCHED FILL DETAILJOB NUM X X X X X X X NONE LENGTH AS NOTED ON PLAN SET LEVEL FROM END TO END DISSIPATOR SHALL BE LOCATED NO CLOSER THAN 10 FEET TO ANY ADJACENT PROPERTY LINE. 6" MIN GROUND COVER OR EROSION CONTROL PLANTING PER ARCHITECT SHOULD BE INSTALLED BELOW DISSIPATOR. MIRAFI 140N FILTER FABRIC 6" MIN "T" DISSIPATOR 2 1MAX 6"Ø PERFORATED PIPE, HOLES SHALL FACE-UP "T" FITTING PLACE TEE LEVEL ABOVE GROUND (ON CONTOUR) ANCHOR DRAIN W/ BENT #2 REBAR 4" Ø PVC CAP THE ENDS W/ THREADED CAP (C.O.) PLAN VIEW SECTION VIEW 5075 COMMERCIAL CIRCLE, UNIT E CONCORD, CA 94520 FAX. (925) 609-6324PH. (925) 609-7224 Project Mngr: Approved By: Checked By: Drawn By: Project No. Scale: Date: File No.Consulting Engineers and Scientists EXHIBIT Project Project Address 1 Project Address 2 DISSIPATER DETAILSGS-XXXX X X E. NUÑEZ X X 05/2015 EXHIBIT X AS SHOWN 1 2 " M I N R E T A I N I N G W A L L 1 0 ' 1 ' O P T I O N A L W E E P H O L E B A C K F I L L E D W I T H E N G I N E E R E D F I L L P I E R F O U N D A T I O N O R O T H E R T Y P E O F F O U N D A T I O N R E I N F O R C I N G S T E E L P E R S T R U C T U R A L D R A W I N G S 4 " Ø P E R F O R A T E D D R A I N P I P E . S L O P E P I P E T O D R A I N A G E A T 2 % M I N S L O P E . P R O V I D E M I N . 1 2 " G R A V E L L A Y E R B E H I N D W A L L , W A S H E D C O N C R E T E A G G R E G A T E ( A S T M C 3 3 . N O . 5 7 O R 6 7 ) G R A V E L D R A I N A G E M A Y B E S U B S T I T U E D W I T H D R A I N A G E C O M P O S I T E T Y P I C A L E A R T H R E T A I N I N G W A L L D R A I N N O N E X P A N S I V E E N G I N E E R E D B A C K F I L L S H A L L E X T E N D H O R I Z O N T A L L Y B E H I N D T H E W A L L A M I N . 2 / 3 T H E H E I G H T O F T H E W A L L . B A C K F I L L E D W I T H N O N - E X P A N S I V E E N G I N E E R E D F I L L W I T H A P I < 1 2 A S I N D I C A T E D I N A P P E N D I X A P r o j e c t M n g r : A p p r o v e d B y : C h e c k e d B y : D r a w n B y : P r o j e c t N o . S c a l e : D a t e : F i l e N o . C o n s u l t i n g E n g i n e e r s a n d S c i e n t i s t s E X H I B I T - - L O C A T I O N M A P - - - - - - - - - - 5 0 7 5 C O M M E R C I A L C I R C L E U N I T E P H . ( 9 2 5 ) 6 0 9 - 7 2 2 4 C O N C O R D , C A 9 4 5 2 0 F A X . ( 9 2 5 ) 6 0 9 - 6 3 2 4 REVISIONS Date: Job No.: By: Scale: #DATE Danville, California 94526 Tel: 925/837-3780EASTON C McALLISTER - R.C.E. 61148 RENEWAL DATE: 12/31/18 DeBolt Civil Engineering 811 San Ramon Valley Boulevard deboltcivil@earthlink.net 10/24/2019 1" = 20' 15246 EM/kl FF FL FLOW LINE FINISH FLOOR LEGEND CYPRESS PROPOSED LAND USE:RESIDENTIAL RESIDENTIALEXISTING LAND USE: GAS & ELECTRIC -- PG&E TELEPHONE -- PACIFIC BELL SEWER -- C.C.C.S.D. WATER -- E.B.M.U.D. OWNER: TENTATIVE NOTES ENGINEER: UTILITIES: BASIS OF ELEVATION: ZONING OF PROPERTY: ASSESSOR'S PARCEL NO: PHILIP & KAREN BURKHART 775 KIRKCREST ROAD DANVILLE, CA 94526 2.06± AC 201-240-023 AREA OF PROPERTY: APPROXIMATE BOUNDARY INFORMATION SHOWN WAS COMPILED FROM AVAILABLE RECORD DATA AND DOES NOT REPRESENT AN ACTUAL FIELD BOUNDARY SURVEY. TREE NOTE: UTILITY LOCATIONS SHOWN ON PLAN ARE APPROXIMATE ONLY BASED UPON RECORD INFORMATION. BOUNDARY NOTE: DRIPLINES OF TREES SHOWN ARE APPROXIMATE ONLY. R-40 DEBOLT CIVIL ENGINEERING 811 SAN RAMON BOULEVARD DANVILLE, CA. 94526 (925) 837-3780 RCE 27818 / EXP 3-31-14 VICINITY MAP CONTRA COSTA COUNTY BENCHMARK #1459 BEING A NAIL AND TAG IN TOP OF CURB OVER A DROP INLET LOCATED AT THE SOUTHWEST CORNER OF THE INTERSECTION OF DANVILLE BLVD. AND HARTFORD ROAD. ELEVATION TAKEN AS 331.024 FEET (NGVD 29) COUNTRY ESTATESGENERAL PLAN: 20 CONTOUR TREE w/DRIPLINE ATTACHMENT E REVISIONS Date: Job No.: By: Scale: #DATE Danville, California 94526 Tel: 925/837-3780EASTON C McALLISTER - R.C.E. 61148 RENEWAL DATE: 12/31/18 DeBolt Civil Engineering 811 San Ramon Valley Boulevard deboltcivil@earthlink.net 10/24/2019 1" = 20' 15246 EM/kl NOTES BASIS OF ELEVATION: APPROXIMATE BOUNDARY INFORMATION SHOWN WAS COMPILED FROM AVAILABLE RECORD DATA AND DOES NOT REPRESENT AN ACTUAL FIELD BOUNDARY SURVEY. TREE NOTE: UTILITY LOCATIONS SHOWN ON PLAN ARE APPROXIMATE ONLY BASED UPON RECORD INFORMATION. BOUNDARY NOTE: DRIPLINES OF TREES SHOWN ARE APPROXIMATE ONLY. VICINITY MAP CONTRA COSTA COUNTY BENCHMARK #1459 BEING A NAIL AND TAG IN TOP OF CURB OVER A DROP INLET LOCATED AT THE SOUTHWEST CORNER OF THE INTERSECTION OF DANVILLE BLVD. AND HARTFORD ROAD. ELEVATION TAKEN AS 331.024 FEET (NGVD 29) ASPHALT PAVEMENT GROOVED CONCRETE LEGEND FIRE APPARATUS ROADWAYS SHALL BE CAPABLE OF SUPPORTING THE IMPOSED WEIGHT OF FIRE APPARATUS (75,000 POUNDS) AND SHALL BE PROVIDED WITH AN ALL WEATHER DRIVING SURFACE. FIRE APPARATUS ROADWAYS SHALL BE CAPABLE OF SUPPORTING THE IMPOSED WEIGHT OF FIRE APPARATUS (75,000 POUNDS) AND SHALL BE PROVIDED WITH AN ALL WEATHER DRIVING SURFACE. 20 490 480 470 460 450 440 430 420 410 490 480 470 460 450 440 430 420 410 REVISIONS Date: Job No.: By: Scale: #DATE Danville, California 94526 Tel: 925/837-3780EASTON C McALLISTER - R.C.E. 61148 RENEWAL DATE: 12/31/18 DeBolt Civil Engineering 811 San Ramon Valley Boulevard deboltcivil@earthlink.net 10/24/2019 1"=10'H & 1"=10'V 15246 EM/kl PLAN 1" = 10' SECTION A-A 1"=10' HOR & 1"=10' VERT SECTION A-A FIRE APPARATUS ROADWAYS SHALL BE CAPABLE OF SUPPORTING THE IMPOSED WEIGHT OF FIRE APPARATUS (75,000 POUNDS) AND SHALL BE PROVIDED WITH AN ALL WEATHER DRIVING SURFACE. FIRE APPARATUS ROADWAYS SHALL BE CAPABLE OF SUPPORTING THE IMPOSED WEIGHT OF FIRE APPARATUS (75,000 POUNDS) AND SHALL BE PROVIDED WITH AN ALL WEATHER DRIVING SURFACE. 20 460460 450 440 430 420 410 400 390 380 450 440 430 420 410 400 390 380 REVISIONS Date: Job No.: By: Scale: #DATE Danville, California 94526 Tel: 925/837-3780EASTON C McALLISTER - R.C.E. 61148 RENEWAL DATE: 12/31/18 DeBolt Civil Engineering 811 San Ramon Valley Boulevard deboltcivil@earthlink.net 10/24/2019 1"=10'H & 1"=10'V 15246 EM/kl PLAN 1" = 10' SECTION B-B 1"=10' HOR & 1"=10' VERT SECTION B-B FIRE APPARATUS ROADWAYS SHALL BE CAPABLE OF SUPPORTING THE IMPOSED WEIGHT OF FIRE APPARATUS (75,000 POUNDS) AND SHALL BE PROVIDED WITH AN ALL WEATHER DRIVING SURFACE. 20 REVISIONS Date:DeBolt Civil Engineering 811 San Ramon Valley Boulevard Danville, California 94526 Tel: 925/837-3780 Job No.: By: Scale: #DATE Fax: 925/837-4378 JED / kl 15246 1" = 30' 10/24/2019 R.C.E. 61148 RENEWAL DATE: 12/31/20 EASTON C. McALLISTER SURFACEAREA SELF-TREATING DMA'S DMA ROOF ASPHALT ASPHALT IMP SIZE IMPERVIOUS DMA'S ROOF ROOF 3,150± SF 6,150± SF 7,600± SF AREADMA SURFACE 1 2 3 4 5 6 9 SELF-TREATING 10 SELF-TREATING SELF-TREATING SELF-TREATING11 12 3,486± SF 5,528± SF 8,939± SF 13,362 SF 1 420± SF 2 360± SF 3 420± SF 5,493± SF 755± SF ASPHALT1,990± SF 7 ROOF2,742± SF 8 ROOF & CONCRETE1,220± SF SELF-TREATING1329,785± SF IMP 4 DETAIL 1" = 20' EX. GARAGE EX. SHED NEW DRIVEWAY