120 Sandringham Drive South - Moraga Sandringham Drive South Design Review DRB 15 ... East Side of...

D E S I G N R E V I E W

B O A R D

S T A F F R E P O R T

329 Rheem Boulevard Moraga, CA 94556 (925) 888-7040 [email protected] www.moraga.ca.us

FOR BOARD ACTIONJANUARY 25, 2016

120 Sandringham Drive South

Design Review DRB 15-15 for four previously constructed retaining wallsand related grading in the side yard of 120 Sandringham Drive South.(3DUA, CMF)

I. Application Basics

A. Design Review Board Approvals Required:

· Design Review of construction of four new retaining walls to replace five existingretaining walls. (MMC 14.12.030)

· Design Board approval for a retaining wall requiring a permit and visiblefrom off-site (ID 11.3)

· Design Guideline exceptions are required for ID 10.6 and 1D 11.4

· Grading Permit. (MMC 14.04.031)

B. CEQA Determination: Categorically exempt pursuant to Section 15303 of theCalifornia Environmental Quality Act (CEQA) Guidelines Class 3(a); NewConstruction or Conversion of Small Structure.

C. Parties Involved:

· Applicant/Property Owner: Bonnie Chimni, 120 Sandringham Drive SouthMoraga, CA 94556.

· Architect: Mohinder Singh Datta, 449 Stonefield Place, Moraga CA 94556

· Civil/Structural Engineer: Ron Campos, 11100 San Pablo Ave. #207, ElCerrito, CA 94530

· Geotechnical Engineer: Kamran Ghiassi, 7567 Amador Valley Blvd. # 310,Dublin, CA 94568

120 SANDRINGHAM DRIVE SOUTH DESIGN REVIEW BOARDPage 2 of 11 January 25, 2016

Table 1: Land Use InformationLocation Existing Use Zoning District General Plan Designation

Subject Property Single-Family Residential 3 DU-Acre Residential 3 du/ac

SurroundingProperties

North Single-Family Residential 3 DU-Acre Residential 3 du/ac

South Single-Family Residential 3 DU-Acre Residential 3 du/ac

East Single-Family Residential 3 DU-Acre Residential 3 du/ac

West Single-Family Residential 3 DU-Acre Residential 3 du/ac

Figure 1: Vicinity Map

II. Background and Chronology

The applicant is seeking retroactive design review approval for construction of four woodenterraced retaining walls. The new walls were constructed to replace five previouslyconstructed retaining walls in the same vicinity, although the placement and location of thenew retaining walls differ from those previously in place. One effect of the change was tosteepen the grade of the terraced slope, and increase the level yard area adjacent to thehome.

DESIGN REVIEW BOARD 120 SANDRINGHAM DRIVE SOUTHJanuary 25, 2016 Page 3 of 11

Work on the project began in late June/July 2015, without the applicant having secured thenecessary approvals. As outlined in the chronology, the Town was made aware of theproject based on a complaint from a neighbor, which resulted in issuance of a Notice toComply on July 20, 2015, based on an assessment from the County Grading Inspector that apermit was required. The Town also issued a notice of violation regarding work without apermit on August 5, 2015, at which point work on the project ceased. However, substantialwork had been completed by the applicant before the Town received an application from theproperty owner, which essentially described the project underway.

On the advice of the Public Works Department, in order to avoid the risk of possible damageto the retaining walls, subject property, and neighboring property, in September, 2015 theTown approved issuance of a building permit for the improvements as a temporaryinstallation, to allow the applicant to stabilize the project by completing its construction beforethe winter rainy season.

As outlined above, the project has been determined to require design review approval by theTown based on compliance with the Design Guidelines, as well as a grading permit subject toDesign Review Board approval. The DRB may approve the project as constructed or withmodifications, thereby allowing for issuance of an approval “after the fact.” If the DRB doesnot approve the project, the site would be required to be restored to its original condition andconfiguration.

III. Project SettingThe project site is a residential lot, developed with an existing home, located near theintersection of Country Club Drive and Sandringham Drive South, which dead ends in a cul-de-sac (Figure 1). The lot is located in the middle of a residential subdivision comprisinghomes developed primarily in the mid 1970’s, with some homes constructed in the 1980’s.Homes on the cul-de-sac are located to the east and south of the project site and include amix of architectural styles and both one and two story homes. Sandringham Drive Southslopes down a hill from Country Club Drive.

The subject property is a rectangular lot with the residence located in the middle of the lot.The existing home is situated on a level building pad. Consistent with other homes onSandringham Drive South, the subject property was graded to create a level area for thehome and yard with a steep, engineered uphill slope on the eastern side yard. The adjacentlot to the east is roughly 10 feet higher, and the lot to the west is roughly 10 feet lower, thanthe subject property (see Figure 3).


Figure 3: Contour Elevation Map

Table 2: Project ChronologyDate Action

Summer, 2015 Initial grading and construction of new retaining walls commenced

July, 2015 Complaint received regarding work without a permit

July 20, 2015 Inspection and Notice to comply issued by County for construction without apermit1

August 4, 2015 Second notice to comply issued due to continued construction without apermit1

August 13, 2015 Notice of Violation send to home owner by Planning Department1

September 8, 2015 Application materials submitted to Planning Department by applicant

September 28, 2015 Temporary building permit issued by Planning Department to completepartially constructed retaining due to concerns over flooding and erosion

January 6, 2016 Construction inspection by Licensed Surveyor2

January 12, 2016 Construction inspection by Civil Engineer2

January 12, 2016 Application deemed complete

January 13, 2016 Public hearing notices mailed/posted

January 25, 2016 DRB Meeting

1 Attachment E2 Attachment F


IV. Project Description

The applicant is seeking retroactive design review approval for construction of four woodenterraced retaining walls. The new walls were constructed to replace five previouslyconstructed retaining walls in the same vicinity, although the placement and location of thenew retaining walls differ from those previously in place. The location of the former retainingwalls is shown on page A.0 of the project plans (Attachment G). One effect of the change isto steepen the grade of the terraced slope, and increase the level yard area adjacent to thehome.

Previously, the closest was located approximately 15 feet from the exterior wall of the home,and the furthest wall was located approximately 8 feet 8 inches from the neighboring propertyline. Initial construction commenced without having secured a permit including removal ofthe existing retaining walls and vegetation (including removal of a 30” diameter conifer tree),regrading of the side yard area to create more usable yard area, and beginning installation offour new retaining walls. The new walls added 9 feet 2 inches of level side yard area adjacentto the residence and placed the fourth, upper wall approximately 3 feet from the easternproperty line.

The work results in a more steeply terraced slope compared to the previous condition, andcloser placement of the walls to one another. The previous retaining walls resulted in a slopewith an aggregate height of approximately 10.5 feet with a distance of 12.5 feet between thefirst and fifth wall. The new walls have an aggregate height of 12 feet with 10 feet betweenthe first and fourth wall (see Figure 4 and 5).

The project also involved approximately 90 cubic yards of grading which requires a gradingpermit per the Moraga Municipal Code. The project also trigged design review. Staffdetermined that a hillside development permit would not be required because construction ofthe new walls occurred on a previously engineered slope, not a natural hillside.

During the course of project review, staff required that the applicant have a geotechnical andstructural assessment of the constructed walls and proposed plans in order to identify anysoil, stability, erosion, or drainage issues (included in Attachment E) Based onrecommendations included in these assessments, minor modifications were made to theproject and design. A licensed engineer has certified that the improvements, as installed, arebuilt per the plans and specifications provided in the application.


Figure 4 and 5: Photos of Completed Project


Table 3: Development Standards

Lot Standards-MMC Section 8.28(3DU/acre)

Existing Proposed Permitted/Required

Lot Area (sq. ft.) 12,000 No Change 10,000

Maximum Height of Residence No Change No Change 35 ft.

BuildingSetback (ft.)

Front (South) 20 ft. No Change 20 ft.

Rear (North) 20 ft. No Change 15 ft.

East Side of Residence 36 ft. 2 in. No Change 10 ft.

West Side of Residence 10 ft. No Change 10 ft.

Sum of Side YardSetbacks

47 ft. 6 in. No Change 20 ft.

Table 4: Retaining Wall Specifications

Retaining Wall StandardsOld RetainingWalls

As BuiltRetainingWalls

Permitted/Required

Maximum Height of RetainingWalls (individual)

~4 ft. 3 ft.3 feet if visible from off-siteper Design Guideline (ID11.2)

Cumulative Height of RetainingWalls

~10 ft. 6 in. 12 ft. No specific standard

Distance between each wall3 ft. and3ft. 6 in.

3 ft. and3ft. 6 in.

Neither cuts nor fills shallresult in slopes steeper than3:1 (horizontal to vertical),except where natural slopesare steeper (ID 10.6). Thehorizontal depth of theterraces between stackedretaining walls should be aminimum of twice the heightof the larger adjacent wall(ID11.4).

StructureSetbacks(RetainingWalls)

Front 20 ft. No Change 20 ft.

Rear 37 ft. No Change 25 ft.

East Side 8 ft. 8 in. ~3 ft. 3 ft.

Residence 15 ft. 23 ft. 2 in. N/A


IV. Community Discussion

The public meeting notice was mailed to 35 property owners within a 300-foot radius of thesite and posted near the site on January 13, 2016. The neighbors to the east of the subjectproperty (110 Sandringham Drive South), expressed concerns to staff about the proximity ofthe grading to their property the closest wall being located 3 feet from the fence locatedbetween their shared property line. They also expressed concerns regarding potentialdrainage issues and erosion when the project was partially completed after a second noticeto comply was issued; a concern which somewhat alleviated when the temporary buildingpermit was issued by staff to complete the construction for safety purposes. However, theneighbors remain concerned that the materials used to construct the retaining walls aredurable and properly engineered. This concern is outlined in detail as Attachment C.

V. Analysis

A. Key Issues, Design Aspects and Design Guideline Conformance:

1. Retaining Wall DesignThe project requires a number of exceptions to those design guidelines regarding retainingwalls, which the DRB must consider. Due to the fact that the four retaining walls included inthe project have already been constructed, achieving the strict standards for retaining walldesign included in the Design Guidelines would be difficult without dismantling the project inits entirety to regrade and rebuild each wall, which may have adverse impacts in other areasof concern, including the overall stability of the slope.

Design Guideline ID11.2 states that “Exterior retaining walls shall be limited to five feet inheight, unless it is visible from off site, in which case it shall be no higher than three feet. Thetotal height of a retaining wall and fencing on top of the wall shall not exceed eight feetwithout Design Review Board approval”. As designed and constructed, each of the fourretaining walls is 3 feet in height. In staff’s analysis, because the fence located along theeastern property line is offset 3 feet from the closest retaining wall, it is reasonable toconsider the fence separate from the closest wall.

Design Guidelines ID11.4 recommends when siting retaining walls the “the horizontal depthof the terraces between stacked retaining walls should be a minimum of twice the height ofthe larger adjacent wall” The aim of this guideline is to retain the natural topographicalfeatures and scenic qualities of a site, and promote the design of site improvements that havea low visual profile. An exception to this guideline is required because the distance betweenthe terraced retaining walls ranges from 3 feet to 3 feet 6 inches, while the height of each ofthe four walls is 3 feet. In order for the project to conform to this guideline, the walls wouldhave to be designed with a minimum of six feet between each wall; twice the distance ascurrently constructed. This would require reconstructing all four retaining walls and adding asignificant amount of fill to the project area. It should also be noted that the retaining wallsthat previously existed on the property, and were removed during construction, did notconform to this guideline. Based on this analysis, staff believes it reasonable to allow thisexception.


Design Guideline ID11.3 states that “a retaining wall exceeding 3 feet requires professionalengineering, a building permit, and may require a grading permit. Design Review Boardapproval is required if the retaining wall is visible from off-site.” As part of the project review,staff required the applicant to have the project plans and partially constructed walls evaluatedby both a structural and geotechnical engineer. The Contra Costa Building Departmentreviewed the project plans and approved the building permit that was issued for the project asa temporary installation, pending planning review and approval. To date all of the requiredinspections have been completed as part of the building permit process. Because the wallsare partially visible from the Sandringham Drive South public right-of-way, Board approval isrequired for the project design. Staff believes that if the Board finds the overall project designconsistent with the intent of the MMC and Design Guidelines, it would be reasonable for theBoard to grant this approval.

Design Guideline ID11.5 requires that “retaining walls should be built a minimum of three feetfrom a property line.” According to the project plans, the retaining wall adjacent to theproperty line is located 3 feet from the eastern property line between 120 and 110Sandringham Drive South, as measured from the face of the wall. If the same wall ismeasured from its outer edge, it would be slightly closer than 3 feet. However, a survey ofthe property line was not conducted prior to construction of the walls. Although it is likely thatthe fence is constructed on the property line, this is not always the case, which would affectthe conclusion as to whether or not the exception is required. However, taking a conservativeapproach, staff recommends the DRB consider an exception to ID11.5 in their approval, inthe event that a survey shows the wall to be located closer than 3 feet from the property line.

Analysis of the project by both the structural and geotechnical engineer found that the sitewas appropriate for the project and the location of the walls would not create erosion ordrainage issues if certain recommendations were implemented (Attachment E). Theserecommendations were incorporated into construction of the project. On this basis, it appearsto be appropriate to grant an exception to ID11.5 by the Board so that, if at a later date, asurvey reveals that the fence is not located on the exact property line, the owner of thesubject property does not have to come back before the Board.

2. Grading:Per MMC §14.04.031, the project requires a grading permit because 1: “The cumulativevolume of earth material moved is fifty (50) cubic yards or greater,” and 2: “The earthworkcreates a slope equal to or steeper than five horizontal to one vertical.” The site waspreviously graded to construct five terraced retaining walls in the eastern side yard of theproperty. The four new retaining walls, which require retroactive design approval, included 90cubic yards of grading which cut into the natural slope that previously existed between the oldretaining walls and the eastern property line, reducing this distance from 8 feet 8 inches to 3feet.

Design Guideline ID 10.6 states that “Neither cuts nor fills shall result in slopes steeper than3:1 (horizontal to vertical), except where natural slopes are steeper. Where steeper slopesare unavoidable, special mitigation measures shall be incorporated into the designconstruction and maintenance of the slopes.” As constructed, the project requires anexception from this guideline because the retaining walls create an engineered slope of 3 to3.5 vertical feet (retaining wall height) to 3 horizontal feet (distance between retaining walls),


or a 1:1 slope between two of the walls. In staff’s analysis, because much of the project areawas previously occupied by the five old retaining walls which also did not conform to thisstandard, and the engineering of the project was evaluated by both geotechnical andstructural engineers as structurally sound and designed a constructed, the grading thatoccurred is not excessive or unwarranted. In addition, planning staff consulted with theTown’s Public Works staff on the design of the project and concluded that because theexisting slope has already be compromised through the grading process, that if the retainingwalls were demolished and redesigned to meet this standard (and the site was restored to itsoriginal condition in order to meet the slope standard) the process of doing so would damagethe site more than maintaining the current design. Because of these factors, staff believes thefindings can be made for an exception to ID 10.6.

Design Guideline ID10.5 states that “cut slopes should be placed behind buildings or otherstructures where they will be screened.” As constructed, the retaining walls are partiallyvisible from the Sandringham Drive South public right-of-way. Due to the location of the wallsin the side yard of the property and fencing located along the property line, staff finds theproject to be adequately screened from neighboring properties. The applicant intends toreplace vegetation removed during construction. This new landscaping, and the conditions ofapproval regarding vegetation will help screen the project from the street.

B. General PlanThe 2002 General Plan contains the following applicable policies:

1. Policy LU1.1- Neighborhood Preservation: Protect existing residential neighborhoods frompotential adverse impacts of new residential development and additions to existingstructures.

Staff Analysis: The project is designed in conformance with the development standards ofthe zoning district. The retaining walls were inspected on multiple occasions and found tobe in conformance with the California Building Code and best practices for erosioncontrol. Conditioned landscaping will help the retaining walls blend into the natural settingof the neighborhood.

2. Policy CD1.2- Site Planning, Building Design and Landscaping: Retain naturaltopographic features and scenic qualities through sensitive site planning, architecturaldesign and landscaping. Design buildings and other improvements to retain a low visualprofile and provide dense landscaping to blend structures with the natural setting.

Policy CD4.1–Property Development Standards: Maintain and enforce existing propertydevelopment standards for the Town’s single-family residential neighborhoods.

PS4.6 – Construction Standards: Ensure that all new construction and applicableremodeling/reconstruction projects are built to established standards with respect toseismic and geologic safety.

Staff Analysis: The design of the retaining walls complements the existing home. Due totheir location in the eastern side yard and fencing along the property lines, the walls arevisually screened from adjacent properties. Although the project is partially visible from


the street, condition landscaping will mitigate the visual impact of the project. Thegeotechnical report indicates that the site is suitable for the proposed project and thedesign is sound.

VII. Recommendation

Due to the project’s consistency with the Zoning Ordinance and General Plan, andminimal impact on surrounding properties, staff recommends that the Design ReviewBoard adopt the attached action memorandum to APPROVE DRB 15-15 subject tofindings and conditions of approval.

Attachments:

A. Draft Action MemorandumB. Design Guideline Conformance TableC. Public CommentD. Notices to Comply and Notice of ViolationE. Structural and Geotechnical ReportsF. Post Construction Inspection Cover SheetsG. Project Plans

Staff Planner: Coleman Frick, [email protected], (925) 888-7039

Reviewed by: Ellen Clark, Planning Director

ATTACHMENT A

DRAFT ACTION MEMORANDUM

Town of MoragaPLANNING DEPARTMENT

329 RHEEM BOULEVARD

MORAGA, CA 94556(925) 888-7040

DESIGN REVIEW BOARD ACTION MEMORANDUM

On January 25, 2016, the Town of Moraga Design Review Board considered the applicationsdescribed below:

DRB 15-15 – Bonnie Chimni (Applicant/Owner), 120 Sandringham DriveSouth: Retroactive approval for four previously constructed, terraced, 3 footretaining walls, and 90 cubic yards of related grading in the side yard of theproperty.

Grading Permit: For grading operations on slopes less than twenty (20) percent.

DESIGN REVIEW BOARD ACTION:

The DESIGN REVIEW BOARD hereby grants approval of the project at 120 SandringhamNorth South in accordance with the following findings and conditions of approval:

PART 1: DESIGN REVIEW FINDINGS:The findings below are required in accordance with Planning Commission Resolution 16-01in order for the Design Review Board to approve an application within a single-familyresidential district:

1. The proposed improvements conform with good design as set forth in the Townof Moraga Design Guidelines, and in general contributes to the character andimage of the town as a place of beauty, spaciousness, balance, taste, fitness,broad vistas, and high quality because as constructed, the retaining walls are anunobtrusive design and of modest height, similar to the walls previously in place. Theterraces of the slope will be landscaped with new vegetation that will screen andsoften the appearance of the walls. The new walls are designed to provide for a moreusable yard area for the home occupants and will be screened from off-site views dueto their low profile, and by landscaping conditioned in this approval.

2. The proposed improvements will not have a substantial adverse effect onneighboring properties or the community due to poor planning; neglect ofproper design standards; or the existence of building and structures unsuitableto and incompatible with the character of the neighborhood and the character ofthe community because the project is consistent with the residential character of theneighborhood, meets the development standards of the 3-DUA residential zoningdistrict, including minimum setbacks and height, and therefore does not negatively

affect the level of privacy, access to light and air or shade for the surroundingproperties. Most properties in the vicinity include similar terraced retaining walls,included in the original subdivision design to create level building pads and yard areas.The retaining walls have been assessed by structural and geotechnical engineersthroughout the construction process and inspected by the Contra Costa CountyBuilding Department, and were found to meet applicable structural standards that willnot adversely affect or cause hazards to neighboring properties.

3. The proposed improvements will not lower property values; discourage themaintenance and improvement of surrounding properties; or preclude the mostappropriate development of other properties in the vicinity because the retainingwall project was constructed substantially in conformance with the Design Guidelinesfor Single-Family Residential Neighborhoods. The project and related grading will adduseable yard area and living area of the home and will represent an investment in theexisting property that will encourage maintenance and improvement of surroundingproperties. As documented in Finding 2, the project meets applicable design andengineering standards such that no hazard to adjacent properties is created.

4. The proposed improvements will not impair public health, safety or welfarebecause the development includes grading and building plans which were reviewed bythe Lamorinda Building Department and the retaining walls are built in accordance withthe California Building Code. The completed project is not expected to have anyadverse health or safety impacts on the community. A geotechnical report wasprepared for the project. Recommendations of the report and were incorporated intothe design of the project during construction.

PART 2: GRADING PERMIT FINDINGS:In accordance with MMC §14.12.030, for grading operations on slopes less than twenty (20)percent, the Design Review Board hereby approves the grading with a determination that thegrading is:

1. Consistent with the town design guidelines because the grading and fill arecontained by retaining walls which will be screened from off-site views by vegetationsimilar to neighboring properties. The walls were constructed in an area where existingretaining wall had previously been constructed, altering the natural topography of thesite.

2. Does not result in any slope of twenty (20) percent or more. Although the project

will create a slope with a grade of more than 20 percent, the area was previously

graded such that a similar condition existed for a similar purpose, and approved as

part of the construction of the subdivision, as engineered terraced slopes. The project,

in and of itself, does not therefore cause non-conformance with the grading ordinance

guideline.

3. Consistent with the requirements of Chapter 8.136 of the Municipal Code and

does not require a modification because it was concluded that the project, which

involves grading of an existing engineered slope, does not require a Hillside

Development Permit.

4. Not detrimental to public safety because a geotechnical review of the project was

provided by the applicant’s engineer, which found that development of the site was

feasible and will incorporate appropriate engineering and design measures that would

protect public safety. The retaining walls were constructed to replace existing retaining

walls which may have been built in accordance with less rigorous building standards.

In approving a building permit for construction of the walls on a temporary basis

pending Town approval of the project, Contra Costa County reviewed and approved

the structural plans submitted by the applicant, with which the walls as a permanent

improvement would be consistent.

5. Not detrimental to stormwater runoff because the grading primarily occurred on a

previously engineered slope which contained existing retaining walls with a similar

amount of impervious surfaces. Adequate drainage is included in the project design as

recommended by both geotechnical and structural engineers. The project will not

result in residential building coverage in excess of 33% consistent with Design

Guideline ID12.1. The retaining walls meet all California Building Code requirements

for storm water runoff.

6. Not inconsistent with the General Plan because the grading was completed for the

purposes of erecting retaining walls. Due to their location in the eastern side yard and

fencing along the property lines, the walls are visually screened from adjacent

properties. Although the project is partially visible from the street, condition

landscaping will mitigate the visual impact of the project. The geotechnical report

indicates that the site is suitable for the proposed project and the design is sound.

PART 4: CONDITIONS OF APPROVAL:

1. The plans submitted for retroactive building permit approval of four previouslyconstructed, terraced, 3 foot retaining walls, and 90 cubic yards of related grading in theside yard at 120 Sandringham Drive South shall be substantially in accordance with theplans approved by the Design Review Board on January 25, 2016, and this DesignReview Board Action Memorandum. Any significant changes to the plans will require re-submittal to the Design Review Board for approval.

Conditions Shall be Printed on Plans

2. The conditions of this permit shall be printed on the first sheet of each plan setsubmitted for a building permit pursuant to this approval, under the title ‘Design ReviewBoard Conditions.’ The second sheet may also be used if the first sheet is not ofsufficient size to list all of the conditions. The sheet(s) containing the conditions shall beof the same size as those sheets containing the construction drawings; 8-1/2” by 11”sheets are not acceptable.

Applicant Responsible for Compliance with Conditions3. The applicant shall ensure compliance with all of the following conditions. Failure to

comply with any condition may result in construction being stopped, issuance of acitation, and/or modification or revocation of the approval.

Subject to all Town and Other Regulations

4. The approved construction is subject to, and shall comply with, all applicable TownOrdinances and laws and regulations of other governmental agencies.

5. The applicant shall apply for and pay all appropriate fees for building permits, planchecks and inspections.

Prior to Construction of New Landscaping

6. The applicant shall submit a landscaping plan to the Town of Moraga PlanningDepartment which shall incorporate fire and drought resistant vegetation, and anyadditional requirements imposed by the State of California or local water agency withregard to emergency water conservation measures, as well as landscape-relatedConditions of Approval specified elsewhere in this approval. Native vegetation should beselected from one of the palettes in Appendix B.

7. Any lawn areas in the project area shall be a drought tolerant fescue variety.

During Construction of Landscaping

8. A drip irrigation system shall be installed which includes automatic rain shut-offcontroller devices.

9. All trees screening the retaining walls shall be a 24” box size.

Prior to Building Permit Final

10. Two native trees shall be planted in the side yard to replace the 30” diameter conifer ofunknown species that was removed during construction of the project without a treeremoval permit or arborist report.

11. All landscaping and irrigation shall be installed prior to final building permit.

At All Times

12. This permit and each condition contained herein shall be binding upon the applicant andany transferor, or successor in interest.

13. The applicant shall maintain the landscape on, and adjacent to, the terraced retainingwalls to provide visual screening of retaining walls from Sandringham Drive South andadjacent properties.

14. If construction is not commenced within one year from the date of final action, the permitbecomes null and void. However, this discretionary action may be renewed by thePlanning Director for a maximum period of one (1) year provided the applicant placessuch a request in writing to the Planning Director showing good cause prior to theexpiration of the discretionary action.

Design Review Board action is appealable to the Planning Commission within ten (10)calendar days after the date of the decision. Questions regarding the action of the Boardshould be directed to the Planning Department at (925) 888-7040.

__________________________Ellen ClarkPlanning Director

ATTACHMENT B

DESIGN GUIDELINE ANALYSIS

D R B # 1 5 - 1 5

ATTACHMENT B

A Design Guideline Conformance Analysis:

Guideline Analysis

MAINTAIN THE TOWN’S SEMI-RURAL CHARACTER (SRC)

These guidelines are intended to help preserve the semi-rural features that make Moraga unique whenconsidering applications for development. Therefore, these guidelines are applicable to all types ofdevelopment.

SRC1 Retain, protect, and utilize existing naturalfeatures, such as trees and other vegetation,interesting ground forms, rocks, water, andsignificant views in the design.

The project is located on a lot that was previouslydeveloped and graded as part of theneighborhood’s subdivision process. One 30”diameter existing conifer tree of unknown specieswas removed during constriction along with thelandscaping that was located between andadjacent to the old retaining walls. According to thesite plan submitted by the applicant the areagraded near the eastern fence line had a slope ofless than 10%. The remainder of the project areawas already occupied by engineered terracedretaining walls, rather than natural features.

SRC5 Preserve natural site amenities.

a. Development should be planned in relation tonatural features.

b. Natural features must be protected both duringand after construction of the project.

c. Retain trees and other native vegetation,consistent with tree preservation ordinance, tomaintain current stability of steep hillsides,retain moisture, prevent erosion, and enhancethe natural scenic beauty. Grading under treedrip lines should be avoided to protect the rootsystem during development.

d. Treat significant natural features, such ascreeks, rock out-croppings, and prominentknolls, as assets.

The conditions of approval require that nativevegetation is used to landscape the retaining wallarea and two native trees are planted to replacethe 30” diameter tree removed without a permit.

SRC7 New trees should be planted to complimentthe natural pattern of tree placement and shouldbe selected from one of the palettes in AppendixB.

See SRC5

SRC8 Mature native tree groupings should beprotected.

It is unknown whether the tree that was removedas part of the project was native.

Complement Existing Landscaping

L1. Fire Safe Landscaping

L1.1 On residential lots located adjacent to openspace or heavily wooded areas, trees should beplanted no closer than 15 feet from the exteriorwall of a residence.

The project is not located near open space or aheavily wooded area.

L1.3 Landscaping should be properly irrigated toassure that plants retain their fire retardantcapability, but shall not be over watered so as tocreate runoff from the site.

Conditions of approval require that the dripirrigation system be installed that includesprogrammable controls that can be set to vary withseasons and weather.

L2.1 Residential properties should be landscapedand irrigated in accordance with the naturalenvironment.

Conditions of approval require that a mix of plantsfrom Appendix B of the Town Design Guidelines isused when landscaping the project area.

L2.2 New irrigation systems shall includeautomatic rain shut-off controller devices.

See L1.3. The project is designed based onrecommendations from engineering consultants toallow for proper drainage.

L2.3 Irrigation runoff shall not be discharged intothe storm drain system. Therefore, over wateringof the landscape shall be avoided. Opportunitiesshall be provided for biofiltration that routesstormwater through landscaping and then to anappropriate drainage facility.

L2.5 Drought tolerant, fire resistant, native tree andshrub species should be selected from one of thepalettes in Appendix B. The Town of Moragaencourages planting of native species over non-native species and encourages applicants to referto the Native Plant Society website at www.nps.orgto check that the plants that you select are notinvasive species.

See L2.1

MINIMIZE THE IMPACTS OF DEVELOPMENTS (ID)

To the extent possible, development should be concentrated in areas that are least sensitive in terms ofenvironmental and visual resources, including: a) areas of flat or gently sloping topography outside offlood plain or natural drainage areas; b) the Moraga Center and Rheem park area; c) Infill parcels inareas of existing developments.

ID1-7 APPLICABLE TO ALL DEVELOPMENT

ID1 Downhill or uphill portions of any project shallprovide landscaped treatment to address potentialerosion, to be in harmony with adjacentdevelopments, and to provide a complimentingview from distant horizons. Dense nativelandscaping should be used to blend hillsidestructures with the natural setting.

Licensed structural and geotechnical engineersassessed the project plans and design of the wallsas constructed and determined that with minormodifications, which have been implemented bythe applicant, the walls would not be substantiallyvulnerable to erosion. See L2.1

Guideline Analysis

ID3 Wind barriers, shade, sound absorption, dustabatement, glare reduction, and proper drainageshould be provided on site.

As constructed, the project has been evaluated byconsulting engineers as providing proper onsitedrainage.

ID5 Geologic hazards shall be addressed:

1. Construction should not take place in geologichazard areas identified as landslides, springs,or earthquake fault zones.

2. Risk of off-site geologic property damageshould be minimized by locating developmentaway from areas which are vulnerable to slopefailure.

3. Professional evaluation of soil conditions andpotential geologic hazards should becompleted for all new homes.

The applicant hired a geotechnical consultant toreview the project plans and retaining wall thatwere constructed without proper permits. Therecommendations of this consultant wereincorporated into the project plans for thetemporary building permit issued to complete theproject for safety purposes. These plans werereviewed and approved by the Contra CostaCounty.

ID6 The level of lighting should not exceed theneeds for security and safety or detract from theaesthetics of the development.

1. Outdoor lighting should be related to thedesign of the structure.

2. Outdoor light fixtures should be designed andmounted so that the source of light hasminimal impact off site.

3. Outdoor lighting should be directed inwardtoward the property and may require additionalscreening to avoid spillage onto adjacentresidential properties.

Conditions of approval require that all exteriorlighting shall be shielded and directed downwardand away from property lines to prevent excessiveglare beyond the subject property.

ID10 Grading

ID10.1 Grading for any purpose may be permittedonly in accordance with an approved developmentplan that is found to be geologically safe andaesthetically pleasing.

See ID5

ID10.2 Where the pre-development slope is lessthan 20% a grading permit may be required. Seethe Moraga Municipal Code 14.08.010 for details.

The project includes 90 cubic yards of grading.Projects with less than 50 cubic yards of gradingrequire a permit. As a result the project requires agrading permit.

ID10.5 Cut slopes should be placed behindbuildings or other structures where they will bescreened.

The retaining walls are partially visible from theSandringham Drive South public right-of-way. Theapplicant intends to replace vegetation removedduring construction which will help screen theretaining walls.

ID10.6 Preserve the natural topography of theland, especially at the horizon:

The project requires an exception from thisguideline because the retaining walls create an

Guideline Analysis

Round off graded slopes, in a manner thatconforms to the natural contours of the landand to the surrounding terrain. Sharp anglesproduced by earth moving, specifically at thetop and toe of graded slopes shall be avoided.

Slopes shall be contour graded to achieve anatural appearance.

Slopes shall be blended with the contours ofcontiguous properties and create a smoothtransition.

Grading shall minimize scars due to cuts, fills,and drainage benches on natural slopes.

Neither cuts nor fills shall result in slopes steeperthan 3:1 (horizontal to vertical), except wherenatural slopes are steeper. Where steeper slopesare unavoidable, special mitigation measures shallbe incorporated into the design construction andmaintenance of the slopes.

engineered slope of 3-3.5 vertical feet (retainingwall height) to 3 horizontal feet (distance betweenretaining walls), or ~1:1. Some of the natural slopeof the property was removed near the easternproperty line during construction.

ID11 RETAINING WALLS

ID11.1 Retaining walls (excluding foundationretaining walls) and other man-made gradingfeatures may only be used to mitigate geologichazards when:

1. Required to decrease the possibility ofpersonal injury or property damage

2. designed to blend with the natural terrain andavoid an artificial or structural appearance

3. appropriately screened by landscaping

4. designed to avoid creating a tunnel effectalong roadways and to ensure unrestrictedviews for vehicular and pedestrian safety

5. designed to ensure minimal public and/orprivate maintenance costs

The proposed retaining walls were constructed toprovide a larger level usable yard area at the sideof the home, and not for mitigation of a geologichazard. The project was constructed withoutconsideration of creating a natural appearance.However, it should be noted that the olderretaining walls also had this design characteristic.The applicant intends to landscape the projectarea and conditions of approval are included thataddress landscaping.

ID11.2 Exterior retaining walls shall be limited tofive feet in height, unless it is visible from off site,in which case it shall be no higher than three feet.The total height of a retaining wall and fencing ontop of the wall shall not exceed eight feet withoutDesign Review Board approval. A guardrail orhandrail (provided a solid fence does not supportit) may be located on top of the retaining wall.

As designed and constructed, none of the fourretaining walls exceeds 3 feet in height. The fencelocated along the eastern property line is offset 3feet from the closest retaining wall.

ID11.3 A retaining wall exceeding 3 feetrequires professional engineering, a buildingpermit, and may require a grading permit.

The project design included an assessment by aprofessional engineer who found the designstructurally sound. The project requires a grading

Guideline Analysis

Design Review Board approval is required ifthe retaining wall is visible from off-site.

permit due to the scale of grading that wascompleted (see ID10.2). Design Review Boardapproval is required because portions of theproject are visible from off-site.

ID11.4 The horizontal depth of the terracesbetween stacked retaining walls should be aminimum of twice the height of the largeradjacent wall.

As constructed the project requires an exceptionfrom this design guideline. The distance betweenthe terraced retaining walls ranges from 3 feet to 3feet 6 inches, while the height of each of the fourwalls is 3 feet. In order for the project to conform tothis guideline the walls would have to be designedwith a minimum of six feet between each wall;twice the distance as currently constructed.

ID11.5 Retaining walls should be built aminimum of three feet from a property line.

According to the project plans the closest distancebetween a retaining wall and the property line is 3feet as measured from the face of the wall (not theclosest point). However, a survey of the propertyline was not conducted prior to construction. ALand Surveyor confirmed that the walls were builtto the specifications included in the project planswhich show that the closest retaining wall islocated 3 feet from the fence which presumed torepresent the eastern property line. However, thiscannot be confirmed without a survey by aLicensed Surveyor.

THOUGHTFULLY DESIGN SINGLE-FAMILY RESIDENTIAL NEIGHBORHOODS (SFR)

The following guidelines pertain to all single-family residential projects (new homes or additions):

SFR1.11 There should be a near level area of atleast 25' x 40', other than the front yard, for usableyard area.

The near level usable yard area has beenexpanded, as a result of the new retaining wallconstruction and grading, over existing conditions

ATTACHMENT C

PUBLIC CORRESPONDENCE

ATTACHMENT D

NOTICES TO COMPLY ANDNOTICE OF VIOLATION

ATTACHMENT E

STRUCTURAL ANDGEOTECHNICAL REPORTS

Geotechnical rec

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GeoEngineering Consultants 4125 Blackford Avenue, Suite 145 San Jose, CA 95117 Phone: 925-321-5550

Project No. 2015.0322

August 26, 2015

Mrs. Bonnie Chimni 120 Sandringham Drive South Moraga, CA 94556 Subject: Proposed Retaining Wall

120 Sandringham Drive South Moraga, CA 94556 Retaining Wall Recommendations

Dear Mrs. Chimni:

In accordance with your authorization, GeoEngineering Consultants (GEC), has performed a limited

geotechnical study at the subject site located in Moraga, California.

This report summarizes our findings, conclusions and recommendations for geotechnical assessment

of the existing retaining walls, based on the subsurface investigation performed to date.

1. PURPOSE AND SCOPE

We understand that you plan to repair the retaining wall at the site.

Our investigation included the following:

a. Field reconnaissance by the Soil Engineer;

b. Geotechnical exploration to obtain soil sample;

c. Geotechnical laboratory testing program;

e. Analysis of the data and formulation of conclusions and recommendations, and

f. Preparation of this written report.

Details of our field investigation are presented in Appendix A.

Limited Geotechnical recommendations 120 Sandringham Dr. S., Moraga, CA August, 26, 2015

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2. PROJECT DESCRIPTION

Based on our site visit and discussions with you, we understood that you replaced damaged terraced

retaining walls with new terraced retaining walls in your backyard. The proposed four retaining

walls are approximately 3 feet high, about 3 to 3.5 feet apart, and about 60 to 80 feet long at the

subject site.

3. SITE DESCRIPTION AND BACKGROUND

The approximate location of the site is shown on Plate 1, “Site Vicinity Map” in Appendix A. The

site is currently occupied by a one-story, wood-framed dwelling, and several retaining walls in the

northeast of the property.

4. SUBSURFACE CONDITIONS

The approximate locations of the borings are shown on Plate 2, “Site Plan and Boring Location

Map” in Appendix-A. Generally, native soils at the site consisted of 1 to 3 feet of stiff of clayey

silt with varying amount of sand and gravel underlain by sandstone in Borings B-1 and B-2,

respectively. Outside of the retaining walls, in Boring B-2, fill was encountered to depth of 8.5

feet. The fill consisted of soft to medium stiff silty clay with sand. The bedrock was observed

between the retaining walls. The bedrock is of Pliocene and early Miocene age. Groundwater

was not encountered during borings.

This study did not assess contamination of on-site soils and water. A more thorough description

and stratification of the soils conditions encountered, along with the results of the laboratory

tests, are presented on the respective “Logs of Borings” within Appendix-A.

5. LANDSLIDING AND SOIL CREEPING Strong earthquake ground motions can cause landsliding. According to work done by the U.S.

Geological Survey (Keefer, 1984), a magnitude 7.0 earthquake can cause landslides up to 70


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miles from the epicenter of an earthquake. These data suggest that landsliding could be

considered a seismic hazard at the site. The hazard of earthquake-induced landsliding cannot be

completely mitigated on site, but it is our opinion that construction of the proposed retaining wall

will reduce landslinding at the site during ground shaking than do natural slopes.

Soil creep is occurring on most of the hillsides on the site. Creep is the slow, downslope

movement of the soil mantle induced by gravity. Downslope movement results from alternate

shrinking and swelling of soil caused by seasonal moisture variations. Mitigation measures for

creep hazards include construction on level building areas with adequate setbacks from slopes. It

is our opinion that construction of the proposed retaining wall will reduce soil creep at the site.

6. FAULTS AND SEISMICITY

Seismicity in the Moraga Area is mainly related to activity on the San Andreas fault system,

including major active faults west of the site. The principal active faults in the vicinity are the

San Andreas, Calaveras, Concord, Greenville, Mount Diablo Thrust, Franklin, and the San

Gregorio.

The site is not within one of the Alquist-Priolo Earthquake Fault Zones established by the CGS

around known active faults. The closest known active fault is situated approximately 1,300 feet

southwest of the site

The San FranciscoBay Area has experienced several large earthquakes during historical times.

The following paragraphs present Richter magnitudes of notable bay-area historic earthquakes.

The largest historic earthquake was the great California earthquake of April 18, 1906, which had

an estimated magnitude of 8.3. Its epicenter was offshore on the San Andreas fault. Other

damaging earthquakes affecting the Moraga area occurred in the early and mid-1800s. The more

notable of these occurred on the San Andreas fault in 1838 and 1865. The 1865 event was in the

vicinity of the Santa Cruz Mountains, but it caused severe damage to structures on filled ground

in Moraga.


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Another damaging earthquake that affected Bay Area occurred on the Hayward fault in 1868.

That earthquake caused considerable damage to buildings on filled ground in Santa Clara

(Lawson, 1908 ). A damaging earthquake also occurred on the Calaveras fault in the Dublin area

in 1861.

The more recent earthquakes in the region include the October 17, 1989, Loma Prieta earthquake

on the San Andreas fault with magnitude of 7.1; the Hollister, Coyote Lake, and Morgan Hill

earthquakes of 1974, 1979, and 1984, on the Calaveras fault, with magnitudes of 5.2, 5.9, and

6.2., respectively; the 1957 Daly City earthquake on the San Andreas fault (magnitude 5.3); and

the two Santa Rosa earthquakes of 1969 on the Healdsburg-Rodgers Creek fault (magnitudes 5.6

and 5.7).

7. CBC EARTHQUAKE DESIGN CRITERIA

The 2013 California Building Code (UBC) Chapter 16, Division IV- Earthquake Design- requires

that structures be constructed using certain earthquake design criteria. The criteria are based in part

on the seismic zone, soil profile and the proximity of the site to active seismic sources (faults).

During an earthquake event, structures located very close to active faults can be subjected to near

source energy motions that may be damaging to structures, if the effects of these energy motions are

not considered in the structural design. The nearest active fault to the site is the San Andreas fault,

which is located approximately 3.5 km southwest of the subject site.

Based on the geotechnical data in this report and the selection of criteria of the 2013 CBC (Chapter

16, Division IV, Earthquake Design), a summary of the earthquake design criteria for use in the

design of future structures, additions and improvements is as follows:


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TABLE 1- 2013 CBC SESIMIC PARAMETERS

Parameter Value

Site Class/Soil Profile Type C

Site Coefficient, Fa 1.0

Site Coefficient, Fv 1.3

MCE Spectral Acceleration (0.2 sec), SMS, g 1.558

MCE Spectral Acceleration (1.0 sec), SM1, g 0.797

Design Spectral Acceleration (0.2 sec), SDS, g 1.039

Design Spectral Acceleration (0.2 sec), SD1, g 0.532

Mapped MCE Spectral Acceleration (0.2 sec), SS, g 1.558

Mapped MCE Spectral Acceleration (1.0 sec), S1, g 0.613

PGAM 0.603

8. DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS

8.1. General The most prominent geotechnical feature of the site is the variable depth to bedrock and

undocumented fill. The undocumented fill was encountered outside of the retaining wall area. The

negative impact of the variable depth to bedrock and documented fill on the proposed replacement

of the retaining wall can adequately be controlled by appropriate structural design of foundations

and civil design of surface grades and gradients for gravity-flow drainage pipes.

From a geotechnical point of view, correction of excessive movements of the northern retaining wall

is feasible provided the recommendations presented in this report are incorporated into the future

plans and specifications. This study did not assess contamination of on-site soils and water.

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8.2. Recommendations

8.2.1. Grading

Grading will consist of cut excavation activities. Engineered fill may be required in areas to backfill

excavations. The grading requirements presented herein are an integral part of the grading

specifications presented in Appendix B of this report and should be considered as such.

Grading activities on clayey materials during the rainy season will be hampered by excessive

moisture. Grading activities may be performed during the rainy season, however, achieving proper

compaction may be difficult due to excessive moisture; and delays may occur. Grading performed

during the dry months will minimize the occurrence of the above problems.

All soils encountered during our investigation are suitable for use as engineered fill when placed and

compacted at the recommended moisture content and provided it does not contain any debris.

All engineered fill should be placed in lifts not exceeding 8 inches in uncompacted thickness and

compacted to a minimum of 90% relative compaction at 2% to 4% above optimum. Relative

compaction is based on the maximum dry density as determined by ASTM D1557-91 Laboratory

Test Procedure.

8.2.2. Excavation Requirements

It is anticipated that during construction of the proposed retaining wall, a cut up to 4 feet in vertical

height may result. The excavation will extend 1 to 2 feet away from the outside face of the below

grade walls to allow proper forming of the wall and construction of a drainage blanket. According

to California Occupational Safety and Health Administration, Title 8, California Code of

Regulations, Construction Safety Orders, Sections 1504, 1539-1547, the soil to be excavated is

classified as Type B based on the laboratory and boring data. It is recommended that temporary

excavations less than 20 feet in height be sloped at 1:1 within Type B materials. It is recommended

that temporary excavations less than 20 feet in height be sloped at ½ :1 within rock materials. The

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temporary slope is based on the excavation being left unsupported for a period of a few weeks

during dry weather. If the slopes are left unsupported for more than a few weeks, some minor

sloughing may occur but is not considered unsafe for workers due to the open nature of the bulk

excavation and shallow depth of excavation.

If wet or rainy weather is imminent and the excavations are still unsupported, the excavation should

be covered with plastic to mitigate against possible sloughing.

No materials or equipment should be stored or vehicles parked within 10 feet of the top of

excavation.

If any utility trenches are known to exist within 10 feet of the top of excavation, the recommended

excavation inclination would need to be re-evaluated once actual distances and depth of trenches are

known.

If any structures on adjoining properties are located very close to where any excavations are planned

to be made, or existing utility trenches, care must be exercised to ensure the safety of these

structures. The top of the cut slope should not be closer than 10 feet from structures with a shallow

spread footing foundation or utility trenches provided the excavation has an inclination of 1:1. If

this is not feasible, then provision must be implemented to ensure the safety of the adjoining

property and the slope itself. Such provisions may consist of:

i) Driving sheet piles or constructing a soldier beam system along the perimeter of the

excavation immediately adjacent to areas where structures and utilities can be affected.

ii) Constructing a bracing system that will support the slope for the duration of constructing the

retaining walls.

The Soil Engineer must observe and monitor the condition of the cut slope during excavation

activities in order to render an opinion pertaining to their stability.

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8.2.3. Surface and Subsurface Drainage

All finish grades should provide a positive gradient to an adequate discharge location in order to

provide rapid removal of surface water runoff away from all foundations. Surface drainage must be

provided and maintained at all times.

Flower beds or planters are not preferred adjacent to the foundations because of the possibility of

irrigation water affecting the foundations. Should planters be constructed, foliage requiring little

irrigation should be planted. It is preferred that irrigation adjacent to the wall foundations consist of

a drip system. Sprinkler systems may be used. However, it is preferred that sprinkler heads do not

water closer than 3 feet from the building foundations. If sprinklers are used within 3 feet, then

excessive watering should not be allowed and good surface drainage in the planter area must be

provided. In any case, it is recommended that area surface drains be incorporated into the

landscaping to discharge any excessive irrigation or rainwater that may accumulate in the planter

area. These surface drains must be constructed such that the surface of the drain is lower than the

surrounding grade so that easy flow of surface water runoff is allowed into the drip inlets.

A sump pump should be installed at the eastern end of the proposed northern retaining wall to collect

all the surface and subsurface water. The sump pump should be maintained properly and be in

service at all time to prevent any hydrostatic pressure on either the northern or eastern retaining

walls.

9. Retaining Wall Recommendations

We recommend that the cantilever retaining structure consists of cast-in-place concrete drilled

piers extending into bedrock and lagging. The drilled piers should extend at least 3 feet into

bedrock and develop their capacity by frictional resistance in the bedrock.

The piers should be designed on the basis of skin friction acting between the soil/rock and that

portion of the pier that extends below a depth of 2 feet. For the rocks at the site, an allowable skin

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friction value of 600 p.s.f. can be used for combined dead and live loads, below these depths. This

value can be increased by one-third for total loads which include wind or seismic forces.

Spacing should be determined as required by the load distribution, but minimum spacing should not

be less than 3 pier diameters, center to center. The piers should have a minimum diameter of

fourteen (14) inches. To minimize differential settlement, all piers should extend 3 feet into

undisturbed native bedrock. GEC should observe the drilling for piers and confirm their embedment

in the field. Minimum depth of piers is to be determined by the Structural Engineer.

All piers within sloped backfill should be designed to resist potential creep loads within the upper 3

feet of the soil. Under this circumstance, it is recommended that an active load of 50 p.c.f.

(equivalent fluid pressure) be applied against twice the pier diameter in the upper 3 feet.

To resist lateral loads, the passive resistance of the soil can be used. The soil passive pressures can

be assumed to act against the lateral projected area of the pier described by the vertical dimension of

twice the pier diameter. It is recommended that a passive pressure equivalent of that of a fluid

weighing 250 p.c.f. be used below the depths specified above.

The bottom of friction piers and end bearing piers must be cleaned to remove excessive loose

material that may accumulate at the bottom during drilling. Up to a maximum of 4 inches of loose

soil is permitted to be left in the bottom of the pier hole for friction piers and should end bearing

piers be designed 1-inch settlement should be incorporated in the design. The Soil Engineer must

verify that the piers have been cleaned. It is important that care be exercised to ensure that any

concrete spills during the concrete pour must be removed and no “mushrooming” effects are allowed

to remain around the top of the pier or bottom of the grade beam.


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10. Retaining Wall Recommendations

The retaining wall shall be designed to resist lateral pressures exerted from a media having an

equivalent fluid weight as follows:

Active Condition = 50 p.c.f. for horizontal backslope

At-rest Condition = 70 p.c.f.

Passive Condition = 250 p.c.f.

Coefficient of Friction = 0.30

For a non-horizontal backslope, the active condition for equivalent fluid weight can be increased by

1.5 p.c.f. for each 2 degree rise in slope from the horizontal.

Active conditions occur when the top of the wall is free to move outward. At-rest conditions

apply when the top of wall is restrained from any movement. It should be noted that the effects

of any surcharge or compaction loads behind the walls must be accounted for in the design of the

walls.

Additionally, the retaining walls should be designed to resist lateral pressure induced by

earthquakes. If the retaining wall is higher than 6 feet, as measured from the top of the footing,

the wall should be designed for an additional rectangular pressure distribution equal to 14H in

p.s.f, where H is the height of wall in feet.

The above criteria are based on fully drained condition behind the retaining wall to prevent the

build-up of hydrostatic pressures from surface water and ground water. In order to achieve fully

drained conditions, a drainage filter blanket should be placed behind the wall. The blanket

should be a minimum of 12 inches thick and should extend from 1 foot below the basement slab

subgrade to the full height of the wall to within 12 inches of the surface. If the excavated area

behind the wall exceeds 12 inches, the entire excavated space behind the 12-inch blanket should

consist of compacted engineered fill or blanket material. The drainage blanket material may

consist of either granular crushed rock and drain pipe fully encapsulated in geotextile filter fabric

or Class II permeable material that meets the latest edition of CalTrans Specification, Section 68,


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with drainage pipe, and optional fabric. A 4-inch perforated drain pipe should be installed, with

perforation facing down, near the bottom of the drainage blanket. A 12-inch cap of native soil

material should be placed over the drainage blanket.

It is anticipated that fully drained conditions are not possible, therefore the hydrostatic pressure

must be included in the design of the wall. A linear distribution of hydrostatic pressure of 63 pcf

should be adopted.

It is anticipated that fully drained conditions are not possible, therefore the hydrostatic pressure

must be included in the design of the wall. A linear distribution of hydrostatic pressure of 63 pcf

should be adopted.

To resist lateral loads, the passive resistance of the rock can be used. The soil passive pressures

can be assumed to act against the lateral projected area of the pier described by the vertical

dimension of twice the pier diameter. It is recommended that a passive pressure equivalent of

that of a fluid weighing 250 p.c.f. be used below a depth of two feet.

It is important that care be exercised to ensure that any concrete spills during the concrete pour

must be removed and no "mushrooming" effects are allowed to remain around the top of the pier.

11. Project Review and Construction Monitoring

All grading and foundation plans for the development must be reviewed by the Soil Engineer prior

to contract bidding or submitted to governmental agencies so that plans are reconciled with soil

conditions and sufficient time is allowed for suitable mitigative measures to be incorporated into the

final grading specifications.

GEC should be notified at least two working days prior to site clearing, grading, and/or foundation

operations on the property. This will give the Soil Engineer ample time to discuss the problems that

may be encountered in the field and coordinate the work with the contractor.


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Field observation and testing during foundation operations must be provided by representatives of

GEC, to enable them to form an opinion regarding the adequacy of the site preparation, the

acceptability of fill materials, and the extent to which the earthwork construction and the degree of

compaction comply with the specification requirements. Any work related to the grading and/or

foundation operations performed without the full knowledge and under the direct observation of the

Soil Engineer will render the recommendations of this report invalid. The degree of observation and

frequency of testing services would depend on the construction methods and schedule, and the item

of work. Please refer to "Guidelines For Required Services" for an outline of our involvement

during project development.

Should another geotechnical consultant be engaged to perform project review and/or construction

monitoring, then GEC, must receive a letter of indemnification releasing us of any responsibility on

the project.

Should you have any questions relating to the contents of this report or should you require

additional information, please do not hesitate to contact our office at your convenience.

Sincerely yours,

GEC.,

Kamran Ghiassi, Ph.D., G.E. Principal Engineer

Geotechnical rec

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APPENDIX A


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FIELD INVESTIGATION

The field investigation was performed on August 19, 2015 and included a reconnaissance of the site

and the drilling of two (2) test borings at the approximate locations shown on Plate 2, "Site Plan and

Boring Location Map."

The borings were drilled to maximum depths of 1.5 to 11.5 feet below the existing ground surface.

The drilling was performed with a 4.5-inch solid flight auger. Visual classifications were made from

the auger cuttings and the samples in the field. As the drilling, disturbed core samples were

obtained. Classifications made in the field were verified in the office after further examination.

The stratification of the soils and descriptions are shown on the "Logs of Test Borings" contained

within this appendix.

PLATE 1JOB NO. P15-0314 DATE: 08/15

SITE VICINITY MAPN

SITE

120 SANDRINGHAM Dr. S.MORAGA, CALIFORNIA

PLATE 2DATE: 8/15

SITE PLAN AND BORING LOCATION MAP

B-2

N

The image is courtesy ofGoogle Earth Pro. The scaleis shown on the lower leftcorner of the image.

B-1

Approximate Boring Locations

B-1

ALMOND ROAD

120 SANDRINGHAM Dr. S.MORAGA, CALIFORNIA


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APPENDIX B

The Grading Specifications

Guide Specifications for Rock Under Floor Slabs

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THE GRADING SPECIFICATIONS

1. General Description

1.1 These specifications have been prepared for the grading and site development of the subject

residential development. GEC, hereinafter described as the Soil Engineer, should be consulted prior

to any site work connected with site development to ensure compliance with these specifications.

1.2 The Soil Engineer should be notified at least two working days prior to any site clearing or

grading operations on the property in order to observe the stripping of organically contaminated

material and to coordinate the work with the grading contractor in the field.

1.3 This item shall consist of all clearing or grubbing, preparation of land to be filled, filling of

the land, spreading, compaction and control of fill, and all subsidiary work necessary to complete the

grading of the filled areas to conform with the lines, grades, and slopes as shown on the accepted

plans. The Soil Engineer is not responsible for determining line, grade elevations, or slope

gradients. The property owner, or his representative, shall designate the person or organizations

who will be responsible for these items of work.

1.4 The contents of these specifications shall be integrated with the soil report of which they are

a part, therefore, they shall not be used as a self-contained document.

2. Tests

The standard test used to define maximum densities of all compaction work shall be the ASTM

D1557-91 Laboratory Test Procedure. All densities shall be expressed as a relative compaction in

terms of the maximum dry density obtained in the laboratory by the foregoing standard procedure.

3. Clearing, Grubbing, and Preparing Areas To Be Filled

Supplemental Geotechnical recommendations Wood Acres Rd., Los Gatos, CA September 8, 2011

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3.1 If encountered, all vegetable matter, trees, root systems, shrubs, debris, and organic topsoil

shall be removed from all structural areas and areas to receive fill.

3.2 If encountered, any soil deemed soft or unsuitable by the Soil Engineer shall be removed.

Any existing debris or excessively wet soils shall be excavated and removed as required by the Soil

Engineer during grading.

3.3 All underground structures shall be removed from the site such as old foundations,

abandoned pipe lines, septic tanks, and leach fields.

3.4 The final stripped excavation shall be approved by the Soil Engineer during construction and

before further grading is started.

3.5 After the site has been cleared, stripped, excavated to the surface designated to receive fill,

and scarified, it shall be bladed until it is uniform and free from large clods. The native subgrade

soils shall be moisture conditioned and compacted to the requirements as specified in the grading

section of this report. Fill can then be placed to provide the desired finished grades. The contractor

shall obtain the Soil Engineer's approval of subgrade compaction before any fill is placed.

4. Materials

4.1 All fill material shall be approved by the Soil Engineer. The material shall be a soil or soil-

rock mixture which is free from organic matter or other deleterious substances. The fill material

shall not contain rocks or lumps over 6 inches in greatest dimension and not more than 15% larger

than 2-1/2 inches. Materials from the site below the stripping depth are suitable for use in fills

provided the above requirements are met.

4.2 Materials existing on the site are suitable for use as compacted engineered fill after the

removal of all debris and organic material. All fill soils shall be approved by the Soil Engineer in

the field.


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4.3 Should import material be required, it must meet the specifications as delineated in the body

of this report.

5. Placing, Spreading, and Compacting Fill Material

5.1 The fill materials shall be placed in uniform lifts of not more than 8 inches in uncompacted

thickness. Each layer shall be spread evenly and shall be thoroughly blade mixed during the

spreading to obtain uniformity of material in each layer. Before compaction begins, the fill shall be

brought to a water content that will permit proper compaction by either (a) aerating the material if it

is too wet, or (b) spraying the material with water if it is too dry.

5.2 After each layer has been placed, mixed, and spread evenly, either import material or native

material shall be compacted to a relative compaction designated for engineered fill.

5.3 Compaction shall be by footed rollers or other types of acceptable compacting rollers.

Rollers shall be of such design that they will be able to compact the fill to the specified density.

Rolling shall be accomplished while the fill material is within the specified moisture content range.

Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips

to ensure that the required density has been obtained. No ponding or jetting shall be permitted.

5.4 Field density tests shall be made in each compacted layer by the Soil Engineer in accordance

with Laboratory Test Procedure ASTM D1556-64 or D2922-71. When footed rollers are used for

compaction, the density tests shall be taken in the compacted material below the surface disturbed by

the roller. When these tests indicate that the compaction requirements on any layer of fill, or portion

thereof, have not been met, the particular layer, or portion thereof, shall be reworked until the

compaction requirements have been met.

5.5 No soil shall be placed or compacted during periods of rain nor on ground which contains

free water. Soil which has been soaked and wetted by rain or any other cause shall not be

compacted until completely drained and until the moisture content is within the limits hereinbefore


GEC Page 23

described or approved by the Soil Engineer. Approval by the Soil Engineer shall be obtained prior

to continuing the grading operations.

6. Pavement

6.1 The proposed subgrade under pavement sections, native soil, and/or fill shall be compacted

to a minimum relative compaction of 95% at 3% above optimum moisture content for a depth of 6

inches.

6.2 All aggregate base material placed subsequently should also be compacted to a minimum

relative compaction of 95% based on the ASTM Test Procedure D1557-91. The construction of the

pavement in the parking and traffic areas should conform to the requirements set forth by the latest

Standard Specifications of the Department of Transportation of the State of California and/or City of

Montara, Department of Public Works.

6.3 It is recommended that soils at the proposed subgrade level be tested for a pavement design

after the preliminary grading is completed and the soils at the site design subgrade levels are known.

7. Utility Trench Backfill

7.1 The utility trenches extending under concrete slabs-on-grade shall be backfilled with native

on-site soils or approved import materials and compacted to the requirements pertaining to the

adjacent soil. No ponding or jetting will be permitted.

7.2 Utility trenches extending under all pavement areas shall be backfilled with native or

approved import material and properly compacted to meet the requirements set forth by the City of

Moraga, Department of Public Works.


GEC Page 24

7.3 Where any opening is made under or through the perimeter foundations for such items as

utility lines and trenches, the openings must be resealed so that they are watertight to prevent the

possible entrance of outside irrigation or rain water into the underneath portion of the structures.

8. Subsurface Line Removal

8.1 The methods of removal will be designated by the Soil Engineer in the field depending on

the depth and location of the line. One of the following methods will be used.

8.2 Remove the pipe and fill and compact the soil in the trench according to the applicable

portions of sections pertaining to compaction and utility backfill.

8.3 The pipe shall be crushed in the trench. The trench shall then be filled and compacted

according to the applicable portions of Section 5.

8.4 Cap the ends of the line with concrete to prevent entrance of water. The length of the cap

shall not be less than 5 feet. The concrete mix shall have a minimum shrinkage.

9. Unusual Conditions

9.1 In the event that any unusual conditions not covered by the special provisions are

encountered during the grading operations, the Soil Engineer shall be immediately notified for

additional recommendations.

10. General Requirements

10.1 The contractor shall conduct all grading operations in such a manner as to preclude wind

blown dirt and dust and related damage to neighboring properties. The means of dust control shall


GEC Page 25

be left to the discretion of the contractor and he shall assume liability for claims related to wind

blown material.


GEC Page 26

GUIDE SPECIFICATIONS FOR ROCK UNDER FLOOR SLABS

Definition

Graded gravel or crushed rock for use under slabs-on-grade shall consist of a minimum thickness of

mineral aggregate placed in accordance with these specifications and in conformance with the

dimensions shown on the plans. The minimum thickness is specified in the accompanying report.

Material

The mineral aggregate shall consist of broken stone, crushed or uncrushed gravel, quarry waste, or a

combination thereof. The aggregate shall be free from deleterious substances. It shall be of such

quality that the absorption of water in a saturated dry condition does not exceed 3% of the oven dry

weight of the sample.

Gradation

The mineral aggregate shall be of such size that the percentage composition by dry weight, as

determined by laboratory sieves (U.S. Sieves) will conform to the following gradation:

Sieve Size Percentage Passing

3/4" 90-100

No. 4 25-40

No. 8 18-33

No. 200 0-3

Placing

Subgrade, upon which gravel or crushed rock is to be placed, shall be prepared as outlined in the

accompanying soil report.

ATTACHMENT F

POST CONSTRUCTIONINSPECTIONS

ATTACHMENT G

PROJECT PLANS

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