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
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FOR BOARD ACTION
OCTOBER 29, 2012
1825 St. Andrews Drive
Design Review #13-2012 to expand an existing upper level deck, construct
a new lower level deck and patio all connected by new stairs; and to
reconstruct an existing lower level deck all at the rear (east elevation) of
the single family residence. Project also includes a hillside development
permit. (3-DUA, K.N.)
I.
Application Basics
A. Zoning Permits Required:
· Design Review, under Moraga Municipal Code (MMC) Section 8.72.030-A
· Hillside Development Permit, under MMC Section 8.136.050-A
B. CEQA Determination: Categorically exempt pursuant to Section 15301 of the
CEQA Guidelines (“Class 1, Existing Facilities”)
C. Parties Involved:
· Applicant/Property Owners
Chris and Nathalie Buck, 1825 St. Andrews
Drive, Moraga, CA, 94556
329 Rheem Boulevard  Moraga, CA 94556  (925) 888-7040  planning@moraga.ca.us  www.moraga.ca.us
1825 ST ANDREWS DRIVE
Page 2 of 10
DESIGN REVIEW BOARD
OCTOBER 29, 2012
Figure 1: Vicinity Map
Table 1: Land Use Information
Location
Existing Use
Zoning District
General Plan Designation
Subject Property
Single family residences
(within Moraga Country Club)
Single family residences
(within Moraga Country Club)
with open space beyond
Single family residences
(within Moraga Country Club)
3-DUA within a
Planned Development
3-DUA within a
Planned Development
Residential 3 du / ac
Surrounding
Properties
North,
South,
West
East
3-DUA within a
Planned Development
Residential 3 du / ac
Residential 3 du / ac
Table 2: Special Characteristics
Characteristic
Applies to
Project?
Yes
Slope/Geotechnical
Native Trees
Yes
Explanation
Project requires a hillside development permit because the
project site has a slope of 20% or greater. A geotechnical peer
review has been prepared.
The property contains three large oak trees all of which will be
preserved. The conferred with a licensed arborist and revised the
drawings in response to his comments.
Table 3: Project Chronology
Date
Action
Aug. 23, 2012
Application submitted
Sept. 18, 2012
Application deemed incomplete
Oct. 12, 2012
Additional materials submitted
Oct. 18, 2012
Application deemed incomplete
Oct. 19, 2012
Public meeting notices mailed/posted
DESIGN REVIEW BOARD
OCTOBER 29, 2012
1825 ST ANDREWS DRIVE
Page 3 of 10
Oct. 23, 2012
Additional materials submitted and deemed complete
Oct. 29, 2012
Design Review Board public meeting
Dec. 22, 2012
PSA deadline1
1.
Project must be approved or denied within 60 days after being deemed complete if exempt from CEQA, or 60 days after adoption of a
negative declaration, or 180 days after adoption of an EIR (Govt. Code Section 65950).
II.
Project Setting
A.
Neighborhood/Area Description: The rectangular-shaped property is located in the
southwest region of the Town, within the Moraga Country Club (MCC) planned
development approximately 400 feet below the ridgeline. The neighborhood is
surrounded on three sides by open space. The homes within the neighborhood are
generally two or two and a half stories situated on sloped lots. The structures are
generally clad with stucco or vinyl siding. Many of the properties contain decks on either
the front or rear elevations which afford views to the across the valley to the north.
Fences which enclose backyard areas or create front courtyard areas are also common.
B.
Site Conditions: Built in 1980, the existing two-story home at 1825 St. Andrews Drive
sits on a double frontage lot that slopes down towards Sea Pines Street. The structure is
clad with bluish, gray-colored stucco and has a fenced-in front courtyard area. There are
two existing wooden decks off the rear of the structure. There is no direct access from
the house to the backyard area. The backyard area contains various shrubs and oak
trees.
1825
St. Andrews Dr.
File: P:\Agenda Packets DRB\2012\102912\1825 St Andrews Dr\01 - Staff Report.docx
1825 ST ANDREWS DRIVE
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DESIGN REVIEW BOARD
OCTOBER 29, 2012
III. Project Description
The applicant proposes expanding the existing 283.9-square foot upper deck by 81.7-square
feet, creating a new 270-square foot lower level deck, reconstructing an existing 199.5square foot lower deck and creating a new 428.1-square foot concrete patio. The upper and
new lower level decks and the patio will all be connected by stairs. The decks would utilize
redwood and cable guardrails. Slatted redwood privacy screens are proposed underneath the
new lower level deck on the south and east elevations and along the north side of the patio.
The deck support posts, except those supporting the connecting stairs, are set back from the
face of the deck. The charcoal-colored concrete patio would sit on top of three, two- to threefoot high skirt walls and would contain a gas fire pit and built-in spa. The patio would require
27.5 cubic yards of grading. The patio and the decks would be at least 10’-6” from the south
(right side) property line, 32’-6” from the east (rear) property line and six feet from the north
(left side) property line.
The applicant proposes adding 21 new light fixtures to the property. Twelve of the fixtures
would be attached to the deck or the house for pathway or area lighting. The other nine
fixtures are within planted areas; five are within the planter boxes along the patio and the
remaining four are at the base of the two oak trees along the north property line; of the nine
fixtures, seven are upward-directed.
Most of the existing landscaping would remain. Two acacia bushes within the development
footprint of the new lower level deck and patio would be removed. New landscaping is
proposed within planter beds along the south and west sides of the patio and within the yard
area along the north, east and west sides of the decks and patio. The new landscaping would
include four trees, sixty shrubs and 13 ground covering plants/vines. A majority of the new
plants are evergreen, and approximately two thirds of the proposed species are considered
low water plants. However, a little less than half of the proposed species are contained within
Appendix B of the Design Guidelines. A slatted redwood fence is also proposed along the
side and rear property lines, set back approximately six feet from the roadway.
IV. Community Discussion
Neighbor/Community Concerns: The Moraga Country Club Architectural Committee
approved the proposed plans on October 10, 2012. Letters from three surrounding
residences in support of the project were submitted to the Planning Department on October
12, 2012. (Attachment B) The public meeting notice was mailed to 53 property owners within
a 300-foot radius of the site and posted at the site on October 19, 2012. The Planning
Department has not received any additional written correspondence regarding the
application.
V.
Issues and Analysis
The following issues apply to the project. Each issue contains the applicable factors or
standards and is followed by staff’s analysis of these standards.
DESIGN REVIEW BOARD
OCTOBER 29, 2012
1825 ST ANDREWS DRIVE
Page 5 of 10
A. Slope Density/Hillside Development Permit – The project is subject to MMC
Section 8.136.070 since the site is considered hillside land. The following apply:
1.
The following factors shall be considered: slope, soil instability, drainage,
soil characteristics, seismic factors, existing and future residential
development, view shed, access, potential traffic congestion, fire risk,
noise, glare, wildlife, dust and impact on existing vegetation.
A geotechnical report submitted for the project was peer reviewed (Attachments
C and D). The peer review comments contain three comments which the
applicant needs to address. Staff recommends a condition of approval requiring
the applicant’s geotechnical engineer provide a satisfactory response to the peer
review comments prior to the issuance of a building permit.
It is not anticipated that the project will have any impact on existing and future
residential development, access, traffic congestion, wildlife, dust and impact on
existing vegetation. A licensed arborist was consulted regarding the project’s
potential impact on the existing oak trees on the site. The applicant followed the
arborist recommendations and revised the project to avoid the trees’ driplines,
Because the decks and the patio are attached to the rear elevation of the house,
and the upper deck extends out at most only 9’-6” from the face of the house,
the project will not protrude into any views from a neighboring property. The
project is not anticipated to have any negative impact on fire risk, noise or glare.
A number of the new plantings are consisted fire resistant. Noise levels will not
be impacted because the spa equipment, the only portion of the project
anticipated to create any new noise, will be concealed within the spa and
underneath the new patio.
2.
The site plan shall provide an appropriate living space on a site consistent
with the site's constraints in relation to the review and approval criteria set
forth in this section.
The project does not affect the interior living space. The amount of outdoor living
space would be increased from approximately 484 square feet to approximately
1,264 square feet. Though substantial, the living space would be distributed
amongst four smaller structures, requiring little disturbance to the site. All three
decks would be elevated off the ground and attached to the rear of the house,
not requiring any significant alterations to the slope. In addition, the patio would
require a minimal amount of grading at 27.5 cubic yards of cut and fill.
3.
A building site which is adjacent to a steep slope not abutting a ridge shall
be located at the lowest possible elevation on the site.
The new patio would make use of a flatter area of the backyard that is adjacent
to the existing residence. It is not the lowest possible elevation on the site;
File: P:\Agenda Packets DRB\2012\102912\1825 St Andrews Dr\01 - Staff Report.docx
1825 ST ANDREWS DRIVE
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DESIGN REVIEW BOARD
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however placing the patio lower would not be practical on a functional level and
would have a greater visual impact on the roadway below.
4.
Residential development that is adjacent to a steep downslope shall be
designed so that the principal and accessory structures blend with the
topography.
As stated in standard #2 above, the decks would have minimal impact on the
topography of the site and the patio would require a minimal amount of grading.
Even though the new patio will have a three foot high skirt wall, the new and
proposed landscaping would help the project blend with the natural environment
of the site.
B. Design Review Standards The project is subject to design review because it
involves the construction of new decks. The design aspects found in MMC
8.72.080(A), listed below, are applied in evaluating compliance with the following
design review standards:
Design Aspects: Maximum height, lot coverage and setbacks (if not covered in the
zoning ordinance); overall mass and bulk of structures; special features of the
development, such as fences, walls, and screens; effective concealment and sound
attenuation of exposed mechanical and electrical equipment; colors and materials on
the exterior face of the building or structures, striving for a limited number of colors
and materials for each project; avoidance of repetition of identical entities whenever
possible; harmonious relationship with existing and proposed adjoining
developments, avoiding both excessive variety and monotonous repetition, but
allowing similarity of style, if warranted; pleasing landscaping which incorporates
existing landscaping and terrain as a complement to the structure, using plants which
thrive in the Moraga climate and which are large enough in size to be effective;
compliance with Chapter 8.132 (scenic corridors); impact on neighboring properties;
impact on public safety; and harmony with the general plan, design review guidelines
and floor area ratio guidelines.
1.
The structure conforms with good taste, good design and in general
contributes to the character and image of the town as a place of beauty,
spaciousness, balance, taste, fitness, broad vistas, and high quality.
The property is located in a planned development in the 3-DUA zoning district.
The only applicable zoning code requirement for a deck is found in MMC Section
8.24.040 (B), which states that
“The minimum side yard setback for an accessory structure of six feet or less in
height is three feet if the structure is set back at least fifty (50) feet from the
front property line. The minimum rear yard setback for an accessory structure of
six feet or less in height is three feet. An accessory structure higher than six
feet is permitted within these setback areas upon approval by the design review
board.”
DESIGN REVIEW BOARD
OCTOBER 29, 2012
1825 ST ANDREWS DRIVE
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The patio and deck that are less than six feet above grade meets the fifty foot
front and three foot side and rear setbacks. The decks over six feet in height are
setback at least 10’-6” from the right side property line, 32’-6” from the rear
property line and 36’ from the left side property line.
Staff initially had concerns regarding the placement of the connecting stairs
along the south side of the decks because they project out from the house,
bringing the new structure closer to the neighboring property; however, the
location of the bay window on the rear elevation of the house limit the options for
locating the stairs and the mature vegetation between the subject property and
the neighboring property to the south would remain, addressing staff’s concerns.
The existing and proposed landscaping would complement each other. Because
most of the species are evergreen, there will be adequate screening and visual
relief year-round for off-site views. Staff recommends a condition of approval
requiring the existing landscaping, excluding the two acacia bushes, remain.
2.
The structure will be protected against exterior and interior noise,
vibrations and other factors which mat ten to make the environment less
desirable.
The new spa would create the only new source of noise for the project. The
placement of the equipment within the spa unit beneath the patio and behind the
skirt walls should effectively conceal and muffle any sounds from the equipment.
3. The exterior appearance of the structure is not of inferior quality as to
cause the nature of the neighborhood to materially depreciate in
appearance and value.
The use of the cable railings along the redwood decks and concrete patio
appear to soften the appearance of the structures as they protrude off the
residence. The varying façade depths of the decks also minimize the bulk of the
decks when viewed as a whole. Existing and proposed landscaping would
obscure most off-site views of the privacy screens. . Architectural changes would
be compatible with the existing residence, including the new door leading from
the house to the new lower deck matching the existing windows and doors.
4. The structure is in harmony with proposed developments on land in the
general area.
There are numerous other cantilevered decks found throughout the
neighborhood. The new decks will be of comparable size and similar design to
those found in the immediate neighborhood. Other decks in the neighborhood
utilize similar wood and cable railings. As stated in standard #1 above, the
current privacy levels will be maintain due to the existing and new landscaping.
File: P:\Agenda Packets DRB\2012\102912\1825 St Andrews Dr\01 - Staff Report.docx
1825 ST ANDREWS DRIVE
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DESIGN REVIEW BOARD
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C. Design Guidelines: All projects must be in conformance with the applicable design
guidelines. The guidelines are used to maintain the Town’s semi-rural character;
protect ridgelines and hillside areas; complement existing landscaping; enhance the
Town’s scenic corridors; minimize the impacts of development; thoughtfully design
single-family residential neighborhoods; thoughtfully design new multifamily
residential developments; and promote commercial centers as community places.
The following findings must be made:
1. The proposed improvements conform to good design as set forth in the
Town’s Design Guidelines and in general contributes to the character and
image of the Town as a place of beauty, spaciousness, balance, taste,
fitness, broad vistas, and high quality.
As stated in Design Review Standard #1, the project would make use of existing
landscaping, incorporate new, complementary landscaping, and comply with the
setback requirements for decks. The patio and lower level decks have been sited
so that existing and new landscaping would screen the structures from most offsite views. The upper deck is narrow in profile which reduces the visual impact of
the deck and allows the vegetative screening to provide only a filtered view of the
deck. Areas around the patio would be contoured to avoid any sharp angle
produced by the grading. (Guideline: SRC1, SRC8, RH1, RH2, RH3, RH5, L3.16
and ID10.3)
2. The proposed improvements will not have a substantial adverse affect on
neighboring properties or the community due to poor planning; neglect of
proper design standards; or the existence of buildings and structures
unsuitable to and incompatible with the character of the neighborhood and
the community.
The upper level deck and the new lower deck both cantilever out from the rear of
the residence similar to other decks in the neighborhood. Both the setting back of
the support posts and the use of cable railings appear to soften the appearance of
the deck. As stated in Design Review standard #1, a majority of the existing
vegetation including the mature oak and elm trees along the north (left side) and
east (rear) property lines would remain and provide a significant amount of
screening for the two decks that are more than six feet in height. This vegetative
screening would also maintain the current level of privacy for the surrounding
properties and filter the view of the expanded upper level deck from the street. The
lower level deck to be reconstructed and the new patio will be screened from
offsite views by the existing and proposed landscaping.
Most of the new light fixtures are directed towards the interior of the property. To
minimize off-site glare from the upward-directed fixtures at the base of the oak
trees and within the center planter box, staff recommends a condition of approval
requiring these fixtures to be hooded and the lights bulbs within these fixtures be
25 watts or less, Existing and proposed landscaping and the proposed fence
would screen or subdue any light that could potentially spill to adjacent properties
DESIGN REVIEW BOARD
OCTOBER 29, 2012
1825 ST ANDREWS DRIVE
Page 9 of 10
from the new light fixtures. A recommended condition of approval requires any
path, wall or post lighting be downward-directed lights that are dark-sky compliant.
All lighting fixtures require final staff approval. Staff also recommends cut-sheets
or a photometrics plan for the lighting be submitted for staff’s approval prior to the
issuance of a building permit. (Guideline: RH3, RH5, L3.6, ID6, ID11.1, ID 11.2 ID
11.5, SRF2.1 and SFR2.12)
3. The proposed improvements will not lower property values; discourage the
maintenance and improvement of surrounding properties; or preclude the
most appropriate development of other properties in the vicinity.
The project would improve and enhance the rear elevation of the subject
residence and have a positive effect on the property values. It would also create
more outdoor usable space on the property, increasing the subject property’s
value. The project will not preclude appropriate development on other properties
because the decks comply with the setback regulations, maintain the single family
residential nature of the neighborhood and privacy levels between the properties
will not be negatively impacted.
4. The proposed improvements will not impair the public health, safety or
welfare.
The proposed improvements will be built in accordance with the uniform building
code, requires a hillside development permit and a drainage permit and will have
no adverse health or safety impacts on the community. A drainage plan has been
prepared which includes the installation of new area drains at the patio and a new
catch basin which would connect with an existing drain line that empties into the
concrete drainage culvert along Sea Pines. As stated in Density/Hillside
Development Permit standard #1, a geotechnical report prepared for the project
was peer reviewed. There are three remaining comments to be addressed. Again,
staff recommends as a condition of project approval that the applicant’s
geotechnical engineer provide a satisfactory response to the peer review
comments prior to the issuance of a building permit. Because the project will
create access to the house from the backyard area, the applicant has proposed a
six foot high slatted redwood fence for security. (Guideline: RH2, RH7, ID10.3 and
ID12.6)
D. General and Area Plan Consistency: The following policies of the 2002 General
Plan apply to the project:
1. Policy LU1.1–Neighborhood Preservation: Protect existing residential
neighborhoods from potential adverse impacts of new residential development and
additions to existing structures.
Staff Analysis: The project makes use of existing landscaping on the property to
provide a level of immediate screening for the project and maintain the privacy
levels for the surrounding properties. New landscaping would amplify the existing
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1825 ST ANDREWS DRIVE
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DESIGN REVIEW BOARD
OCTOBER 29, 2012
screening for the lower level decks and patio and aid in providing an adequate
level of screening for the upper level deck.
2. Policy CD1.2–Site Planning, Building Design and Landscaping: Retain natural
topographic features and scenic qualities through sensitive site planning,
architectural design and landscaping. Design buildings and other improvements to
retain a low visual profile and provide dense landscaping to blend structures with
the natural setting.
Policy CD4.1–Property Development Standards: Maintain and enforce existing
property development standards for the Town’s single-family residential
neighborhoods.
Staff Analysis: Though the project involves grading on a slope of greater than 20
percent to accommodate the new patio, the amount of grading is minimal and the
patio would be screened from offsite views by the existing and new vegetation.
The upper deck, which is the most visible from offsite, extends at most 9’-6” from
the face of the house. The narrow profile of the deck in combination with the use
of cable railings minimizes the appearance of the deck. Existing landscaping and
the new landscaping would provide a filtered view of the upper level deck.
VI. Recommendation
Because of the project’s consistency with the Zoning Ordinance and General Plan, and
minimal impact on surrounding properties, staff recommends that the Design Review Board
adopt the attached draft action memorandum to approve DRB 13-12 with conditions pursuant
to MMC Sections 8.72.080 and 8.136 subject to findings and conditions of approval.
Attachments:
A.
B.
C.
D.
E.
F.
Draft Action Memorandum
Letter from Applicant, Moraga County Club and Neighbors
Geotechnical Report dated July 2012
Geotechnical Peer Review Letter dated October 17, 2012
Project Plans
Site and Neighborhood Photos
Staff Planner: Kathrine Nasset, planner1@moraga.ca.us, (925) 888-7041
Reviewed by: Shawna Brekke-Read, sread@moraga.ca.us, (925) 888-7043
ATTACHMENT A
DRAFT ACTION MEMO
Town of Moraga
PLANNING DEPARTMENT
329 RHEEM BOULEVARD
MORAGA, CA 94556
(925) 888-7040
DESIGN REVIEW BOARD ACTION MEMORANDUM
On October 29, 2012, the Town of Moraga Design Review Board considered the application
described below:
DRB 13-12 – Chris and Nathalie Buck (Applicant/Owner), 1825 St.
Andrews Drive: Design Review to expand an existing upper level deck,
construct a new lower level deck and patio all connected by new stairs; and to
reconstruct an existing lower level deck all at the rear (east elevation) of the
single family residence. Project also includes a hillside development permit.
DESIGN REVIEW BOARD ACTION:
The DESIGN REVIEW BOARD hereby grants approval of the project at 1825 St. Andrews
Drive 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 16-01
in order for the Design Review Board to approve an application within a single-family
residential district:
1. The proposed improvements conform with good design as set forth in the Town
of Moraga Design Guidelines, and in general contributes to the character and
image of the town as a place of beauty, spaciousness, balance, taste, fitness,
broad vistas, and high quality because the project makes use of existing
landscaping which is conditioned to remain and incorporates new, complementary
landscaping and it complies with the setback requirements for decks. The patio and
lower level decks have been sited so that existing and new landscaping will screen the
structures from most off-site views. The upper deck is narrow in profile which reduces
the visual impact of the deck and allows the vegetative screening to provide only a
filtered view of the deck. Areas around the patio will be contoured to avoid any sharp
angle produced by the grading.
2. The proposed improvements will not have a substantial adverse affect on
neighboring properties or the community due to poor planning; neglect of
proper design standards; or the existence of building and structures unsuitable
to and incompatible with the character of the neighborhood and the character of
the community because both the setting back of the support posts and the use of
Page 1 of 4 – Draft Action Memorandum for 1825 St. Andrews Drive (File No. DRB-13-12)
cable railings appear to soften the appearance of the deck. The existing mature
landscaping will provide a significant amount of screening for the two decks that are
more than six feet in height so as to maintain the current level of privacy for the
surrounding properties and provide screening. The new and existing vegetation will
provide a filtered view of the expanded upper level deck as viewed from the street.
The lower level deck to be reconstructed and the new patio will be screened from
offsite views by the existing and proposed landscaping. Most of the new light fixtures
are directed towards the interior of the property. Existing and proposed landscaping
and the proposed fence will screen or subdue any light that could potentially spill to
adjacent properties from the new light fixtures.
3. The proposed improvements will not lower property values; discourage the
maintenance and improvement of surrounding properties; or preclude the most
appropriate development of other properties in the vicinity because the project
will enhance the rear elevation of the subject residence which will have a positive
effect on the property values. It will also create more outdoor usable space on the
property which will increase the subject property’s value. The project will not preclude
appropriate development on other properties because the decks comply with the
setback regulations, maintain the single family residential nature of the neighborhood
and privacy levels between the properties will not be negatively impacted.
4. The proposed improvements will not impair public health, safety or welfare
because the proposed improvements will be built in accordance with the uniform
building code, requires a hillside development permit and a drainage permit and will
have no adverse health or safety impacts on the community. A geotechnical report
prepared for the project was peer reviewed. As conditioned the applicant’s
geotechnical engineer shall provide a satisfactory response to the peer review
comments prior to the issuance of a building permit. The new fence will provide
security for the house which will now have direct access from the backyard area.
PART 2: CONDITIONS OF APPROVAL:
1.
The plans submitted for a building permit to create and reconfigure existing decks and
construct a new patio at the rear of the home at 1825 St. Andrews Drive shall be
substantially in accordance with the plans approved by the Design Review Board on
October 29, 2012, and this Design Review 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 set
submitted for a building permit pursuant to this approval, under the title ‘Design Review
Board Conditions.’ The second sheet may also be used if the first sheet is not of
sufficient size to list all of the conditions. The sheet(s) containing the conditions shall be
of the same size as those sheets containing the construction drawings; 8-1/2” by 11”
sheets are not acceptable.
Page 2 of 4 – Draft Action Memorandum for 1825 St. Andrews Drive (File No. DRB-13-12)
Applicant Responsible for Compliance with Conditions
3.
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 a
citation, 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 Town
Ordinances and laws and regulations of other governmental agencies.
5.
The applicant shall apply for and pay all appropriate fees for building permits, plan
checks and inspections.
Prior to Building Permit Issuance
6.
The applicant shall satisfy the comments in the geotechnical peer review letter dated
October 17, 2012 and shall comply with any additional comments regarding the soils
peer review.
7.
Any path, wall and post lighting shall be downward-directed lights that are dark-sky
compliant. The final decision on all lighting fixtures is subject to staff’s approval.
8.
The light bulbs within any upward-directed light fixtures shall be no more than 25 watts.
The final decision on all lighting fixtures is subject to staff’s approval.
9.
The applicant shall submit for staff’s approval cut-sheets or a phometrics plan for the
lighting.
During Construction
10. Construction hours shall be limited from 8 a.m. to 5 p.m. Monday through Friday to
minimize potential disturbance of adjacent residents.
11. The applicant and their contractors shall be responsible for preventing spills of any
demolition debris or construction materials on Town streets. If any spills of debris occur,
then the applicant will be held responsible for the immediate cleanup of the spill and
repair of any damage that may have been done to the street. The correction of the
problem shall be made to the satisfaction of the Town Engineer.
At All Times
12. The applicant shall keep and maintain the existing landscaping at the back of the
property and along the north and south property lines, excluding the two acacia bushes
slated for removal, in order to maintain the current levels of screening and privacy for
the surrounding properties.
13. The property owner shall be responsible for maintaining all landscaping, including the
existing trees along the rear property line adjacent to Canyon Road.
Page 3 of 4 – Draft Action Memorandum for 1825 St. Andrews Drive (File No. DRB-13-12)
14. Any new exterior lighting is subject to staff review and approval. Outdoor lighting shall
be related to the design of the structure. Outdoor light fixtures shall be designed and
mounted so that the source of light has minimal impact off site. Outdoor lighting shall be
directed inward toward the property and may require additional screening to avoid
spillage onto adjacent residential properties.
15. This permit and each condition contained herein shall be binding upon applicant and any
transferor, or successor in interest.
16. If construction is not commenced within one year from the date of final action, the permit
becomes null and void. However, this discretionary action may be renewed by the
Planning Director for a maximum period of one (1) year provided the applicant places
such a request in writing to the Planning Director showing good cause prior to the
expiration 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 Board
should be directed to the Planning Department at (925) 888-7040.
Page 4 of 4 – Draft Action Memorandum for 1825 St. Andrews Drive (File No. DRB-13-12)
ATTACHMENT B
LETTERS FROM APPLICANT,
MORAGA COUNTRY CLUB AND
NEIGHBORS
ATTACHMENT C
GEOTECHNICAL REPORT DATED
JULY 2012
Peters & Ross
Geotechnical & Geoenvironmental Consultants
Geotechnical Investigation
Buck Residence Deck
1825 St. Andrews Drive, Moraga, California
Project No. 12219.001
July, 2012
P e t e r s & R o ss
Geotechnical & Geoenvironmental
Consultants
July 20, 2012
Project No. 12219.001
Mrs. Nathalie Buck
1825 St. Andrews Drive
Moraga, CA 94556
Geotechnical Investigation – Buck Residence Deck
Dear Mrs. Buck:
In accordance with your authorization, Peters & Ross has completed a geotechnical investigation
for the above referenced project. The accompanying report presents the results of our field
investigation, laboratory testing, and engineering analyses. Based on this information, it is Peters
& Ross’ opinion that the site is suitable for the proposed improvements.
Peters & Ross should also be retained:



to review geotechnical aspects of project plans and specifications,
to provide supplemental recommendations should significant changes in the planned
improvements be made, and
to provide geotechnical engineering observation and testing services during construction, in
order to check that the recommendations presented in this report are properly implemented
into the completed project.
We appreciate the opportunity to provide geotechnical engineering services to you. If you have
any questions, please call.
Sincerely,
Peter K. Mundy, P.E., G.E.
Geotechnical Engineer 2217
114 Hopeco Road, Pleasant Hill, CA 94523 Phone: (925) 942-3629 Fax: (925) 665-1700 Email: PetersRoss@aol.com
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 1 of 10
INTRODUCTION
This report presents the results of a geotechnical investigation performed by Peters &
Ross for a deck to be added to the back of the existing residence located at 1825 St.
Andrews Drive in Moraga, California. The location of the site is shown on the Site
Vicinity Map (Figure 1). The ground surface topography near the site is shown on Figure
2.
Project Description
The project site is a developed trapezoidal downslope lot located on the northeast side of
St. Andrews Drive. Based on a topographic map provided by the owner, the site slopes
to the northeast at an inclination of 3:1 (horizontal to vertical) and steepens in the lower
northeast quadrant to 2.5:1. A two-story wood-frame house occupies the southeastern
portion of the lot. Mrs. Buck also provided a Landscape plan which indicates that the
deck area will include a concrete patio supported by a concrete retaining wall, a spa, fire
pit, and wood decking.
Scope of Services
Peters & Ross scope of services for the project was presented in our proposal dated July
8, 2012, and authorized by the owner. Our services on the project were limited to the
following:
•
•
•
•
Drilling two exploratory test borings
Logging and obtaining samples of the materials encountered
Performing laboratory tests on selected samples
Performing engineering analyses sufficient to develop conclusions and
recommendations regarding:
1.
2.
3.
4.
5.
6.
7.
8.
9.
•
Site geology and seismicity
Soil and groundwater conditions
Site preparation, excavation, and grading
The most appropriate foundation type for the planned improvements
Geotechnical design parameters for the recommended foundation type
Lateral earth pressures for retaining wall design
Subgrade preparation for concrete slabs-on-grade
Geotechnical aspects of site drainage
Construction considerations
Preparing this report.
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 2 of 10
FIELD EXPLORATION AND LABORATORY TESTING
Peters & Ross explored subsurface conditions by drilling two test borings to a maximum
depth of 12 feet using hand auger equipment. The locations of the borings are shown on
the Site Plan (Figure 3). Samples of materials encountered in the borings were obtained
at frequent depth intervals, for field classification and laboratory testing. A description of
the drilling and sampling equipment used and other details of our subsurface exploration,
as well as logs of the test borings, are presented in Appendix A. A brief description of
the laboratory tests are included in Appendix B and the results of the laboratory tests are
shown on the boring logs presented in Appendix A.
SITE CONDITIONS
Site Geology and Seismicity
The site is located within the California Coast Ranges geomorphic province, which is
dominated by northwest-trending faults and folds. Geologic mapping by Radbruch (1975)
indicates that the site is underlain by recent alluvium and colluvium. Landslide mapping
by Nilsen (1975), shows that the site is in a very large landslide. The Dibblee (2005)
map shows the site to be at the toe of a large landslide, which occurs within the Orinda
Formation. During our site visit however, Peters & Ross did not observe any obvious
signs of major slope instability on the subject property.
The site is about 5.5 kilometers northeast of the Hayward Fault and about 7.5 kilometers
southwest of the Calaveras Fault. These and other regional faults are capable of
generating large magnitude earthquakes that could cause strong groundshaking at the site.
The site is not within an Alquist-Priolo Earthquake Fault Zone delineated by the State
Geologist, and therefore the risk of fault offset across the site is remote. However, it is
reasonable to assume that the home will be subjected to at least one moderate to severe
earthquake.
Subsurface Conditions
Generally, from 5 to 7 feet of lean clay fill materials, with sand and rock fragments, were
encountered in exploratory test borings. Atterberg limits tests indicate that the lean clay
materials at a depth of 2.5 feet in Boring 1 have a liquid limit of 46.3 percent and a
plasticity index of 24.3 percent, with 73.6 percent passing the #200 sieve. These results
indicate that the clay materials have a moderate expansion potential (expansive soils
shrink and swell in response to changes in moisture). The lean clay fill materials are
underlain by sandstone, siltstone, and claystone of the Orinda Formation which extended
to the depths explored.
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 3 of 10
Groundwater
Groundwater was not encountered in any of the exploratory test borings. It should be
noted that fluctuations in the groundwater level may occur due to variations in rainfall,
temperature and other factors not evident at the time the measurements were made.
CONCLUSIONS AND RECOMMENDATIONS
Based on the field investigation, laboratory testing, and engineering analyses, it is our
opinion that the site is suitable for the proposed construction from a geotechnical
standpoint. The primary geotechnical concerns that need to be addressed are the presence
of fill and expansive soils. However, all of the conclusions and recommendations
presented in this report should be incorporated in the design and construction of the
project to avoid possible soil and foundation problems.
It should be noted that the primary landslide map by Nilsen (1975) indicates that a large
landslide underlies the site and several subdivisions to the northwest and southeast. The
characterization of this large landslide is outside the scope of work for the deck. The
large slide may reactivate during future ground shaking, or unusually severe storms. This
movement may result in significant damage to the structures supported within the slide
mass. This condition exists over a large area making the application of a single
mitigation measure for the proposed deck not practical or feasible. In lieu of complete
protection, the owner must accept such risks.
1.
Presence of Existing Fill
Fill materials were placed on the lot during mass grading for Subdivision 5118. Based on
the subsurface data, it appears that an acceptable compactive effort was made in the fill.
The materials that comprise the fill are moderately expansive and will tend to creep.
Therefore, we recommend that the deck and associated retaining walls be supported on
drilled pier foundations. Specific recommendations for foundation design are presented
below.
2.
Expansive Soil Considerations
The clayey soils that blanket the site have a moderate expansion potential. When
expansive soils are subjected to increases in moisture content, such as during the rainy
season, they swell if unconfined. If concrete slabs or shallow foundations confine the
expansive soils, they can exert significant pressures when subjected to moisture
increases. These pressures can cause slabs and shallow foundations to heave and crack.
When the soils dry, they shrink, causing slabs and shallow foundations to settle.
Expansive clays are common in the San Francisco Bay Area. Over the past several
decades, expansive soil movements have caused extensive damage to residential and
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 4 of 10
commercial structures, slabs, and pavements throughout the Bay Area. The local climate,
with its pronounced wet and dry seasons, is a main cause of significant seasonal moisture
changes that cause the expansive soils to shrink and swell.
There are a number of methods available for reducing the adverse effects of expansive
soils. These include removing the expansive soils, replacing expansive soils with nonexpansive engineered fill, deepening foundations to develop support below the zone of
significant seasonal moisture change (about 24 to 32 inches), designing foundation/slab
systems to resist uplift pressures generated by swelling soils, and/or providing drainage
and landscaping to minimize seasonal moisture fluctuations in the near-surface soils.
Drainage and landscaping improvements adjacent to slabs and foundations should be
designed to promote efficient runoff during the rainy season, and provide occasional
sprinkling during the summer.
3.
Seismic Concerns
In accordance with Section 1613 of the 2010 CBC, Peters & Ross classifies the site as a
C Site Class with a latitude of 37.8321 degrees and a longitude of -122.1383 degrees.
The CBC parameters presented in the following table should be used for seismic design.
SITE CLASS B - PERIOD (sec)
SPECTRAL RESPONSE Ss, Sl
SITE COEFFICIENT Fa, Fv (SITE CLASS C)
MAXIMUM SPECTRAL RESPONSE Sms, Sml
DESIGN SPECTRAL RESPONSE SDs, SDl
0.2
1.500
1.0
1.500
1.000
1.0
0.600
1.3
0.780
0.520
The site is not within an Alquist-Priolo Earthquake Fault Zone, and therefore the risk of
fault rupture at the site is remote. No loose, clean sands were observed in the exploratory
test borings. Therefore, the risk of significant foundation settlement due to liquefaction or
densification during a large magnitude earthquake is low.
4.
Site Preparation, Excavation, and Grading
4.1
Clearing and Site Preparation
Any foundations, flatwork or structures identified for demolition on the construction
plans should be demolished and removed from the site. Holes resulting from the removal
of any obstructions that extend below the proposed finished grade should be cleared and
backfilled with suitable material compacted to the requirements given below under
Compaction. We recommend that the excavations to remove deleterious material be
carried out under the observation of the soil engineer, so that these excavations will be
properly backfilled.
After clearing, the portions of the site containing trees, surface vegetation or organic
laden topsoil should be stripped to an appropriate depth to remove these materials. The
amount of actual stripping should be determined in the field by the soil engineer at the
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 5 of 10
time of construction. The cleared and stripped layer should be removed from the site or
stockpiled for later use in landscaping, if desired.
4.2
Subgrade Preparation
After the site has been properly cleared and stripped and any necessary excavations
made, the exposed soils which will receive structural fill should be scarified to a depth of
12 inches, moisture conditioned to slightly above optimum water content, and compacted
to the requirements for structural fill.
4.3
Material for Fill
All on-site soils below the stripped layer having an organic content of less than 3 percent
by volume are suitable for use as fill. However, we should note that because of the high
plasticity of these clayey soils, they would probably be difficult to moisture condition and
compact, particularly if they have excessive moisture from winter rains. Fill placed at the
site, should not contain rocks or lumps larger than 6 inches in greatest dimension with not
more than 15% larger than 2.5 inches. Import fill should be predominantly granular with
a plasticity index of 12 or less.
4.4
Compaction
All structural fill less than 5 feet thick should be compacted to at least 90% relative
compaction as determined by ASTM Test Designation D 1557-78, except for the upper 6
inches of subgrade soils under pavements which should be compacted to at least 95%
relative compaction. Structural fill or wall backfill greater than 5 feet high should be
compacted to at least 95% relative compaction. Fill material should be spread and
compacted in lifts not exceeding 8 inches in uncompacted thickness. We should note that
if construction proceeds during or immediately after the wet winter months, it may
require time to dry the on-site soils to be used as fill, since their moisture content will
probably be appreciably above optimum.
4.5
Drainage
Positive surface gradients of at least 5% for a minimum distance of 5 feet should be
provided adjacent to the buildings so as to direct surface water away from foundations
and slabs toward suitable discharge facilities. Ponding of surface water should not be
allowed adjacent to the structure or on pavements. We also recommend that rainwater
collected on the roof of the building be transported through gutters, downspouts and
closed pipes to a suitable discharge facility as designed by the project civil engineer and
landscape architect.
Peters & Ross
Buck Residence Deck
Project No. 12219.001
5.
July 20, 2012
Page 6 of 10
Foundations
We recommend that the deck be supported with a drilled, cast-in-place, straight-shaft
piers and grade beam foundation system. The piers should be designed to develop their
load carrying capacity through friction between the sides of the piers and the surrounding
subsurface materials. Friction piers should have a minimum diameter of 12 inches, and
there should be a minimum center-to-center spacing of at least 3 pier diameters between
adjacent piers.
The piers should generally extend to a depth adequate to provide at least 10 feet of
embedment into bedrock. Since bedrock was encountered at depths of 5 to 7 feet in the
exploratory borings, the piers should generally extend to a minimum depth of about 15 to
17 feet below the existing ground surface. Piers should be designed to resist an uplift
pressure of 750 pounds per square foot acting on the bottoms of the grade beams. The
dead weight of the structure can be used to resist uplift, in addition to the skin friction on
the piers presented below. Peters & Ross should observe the drilling of the piers to
ensure that minimum embedment is achieved in the field.
To determine whether these depths are adequate to carry the structural loads of the
residence, the following allowable (factored) skin friction values should be used. Starting
at a depth of 3 feet use an allowable (factored) friction value of 500 pounds per square
foot for dead plus live loads (factor of safety » 2) and 650 pounds per square foot for all
loads, including wind or seismic (factor of safety » 1.5). In bedrock use an allowable
(factored) friction value of 800 pounds per square foot for dead plus live loads (factor of
safety » 2) and 1100 pounds per square foot for all loads, including wind or seismic
(factor of safety » 1.5). Up to two-thirds of the allowable dead plus live load capacity
can be used to resist uplift forces.
To minimize damage resulting from the potential "downward creep" type movements, we
recommend the new piers also be designed to resist an ultimate, uniform lateral pressure
of 300 pounds per square foot acting against the projected diameter of the pier for the
upper 3 feet. Lateral loads on the piers may be resisted by passive pressures acting
against the sides of the piers. We recommend an allowable passive pressure equal to an
equivalent fluid weighing 400 pounds per square foot per foot of depth to a maximum
value of 4000 pounds per square foot (factor of safety » 2). This value can be assumed to
be acting against 1.5 times the diameter of the individual pier shafts starting at a depth of
2 feet.
The bottom of pier excavations should be reasonably free of loose cuttings and soil fall-in
prior to installing reinforcing steel and placing concrete. It is our recommendation that
the contractor be made aware of the subsurface conditions outlined in this report and that
he obtain construction equipment appropriately sized to perform the recommended work.
In particular, the piers must extend a minimum of 15 to 17 feet below the existing ground
surface. Equipment capable of performing this recommendation should be employed.
Any accumulated water in pier excavations should be removed prior to placing
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 7 of 10
reinforcing steel and concrete, or the concrete should be tremied from the bottom of the
hole. Care should be taken during concrete placement to avoid "mushrooming" at the top
of the pier because distress in the building may result from expansive soil uplift forces on
the "mushroom caps".
6.
Retaining Walls
Retaining walls should be designed using soil pressures corresponding to an equivalent
fluid weight of 45 pcf for level backfill, 55 pcf for backfill sloped at 3:1, and 70 pcf for
backfill sloped at 2:1. These fluid weights should be increased by 20 pcf for restrained
walls. For surcharge loads, increase design pressures behind the wall by an additional
uniform pressure equivalent to one-half (for restrained condition) or one-third (for
unrestrained condition) of the maximum anticipated surcharge load applied to the surface
behind the wall. Retaining wall foundations should be designed in accordance with the
recommendations of the previous subsection. To resist overturning use an allowable
bearing pressure not exceeding 2000 pounds per square foot (psf) for dead loads, 3000
psf for dead plus live loads, and 4000 psf for total loads, including wind and seismic.
The above pressures assume that sufficient drainage will be provided behind the walls to
prevent the build-up of hydrostatic pressures from surface and subsurface water
infiltration. Adequate drainage may be provided by a subdrain system consisting of a 4
inch, rigid, perforated pipe, bedded in ¾ inch, clean, open graded rock. The
recommended location of the subdrain pipe is behind the heel of the footing. Although
we have observed that the subdrain pipe is often placed on top of the heel of the footing,
it has been our experience that this may lead to moisture seeping through the wall
resulting in dampness and staining on the opposite wall face despite the application of
waterproofing. However, if such seepage or dampness is acceptable (in front of
landscape walls, for example), then the subdrain pipe may be placed on top of the heel of
the footing. To prevent ponding of water on top of the heel of the footing, we
recommend that the top of the heel be sloped to drain away from the wall with a
minimum positive gradient of 5 percent. The perforated drainpipe should slope to drain
with a minimum positive gradient of 2 percent. The entire rock/pipe unit should be
wrapped in an approved, non woven, polyester geotextile such as Mirafi 140N or 140NL,
or a 4-ounce equivalent.
The rock and fabric placed behind the wall should be at least one foot in width and
should extend to within one foot of finished grade. The upper one foot of backfill (6
inches for walls less than 5 feet in height) should consist of on site, compacted, relatively
impervious soils (an impermeable plug). Alternatively, the wrapped rock could be
replaced with a MiraDrain system with appropriately selected waterproofing. The
subdrain pipe should be connected to a system of closed pipes that lead to suitable
discharge facilities.
We should note that flexible, perforated pipe (flexline), 2000 Pound Crush, Leachfield,
and ASTM F810 pipe are not acceptable for use in the subdrain because of the likelihood
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 8 of 10
of damage to the pipe during installation and the difficulty of future cleaning with
mechanical equipment without damaging the pipe. We recommend the use of Schedule
40 PVC, SDR 35 PVC or ABS, Contech A-2000 PVC drainpipe, or equivalent for the
drain system. The subdrain pipe should be connected to a system of closed pipes (non
perforated) that lead to suitable discharge facilities. At the location where the perforated
subdrain pipe connects with the solid discharge drainpipe, drainrock backfill should be
discontinued. A "clay plug" should be constructed out of relatively impervious soils to
direct collected water into the perforated pipe and minimize the potential for water
collecting around the solid drainpipe and saturating the adjacent soils. We recommend
that waterproofing be applied to any proposed retaining walls where applicable. The
specification of the type of waterproofing and the observation of its installation should be
performed by the architect and/or structural engineer.
In addition, the "high" end and all 90 degree bends of the subdrain pipe should be
connected to a riser which extends to the surface and acts as a cleanout. The number of
cleanouts can be reduced by installing "sweep" 90-degree bends or pairs of 45-degree
bends in succession instead of using "tight" 90-degree bends. "Sweep" 90-degree bends
are similar to those used in sanitary sewer pipe connections.
7.
Slab-on-Grade
We recommend that any slabs-on-grade be supported on a minimum of 9 inches of
imported, compacted, non-expansive fill. The subgrade should be recompacted to at least
90 percent relative compaction at a moisture content of 3 percent above optimum. The
subgrade should be kept moist until the slab is poured. In any slab area where minor
floor wetness would be undesirable, at least 4 inches of ¾ inch gravel should be placed
over the prepared subgrade, to provide a capillary moisture break. A 10-mil thick vapor
barrier blanketed with 2 inches of clean sand should be placed over the gravel. This can
be used in lieu of the upper 6 inches of the non-expansive fill.
The slab should have a minimum thickness of 4-inches and should be reinforced with
steel reinforcing bars rather than welded wire mesh. At a minimum, slab reinforcement
should consist of No. 4 bars on 18-inch centers in both directions, placed at the center of
the slab thickness. Spacers should be placed beneath the mesh of reinforcing bars, to
maintain their positioning near the center of the slab during the concrete pour. The
garage slab should be doweled into the perimeter foundation system. Exterior slabs
should be structurally independent from the perimeter grade beams and be free floating.
Score joints should be provided at a maximum spacing of 10 feet in both directions. The
slabs should be appropriately reinforced according to structural requirements;
concentrated loads may require additional reinforcing.
8.
Plan Review and Services during Construction
Peters & Ross should be retained to review project plans, to check that the geotechnical
engineering recommendations contained in this letter are properly incorporated.
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 9 of 10
Peters & Ross should also be retained to provide geotechnical observation services on an
as-needed basis during construction, to check that geotechnical aspects of the work are
completed in accordance with the plans. These services should include observing any
excavations, pier drilling, and providing consultation to the contractor regarding any
geotechnical concerns that arise during construction. Peters & Ross cannot accept
responsibility for geotechnical aspects of construction that are not observed by its staff.
Peters & Ross will make every reasonable effort to accommodate the contractor’s work
schedule during construction, so that necessary observations can be performed in a timely
manner to avoid construction delays. However, since our field services are often required
on several projects concurrently, we request that 48 hours advance notice be given for
site visits, in order to minimize scheduling conflicts.
LIMITATIONS
Peters & Ross services consist of professional opinions and recommendations that are
made in accordance with generally accepted geotechnical engineering principles and
practices. The opinions and recommendations presented in this report are based on a site
reconnaissance, review of published and unpublished geologic maps, two exploratory test
borings, laboratory testing, and engineering analyses. This warranty is in lieu of all other
warranties either expressed or implied.
Subsurface conditions commonly vary significantly from those encountered at the test
boring locations. Unanticipated, adverse soil conditions encountered during construction
often require additional expenditures to achieve a properly constructed project. It is
advised that a contingency fund be established to accommodate possible consulting and
construction cost increases due to unanticipated conditions.
Peters & Ross
Buck Residence Deck
Project No. 12219.001
July 20, 2012
Page 10 of 10
LIST OF FIGURES
Figure 1
Figure 2
Figure 3
Site Vicinity Map
Site Topography
Site Plan
APPENDICES
Appendix A
Appendix B
Field Investigation
Laboratory Testing
DISTRIBUTION
5 copies:
Mrs. Nathalie Buck
1825 St. Andrews Drive
Moraga, CA 94556
Peters & Ross
PROJECT No.
Geotechnical and
Geoenvironmental Consultants
12219.001
DATE
July 2012
Buck Residence Deck
1825 St. Andrews Drive
Moraga, California
Figure 2 - Site Topography
Peters & Ross
Geotechnical and
Geoenvironmental Consultants
PROJECT No.
12219.001
DATE
July 2012
B-1
B-2
Figure 3 - Site Plan
Peters & Ross
Geotechnical and
Geoenvironmental Consultants
PROJECT No.
12219.001
DATE
July 2012
Buck Residence Deck
Project No. 12219.001
APPENDIX A – FIELD INVESTIGATION
Peters & Ross explored subsurface conditions at the site by drilling two test borings to a
maximum depth of 12 feet. The location of the borings are shown on the Site Plan.
The borings were drilled using a 3.5 inch hand auger and our field engineer continuously
logged the materials encountered. The boring logs that shows the materials encountered
is included in this Appendix. Soils are classified in accordance with the Unified Soil
Classification System.
The boring logs indicates Peters & Ross interpretation of subsurface conditions
encountered at the locations and times the borings were drilled, and may not be
representative of subsurface conditions at other locations and times. Stratification lines
represent the approximate boundaries between soil and rock types. The transitions
between soil and rock layers are often gradual.
Samples of the materials encountered were obtained at frequent depth intervals, for visual
classification and laboratory testing. Samples were obtained using a Modified California
sampler (outer diameter of 3.0 inches, inner diameter of 2.5 inches) with thin-wall brass
sampler liners, and a Standard Penetration Test sampler (outer diameter of 2.0 inches,
inner diameter of 1.375 inches). The samplers were driven using a fence post hammer
weighing 20 pounds, lifted and dropped for 20 inches.
Page A1
BOREHOLE B-1
Peters & Ross
114 Hopeco Road
Pleasant Hill, CA 94523
Phone: 925-942-3629
Page: 1 of 1
Project Name: Buck Residence Deck
Project No.: 12219.001
Location: 1825 St. Andrews Drive, Moraga, CA
Client: Mrs. Nathalie Buck
Drilling Method: Hand Auger
Date Drilled: 7/16/2012
Elevation: 586.5
Water Level: Not encountered
MOISTURE %
DRY DENSITY
PCF
MC
(9)
19.7
100.5
MC
(15)
17.2
109.9
MC
(11)
13.5
110.4
SS
(48
6")
7.7
UNCONFINED
STRENGTH PSF
BLOWS/FT.
Ground Surface
Lean CLAY with Sand (FILL)
SAMPLE TYPE
SYMBOL
DESCRIPTION
DEPTH FT.
Remarks: Sampler driven with 20 lb hammer lifted and dropped 20 inches
REMARKS
0
mottled olive brown with black, wet to moist, roots,
angular rock fragments, stiff
LL=46.3%, PI=24.3
-200 = 73.6%
(2.0)
5
SANDSTONE
olive yellow, fine grained, moist, moderate
hardness
End of Borehole = 9 feet
10
NOTES:
1. Penetration resistance values in parenthesis represent standard N values using an energy conversion of 0.095 and a
Modified California Sampler conversion of 0.67.
2. Stratification lines represent the approximate boundaries between material types, and the transitions may be gradual.
3. Groundwater was not encountered during drilling and the borehole was backfilled with cuttings immediately after
drilling.
4. Unconfined Strength values in parenthesis are in tons per square foot obtained from a pocket penetrometer.
15
BOREHOLE B-2
Peters & Ross
114 Hopeco Road
Pleasant Hill, CA 94523
Phone: 925-942-3629
Page: 1 of 1
Project Name: Buck Residence Deck
Project No.: 12219.001
Location: 1825 St. Andrews Drive, Moraga, CA
Client: Mrs. Nathalie Buck
Drilling Method: Hand Auger
Date Drilled: 7/16/2012
Elevation: 580.0
Water Level: Not encountered
MOISTURE %
DRY DENSITY
PCF
MC
(17)
10.2
109.0
MC
(13
6")
11.8
127.8
SS
(15)
12.0
SS
(16
6")
13.6
SS
(29
6")
10.4
UNCONFINED
STRENGTH PSF
BLOWS/FT.
Ground Surface
Lean CLAY with Sand (FILL)
SAMPLE TYPE
SYMBOL
DESCRIPTION
DEPTH FT.
Remarks: Sampler driven with 20 lb hammer lifted and dropped 20 inches
REMARKS
0
mottled olive brown with black, wet to moist, roots,
angular rock fragments, stiff
SILTSTONE
5
olive brown, iron staining on joints, soft hardness,
moist
CLAYSTONE
dark greenish gray, iron staining on joints, soft
hardness, severe weathering
10
End of Borehole = 12 feet
NOTES:
1. Penetration resistance values in parenthesis represent standard N values using an energy conversion of 0.095 and a
Modified California Sampler conversion of 0.67.
2. Stratification lines represent the approximate boundaries between material types, and the transitions may be gradual.
3. Groundwater was not encountered during drilling and the borehole was backfilled with cuttings immediately after
15
drilling.
4. Unconfined Strength values in parenthesis are in tons per square foot obtained from a pocket penetrometer.
Buck Residence Deck
Project No. 12219.001
APPENDIX B - LABORATORY TESTING
Laboratory tests were performed on representative samples of the materials encountered
in the test boring, to achieve a quantitative and qualitative evaluation of the physical and
mechanical properties of the materials that underlie the site. The tests included moisture
content/dry density determinations, #200 washed sieve tests, and Atterberg limits tests.
The test results are presented on the boring log in Appendix A. Test reports provided by
the testing laboratory are included in this Appendix. Brief descriptions of the tests
performed follow.
Moisture Content/Dry Density (ASTM 2937): Performed on undisturbed samples to
determine the moisture content (the ratio of the weight of water to the weight of solids in
the field sample, expressed as a percentage) and dry density (the ratio of the weight of
solids in the field sample to its volume, expressed in pounds per cubic foot).
#200 Washed Sieve Test (ASTM D-1140): Performed on undisturbed or disturbed
samples to determine the fine-grained (silt and clay) fraction of the materials. The finegrained fraction is used to classify the soils according to the Unified Soils Classification
System.
Atterberg Limits Test (ASTM D-4318): Performed on undisturbed or disturbed samples
to determine the liquid limit (LL) and plastic limit (PL) of the samples. These limits are
used to classify fine-grained soils and to evaluate the plasticity index (PI), the moisture
content range over which the material exhibits plasticity. Atterberg limits correlations
also provide an indication of the compressibility and expansion potential of the sample.
Page B1
Moisture-Density-Porosity Report
Peters & Ross (ASTM D 2937)
Job No:
Client:
Project:
Boring:
Sample:
Depth, ft:
Visual
Description:
Actual
12219.001
Peter & Ross
Buck Residence Deck
B-1
B-1
07/18/12
PKM
Date:
By:
B-1
B-1
2.5
5.0
7.5
9
Sandy
Sandy
Sandstone Sandstone
Lean
Lean
CLAY FILL CLAY FILL
Gs
Assumed Gs
Total Vol cc
Vol Solids,cc
Vol Voids,cc
Moisture, %
Wet Unit wt, pcf
Dry Unit wt, pcf
Saturation, %
Porosity, %
Void Ratio
Series
2.70
430.2
256.2
173.9
19.7
120.3
100.5
78.5
40.4
0.68
1
2.70
456.3
297.2
159.2
17.2
128.8
109.9
86.8
34.9
0.54
2
2.70
441.9
289.3
152.6
13.5
125.3
110.4
69.0
34.5
0.53
3
2.70
2.70
2.70
2.70
2.70
5
6
7
8
7.7
4
Note: If an assumed specific gravity (Gs) was used then the saturation, porosities, and void ratio should be considered approximate.
Moisture-Density
Zero Air-voids Curves, Specific Gravity
140
2.6
130
The Zero Air-Voids curves
represent the dry density at
100% saturation for each
value of specific gravity
2.7
2.8
Series 1
Series 2
Density, pcf
120
Series 3
Series 4
110
Series 5
100
Series 6
90
Series 7
80
Series 8
70
0.0
5.0
10.0
15.0
20.0
Moisture Content, %
25.0
30.0
35.0
40.0
Moisture-Density-Porosity Report
Peters & Ross (ASTM D 2937)
Job No:
Client:
Project:
Boring:
Sample:
Depth, ft:
Visual
Description:
Actual
12219.001
Peter & Ross
Buck Residence Deck
B-2
B-2
2.5
4.0
Sandy
Sandy
Lean
Lean
CLAY FILL CLAY FILL
07/18/12
PKM
Date:
By:
B-2
B-2
B-2
7.5
Siltstone
9.5
Claystone
12
Claystone
2.70
2.70
2.70
12.0
13.6
10.4
3
4
5
Gs
Assumed Gs
Total Vol cc
Vol Solids,cc
Vol Voids,cc
Moisture, %
Wet Unit wt, pcf
Dry Unit wt, pcf
Saturation, %
Porosity, %
Void Ratio
Series
2.70
430.2
278.1
152.1
10.2
120.1
109.0
50.2
35.4
0.55
1
2.70
252.9
191.5
61.3
11.8
142.8
127.8
99.4
24.3
0.32
2
2.70
2.70
2.70
6
7
8
Note: If an assumed specific gravity (Gs) was used then the saturation, porosities, and void ratio should be considered approximate.
Moisture-Density
Zero Air-voids Curves, Specific Gravity
140
2.6
130
The Zero Air-Voids curves
represent the dry density at
100% saturation for each
value of specific gravity
2.7
2.8
Series 1
Series 2
Density, pcf
120
Series 3
Series 4
110
Series 5
100
Series 6
90
Series 7
80
Series 8
70
0.0
5.0
10.0
15.0
20.0
Moisture Content, %
25.0
30.0
35.0
40.0
LIQUID AND PLASTIC LIMITS TEST REPORT
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-Source:
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LIQUID AND PLASTIC LIMITS TEST REPORT
PETERS & ROSS
Figure
R-:1
ATTACHMENT D
GEOTECHNICAL PEER REVIEW
LETTER DATED OCTOBER 17, 2012
1870 Olympic Blvd. Suite 100 Walnut Creek California 94596 Tel: 925.935.9771 Fax: 925.935.9773 www.caleng.com 17 October 2012
Shawna Brekke-Read
Town of Moraga
329 Rheem Boulevard
Moraga, California 94556
RE:
Review of Geotechnical Report and Preliminary Plans
Proposed Backyard Improvements
1825 St. Andrews Drive
Moraga, California
Dear Ms. Brekke-Read:
At your request, we have completed our geologic and geotechnical review of the geotechnical
report and preliminary plans for the proposed backyard improvements to the property located at
1825 St. Andrews Drive in Moraga, California. The following documents were reviewed as part
of this project:
1.
Geotechnical report by Peters & Ross titled, Geotechnical Investigation Buck Residence
Deck, 1825 St. Andrews Drive, Moraga, California dated July 2012.
2.
Plans by Miller Landscape Architecture titled, Buck Residence, Sheets L.01- L.06 dated
8/23/12.
Our review of the geotechnical report and the plans for the proposed project has included the
examination of the above referenced materials for pertinent information regarding the technical
feasibility of the project. We have also reviewed published geologic reports and maps of the
area in our files and made reconnaissance level observations of the project site.
PROPOSED PROJECT
The proposed project will consist of the construction of a new multi-level deck and patio
structure along the rear of the existing residence. The proposed improvements will include an
attached second story deck, stairs leading down to a new patio area, and a lower level deck. The
new patio will contain a hot tub and a fire pit. Stairs from the patio area will provide access to
the backyard slope below.
120690.001
Cal Engineering & Geology, Inc.
17 October 2012
Proposed Backyard Improvements - 1825 St. Andrews Drive Moraga, California
Page 2
REVIEW OF GEOTECHNICAL REPORT AND PRELIMINARY PLANS
Our review of the provide geotechnical report and preliminary plan set revealed that they are
generally complete with respect to the assessment and mitigation of the known geologic and
geotechnical constraints of the site. However, we have a few items (comments) for which we are
requesting additional information and/or clarification. Our comments are provided below.
Comment 1
It is unclear if the geotechnical engineer is recommending that the proposed retaining walls be
supported on drilled piers or spread footings. On page 3 of their report, they recommend that the
deck and retaining wall be supported on drilled piers. Elsewhere in the report geotechnical
parameters are provided for the drilled piers. However, on page 7 of the report geotechnical
design parameters were provided for retaining walls supported on spread footings. It is
recommended that the geotechnical engineer provided clarification regarding his
recommendations for supporting the required retaining walls.
Comment 2
The proposed new second story deck will be attached to the rear of the existing residence. The
new deck will be supported by a system of deep, drilled, cast-in-place concrete piers. As the
deck and house are supported by separate foundations, there may be some potential for
differential movement between the two structures. It is recommended that the geotechnical
engineer and engineer designing the deck evaluate this potential issue and provide an opinion
regarding the need for special design considerations to mitigate this potential condition.
Supplemental recommendations should be provided in writing for our review and comment.
Comment 3
It is recommended that the geotechnical engineer review the final plans for the deck and
retaining walls for conformance with the recommendations of his report. This review should be
documented in writing. It is also recommended that the final plans be provided for our review
and comment.
CLOSURE
This review has been performed by request of the Town of Moraga. Our role has been to
provide technical advice to assist the Town in its discretionary permit decisions, and we are
afforded the same protection under state law. Our services have been limited to the review of the
documents listed above, and a visual review of the property. We have no control over the future
construction on this property and make no representations regarding its future conditions.
120690.001
Cal Engineering & Geology, Inc.
ATTACHMENT E
PROJECT PLANS
ATTACHMENT F
SITE AND NEIGHBORHOOD
PHOTOS