2006-110 SG Nis) Af
GEOPACIFICA INC.
REVIEW MEMORANDUM
March 24, 2006/updated April 7, 2006
To: Stephanie Kellar
Engineering Department, City of Encinitas
505 South Vulcan Avenue, Encinitas, California 92024-3633
From: Jim Knowlton, RCE/CEG, Consultant
Subject: Third Party Review of Proposed Pool/Wall project
Averett Property, 2529 Newport Avenue
APN 261-142-23 - Encinitas, California
Grading Plan 110-SG
I have reviewed the following new document:
1. Slope Stability Analysis, Averett Swimming Pool Project, 2529 Newport Avenue,
Cardiff by the Sea, California; by Terra Pacific Consultants, Inc., dated April 3,
2006, no 25137.
I had previously reviewed the following documents:
2. Project Plans — Averett Property — 2529 Newport Avenue; by Torrey Pines
Engineering & Construction Inc., 5 sheets, revised date 3/16/06, signed.
3. Retaining Wall Design — Averett Residence; by Torrey Pines Engineering &
Construction Inc., dated 3/17/06, 8 pages with Soil Calculations — Averett
Residence; by Torrey Pines Engineering & Construction Inc., 1 page, dated
3/16/06.
4. Geotechnical Investigation, Averett Swimming Pool, 2529 Newport Avenue,
Cardiff by the Sea, California; by Terra Pacific Consultants, Inc., dated
September 8, 2005, no. 25137.
My review has been performed to see if the submitted documents and project plans
provide adequate soil/geologic data/information to meet the standards of practice within,
and the requirements of, the City of Encinitas.
Even though our review is addressed to City staff, the following sections are specifically
directed to and are to be addressed by the consultants for the project.
Based on this review, the project documents do not provide adequate data and are not
accepted or approved.
The following items still require clarification, professional statements and/or re-
submittal.
Page 2
GP 110-SG
April 7, 2006
1. The project includes a swimming pool and keystone retaining wall. These
projects require separate plans and submittals. Please provide revisions with
separate plans and separate submittals as required.
2. The geotechnical consultant has not addressed the keystone wall. Please provide
geotechnical analysis, design parameters, and geotechnical foundation and
earthwork recommendations for the wall.
3. The consultant needs to assess the potential of impact of the existing wall
foundation, proposed swimming pool, and proposed keystone wall to each other
based on the drawn sections (document 1).
END
TerraPacific
,- C O N S U L T A N T S I N C `
Mr. David Peterson April 1J � April 25, 2006
Torrey Pines Engineering & Construction File No. 25137
2091 Las Palmas Drive, Suite F
Cardiff by the Sea, California 92007
Subject: Supplemental Slope Stability Analyses
Averett Swimming Pool Project
2529 Newport Avenue
Cardiff by the Sea, California
Reference: "Slope Stability Analyses, Averett Swimming Pool Project, Averett
Residence, 2529 Newport Avenue, Cardiff by the Sea, California," prepared
by TerraPacific Consultants, Inc., dated April 3, 2006.
"Geotechnical Investigation, Proposed Swimming Pool, Averett Residence,
2529 Newport Avenue, Cardiff by the Sea, California," prepared by
TerraPacific Consultants, Inc., dated September 8, 2005.
Dear Mr. Peterson:
In accordance with your request, TerraPacific Consultants, Inc. is pleased to present the
results of our supplemental slope stability analyses and our review of plans for the above
referenced project.
Background
This letter has been composed to specifically address items that "still require clarification",
as per the memorandum issued April 7, 2006 by Geopacifica, Inc. regarding 'Third Party
Review of Proposed Pool/Wall Project' at the above referenced property. The two items
which involve the geotechnical consultant include numbers 2 and 3 on page two of the
referenced memorandum. Below is a discussion of our analysis as it pertains to requested
information.
Response to Inquiry Number 2
With regards to inquiry number two, we have reviewed the design parameters for the
keystone wall. It is our opinion that the engineering properties used to represent the
granular backfill are conservative estimates from a design standpoint. We understand that
the wall stability analysis was undertaken by a registered Professional Engineer and as
such is not included in the scope of this report. With that said, upon review of the
keystone wall design we observed that only one layer of geogrid was used for analysis;
although an acceptable factor of safety was achieved with one layer of geogrid we would
prefer to see a geogrid spacing of not more than 16 inches along the vertical.
12245 World Trade Drive, Suite G • San Diego, CA 92128 • 858 521-1 190 • 858 521-1 199 fax • terrapac.net
it
As noted in our report issued April 3, 2006, the minimum depth of embedment for the
gravel leveling pad shall be no less than 1 .5 feet into competent formational material. In
addition, this embedment depth should be field verified by a representative of TerraPacific.
Moreover, the Standard Unit Specifications provided by Keystone Retaining Wall Systems
(can be found on their website) should be strictly adhered to. This includes providing for
laboratory analysis, as per ASTM D-422, of the material to be used for drainage fill and the
material to be used for the reinforced granular backfill. In our geotechnical report issued
September 8, 2005, referenced above, we found that the upper 5 feet of fill material in the
area where the pool is to be excavated consists of a granular material which will be
suitable as backfill for the keystone retaining wall. This material should be field verified by
a representative of TerraPacific prior to placement and if a different material is to be used
separate from or in conjunction with this material it must be analyzed as per Keystone
specifications.
Backfill compaction specifications have also been specified by Keystone Retaining Wall
Systems and can be found on their website. As stated in our report issued April 3, 2006,
compaction testing of the reinforced earth zone of the Keystone Wall is required and must
meet the specifications by Keystone.
Response to Inquiry Number 3
We understand that the temporary stability of the existing retaining wall with respect to
the proposed keystone wall excavation is desired. The analysis for this relationship has
been accomplished using the software program GeoStudio - Slope/W and considering two
scenarios: the proposed pool excavation is performed prior to the excavation for the
keystone wall construction; and the keystone wall is constructed prior to the proposed
pool excavation. Results of stability analyses indicate that the existing retaining wall will
be stable for the proposed conditions (see Figures 1 and 2). It should be noted that our
analyses are based on an assumed depth of embedment that must be field verified. If
deeper excavation is required temporary shoring of the existing retaining wall may be
necessary.
We appreciate the opportunity to be of service. If you should have any questions or
comments, please do not hesitate to call.
Sincerely,
T raPacific Consultants, Inc. Exp
NO
Lxpt 23iJason A. Hef r � � Daniel P. Connery, GE 2599
associate Engineer _-.< f' Senior Engineer
Averett Swimming Pool • 2529 Newport Ave., Cardiff by the Sea, CA File No. 25137 • April 25, 2006
- 2 -
ATTACHMENTS
� Cl) N
H
Cyr
W.�
•r.rw�
1�
O
r
of
LL
°v U
C
(D
_y
b0
a •
U �
N • • O
o
o a
a};
U�
m �
C.o
� v�
� N�
N EO
Hzo
(;aa3) U01lena13
� � N
O
N
6)
it
f1,
0
OD
r
zI•
N
LL.
ov U
C
uq
G �
I
U
O
m
o a.
d
[ N
U¢
y C
O O
O M N o
co
FzQ
o 0
� O N
(}aa�) U011enal3