HomeMy WebLinkAboutPD 2019-0032; GOERTZEN RESIDENCE; GEOTECHNICAL RESPONSE TO THIRD PARTY 2ND REVIEW; 2020-02-26IIOII, T81Tlltl tiij --------------------------------
February 26, 2020
Greg Goertzen
3466 Camino Michelle
Carlsbad, California 92009
SUBJECT:
Dear Mr. Goertzen:
File No. 1127H6-19
SITE INSPECTION
Response to Third Party Geotechnical Review
Proposed Residential Building Site
El Fuerte Street and Acuna Court
City of Carlsbad
In response to the third party review by Hetherington Engineering, dated January 20, 2020.
1. The consultant should review the project foundation plans.
P.O. Box 1195
Lakeside, California
92040
(619) 443-0060
We will review the structural and architectural plans when available and confirm that
the plans have been prepared in accordance with the geotechnical recommendations
provided in our revised report.
2. The consultant should provide a legible geological cross section utilizing the current
grading plan to clearly show a) existing site topography, b) proposed
structures/improvements, c) proposed finished grades, d) geologic units and contacts,
e) locations of the subsurface exploration, f) remedial grading, etc.
Please see enlarged Plate IV attached to our revised report.
3. The consultant should discuss regional geologic conditions, geologic structure.
The project is situated on volcanic basement rocks several hundred feet east of the
contact with Eocene age sediments correlated with the Santiago Formation. The
Eocene sediments located west of the site generally have dips of less than 5 degrees
to the west and southwest attesting to the lack of significant folding and faulting in
the general area of the site. The closest significant fault to the project is the Rose
Canyon fault that lies offshore approximately seven miles to the west.
Greg Goertz File No. 1127H6-19 February 26, 2020
Mapping by Tan and Kennedy (1996) indicates the site is underlain by the Santiago
Peak Volcanics a Jurassic to Cretaceous fonnation consisting of metamorphosed
volcanic flow rocks, tuff, and volcanic breccia. Here this unit consists of massive
light-brown to grey aphanitic volcanic flow rocks. Outcrops of this rock in road cuts
along El Fuerte Street and Acuna Court indicate that the rock is highly fractured near
the surface with the primary joints and fractures striking northeast and northwest with
dips exceeding 50 degrees to the east and south. This unit is overlain by topsoils
varying from two to four feet thick consisting of silty to clayey sand with a high
percentage of angular rock fragments.
Reference:
Tan, S.S. and Kennedy, M.P., 1996, Geologic Maps of the Northwestern Part of San
Diego County, California, Plate 2, Geologic maps of the Encinitas and Rancho
Santa Fe 7.5 min. Quadrangles
4. The consultant should specify the sulfate exposure category (ACI 318) based on
soluble sulfate testing and provide recommendations for sulfate resistant concrete if
necessary, or default to a severe exposure category, if testing is not available.
Please see our revised Site Inspection dated February 25, 2020. We can provide this
testing during the grading operation for the import soils. The proposed structure is to
be located entirely in the import soils.
5. The consultant should provide the site seismic design category. Page 2, #3 of
Reference 1 provides the Site Class not the Seismic Design Category.
Please see our revised report. The Seismic Design Category is II.
6. The consultant should include footing observations, trench backfill, and retaining wall
backdrains and backfill in the list of recommended observation and testing during
grading and construction.
Please see our revised report.
7. The consultant should address the surficial stability of the proposed site slopes.
Please see our revised report.
8. The test pit logs do not include a geologic unit or bedrock identification. The
consultant should clarify the test pit logs to include bedrock descriptions.
Bedrock was not encountered in the test pits. Please see our updated logs.
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Greg Goertz File No. 1127H6-19 February 26, 2020
9. The consultant should provide retaining wall recommendations, if necessary.
Please see our revised report.
If we can be of any further assistance, please do not hesitate to contact our office. This
opportunity to be of service is sincerely appreciated.
Respectfully submitted,
Chin C. Chen, RPE C34442
CCC/mlj
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