HomeMy WebLinkAboutMS 16-04; VIASAT BRESSI RANCH CAMPUS; RESPONSE TO CITY COMMENTS; 2016-08-03GEOCON
INCORPORATED
GEOTECHNICAL . ENVIRONMENTAL
Project No. G1928-52-01
August 3, 2016
MATE R I AL S
ViaSat
6155 El Camino Real
Carlsbad, California 92009 AUG 162016
Attention: Mr. Ryan Hatch CITY OF CARLSBAD
PLANNING DIVISION
Subject: RESPONSE TO CITY COMMENTS
VIASAT - BRESSI RANCH
CARLSBAD, CALIFORNIA
References: 1. Geotechnical Investigation, Viasat, Bressi Ranch, Carlsbad, California, prepared
by Geocon Incorporated, dated July 5, 2016 (Project No. G1928-52-01).
P' Review for SDP 16-14/PUD 16-05/SUP 16-01/MS 16-04 - Viasat Bressi Ranch
Campus, Carlsbad, California, prepared by the City of Carlsbad, dated July 18,
2016 (SDP 16-14, PUD 16-05, MS 16-04).
Tentative Parcel Map and Site Development Plan for: Viasat Bressi Ranch
Campus, Bressi Ranch P.A. 2, Lots 2-9 of Map 14960, prepared by Pasco Laret
Suiter & Associates, dated June 20, 2016.
Dear Mr. Hatch:
We prepared this letter to address the Engineering review comment provided by the City of
Carlsbad dated July 18, 2016, regarding the subject site. The city's comments are listed herein
with the Geocon response immediately following.
Comment 5: Geocon 's Geotechnical Investigation, dated May 23, 2016, classifies the site as
Type D (low infiltration) per the US Department of Agriculture Hydraulic Soil
Group Map. This is an acceptable source for the planning phase and justifies
designing with biofiltration at this time. However, additional analysis (i.e.
infiltration testing) will be needed at the grading plan check phase. Per Section
7.16.5 of the report, Geocon has not been notified of the proposed biofiltration
basins. The report further states that they will need to review the plans to provide
further recommendations. The downstream distress will vary based on the
amount of water retained, residence time, soil permeability, etc. Based on this
comment, the author cannot determine if partial retention is feasible or if
additional protective measures need to be implemented in some areas until more
information is provided.
Response: Based on our review of the referenced report, the property is underlain by
compacted fill over the Santiago Formation and consists of sandy clay.
Infiltration should not be allowed in the compacted fill. Allowing water to
6960 Flanders Drive • San Diego, CaliFornia 92121-2974 • Telephone 858.558.6900 • Fax 858.558.6159
fh6iT+
Shawn Foy Weedon
GE 2714
(e-mail)
(e-mail)
SFW:AS:dmc
Addressee
Pasco Laret Suiter & Associates
infiltrate would destabilize the fill and cause distress to the existing and proposed
improvements from both settlement and expansion. The rate of settlement
discussed in the referenced report would increase and likely cause distress to the
planned development.
In addition, the formational materials consist of the Santiago Formation that
consists of layers of silty sandstone and hard layers of siltstone and claystone.
Section 6.4 states several landslides were encountered during the development of
the property. The landslides were removed and replaced with properly
compacted fill to stabilize the property. Allowing storm water infiltration on the
property would decrease the factor of the safety of the slopes and could cause
slope instability.
Therefore, we opine storm water infiltration is infeasible due to the presence of
the compacted fill, existing fill buttress for slope stability and the clayey nature
of the existing materials on the property. Therefore, additional infiltration testing
would not be necessary.
We reviewed the referenced plans including details for the biofiltration basins.
Based on our review of the plans, the biofiltration details are in accordance with
the referenced report and the discussion presented herein.
If you have any questions regarding this response, or if we may be of further service, please contact
the undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
Ali Sadr
CEG Sp
ALI
Attention: Mr. Dan Loss
Project No. G1928-52-01 - 2 - August 3, 2016