HomeMy WebLinkAboutPA2023-0040_20230427_ Response to Comment 13542.001April 25, 2023
Project No. 13542.001
Intracorp SoCal 1, LLC
895 Dove Street, Suite 400 Newport Beach, California 92660
Attention: Mr. Rick Puffer, Vice President Development
Subject: Response to Project Review Request Community Development Department Planning Division for 1401 Quail Residences, dated March 9, 2023
References: Leighton and Associates Inc., Geotechnical Exploration Report Proposed
Multi-Family Residential Development 1401 Quail Street Newport Beach,
Orange County, California, dated June 23, 2022
City of Newport Beach, Community Development Department, Planning
Division, Project Review Request - Applicant: Intracorp Homes; Project:
1401 Quail Residences; Address: 1401 Quail Street, dated March 9, 2023.
In accordance with your request Leighton and Associates, Inc. (Leighton) is providing this
response to the Project Review Request Community Development Department Planning
Division dated March 9, 2023. The proposed project is a 6-story podium building which
consists of 78 residential units and approximately 159 parking spaces. A proposed
parking garage on the first floor will provide approximately 68 spaces while the remainder
of the spaces will be in a subterranean-level parking garage. The site is currently
improved with a 22,956-square-foot commercial office building.
Leighton and Intracorp held a virtual meeting on April 13, 2023 at 1400 hours with the
City reviewer to discuss our response. The comment is provided below in italics followed
by our response.
City Comment: For Basement Geotechnical Engineer to analyze Liquefaction Potential
if ground water is within 30 feet from the bottom of basement finish floor elevation.
Response to Project Review Comment 13542.001
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Leighton Response:
Groundwater Conditions
Groundwater was encountered in our subsurface investigation and measured at a depth
of 25 feet bgs in borings excavated as part of our referenced study. Historic groundwater
depth referenced from a Case Closure Summary Leaking Underground Fuel Tank report
dated November 13, 1996 and provided by the Orange County Health Care Agency,
indicates highest groundwater at 1500 Quail Street was measured at 23 feet below
ground surface. This depth to groundwater is consistent with our recorded data and for
purposes of liquefaction analyses we suggest using a groundwater depth of 23 feet bgs.
Site Soil Conditions
Based on interpretation of samples recovered during the referenced subsurface
exploration (Leighton, 2022) fill at the site is underlain Pleistocene-age very old, playa,
and estuarine deposits characterized as alternating beds of orange brown, reddish brown
and gray brown, slightly moist to moist very stiff carbonate impacted sandy clay (CL) and
bluish gray fat clay (CH) with dense silty sand (SM) to poorly graded sand (SP). Poorly-
graded sand is notably thickest at 25 feet and deeper.
Liquefaction Potential
Review of the Seismic Hazard Zones map for the Tustin Quadrangle prepared by the
California Geological Survey (2001), indicates the project site is not located within an area
that has been mapped by the State of California as being potentially susceptible to
liquefaction due to the underlying density and stiffness of the Pleistocene age soils.
Pleistocene age low plasticity clayey soil below the site is very stiff and impacted with
carbonate, soils of this type are generally not subject to the adverse effects of liquefaction.
Based on these findings and blow counts of the encountered soils, it is this firm’s
professional opinion liquefaction is not considered a hazard at the site.
Recommendations
Upon demolition of the existing structure, Leighton recommends that Cone Penetrometer
Test (CPT) soundings or Hollow Stem Auger (HSA) borings be performed in previously
inaccessible areas of the site to evaluate pore water pressure, seismic shear wave velocity
and for use in liquefaction analyses as requested by City reviewer.
Response to Project Review Comment 13542.001
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We appreciate the opportunity to be of service to you on this project. If you have any
questions or if we can be of further service, please contact us at (866) LEIGHTON; or
specifically at the phone extensions or e-mail addresses listed below.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
Joe A. Roe, PG, CEG 2456 Senior Principal Geologist Extension 4263, jroe@leightongroup.com
Ronald A. Reed, PE, GE Senior Principal Engineer Extension 4256, rreed@leightongroup.com
JAR/RAR/lr
Distribution: (1) Addressee