HomeMy WebLinkAboutPIP 98-03; Cornerstone Corporate Centre Lot 7; Planned Industrial Permit (PIP) (15)GEOCON
INCORPORATED
Project No. 05724- 12-01
October 2 1, 1997
Newport National Corporation
5050 Avenida Encinas, Suite 350
Carlsbad, California 92008
Attention:
Subject:
Mr. John Couvillion
CORNERSTONE CORPORATE CENTER
PALOMAR AIRPORT ROAD
CARLSBAD, CALIFORNIA
GRADING PLAN REVIEW
Gentlemen:
In accordance with your request, we have reviewed the grading plans entitled Grading Plans for
Cornerstone Corporate Center prepared by Latitude 33 (no date) to address the stability of the
proposed variable fill slope adjacent to Palomar Airport road along the southern property boundary.
The inclination of the proposed fill slope varies between 3: 1 (horizonta1:vertical) and 1.5: 1. Portions
of the slope steeper than 2:1 do not conform to the requirements of the City of Carlsbad's grading
ordinance. In addition, our preliminary calculations indicate that the portions of the slope steeper
than about 1.75:l will not possess a factor of safety of at least 1.5 against deep-seated failure if
constructed of the prevailing on-site clayey soils. For this reason, we recommend that one of two
alternative mitigative measures be used to increase the factor of safety of the slope to at least 1.5.
The first alternative would be to reinforce portions of the slope steeper than 1.75:l with a geogrid
reinforcement system. Our firm has performed calculations that indicate that the desired factor of
safety of 1.5 could be achieved by incorporating layers of geogrid such as Miragrid 10T at vertical
intervals of approximately 4 feet into the fill mass. The length of the geogrid would be
approximately 35 feet measuring horizontally from the face of the slope. We are in the process of
completing sketches depicting the appropriate configuration of the geogrid reinforcement.
A second method to achieve the necessary factor of safety would be to import granular fill material
meeting minimum shear strength requirements to use in construction of the outer 25 to 35 feet of the
proposed slope. It would be necessary for our firm to perform parametric calculations using various
strength parameters to develop the actual geometry and soil types to be used in the slope.
6960 Fbnden Wie San Diego, California 92121-2974 Telephone (619) 558-6900 Fax (619) 558-6159
It is our opinion that either of these approaches would satisfactorily mitigate the oversteep
configuration of the slopes as designed.
If you have any questions regarding this review, or if we may be of further service, please call.
Very truly yours,
GEOCON MCORP(
Michael S. Chapin 1
CEG 1 149
GE 2248
MSC:dmc
(4) Addressee
Project No. 05724- 12-0 1 -2- October 2 1, 1997