Loading...
HomeMy WebLinkAboutSDP 15-14; ADDENDUM GEOTECHNICAL INVESTIGATION; 2015-11-19r4E Geotechnical Exploration, Inc. SOIL AND FOUNDATION ENGINEERING S GROUNDWATER I ENGINEERING GEOLOGY 19 November 2015 Lloyd H. Wells Gift Trust 17083 Old Coach Road Poway, CA 92064 Attn: Mr. Ed Fudurich DEC 29 2015 L ENGINEERING ;;P;-- _1 30b No. 15-10840 Subject: Addendum Geotechnical Investigation L.W. Office Building 2055 Corte Del Nogal Carlsbad, California Dear Mr. Fudurich: In accordance with your request, we herein provide this addendum geotechnical investigation. This addendum has been requested to address the site drainage conditions, specifically the infiltration rates at the location of the proposed permanent BMPs. On October 7, 2015, we placed four hand-auger borings on the lot for evaluation of the storm water infiltration/percolation BMPs, per the requirements of the County of San Diego Storm Water Pollution Program in accordance with the Guidelines for Geotechnical Reports. We performed percolation testing at four locations at a depth between 28 and 36 inches to confirm infiltration/percolation rates of at least 0.57 inches/hour. Testing at the four locations revealed percolation rates of 1.17 inches/hour. Due to the depth to impermeable formation and the depth to the high water table being greater than 10 feet, we understand that the project civil engineer requires an infiltration rate between 0.57 and 1.42 inches/hour for design of the on-site storm water runoff infiltration/percolation BMP plan and the requirements of the County of San Diego Storm Water Pollution Program. Based on the results of our percolation 7420 TRADE STREETS SAN DIEGO, CA. 921210 (858) 549-72220 FAX: (858) 549-1604• EMAIL: geoteth©gei-sd.com L.W. Office Building Job No. 15-10840. Carlsbad, California Page 2 testing, the site has been assigned to soil group (HSG) B. A s p a r t o f o u r geologic/geotechnical site evaluation we considered the followin g i s s u e s : The site is not subject to high groundwater conditions (within 10 feet of the base of the infiltration facility. The site is not in close proximity to contaminated soil. The site Is underlain by artificial fill over dense formation, but not subject to hydroconsolidation. The site has infiltration rates between 0.57 and 1.42 inches/hour. The site has a silt plus clay percentage of less than 25. The site is not underlain by impermeable formation within 10 feet. The site is not located within 100 feet from a drinking water well. The site is not located within 100 feet from an on-site septic system or designated expansion area. 9.. The site is located adjacent to a slope steeper than 25 percent ( 4 h o r i z o n t a l to 1 vertical), but it is not prone to instability. Based on the results of our percolation testing and evalua t i o n o f t h e p r o p o s e d infiltration rates, it is our professional opinion that this sit e h a s f a v o r a b l e s o i l conditions and infiltration rates for design of the proposed perma n e n t B M P s . L.W. Office Building Job No. 15-10840 Carlsbad, California Page 3 LIMITATIONS The findings, opinions, and conclusions presented herein have been made in accordance with generally accepted principles and practice in the field of geotechnical engineering within the City of Carlsbad. No warranty, either expressed or implied, is made. If you have any questions regarding this letter, please contact our office. Reference to our Job No. 15-10840 will help expedite a response to your inquiry. Respectfully submitted, GD(ECHNICAL EXPLORATION, INC. V1114Y4—a-'L 30 K. Heiser Senior Project Geologist ... ... Jaime A. Cerros, P.E. R.C.E. 34422/G.E. 2007 Senior Geotechnical Engineer CeD £5 ( No. 002097 i PU " 51 3°! -j11'J /