SU0004308 SSNL - Laserfiche WebLink

Home Browse Search

K L E I N F E L D ER r levels in the project area ranging from about 15 to 30 feet below ground surface from Spring ` 1981 to Spring 1999. FIELD EXPLORATIONS AND TESTING The subsurface conditions at the proposed addition were initially explored on March 21, 2002, by drilling four borings to depths ranging from approximately 15.5 to 20.5 feet below existing grade. The borings were drilled using a Simco 2400 truck-mounted drill rig equipped with 4- inch O.D. solid-stem auger. Based on our findings, the near-surface subsurface soils encountered generally consisted of loose to medium dense silty and relatively clean sands to depths of about 8 to 14 feet below site grade, which were underlain by approximately 0.5 to 2.5 feet of very stiff silt. The silts were underlain by interbedded strata of soft to very stiff sandy clays and medium dense silty and relatively clean sands to the depth explored. At the time the test borings were drilled, a staff engineer with our firm obtained samples of groundwater using clean procedures from a valve on the water tank adjacent to the on-site well. The well was located approximately 300 feet east and 200 feet north of the existing office. That ` same day, the water sample was submitted to Sequoia Analytical using chain-of-custody procedures for DBCP and nitrate testing. The results of our tests and a copy of the chain-of- custody are attached. r On August 28, 2002, two percolation tests were performed in the vicinity of the existing leach ` field. The percolation tests were performed in accordance with accepted guidelines using clear potable water. The procedure calls for first placing about 2 inches of fine gravel at the bottom of the borehole. The hole is then pre-soaked with water at least 24 hours prior to performing the ` test. The test is performed by first adding about 6 inches of water above the gravel in the hole. From a fixed reference point, the drop in water level is typically measured in approximately 30- minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water L over the gravel. Due to the take of water in the shallow test hole (P-1) after one hour of testing, the interval upon which measurements were taken was reduced to approximately 10-minutes. Under the observation of a registered environmental health specialist from the San Joaquin ` County Public Health Department (SJCPHD), the last 10 and 30-minute readings were recorded for P-1 and P-2,respectively, and used to calculate the percolation rates in minutes per inch. The estimated percolation rates at each test location are as summarized below. A copy of our field percolation test results for test numbers P-1 and P-2 is attached. Test Number Depth, ft. Percolation Rate (min./inch)' ` -- -- P-1 3.05 4.9 P-2 7.55 S.9 NITRATE LOADING CALCULATIONS Per SJCPHS/EHD requirements, the following summarizes our nitrate loading calculations for ` the existing leach field. The State drinking water standard for nitrate is 45 milligrams per liter 13257.G01/ST02R023 September 18,2002 r ©2002 Meinfelder,Inc. Page 2 of 4