SU0009663 SSNL - Laserfiche WebLink

Home Browse Search

Soil Suitability Study Page 7 Sandhu Farms,260 E.Linne Rd.,Tracy CA ' Project No. 692.1 September 18,2014 6.0 PERCOLATION TESTS A shallow percolation test was performed on each of the proposed 17 new parcels under ' permit of the San Joaquin County Environmental Health Department and using EHD guidelines. The agency defines a shallow percolation test as between 36 and 42 inches, while a deep percolation test is between 42 inches and 25 feet. In this case, all tests were shallow 1 with 42 inch borings. A test percolation rate of less than 60 minutes per inch for a shallow test, or less than 30 minutes per inch for a deep test is considered a"passed"test. An agency representative was notified in advance of the test so that an inspector could witness the tests. ' The percolation tests are to be made within the "footprint' of the proposed new leach fields. In view of the fact that no building plans having yet been developed, the locations of the future septic tanks and leach fields remain unknown. The percolation tests within the proposed new parcels were thus selected for convenience. It is recognized that as building ' plans are developed for individual parcels, new percolation testing is likely to be required at the actual building sites. The exact location of each percolation test was identified using a Garmin 76CSx GPS Device, capable of accuracy as close as 3 meters. The GPS coordinates were converted to map locations with the assistance of the San Joaquin County GIS mapping system. The locations of the percolation tests along with proposed parcel outlines are indicated on an air-photo based map included in Appendix C. ' 6.1 Test Description The percolation tests occurred at various times from July 15, 2014 to September 9, 2014. They occurred in five groups of from 2 to 4 tests. North American Testing Service (HATS) installed 4-inch diameter soil borings to a depth of 42 inches using hand auger soil boring tools. An approximately 2-inch thick layer of gravel was placed at the bottom of each boring, and a perforated 3-inch diameter temporary casing, open at the bottom, was placed on top of the gravel pad. The top of the PVC casing was used as a fixed point of reference from which to measure the decreasing water level in the boring. In the 24 hours prior to completing the tests, the borings were pre-soaked by filling the packed boring with water to a depth of 12 ' inches. The duration of each of the tests was four hours. An electronic well sounder with accuracy of 0.01 feet was used to monitor the fall of water during the test from a fixed point of reference. On the day of testing, each of the test borings were was found to be intact and dry. The 4- hour tests were conducted in the presence of the County inspector. 6.2 Test Results The percolation tests in all 17 shallow (42") borings yielded percolation rates substantially faster than the minimum required of 60 minutes per inch. Indeed, the slowest percolation test was still more than twice as fast as this minimum. Based on the test results and the EHD ' 2937 Veneman Ave.,#B240 Geo-Phase Environmental Inc. Phone: (209)569.0293 Modesto,CA 95356 Fax: (209)569-0295