SU0004406 SSNL - Laserfiche WebLink

Home Browse Search

_ The important parameters for nitrate loading assessment are the organic matter,pH, cation f '- exchange capacity (CEC), along with nitrate-nitrogen content. As noted, the organic matter - _- throughout the soil profile can be considered low for surface agricultural soils, but comparatively high for dee er soils.. _Since septic effluent is.composed predominately of ammonium.(NHwith .the the pH, along wit .the CEC, have significant influences on ammonium molecules. The pH of the soil is alkaline which may-inhibit ammonium formation and stability. The CEC measures the ability of the soil.to f. = theoretically trap and hold ammonium molecules Throughout the soil profile-to the 45-ft depth- - ' s the CEC-is relatively high and suggests thereis considerable potential for the retention of. s _ - ammonium molecules for microbial uptake and suppression of -nitrification. C.-PERCOLATION AND:HYDRAULIC CONDUCTIVITY TEST RESULTS - -- The three percolation.te st borings (and,.the hydraulic conductivity test and 45 ft deep borings) - i were drilled with a CME-75 Drill Rig 66 November 11, 200. 1 in locations denoted on the attached Site Plan:. The three perc test_borings were drilled to 42 inches (representing leachlines); 12 ft(representing sumps) and 23 ft (representing seepage pits). The auger was not completely extended to 25 ft by the drillers. Due to_inclement weather,-the pert test borings were not prepared and the actual perc tests were not conducted until November 19 and 20, - - I respectively. Percolation test boring preparation included.scarification of the 42-inch and 12 ft - borings, pre-saturation to 75%of the test boring volumes and PW pipe installation. The-23 ft. boring could not be scarified its Entire deptll:`.�The subsurface soils were considerably moist before pre-saturation due to the last irrigation of the-walnut.orchard and the recent rainfall': Percolation testing was completed under U.S.E.P.A7 and San Joaquin County Environmental -- = hfield area. `As illustrated on the attached FIELD Health guidelines in the proposed leac - _ -,PERCOLATION TESTING-REPORT::the perc rate at the shallow depth of-42 inches(Test Hole. - # P=1) was non-existent eventhough the test boring had been properly scarified. After two hrs into the test, an experiment was done to test if head pressurewould influence the perc rate in this boring: The boring was filled with 24 inches of water; instead of the initial six'inches. No . percolation was observed after.a four-fold increase in head pressure. 'Therefore,-another Y experiment was started in which a second 42 inch boring was hand-drilled. Althou h this test ` borin w s re-saturated, there,was significant moisture content within the soil profile from _ the last irrigation, as referenced above:.The-test boring was scarified after drilling. The perc rate-.. for this boring, denoted as Test Hole #'P-TA on the TESTING.REPORT, only slowed from an initial'rate=of,10'min/in to a final rate-of 15.mirdin over the four-_hour test period, indicating that soil'satVratiari was not an important factor in the perc rate. The significant issue with these experiments was the apparent fact that when-drilling a power auger in moist-to-wet clay _ soils,the auger flights cause the boring sidewalls to become highly compacted. Even scarification of two inches into the side-walls had no effect on opening the smeared soil surfaces With the hand-boring, the soil was not compacted because it did not-have to-be brought up out of T - the boring by auger flight and consequently; the boring sidewall soils remained "open." During the drilling of the deep-23 ft boring, a.sand stratum was encountered from roughly 15 to 19 ft belowrade. Since the borin was filled with water.to a atel 75% of its volume g g: _. pproxim ;Y� t = 4 ` = valley AB Resear6h.