SU0006319_SSNL - Laserfiche WebLink

Home Browse Search

o LEACHLINE REQUIREMENT CALCULATIONS BASED ON SAN JOAQUIN COUNTY SEWAGE STANDARDS FOR COMMERCIAL SEPTIC SYSTEMS: Base Tank Capacity= 1,200 gal. ADF=300 gpd Leachline Equivalent Requirement= 1,200 gallons BTC+300 ADF x 0.20 Sand Soil Factor(SF)at native soil- effluent interface=300 lineal feet of leachline(LFLL). 100%Reserve Replacement Area: This area can easily be accommodated to the south of the primary . leachfield area. The replacement area may encroach into the small agricultural production acreage if this replacement area should ever need to be activated IV. CONCLUSIONS AND RECOMMENDATIONS SSS§ 5.4: The soils underlying the proposed leachfield disposal area to serve the Jacob's Brothers Produce Stand show exceptional permeability that exceeds EHD regulations. The EHD regulations specify an"On ate less than 5 min/in as being too rapid. As referenced in Table 2, the official perc rate w 3.2 in. Rapid permeability is also referenced in the EPA Design Manual: Onsite WastewatefTreatment and Disposal Systems,pg. 213 stating that soils "with perc rates less than 1 min/in can be used for trenches and beds if the soil is replaced with a suitably thick(>2 ft) layer of loamy sand." Since a silty sand is indigenous, a 2 ft thick clay loam soil will be imported onto the floors of the four- 80 foot leachline trenches. The leachline trenches should be excavated to approximately 64 inches, to account for this clay loam importation. This soil type of clay loam was determined by laboratory soil particle size analysis as referenced in Table 3. The EHD concurs with EPA's determination, however, the actual thickness of t"i ort clay loamm oil may be stipulated by EHD. The amount of import clay loam fill needed-if-two-feet of fl-Wis placed in each leachline iat has been excavated an additional two feet in depth will be:_.2,ft._dgep._x 2 ft_width_x 300 ft length= 1,200 cubic feet or 44.5 cubic yards. -� By importing loam material with slower permeability, this will be theoretically beneficial for the mitigation of nitrification. As the effluent percolates through this loam material, it will encounter the native coarser sand material below this import material. As it encounters this coarser fraction, i water will not immediately enter this stratum. Soil above it must become relatively saturated before water will flow into this coarser material. This can create saturated soil microsites that are anaerobic and conducive for inhibiting nitrification and promoting denitrification for ammonium molecules that have nitrified. _ l S§4.2, SSS§'6.7. �rom the soil chemistry test results, it appears that denitrification potential will be severely restricted due to the sandy soil structure. However, as explained above, there should be some nitrate loading mitigation potential by the importation of the clay loam material. The denitrification potential in combination with comparatively shallow-rooted landscape plants in the leachfield area should also reduce nitrate impact by evapotranspiring and mineralizing a percentage of the effluent during favorable weather times of the year(i.e., April through September). 13 Chesney Consulting