SU0000021 SSNL - Laserfiche WebLink

Home Browse Search

FrTheantzsche/Finnemore Formula predicts a yearly average nitrate-nitrogen concentration in harge septic effluent from the two proposed SFRs to be 5 ppm NO3-N. The yearly amount ontrate-nitrogen leaching into the groundwater,from the two SFRs may be as high as 88 lbs NO3-N. Fertilizer and organic matter nitrate-nitrogen concentration calculated from the observed chemical analyses of the soils under the existing almond orchard is 8 ppm NO3-N. The total yearly amount of nitrate-nitrogen leaching from nitrogen fertilizer applications over the growing season may be as high as 180 lbs NO3-N. Therefore, nitrate impact from the proposed development will be theoretically lower than nitrate impact from the almond tress, both in terms of concentration (5 ppm NO3-N vs. 8 ppm NO3-N) and amount(88 lbs NO3-N vs. 180 lbs NO3-N). It is recommended the two wells that will serve the new SFRs be drilled and perforated in deeper auarant that qst future nitrate ft h m ract willout shouI extend o at"Ieas 1 rl ft T o.... r;there is no �.�_ gp 1 not affect these deeper aquifers. Considering the age of k the high density housing on Cottage Avenue and the intensity of farming in this area, higher nitrate levels would have been predicted in these deeper aquifers. The percolation test results indicate the leachline soils of approximately 40 inches below grade have a porosity that allows rapid percolation. However, as the soil becomes saturated, the perc rates noticeably decrease. This rate decrease can be primarily attributed to the underlying hardpan layer. Therefore, it is recommended that during leachline emplacement, the hardpan layer should be broken up with a backhoe and backfilled into the leachline trench. This will allow percolation into the hardpan strata and promote soil saturation. Soil saturation will in-turn create anaerobic conditions which will stimulate the denitrification process. Seepage pits are not warranted or allowed in this area. However, sumps or preferably filter beds can be installed if there are area constraints. As noted on the attached septic system permits, sumps were installed at the Sephos residence. It is important to note that all septic systems have a lifespan. This lifespan is dependant on several factors and is therefore, difficult to determine. If there was septic system failure, it would probably result from the advanced formation of the biomat on the wetted soil/effluent interface. This mat is composed mostly of aerobic and anaerobic bacteria and bacterial products consisting of a slime of polyuronides and polysaccharides. If the soil/effluent interface is well aerated, a variety of soil microfauna such as nematodes and protozoa may digest the clogging mat bacteria. Since the shallow subsurface soils consist mostly of a sandier soil material, aerobic conditions may prevail over time which may inhibit leachline failure. The total length of leachline will be dependant upon the number of bedrooms each new home will have. Additionally, the system should be oversized if a number of people, especially children, will inhabit the residences. A 50%replacement area must be incorporated into the design. 12 Naffey Ag Research