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rFeffluent. , the formation of a biomat will reduce effluent infiltration and percolation within the enches,and due to the fine soil structure,the long-term acceptance rate(LTAR) of the ill diminish significantly. When this happens,the seepage pits will manage most of the he clay soil found at the leachline depth of 42 inchesand at the bottom of the seepage pit 25 ft)is theoretically conducive for impeding nitrate formation. tem failure would primarily result from the advanced formation of the biomat or "clogging mat" 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 clayey silty gravel soil material, aerobic conditions may prevail over time which may impede leachline failure. The total length of leachline and seepage pits have been determined above and are in compliance with the San Joaquin County Sewage Standards. A 100%replacement area has been designated and extends further south from the primary disposal area. If this replacement area should ever have to be used, it may require the pumping of the effluent to this replacement area. 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. From the lack of repairs to septic systems within the sparsely populated area, it is evident that systems in this area have a definite lifespan. The other percentage of nitrate loading can be from lawns/landscaping/gardens,which is estimated to be 20%and could be significantly higher. It is recommended to use "slow-release" nitrogen fertilizers to reduce nitrate loading from the landscaping, if at all. Contemporary scientific literature suggests that denitrification may be enhanced by placing proposed leachlines higher in elevation toward the soil surface. This would be advantageous since the surface soils consist of approximately 20% of the fine soil fraction (silts and clays). Deciduous and evergreen plants may be planted near the leachfield to uptake ammonium ions and nitrate ions which may form. Caution must be given to prevent serious root infiltration into the leachlines. These two procedures would theoretically provide a triple nitrate mitigation system of denitrification, absorption and evapotranspiration. Without sophisticated groundwater monitoring,the groundwater depth at different times of the year, the groundwater directional flow, and potential upgradient nitrate sources impacting the underlying groundwater is unknown. This report did not utilize highly complex groundwater modeling techniques since it has been well-documented that the nitrate impact is variable and not all information such as well logs or other geophysical information is available. LL�_ Page -9- Chesney Consulting