SU0011908 SSNL - Laserfiche WebLink

Home Browse Search

i A. Underlying Water Table and Lake Water Test Results A groundwater sample (Sample iD: GwIJFLG-Groundwater tinder punire L.eachfield)was retrieved from this exploratory boring for analysis. After retrieving the water table sample, the soil boring was backfilled with hydrated bentonite pellets. The water table sample from the exploratory boring and a lake water sample from the western shore lint reveals nitrate concentrations of 0_m_,g(Lb.,aiji),Qr Below Detectible Levels (BDLj for bothsamples. The Maximum Cpntaminant Level (MCL) for nitrate is 45 ppm (as nitrate). The alkalinity was comparatively higl"t 403 ppm. For nitrification to occur, alkalinity must be consumed, as calculated below. Chloride was also quantified in the groundwater and found to be in an inexplicably, excessive concentration. High chloride in top groundwater. indi a e 'fit from septic systems. Human wastes are generally high in chloride content and chloride is not absorbed by the soil, in the way clay soil traps the ammonium found in septic effluent. Chloride may travel faster in the saturated zone than nitrate, and thus may be a first indicator of septic effluent contamination. However, there are no septic systems in this area. B. Supplied Domestic Water Test Results As referenced. the domestic water supply was available for analysis from the existing Brown Sand office well. The attached well log for this well indicates intervening strata of sand and clav, with water being drawn from 168 to 188 feet._, Test results reveal the well water to also contain no nitrate (BDL), and a low alkalinity of 158 ppm: ; C. Calculation of Alkalinity Requirement for Nitrification The nitrate-nitrogen loading calculations below are contingent upon the environmental factors required for nitrification to occur. Alkalinity in wastewater effluent plays a role in nitrification i and is derived from the domestic water supply and the introduction of wastes to the wastewater. Nitrification consumes approximately 7.1 mg of alkalinity for eyzry milligram of ammonia- I nitrogen -N) oxidized. Water chemistry for the existing domestic wellforthe project is 158 ppm. while the water table possesses 403 ppm. Nitrification of the average Total Nitrogen (TN) concentration of 88 mg/L is determined in Section iV C, below. Considering that ammonium typically composes 70 30%of the total nitrogen in septic tank effluent: 88 mg/L x 80% = 70 mgtL NHa N x 7.1 mg -3 —_500 mglL alkalinity required. Therefore the alkalinity in the domestic water supply is deficient if the TT;-v6ilfbc approximately 88 ppm,and nitri/icutiorr nrup he inhihiled, because there is insufficient alkalinity. D. Mounding Analysis Due to the fact that the groundwater is comparatively deep below the proposed location of the disposal area on top of the embankment, Mounding Analysis is not required or necessary. If it is determined at some time in the future that mounding effects from the effluent encountering the differing soil strata are preventing proper effluent treatment and disposal, the 100% replacement area may have to be activated. This may occur prior to failure of the primary filter bed. Paee-5- _-_-- Chesney Consulting