SU0004272 SSNL - Laserfiche WebLink

Home Browse Search

It appears that the maximum mound hei t that ay occur under mound system is 0.57 f et. This would leave a distance of approximate) 6.5 et between the soil//effluent inter an e top of the theoretical mound above the elevation of the water table. For wastewater treatment to occur, the distance effluent should travel under unsaturated conditions through the soil environment is generally regarded to be 5 fe)t. Additionally, the California State Water Resources Control Board- Guidelines for the Design Installation and Operations ofMound Sewage Disposal S stems document states in Section 31.0 that in cases where peak wastewater flows for a commercial system exceed 1,500 gallons per day, an evaluation of hydraulic mounding below the disposal area shall be performed. Although the daily flows will be substantially lower than this,mound potential analysis remains viable. In the Finnemore and Hantzsche paper, they discuss three options to consider as potential methods of reducing the mounding phenomenon. The first is increasing the size of the disposal field. Based upon the average daily flow calculations found on Page 12, it is anticipated the disposal area is sufficient in size to accommodate the projected flow volumes after completion. The disposal area is based on mathematical computations for sizing found in the EPA Design Manual- On Site Wastewater Treatment and Disposal Systems. The second method is elongating the shape of the az�ja co red by the disposal field. As noted on the design plans, nd system is elongated in T 2.8:1 1 ngth-to-width ratio. Thirdly, operating the field inte tently shou ecrease the moundiri effe As noted in this Rep (fluent will i be pumpedtwo alternating umps that will pump sma 1 doses of approximately 75 gallons per dose. If it is determined at some point in the future that mounding effects are preventing proper effluent treatment and disposal, the area designated as the 100%replacement areas may have to be activated. The reserve area is located directly to the south of the primary disposal area. E. SURFACE WATER INFORMATION Storm water management is proposed to be an on-site retention basin that will be constructed with minimal excavation and built-up embankments. This is to maintain a five-foot separation distance between the floor of the basin and the depth to groundwater. There should be no impact to percolating effluent from the retention basin, and in fact are crossgradient to the future wastewater disposal area. Since the groundwater directional flow is north-northeast, percolating rainwater from this basin into the top aquifer mixing layer may create a dilution effect to the crossgradient percolating septic system effluent. Groundwater dilution effects can only be truly discerned with groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk (1994),reduction of nitrate concentrations in groundwater can occur primarily through dispersion, or by percolating rainwater recharge. 9 Chesney Consulting