Laserfiche WebLink
IV. CONCLUSIONS AND RECOMMENDATIONS <br /> The percolation rates obtained indicate a marginally acceptable soil permeability with the <br /> permeability decreasing as the soil becomes saturated. Effluent management, and therefore <br /> design criteria should be based on the permeability of the soil eventually reaching a long term <br /> application rate (LTAR) of approximately 0.5 gals/fl'/day due to biomat formation. It is <br /> imperative that a 100% replacement area be designated in the event a repair is needed or an <br /> additional system installed. It may be a requirement by the Environmental Health Department to <br /> install a flow meter on the new system. <br /> A new on-site domestic well is proposed to be installed potentially downgradient from existing <br /> and future leachfields. It is recommended there be periodic monitoring of this new well. If there <br /> is an increase in nitrate concentration, further treatment to prevent nitrification may be warranted. <br /> Although the nitrate loading calculations indicate the potential for recharge effluent to exceed <br /> Drinking Water Standard/Maximum Contaminant Levels, it is anticipated that City water and <br /> sewer should be available to the subject property within ten years. <br /> High elevation or shallow leachfields will take advantage of the indigenous clay soils that will <br /> promote denitrification. The denitrification potential in combination with landscape plants in the <br /> leachfield should reduce nitrate impact to the calculated extent. However, leachlines within <br /> landscaped areas should be assessed carefully. Ammonium in high concentrations can be toxic <br /> to plants under certain conditions whereby the ammonium ion is hydrolyzed to ammonia. If the <br /> landscape plants show signs of stress, this may be the reason. <br /> Additionally, deciduous plants should not be irrigated in the winter or they may drown. <br /> Scientific studies have indicated that leachfields in clay soils may rejuvenate when allowed to <br /> "rest." This should be a design consideration whereby one-half of the leachfield can rest during <br /> the winter months to prevent inundation of the landscape plants, then switch during spring and <br /> summer when irrigation is needed. <br /> Without sophisticated groundwater monitoring over a long period of time, it is unknown as to the <br /> exact groundwater depth at different times of the year, as well as the groundwater directional <br /> flow. However, sufficient data has been collected and analyzed to determine that the water table <br /> is currently an acceptable distance below grade for there to be adequate biological treatment, <br /> according to published scientific literature. <br /> Mounding effects under the leachfield areas may be of a concern since the saturated zone is at <br /> comparatively shallow depth. Under severe climactic stress and heavy wastewater flows, <br /> percolating effluent and rainwater may pool on top of the saturated zone, inducing a mound. <br /> Accurate "as-builts" of the septic system to be installed in the future must be supplied to the <br /> Environmental Health Department and all applicable"distance"requirements must be strictly <br /> adhered to. <br /> 10 <br /> Chesney Consulting <br />