SR0080748 SSNL - Laserfiche WebLink

Home Browse Search

Access risers (indicated as 24" for septic tanks, 30" for surge/dosing tank) inadequate for physical entry; normally minimum 36 to 48 inches with ladder required for entry. The above operational issues should be addressed or the design modified to eliminate the anticipated risks and problems. The rational for proposing such deep tanks and sewer lines is unclear. 3. Problematic Effluent Sewer Design. The effluent sewer design which incorporates a dozen or more conventional sewer manholes is problematic and contrary to industry practice for effluent sewer systems conveying septic tank effluent. Sewer manholes are unnecessary since the sewage solids are retained in the septic tanks. More importantly, concrete manholes (not vented) will rapidly deteriorate from the corrosive gases given off by the anaerobic septic tank effluent passing though the pipes. They will be a constant source of nuisance odors — and also a potential safety issue due to collection of hazardous gases. Conveyance of septic tank effluent from septic tanks to the surge/dosing tank should be via fully sealed piping. The only access to the pipes (e.g., for flushing) should be through capped clean -outs installed at various points in the collection system. Also, for the deep sewer line depth proposed, the manholes will introduce additional points of entry for groundwater infiltration into the wastewater system, which has very limited capacity for extraneous water. 4. Filter Bed Drain Rock Depth. Detail 9 ("Leach Field Line") on Sheet C7.3 indicates an 8 - inch depth of drain rock below the 4" perforated pipe; 12 inches is required. APPENDIX A — NITRATE LOADING STUDY (Chesney Consulting, dated May 6, 2019) The appended Nitrate Loading Study by Chesney Consulting utilizes an annual chemical -water mass balance analysis (per Hantzsche-Finnemore Equation) to estimate the nitrogen loading impact on groundwater from onsite disposal of wastewater for the E&E Trading project. The analysis projects a resultant percolate concentration of 1.55 mg-N/L reaching the groundwater table, averaged over the 42 -acre footprint of the E&E Trading project site. This is compared against the drinking water nitrate -nitrogen standard of 10 mg-N/L to conclude that the discharge is within appropriate Iimits and will not significantly degrade groundwater quality. Comments: Methodology. The mass balance analysis per the Hantzsche-Finnemore Equation is a simplified method for assessing wastewater -nitrogen loading for typical rural residential properties served by septic systems. It doesn't explicitly account for large amounts of impervious surface, nor drainage retention facilities, as proposed for this proposed project. The improvement plans indicate nearly the entire site will be covered with buildings and paving, leaving very limited amount of open land area for deep percolation/recharge. The rainfall -runoff from impervious surfaces is planned to be collected and routed to an adjacent detention/retention basin for percolation and downstream discharge. The concept and