SU0007337_SSNL - Laserfiche WebLink

Home Browse Search

Q 4.2) Any of the above land use could create environmental concerns that may be discovered in the future. As evidenced by the testing of the on-site domestic well, groundwater nitrate concentrations are above the Maximum Contaminant Level (MCL) at 123 ppm. The agrichemical Dibromochloropropane (DBCP) was found to be Below Detectable Limits (BDL). Nitrate concentrations are from agricultural fertilizer inputs and nitrogen mineralization. As depicted on the Tentative Parcel Map, the topography of the site is approximately-5 feet below MSL, and relatively level. Therefore, septic system design criteria for slopes do not have to be considered. (§ 3.1,3.2,3.3,and 3.4) It is known from conversations with EHD staff that the septic system serving the existing residential structure has had problems in the past when the structure was used as a farm labor camp. However, no record of repairs, etc. were found in the microfiche files at EHD. A malfunctioning septic system in this locale may be attributable to the indigenous shallow peat soils, although the soils at the typical leachline depth did exhibit a surprisingly high degree of permeability as evidenced by the percolation test results obtained on both proposed Parcels. (§ 3.4) The subject property is in an area designated as "High Water Table Area"by EHD's map denoting the various soil types and septic system requirements throughout the County. EHD requirements in this area are for leachlines exclusively, with no sumps or seepage pits. One hundred feet of leachline per bedroom are required. (§ 5.4) Since the water table is comparatively shallow in this area at approximately seven feet below existing grade and the fact that the shallow soil structure at typical leachline depth appears to be adequate for proper effluent management, seepage pits are not allowed to be installed in this area. (§ 3.5 and 3.6) A review of Application Permits on microfiche file at EHD reveals there have been two (2) Applications or Permits for Repairs/Additions/Replacements to septic systems within a one-half mile radius on State Route 12 exclusively. As referenced, there are probably more Permits that may not have been microfiched. (§ 5.4) This can be considered a low number of Repairs/Additions/Replacements and appears to be mainly attributable to not only the very sparse development in this locale, but also the referenced relatively permeable soil at the shallowest acceptable leachline depth of 36 inches. Failures that may have occurred at the on-site farm labor camp in the past may have been from excessive water use. The permits found in EHD microfiche files are located in Appendix D. (§ 5.1 and 6.0) SOIL PROFILE AND PERCOLATION TESTING (§ 5.4) The USDA Soil Map shows the on-site soil to consist of a Shinkee muck (#247). Typically, these soil types are poorly drained with slow permeability. However, as referenced, below two feet, there is a fine, sandy yellowish brown silt with a fair degree of permeability. Sufficient soil "fines" exist in this soil type to impede rapid percolation so treatment of effluent can occur before reaching the water table, unlike what would be encountered with a sandy soil. Page -2- Chesney Consulting