SR0081494_SSNL (2) - Laserfiche WebLink

Home Browse Search

F . SOIL SUITABILITY STUDY FINDINGS A. SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION SSS§ 1.1. As referenced, surrounding land use consists of residential, commercial, and some industrial. Those properties within the County have on-site domestic well water and septic systems. SSS§3.1,3.2,3.3,3.4,3.5,3.6,3.7, 6.8. EHD Permit Application files for septic system repairs/ replacements/additions reveal one Permit within half-mile radius from the subject property. This one permit can be attributed to the sparse development in the locale of the subject property. As noted, the shallow soils have slow permeability. However, the deeper soils possess exceptional permeability. Therefore, a deeper disposal structure, specifically a sump, is incorporated in the system design for this project, as referenced in Section IV of this report. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS The United States Department of Agriculture - Soil Conservation Service (USDA-SCS) indicates the property soil consists predominately of Jacktone clay(#180) with the extreme southern end of the property as Veritas clay(#266). The effluent disposal area will be installed in the Veritas clay soil. SSS§5.2. The surface and subsurface soil investigation began on October 10,2019 with the drilling of a 36-inch and 96-inch deep perc test.borings. The perc test borings were drilled using a truck-mounted B-24 drill rig, adjacent to the proposed location of the disposal area so that no disturbance of the effluent accepting soil profile would occur. NLS§ 1.1, 1.2. Composite soil samples from the test boring were retrieved for chemical and particle size analysis from the 3 ft and 8 ft depths. As the noted on the attached A&L Laboratory Soil Analysis Report,chemical analyses of the retrieved soil sample quantify several constituents that influence nitrate loading for this project. The important parameters for nitrate loading assessment are the organic matter, clay content,pH, cation exchange capacity(CEC), and the nitrate-nitrogen content of the soil. As noted,the organic matter at both depths are low, as to be expected. These O.M. concentrations suggest there is a small potential for future nitrate forming from organic matter. Because septic effluent is composed predominately of ammonium(NH4),the pH, along with the CEC, are significant influences on ammonium molecules. The pH of the soil is alkaline which may have a positive effect in promoting ammonia formation and not ammonium formation, which is the precursor to nitrate formation. The CEC measures the ability of the soil to theoretically trap and hold ammonium molecules. Cation Exchange Capacities of the soil samples illustrate a CEC of 20.0 and 7.9 meq/100 g,respectively,which was expected given the clay content of the surface soils. A low CEC of 7.9 was expected of the deeper soils. This suggests that the surface soils (3-4 ft depth)have a high potential for the retention of ammonium molecules for microbial and plant root assimilation within these soils,thus the very low nitrate-nitrogen concentration. The 8-ft depth indicates a nitrate concentration 3x the shallow soils. Therefore, design criteria found on Page 7, will force septic system effluent to primarily stay in the filter bed,with a sump acting as a safety valve. Chesney Consulting