SR0080751 SSNL - Laserfiche WebLink

Home Browse Search

H. SOIL SUITABILITY STUDY FINDINGS A. SUBJECT PROPERTY AND SURROUNDING STUDY AREA INFORMATION SSS§ 1.1. The Parcel is directly west and north of the existing Holly Commerce Center Complex, and the City of Tracy Wastewater Treatment Facility. These surrounding bodies of water have contributed significant influence to the water table underlying the project. Land use to the immediate west is agricultural production land and to the north is the proposed Building E&E which is also associated with this development. SSS§3.1,3.2,3.3,3.4,3.5,3.6,3.7, 6.8. Applications permits found in EHD files were available for review to determine the number of.permits issued for repairs/replacements/additions to existing systems within the one-half mile radius study area. The septic systems in this locale are sparse, so data is limited. There were no applications found on Sugar Road and six on Holly Drive. Given the clay content of the on-site and surrounding soils, septic system longevity can be considered limited and septic system failures will eventually occur. However, all the permits for repairs/replacements, except one, is decades old. This may indicate that originally installed systems were insufficient in size to manage ultimate effluent flow volumes. The project site will have level terrain after earthwork grading is completed; consequently, there is no need to incorporate design considerations for slopes within the effluent disposal area. B. SOIL PHYSICAL CHARACTERISTICS AND ANALYTICAL TEST RESULTS SSS§ 5.2. The UC Davis Soil Web indicates.the property as 85% Pescadero clay loam(#211), 4% Egbert clay loam, 4%Merritt clay loam, 4% Capay clay, and 3% Willows clay. NLS§ 1.1, 1.2. Surface soil samples and auger cutting samples from the bottom of each 36" perc test boring for the North and South sides of Buildings A&B were obtained for chemical analysis. As noted on the A&L Laboratory Soil Report in Appendix B, analyses of the soil sample quantify a number of constituents that influence nitrate loading for this project. The important parameters for nitrate loading assessment are the organic matter(OM), Estimated Nitrogen Release (ENR),pH, cation exchange capacity(CEC), and the nitrate-nitrogen content of the soil. The OM and ENR for all four samples are low. The soil nitrate-nitrogen concentration for the surface soils (Sample ID= SURF) indicate a medium concentration at 14 ppm. The four sample sites from the 36" sample depth show a marked decrease in nitrate-nitrogen content, except for Building B-South (BG-BS)which remained at the same concentration. This decrease may be attributable to denitrification. 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 at sample depth is alkaline which has a positive effect in promoting ammonia and not the nitrate substrate ammonium within the soil environment. Page-2- Chesney Consulting