ARCHIVED REPORTS_2008_26 - Laserfiche WebLink

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"WASTE DISCHARGE REQUIREMENTS -6- FORWARD INC.,FORWARD LANDFILL SAN JOAQUIN COUNTY Stockton proposes to expand its facility to include the property adjacent to Forward's northern boundary. 18. The shallow ground water beneath the site is contained in the Victor Formation. These sediments generally have moderate permeabilities with locally high peimeabilities in the sandy and gravelly lenses. Ground water in the Victor Formation is unconfined and flows in a north-northeasterly direction beneath the site. Locally, ground surface is about 40 feet in elevation. The regional groundwater table is about 60 to 70 feet below ground surface or-20 to -30 feet in elevation. The quality of this water is suitable for domestic or agricultural use. 19. Low levels of volatile organic compounds (VOCs)have been found in monitoring wells (NfWs) at the facility beginning in June 1988. Wells MW-2B, MW-3B,MW-5B, and MW-13B have been impacted by a release of VOCs from the landfill. These VOCs included halogenated compounds such as trichloroethane, tetrachloroethane, 1,1- dichloroethane, 1,2-dichloroethane, 1,1-dichloroethane, cis-l,2-dichloroethane, chloroethane and dichlorodifluoromethane in concentrations between 0.7 and 3.6 µg/1. Phenolics (total phenols)were reported in wells -12B, -27 and -20 at levels i between 10 and 20 µg/l. Other aromatic VOCs including benzene, toluene and xylenes were also found in ground water samples. Staff Diagrams indicate that the downgradient water chemistry in the vicinity of MW-2B and MW-18 had higher relative concentrations of chloride than the other wells during 1994. The total concentration of ions was generally higher in MW-2B and to a lesser degree MW-5B and MW-13B,than the other wells. Overall,there are sporadic occurrences of organics at low concentrations in a few wells, except for MW-2A/2B and MW-5A/5B where two to three compounds have been detected consistently. In 1994, there were fewer detections of halogenated compounds in the wells and the concentrations were generally much lower than previous years. 20. The beneficial uses of ground water are municipal, domestic, agricultural, and industrial supply. 21. The site receives an average of 14.27 inches of precipitation per year based on precipitation data from the Stockton WBAP Station number B00-8560 approximately 8 miles northwest of the site. The mean evaporation for this site is 78.43 inches per year as measured at Oakdale Woodard Reservoir between the years 1919 and 1968. Based on these data, average annual net evaporation at the site is 64.16 inches. 22. The 1,000-year, 24-hour precipitation event for the site is 4.11 inches. The 100-year, 24-hour precipitation event is 3.25 inches. The estimated 100-year annual precipitation is 25.42 inches.