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Map ID MAP FINDINGS Direction Distance EDR ID Number Elevation Site Database(s) EPA ID Number TRACY DEFENSE DEPOT(USARMY) (Continued) 1000182407 the primary disposal method as discharge of extracted and treated groundwater to shallow aquifers using the injection wells and infiltration galleries located on the main base property and in the annex. Groundwater is presently being extracted from the Upper,Middle,and Lower Horizons of the underlying Tulare Formation and is being treated by air stripping.The groundwater from four extraction wells is being treated to remove pesticides using liquid-phase granular activated carbon.Treated groundwater is reinjected into the Upper Tulare Formation using infiltration galleries.Treatment of the contaminated water is the primary remedy specified in the OU 1 ROD;however,an Explanation of Significant Differences(ESD)supported the modification of the original remedy to include natural attenuation for the portion of the plume east of South Banta Road. Optimization activities were conducted at Groundwater Treatment Plant 1 (TP-1)and TP-2 in the 2003 monitoring period to improve the systems'performance and reliability.From 23 May 2003 through 20 August 2003, TP-1 was converted from an air stripper system to a granular activated carbon in order to provide treatment for pesticides,which could not be removed by the air stripper. SWMU 2/3 SWMU 2 consists of two active sewage lagoons that have been in operation since 1942.The lagoons are unlined but bounded by earthen berths.The northern lagoon historically supported abundant vegetation and animal life;this lagoon was Geared annually,sometimes by burning.The southern lagoon historically contained grassy vegetation and reeds.The lagoons currently receive treated effluent discharged from the sewage treatment plant. The lagoons previously received effluent from the motor pool wash rack. Sometime between 1971 and 1979,industrial wastes from a SWMU 3 lagoon overflowed into SWMU 2. SWMU 3 consisted of two industrial waste lagoons that were situated within the southern lagoon of SWMU 2.The smaller lagoon was installed in 1972 and was unlined during its first year of use.The larger lagoon was installed between 1975 and 1979 and was lined at the time of construction.Historically,the lagoons received wastewater from the Industrial Waste Pipe Line(IWPL).This wastewater included effluent from the recoup operations from Building 26(wastewater from repackaging of petroleum products) and effluent from Building 10(wastewater from paint-stripping,degreasing,and steam-cleaning operations). A removal action was performed at SWMUS 2 and 3 in 1997-1998;approximately 17,951 tons of soil contaminated with pesticides were removed.During the action the industrial waste lagoons(SWMU 3)were removed to expand the southern sewage lagoon.The sewage lagoons were restored and continue to receive effluent from the sewage treatment plant.Standing water is normally just a few inches deep and covers only a small fraction of the total surface of the lagoons.Water may not be present throughout the entire year.The northern lagoon historically supported vegetation and animal life,and the southern lagoon previously contained grasses and reeds.However, all vegetation was removed in the 1997-1998 excavation and has not yet reestablished itself in the lagoons. SWMU 4 SWMU 4 is an unlined storm water detention pond located at the northern tip of the DDJC-Tracy site.Storm water has been discharged to the detention pond since 1971 through a network of underground storm drains and open surface drainage ditches.The detention pond is bounded by earthen berms approximately 12 feet high and collects runoff through inlets in the southern and eastern portion of the pond.The pond reportedly received rinse water from former paint-stripping,degreasing,and steam-cleaning operations.Selenium,lead,DDT,DDE,and DDD have been found in the pond sediment and were identified as chemicals of concern(COCl)in the ROD.The site attracts waterfowl that inhabit the area.Some of the water in the pond may be drained during the wet season if the pond is more than half full.During the summer,the water in the pond percolates/evaporates,and most or all of the pond usually dries up.The pond sediment has been scraped at least once over the past 20 years. Some of the water in the pond may be discharged to the West Side Irrigation Ditch during the wet season if the pond TC3372962.1s Page 38