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' Supplemental Investigation Report,Problem Assessment Report and Work Plan Cleanu and Abatement Otder No 5-00-7a7 EAI Pro ect No 1232 2.0 BACKGROUND INFORMATION 21 Delta College - Robinhood Irrigation Well (RIW) The RIW owned and operated by Delta College is located southwest of the intersection of Robinhood Drive and Pacific Avenue (see Figure 2) The RIW was installed in 1950 and is reported to be 322 feet deep with perforations in multiple zones as follows PERFORATIONS (feet bo-) 40 to 70 94 to 118 184 to 190 196 to 202 208 to 214 220 to 226 ' 232 to 238 1 244 to 250 256 to 262 268 to 274 280 to 286 292 to 322 According to the Water Well Driller's Report for the RIW, "no strata were sealed against pollution " Information provided by Delta College indicates that the RIW is typically used (pumped) principally only during the months of May through October at an average rate of 600 gallons per minute (gpm) Ground water from the RIW was used to irrigate portions of Delta College's campus Ground water monitoring data for the Unocal and Wards sites show that pumping of the RIW influences and changes the natural direction of ground water flow in the area from easterly, to towards the RIW, 1 e , southwesterly for the Unocal site and westerly for the Wards site ' Sampling of the RIW by Unocal and/or Wards for dissolved petroleum constituents began in 1997 and continued through June 15, 2000 Copies of the results of testing ground water ' samples from the RIW were provided to Delta College on a timely basis Table 4 summarizes the results of testing ground water samples from the RIW ' In August 2000, Delta College students and staff reportedly complained of a gasoline odor from the water derived from the RIW As requested by the RWQCB, the RIW was taken out of service as of 6 00 AM August 22, 2000, and may not be put back into use without prior RWQCB approval BS 1232P IPW_WP -2- ENWRONMENTAL AUDIT, INC 8