SITE INFORMATION AND CORRESPONDENCE

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WASTE DISCHARGE REQUJREMERS ORDER NO. • 5 CITY OF LATHROP AND METROPOLITAN LIFE INSURANCE COMPANY CROSSROADS TREATMENT PLANT NO. 1, SAN JOAQUIN COUNTY 27. To evaluate the longterm infiltration rate, the Discharger performed double ring infiltrometer tests at each proposed land application area using treated effluent. Two tests were performed at each area. The test results are summarized below: TEST SITE INFILTRATION RATE (in/hr) Land App. Site 1 Land App. Site 2 Land App. Site 3 NDR-1 NDR-2 NDR-3 NDR-4 NDR-5 NDR-6 Average 0.95 0.77 2.56 2.70 1.16 3.32 28. Based on the National Resource Conservation Service soil survey, the soils in the proposed land application areas are Tinnin loamy coarse sand, Veritas fine sandy loam, Merritt silty clay loam, and Timor loamy sand. Published infiltration rates for the soils range from 0.3 to 3.0 in/hr. Groundwater Considerations 29. Based on groundwater elevations measured on 25 January 2001 in wells located in the land application areas,the groundwater flow direction was to the west-southwest; the groundwater gradient was approximately 0.0012 foot per foot. Groundwater flow direction measured at the evaporation/percolation ponds is influenced by groundwater mounding. Therefore the flow direction measured in the land application areas is considered to be more reliable. 30. The Discharger has been monitoring groundwater quality in Wells W-1, W-2, W-3, and W-4 at the treatment plant 1995 to 2001. Average groundwater quality is provided in the table below: Well TC N TDS (mg/1) NO,as N Depth (ft) W-1 <1.1 1,550 0.5 13.7 W-2 <l.l 1,742 12.0 12.9 W-3 2.1 1,879 60.1 15.6 W-4 <l.l 1,199 0.6 12.8 TC denotes total coliform organisms,MPN denotes most probable organisms per 100 nil sample,TDS denotes total dissolved solids,NO3 as N denotes nitrate reported as nitrogen. 31. Of the wells located at the treatment facility, only Wells W-1 through W-4 are sampled for chemical analyses. Well W-4 is located upgradient of the facility and wastewater ponds; Well W-4 possesses lower concentrations of TDS and nitrate concentrations. This data indicates the existing wastewater treatment facility has impacted groundwater quality. This Order includes provisions that will improve the quality of wastewater in the future. 32. Background groundwater quality at the land application areas was measured in a sampling event performed on 29 and 30 January 2001. The analytical data is presented in the table below: Well TDS EC Sodium Chloride Sulfate NO3 TKN TCO FC MW-1 2,540 3,750 496 543 904 0.107 <0.5 DET <1.0 MW-2 2,450 3,380 422 420 934 8.89 <0.5 DET <1.0 MW-3 1,310 1,990 330 123 439 <1.0 <0.5 DET <1.0