SITE INFORMATION AND CORRESPONDENCE

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WASTE DISCHARGE ../ 3 RL�rOIREMENTS ORDER NO.R5-2003-0017 VILLAGE WEST MARINA MAINTENANCE DREDGING PROJECT SAN JOAQUIN COUNTY Average Concentration Solid analysis DI extraction Modified elutriate Constituent (mg/kg) (µg/1) test (µg/I) r Tributyltin 0.05 25 ng/L(24 hour)�K** Polyaromatic Hydrocarbons ND ND T>+ Polychlorinated biphenyls ND ND Organochlorine pesticides ND . ND -ter: ** Averages of detected and non-detectable results were computed with q4 non-detectable levels assumed to be 0. 12. Results from the pre-dredge solids analysis and DI extraction tests indicate that sediments will not contain pollutants at concentrations in excess of applicable screening values. Modified elutriate analysis indicate the potential for soluble arsenic in the effluent from the DMD to be 12.5 ppb, which is 2.5 ug/l above Receiving Water Limits. 13. Flows within 14 Mile Slough are influenced by tidal change. Tidal flow rate calculations and average background concentrations of soluble arsenic indicate dilution will result in an estimated soluble arsenic concentration of 1.9 ug/L within 14-Mile Slough. The Basin Plan Objective for arsenic within the Sacramento-San Joaquin Delta is 10 ug/L. Although there will be monitoring during the dredging operation, this project is not expected to exceed Receiving Water Limits for arsenic. - 14. Solids analysis indicated the presence of Tributyltin(TBT) in the sediment. The modified elutriate analysis indicate that levels of TBT in the supernatant are below water quality objectives after settling. TBT is an antifouling compound commonly found in marine paints. TBT is toxic to aquatic organisms and bioaccumulates in the aquatic environment. Characteristics of TBT promote sorbtion to sediments, although agitation through hydraulic dredging can partition TBT into the dissolved phase. Pre-dredge testing indicates that TBT is likely to resorb to the sediments within 24 hours and the effluent is not likely to exceed water quality objectives. TBT is not likely to leach from the material at the disposal site. Bacteria or ultraviolet light readily degrade TBT in the upland environment. The expected % life of TBT in aerobic environments (upland) is 1 to 3 months compared with approximately 2 years under anaerobic conditions (in- water). Although monitoring will be required, TBT is not expected to exceed water quality objectives or cause any environmental impacts in the upland disposal site or reuse areas where there is no substantial runoff to waterways. 15. The predredge testing of TBT indicated a minimum holding time of 24 hours at the DMD site to allow adequate settling of TBT. The DMD site is designed to allow for a 96 hour holding time.