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James Sandner -2 - 3 March 2004 Juan Mercado Gordon Palmer contributing to the production of methyl mercury,the revised tentative WDRs have been modified to include a methyl mercury study for the Sherman Island DMD sites. The commenter also expressed concerns over possible reuse of the dredge sediments and how sediment should be evaluated for reuse activities. Staff concur that sediment quality may influence reuse activities. The proposed revision would require that the Discharger submit a Report of Waste Discharge prior to any reuse of dredge material from the two DMD sites. The Report Waste Discharge would provide staff with the opportunity and information to determine if the proposed reuse activity is a threat to water quality. Maintenance dredging operations are extremely variable and may range from several hours to 24 hour per day operations. Staff has changed the surface water sampling frequency to address the variability in dredging operations. Surface water monitoring near dredge operations would be conducted every four hours during dredging operations including operation of tugs and barges. Staff believe that the proposed monitoring frequency is also sufficient to account for tidal and diurnal changes that may occur within the river and therefore is adequate to determine compliance with the prohibitions and limitations contained in the Order. One commenter suggested that the Order include the Basin Plan's surface waters limitation for E. coli. that was recently adopted by the Regional Board. However, at this time the Basin Plan amendment has not been approved by the State Water Control Board or U.S. EPA. Until the amendment has been approved, staff cannot implement the proposed Basin Plan amendment. Studies have shown that sufficient levels of copper can reduce the olfactory senses of many salmonids, as well as affecting normal ion transport across the gills. Sediment in the vicinity of Sherman Island may contain copper which potentially could be discharge from the DMD sites via the decant water. The National Marine Fisheries Services provided comments to the EA that included a recommendation to ensure salmon species are not significantly impacted by copper in the decant water. In order to address concerns for salmonids, the EA specified a mitigation measure that prohibits total copper concentrations in decant flows from exceeding ambient river levels. In particular, EA Mitigation Measure No. 3.3.3 state "Total copper concentrations in the decant water would be hold to within 3 to S parts per billion (ppb) of the ambient river levels. Decant water that has copper levels above ambient conditions in the San Joaquin River would be held in the DPM sites until those levels decline to within 3 to 5 ppb of the ambient copper concentrations in the river at the point of discharge." The late revisions incorporate the listed EA mitigation measures by adding a new discharge prohibition for decant water from the DMD sites on Sherman Island. Staff has also made a number of minor language changes that were necessary to clarify the Order. Please see the attached late revisions for these late editorial changes. For your convenience, the changes to the revised WDRs are shown in bold, italics and strike out mode. Due to the number of changes, the tentative late revisions for the revised WDRs are being circulated for public comment. Any written comments or recommendations you may have concerning the enclosed late revisions should be submitted to this office by 18 March 2004 in order for us to give them full