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GROUND WATER MONITORING WORK A DREDGE MATERIAL DISPOSAL SITE 1,ROBERTS ISLAND,PORT OF STOCKTON ■ 15N/14N (expressed as WIN) in nitrate-All water samples containing sufficient nitrate will be analyzed for nitrogen isotope ratio (15N/14N in the nitrate) to determine nitrogen sources. The sources for dissolved nitrate include oxidation of ammonia (known to exist within the dredge sediments), the decomposition of organic forms of nitrogen, atmospheric deposition, and the use of agricultural nitrogen fertilizers. Nitrates from these sources often have distinctive nitrogen isotope ratios. Because nitrate is highly soluble, it can serve as a conservative tracer. Therefore, it may be a good indicator of water in dredged materials migrating to underlying ground water. Conversely, the absence of nitrate derived from the dredged materials in underlying ground water would be indicative of significant attenuation. [Although widely used in academic research,no method of stable isotope analysis for nitrogen or any other element has been approved by the United States Environmental Protection Agency (EPA). However, the EPA and the United States Geological Survey (USGS) routinely contract Zymax Laboratory in San Luis Obispo, California to perform stable nitrogen isotope analysis in water samples. Accordingly,Zymax will perform the stable nitrogen isotope analysis (Silva, 2000).] ■ D/H and 180/160 (expressed as bD and b180)-[optional] oxygen and hydrogen isotope ratios of waters may be useful in identifying waters from differing sources. The three water types to be monitored (river water, sediment water, and groundwater) are likely to have distinctive dD and d180 values due to variations in source elevation(river water vs groundwater) and evaporation history (sediment water). These potentially distinct signatures may enable tracking the migration and mixing of these different sources of water. These ratios may be measured if nitrogen isotope ratios prove ineffective due to inadequate differences in ratios or concentrations of nitrate. 3.1.4 Task 4-Data Evaluation and Monitor Well Recommendations The data will be analyzed pursuant to the goals and objectives of the project and as described above. The evaluation of the data will yield waste characteristics of the dredge material; geologic cross-sections; comparisons of geochemical characteristics of dredge materials, foundation soils, peat, and aquifer materials; comparisons of the geochemical characteristics and quality of surface water, water within dredge materials and peat layer, and water within the shallow sandy aquifer. All analytical data will be summarized, and as appropriate, presented graphically. Once the data area evaluated, the results will be presented in a meeting with the RWQCB. The purpose of the meeting is to present the understanding of the site conditions and a site conceptual model, and as appropriate, recommend alternatives to the monitor well locations and construction details proposed in Phase 2. January 2005 Page 16 Environmental Risk Services,Corp.