GLEC has extensive experience in the two most commonly used procedures for adjusting criteria to account for the water chemistry of a site and the assemblage of species that occur at a site, namely the Water-Effect Ratio (WER) Procedure and the Recalculation Procedure. Over the past decade GLEC has performed over 25 of these types of investigations for both municipal and commercial clients. In one project, GLEC was engaged by the New York City Department of Environmental Protection to investigate several mechanisms approved by the USEPA for deriving site-specific water quality criteria for chlorine, ammonia and cyanide. The objective of the program was to evaluate site-specific approaches to determine their possible utility in modifying the permit limits for chlorine, ammonia and cyanide at the City’s wastewater treatment plants. A mobile laboratory was deployed by GLEC at the 26thWard Wastewater Treatment Plant to conduct toxicity tests using site waters to assess if the water effect ratio procedure would be a viable approach to increase the permit limits for chlorine and ammonia at the treatment plant. Preliminary WERs using the site and reference waters relevant for the 26thWard WWTP indicated the WER approach would not increase the permit limit for chlorine, but may provide a slight increase for ammonia. Additional site-specific work using GLEC’s mobile laboratory is planned for both 26thWard and other NYC WWTPs.