TECHNICALLY BASED LOCAL LIMITS THE POC, PLANNING, AND THE PUBLIC

The Dallas Water Utilities (DWU) has operated an industrial pretreatment program since 1959. This program has grown over the years to become one of the largest in the United States, with 130 permitted significant industrial users (SIUs), 81 of which are categorical industries. Recently, a study was commissioned to evaluate DWU's existing technically based local limits (TBLL) for SIUs. Since the previous limits were developed in 1991, the wastewater flows have increased by 39 percent. The goal of updating the TBLLs was to account for the increases and changes in the wastewater system, to identify the applicable pollutants and standards, and continue providing protection to the public, utility staff, and the receiving streams.A computer model, specific to the DWU system, was used to evaluate the pollutants of concern (POCs) and to establish the headworks limits at the treatment plants. The existing ordinance (Chapter 49 – Dallas City Code) and local limits included various pollutants whose inclusion was found to be unnecessary based on the results of the POC analysis. A Monitoring Plan was developed and a seven-day sampling program was conducted at ten domestic sites and at both wastewater treatment facilities.The redevelopment of the TBLLs included formation of an Advisory Group made up of industry representatives and other interested parties who volunteered to attend various meetings and to review the POC analysis, the Monitoring Plan, and the TBLL Report. With more than 30 participants this was one of the largest public involvement efforts for a TBLL study in the United States.