13-Resolution authorizing contract with Weaver Boos Consultants

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may extend beyond the MSD boundary, currently or in the future. There may be no other naturai or legal controls or safeguards outside the boundary of the MSD that prevents installation of a potable-water well within one- half mile of the MSD property, subsequent to MSD certification. If the TCEQ becomes aware of such a situation, then the person responsible for the MSD groundwater contamination will have to assess and remediate for potable purposes in accordance with 361.808 of the MSD statute. Unfortunately, the TCEQ may not be made aware of new wells in the vicinity of the MSD. If future potable use of groundwater in the vicinity of the MSD property is a concern, then local initiatives to monitor and report water-well installation in the vicinity of existing MSDs may have merit. Some cities may already have other ordinances or controls that prohibit water wells or require a city permit to be obtained before a water well can be installed. Such controls are not typically sufficient to satisfy the MSD ordinance requirements, but can effectively give added protection. Alternatively, the city may also consider notifying local citizens as a means to safeguard against future potable-water use in the MSD area. Technical expertise and technical information When evaluating the appropriateness of MSDs, a city may encounter some complex legal and technical matters. Considerations include which departments should evaluate MSD proposals; what problems, if any, they anticipate in arriving at a conclusion; and what information is needed to support a good decision on the matter. The MSD statute requires the applicant to supply the specific information listed in the statute, but the city might have a need for other information. In that case, it might consider defining procedures for MSD applicants. Contaminant Considerations The appropriateness of a particular MSD can depend on the nature of the contaminants and the expected behavior of the groundwater contaminants over time. Detailed information on contaminant behavior is not required at the time of submitting an MSD application. Therefore, the MSD application may be prepared and submitted to the TCEQ at the front end of a remediation project. This may result in the TCEQ having little to no technical information regarding contaminant conditions at the property at the time of processing the application. Further, once an application is certified by the TCEQ, the requirements of THSC 361.808 take effect. As discussed previously, depending on the presence or absence of local potable-water wells and the applicability of other exposure concerns in the MSD property and surrounding area, there may not be a requirement to define the nature and extent of groundwater contamination, or to evaluate the potential for the contamination to spread further (laterally, or to deeper groundwater zones). Also, the groundwater contamination at an MSD property may have a potentially short or long legacy, depending on the nature of the contaminant and site conditions. Some groundwater contaminants, such as benzene, are less persistent in the environment than others. That means that once the contaminant source is mitigated, the dissolved groundwater contaminant commonly degrades or its concentration naturally diminishes due to bacterial, chemical, and/or physical processes. Other contaminants, such as some chlorinated solvents, are not as readily amenable to natural degradation and may be more persistent in the environment. Additionally, some contaminants degrade to a more toxic groundwater contaminant. For example, tetrachloroethylene, also known as perchloroethylene or "perc"-a commonly used dry-cleaning chemical- degrades through several intermediate chemicals to the more toxic chemical, vinyl chloride. All other factors being equal, the longer-legacy contaminants might naturally warrant more concern than short-legacy contaminants. Unfortunately, in many instances the longer- Iegacy contaminants are also among the most difficult, and therefore among the most expensive, to clean up. GI-326 Page 8 ~ ~ 1