Monitoring, continued

Monitoring answers these questions: Is the water safe for humans and fish? Can it be treated economically for domestic use? Is the treatment plant meeting its permit limits? Are the BMPs working as intended? The “why” of monitoring guides the type of program needed.

Decisions about what, where, and when to monitor are most important, and the answers to these questions can vary depending on the purpose of the monitoring program. For example, if the program is supposed to measure the effectiveness of the CWA’s regulatory program dealing with “point sources,” then monitoring should generally take place just above and just below the discharge pipes coming from such sources. In addition, it would usually make most sense to analyze for pollutants that are covered in the source’s permit. A similar approach could be taken to assess the effectiveness of best management practices installed on farm land, logging sites, or other nonpoint pollutant source locations. Note that the monitoring above and below point sources is often a requirement for the point source in NPDES permits, not just the state.

Monitoring efforts also can be organized to determine short- or long-term water quality trends. For example, monthly or quarterly sampling in an area experiencing rapid development can help to determine if post-construction stormwater design standards are indeed minimizing water quality impacts to the maximum extent practicable. Likewise, follow-up ambient monitoring can be used to determine whether or not load reductions called for in a TMDL are being met.

If the aim is to get an overall picture of water quality in a state (e.g., what percentage of all waters are meeting WQS), then a statistically chosen random set of sampling locations would usually be best. (See National Aquatic Resource Surveys for more information on this topic.) Moreover, the types of pollutants to be tested for would need to be broader than just those known to be coming from a particular type of discharger. Currently, state ambient monitoring programs tend to be focused on waters that the state has declared impaired or suspects is polluted.