Monitoring Should Be Comprehensive
In response to the Aug. 13 story “Westbrook Digs in with Groundbreaking New Septic System,” I’d like to voice concern about the monitoring plan for this system as an environmental scientist employed by Geomatrix LLC in Old Saybrook and an expert on passive nitrogen removing systems.
Westbrook Water Control Authority Chair Lee McNamar is quoted as saying, “Two to four months will [provide] a good spread of test results.” Nitrogen removal diminishes significantly after the first few months of system use so if sampling only occurs during this time frame, an unrealistic expectation for treatment is likely.
Monitoring should span multiple years and throughout all seasons as nitrogen removal in drainfields is known to vary seasonally. They indicate that samples would be collected and analyzed daily; daily sampling for two to four months will only provide a snapshot of the potential nitrogen removal, though we admit a detailed snapshot. Less intensive sampling over a longer period of time provides much more robust analysis of the potential nitrogen removal of the system.
For example, Geomatrix has sampled the passive nitrogen removing system at the Old Saybrook Town Garage quarterly since 2017. Capturing nitrogen removal at varying times of the year allows us to understand how the system performance changes with temperature, precipitation, system use, etc. An additional strength of our system is that half of the drainfield was designed without the sawdust addition; this paired design allows us to compare, apples-to-apples, the nitrogen removal performance of a system with and without the addition of sawdust.
Passive nitrogen removing septic systems have the potential to save taxpayer money while benefiting our state’s waterways. These systems, however, are in their infancy, so monitoring plans should be comprehensive in order to stand up against scrutiny from interest groups promoting proprietary nitrogen removal systems.