The Carlisle Mosquito Online

Friday, November 23, 2007


BOH may revise septic regs, allowing systems nearer wetlands

Board of Health (BOH) Chairman Jeffrey Brem conducted a mini-seminar on septic system science at the November 13 Conservation Coffee. The aim was to enlighten attendees on the science behind proposed changes to Carlisle's Supplementary Regulations. These are the rules that strengthen or add to the state's Title 5 requirements, taking into account local geological, environmental and demographic factors. Unlike Town Bylaw changes, regulations can be altered by the board without Town Meeting action.

Noting that a majority of the proposed changes are merely "housekeeping matters," he identified four regulations on which significant amendments are under consideration, namely setback requirements, flow rate specifications, garbage disposal units, and encouragement or a requirement for alternative technologies as compared to traditional soil absorption systems.

Alternative technologies

Brem explained that, because these alternative systems provide for more effective breakdown and treatment prior to release of the effluent to a leaching field, more flexibility can be introduced as to system size and location. He devoted considerable time to the basic science behind most common types of alternative technologies, always stressing that the aim of any septic system is to keep harmful contaminants out of the groundwater. He described the major omponents of the new systems as "miniature sewage treatment plants" that produce nearly clear effluent, thus reducing the work of the soil absorption (leaching field) components. Since keeping contaminants out of the very mobile groundwater is the goal, he maintained that it is the vertical specifications, far more than the lateral ones, that protect the nearby water bodies and wetlands.

Setback changes

Based on the above concepts, and indicating a desire for more flexibility in the application of BOH rules and regulations, Brem presented the major changes currently under BOH consideration. The first would reduce the setback regulations that require septic tanks, pumps and leaching fields to be at least 100 feet from all streams and wetlands to 50 feet, perhaps dependent on whether alternative technologies are chosen and/or the results of a review of soil conditions and environmental impacts are favorable. Alternative technologies are currently more expensive for small family systems but are often more economical for larger homes and shared systems, because they allow for smaller soil absorption components and fewer aesthetic challenges.

Garbage grinders banned?

A second possible modification applies to water flow requirements that depend on the number of bedrooms (the total number of rooms divided by two, minus one). The state's standard under Title 5 is 110 gallons of inflow per day per bedroom (GPD), but Carlisle presently adds 50% to that figure to counter the extra burden on the system caused by garbage disposal units, bringing the total requirement to 165 GPD. This applies whether or not such a unit is in use in the residence.

The changes under consideration would allow the GPD to drop to the state level as the number of bedrooms increase. The board is also contemplating an outright ban on garbage disposal units and dropping the 50% add-on completely. Were that proposition to be adopted, they might require a permanent "sticker" to be attached to kitchen plumbing to remind both present and future owners of the ban — this in addition to a permanent deed restriction to that effect. The board's decision on the matter is still very much up in the air.

Smaller setback

allows more development

Foreseeing that reduction of septic system setbacks from 100 feet to 50 feet would arouse opposition, in part because it would allow more lots to be developed, Brem admitted that, indeed, this would occur, but emphasized that it was definitely not the goal of the change. He reiterated that the aim is greater flexibility for the landowner and the board. At this point, Planning Board associate member David Freedman asked whether the setbacks would remain the same for large, shared systems like Coventry Woods, and Brem assured him that they would. "Everything we do is based on science, unlike the Planning Board," he said.

Work near wetlands

Toward the end of the discussion, Conservation Administrator Sylvia Willard made a "personal" observation that allowing leaching fields to be installed as close as 50 feet from a wetland would mean more work for both the Conservation Commission (ConsCom) and the applicant. Because any work within the 100-foot wetland buffer zone must be reviewed by the ConsCom according to the Wetland Protection Act, the applicant might need to file twice with ConsCom — once for disturbance caused by soil and water tests (e.g. "perc" tests) required by the BOH and once for the septic system itself.

Also, a 50-foot limit would often mean more clearing and less vegetation near the resource area and lead to faster evaporation during hot weather. Brem agreed that for this and other reasons, the changes would require closer cooperation between the Planning Board, ConsCom and BOH.

A final comment from arborist John Bakewell reminded participants that no board in Carlisle can begin to control pesticide use on private property, and that an increase in buildable lots would mean more lawns and gardens close to water resource areas. "Many homeowners, and even lawn care contractors, don't know what they're doing with these substances," he said, suggesting it might be detrimental to groundwater.

2007 The Carlisle Mosquito