The short version
Zenas "Zee" Crocker's talk "Shubael Pond Project: Lessons Learned," given June 18, 2024 at the Waquoit Bay Reserve's Cape Coastal Conference in Hyannis, asks whether upgrading old septic systems in a neighborhood on Shubael Pond (Marstons Mills, Barnstable) can cut nitrogen at lower cost where sewers are decades away. The slides carry the Barnstable Clean Water Coalition's logo and show monitoring data from 13 homes fitted with a woodchip-based nitrogen-reducing system: median nitrogen in the treated wastewater was 2.9 mg/L, against 87.4 mg/L going in. They also compare costs and funding for sewers, upgraded septic systems and cranberry bog restoration. This summary rests only on what the slides show. We had no recording, speaker notes or underlying reports, and slides are not peer reviewed.
What the report covers
The slides run from Cape-wide background to the Shubael Pond neighborhood, then to costs.
- Background: a map of how little of the Cape is sewered, land cover maps for 1951 and 1999 (Woods Hole Research Center), and a chart of rising nitrate in Osterville wells from 1960 to 1999.
- Rules and plans: the state's Title 5 (septic code) changes for nitrogen-sensitive areas, Barnstable's 30-year sewer plan, and Tisbury's new septic rules, drawn from two Vineyard Gazette articles.
- The neighborhood: the Sand Shores area around Shubael Pond (about 350 homes), with 14 target homes and some alternates in its southwest corner. The slides credit the Horsley Witten Group with the surveys and septic inspections.
- Groundwater monitoring: more than 35 shallow wells drilled in the neighborhood, managed and funded by the US Geological Survey and US EPA Region 1, sampled quarterly.
- System performance: nitrogen in and out of the NitROE® systems (made by KleanTu) at 13 homes, December 10, 2021 to January 24, 2024, as medians, plus forecast yearly nitrogen removal per home.
- Cost comparisons: cost per kilogram of nitrogen removed for three approaches, who pays under three funding scenarios, and as-built costs of local systems from Scott Horsley, a water resources consultant.
What it found
- Nitrogen cut to a few mg/L. Across the 13 monitored homes, the median nitrogen in untreated household wastewater was 87.4 mg/L and in treated wastewater 2.9 mg/L, about a 97% drop by our arithmetic (Crocker, 2024). Individual systems ranged from 1 to 7 mg/L coming out. The newest system, installed in September 2023, was the highest at 7 mg/L.
- Per-home removal of 3 to 17 kg a year. A chart forecasts yearly nitrogen removal for each home from its water use, between about 3 and 17 kilograms; one home has no data (Crocker, 2024).
- Cheaper per kilogram than sewers. The slides put the cost of removing a kilogram of nitrogen at $850–935 for sewer construction, $308–417 for septic upgrades and $110–155 for cranberry bog restoration (Crocker, 2024).
- A different bill for homeowners and town. In the slides' funding scenarios, a sewer costs roughly $140,000 per home, split between a state loan subsidy, town taxes and about $20,000 from the homeowner. An upgraded septic system comes to roughly $46,000, with the homeowner share between $0 and $10,000 depending on tax credits and loan subsidies (Crocker, 2024).
- Real local costs. Scott Horsley's table of as-built costs, including engineering, averages $33,409 per system across Buzzards Bay Coalition and Barnstable Clean Water Coalition projects. Adding $10,000 for 2023 prices gives $43,409. Retrofitting an existing system ran lower and full replacements higher. The treatment tank is about 53% of the cost, installation and parts 35%, engineering 10%, and electrical and permitting 2% (Crocker, 2024).
- Sewers will reach only part of Barnstable. The slides describe a $1.46 billion, 30-year sewer plan covering 11,823 of the town's 26,965 parcels. With about 3,100 parcels already sewered, only 55% of the town would be served. They also note more than 100 nitrogen-reducing septic systems in town, 85% of them reducing nitrogen (Crocker, 2024).
- A big nitrogen source near one bay. For Cotuit Bay, the slides count 106 single-family homes within 400 feet of shore, discharging about 12 million gallons of wastewater a year and an estimated 4,500 pounds of nitrogen. Systems performing at 4 mg/L could eliminate about 3,600 pounds, based on Cape Cod Commission software and Cotuit Water Department data (Crocker, 2024).
- New state rules put the choice to towns. For designated nitrogen-sensitive areas on the Cape and in southeastern Massachusetts, the slides summarize the revised Title 5 as offering towns two paths: a watershed permit within 20 years, which makes the town responsible, or required home upgrades to nitrogen-reducing systems within 5 years, which makes the homeowner responsible. A Tisbury example shows rules requiring a system that removes at least 95% of nitrogen at sales, repairs, new construction and additions (Crocker, 2024).
What it means for Waquoit Bay today
Shubael Pond is in Marstons Mills, in Barnstable's Three Bays watershed, outside the Waquoit Bay watershed, and the Cotuit Bay figures are also Barnstable's. The same woodchip-style system has been tested here, and the same state rules apply to Falmouth and Mashpee: the slides' map appears to place both towns among the watersheds MassDEP will automatically designate as nitrogen sensitive. The choice the slides lay out, between a town-run watershed permit and home-by-home upgrades, is one our towns face too. Our summary of the published study of these Barnstable systems, Can a box of woodchips fix a septic system?, reports averages over a longer period and found that most, though not all, met the state's 10 mg/L goal. Slide medians and study averages are not directly comparable.
The cost figures are one group's estimates, so read them as estimates. The $110–155 figure for bog restoration sits beside research on our side of the Cape: in Falmouth's restored Coonamessett bogs, the researchers estimated that nitrogen removal was well under 1% of what the river carried. Restoration helps fish and wildlife, but it may not stand in for wastewater cuts. This talk was given at the Waquoit Bay Reserve's 2024 Cape Coastal Conference, and our conference roundup lists all the talks, with slides and videos.
See the presentation
Crocker, Z. (2024, June 18). *Shubael Pond project: Lessons learned* [Conference presentation slides]. Cape Coastal Conference, Waquoit Bay Reserve, Hyannis, MA. Barnstable Clean Water Coalition. https://waquoitbayreserve.org/wp-content/uploads/Shubael-Pond-Project_Zee_Crocker.pdf
License: The slide deck shows no open license and reuses others' maps, charts and news headlines, so we link to the Reserve's copy and do not host it here. This is a summary of the slides only (not a peer-reviewed paper), made without a recording or speaker notes. The card image is a title card made from the citation.
Drafted with AI assistance from the linked source.
