The short version
This four-page summary is the Waquoit Bay chapter of the Cape Cod Commission's regional water quality plan (the "208 Plan" update). It asks a simple question: how overloaded is the bay, where does the nitrogen come from, and what has to change? The Commission pulled together the state's Massachusetts Estuaries Project (MEP) findings, land and wastewater data, stream and well measurements, and each town's planning history. It rates the bay's water threat level "high." The bay is over its nitrogen limit, septic systems supply about three-quarters of the controllable nitrogen, and the MEP restoration scenario calls for cutting total nitrogen by 53% and septic nitrogen by 76%. We read the full four-page appendix, which summarizes other studies and reports no new research.
What the report covers
The appendix is a fact sheet that gathers existing data for the Waquoit Bay watershed into one place, in these parts:
- The problem: the bay's nitrogen status under the MEP technical report and state and federal nitrogen limits (TMDLs, or total maximum daily loads).
- Nitrogen loads and sources: total wastewater flow, the nitrogen load before and after natural removal, and the share from septic systems, lawn fertilizer and stormwater.
- The bay and its watershed: size, number of parcels, how developed the land is, and wastewater treatment plants.
- Fresh water: ponds, the Childs and Quashnet rivers (flow and nitrate), and drinking water wells.
- Degree of impairment: the ecological condition of each part of the bay, and nitrogen readings at three monitoring stations.
- Local progress: what Mashpee, Falmouth and Sandwich had done on wastewater planning, and how much of the load each town contributes.
What it found
- Over the limit. The bay system exceeds its critical nitrogen threshold, which the report says results in impaired water quality (Cape Cod Commission, 2015). State and federal nitrogen limits were set in 2006 for the Quashnet River, Great River, Jehu Pond and Hamblin Pond, but not for the rest of the system, and the report lists the limit-setting status as "in progress."
- Septic systems dominate. Of 333 million gallons of wastewater a year, 304 million go to septic systems and 29 million to treatment plants. The report attributes 75% of controllable nitrogen to septic systems, 12% to lawn fertilizer and 13% to stormwater running off hard surfaces. The total load is 48,319 kg a year before natural removal and 40,233 kg after it.
- A 53% and 76% cut. The MEP restoration scenario, which adds up the targets for each part of the bay, calls for cutting the watershed's total nitrogen by 53% and septic nitrogen by 76%.
- Three towns share the load. Falmouth contributes 54% of the wastewater nitrogen that reaches the bay after natural removal, Mashpee 42% and Sandwich 4%. The report notes that part of Mashpee and Sandwich land belongs to Joint Base Cape Cod, which the towns do not control and whose treatment plant discharges outside the watershed.
- A heavily developed watershed. The watershed covers 15,021 acres and 7,171 parcels, about 80% of them developed residential parcels, at roughly 2.1 acres per parcel. It has three wastewater treatment facilities: Mashpee High School, a commercial park and the Southport retirement community.
- Streams carry the signal. Average nitrate was 0.21 mg/L in the Childs River and 0.20 mg/L in the Quashnet River. The report notes that pristine parts of the aquifer sit below 0.05 mg/L, and takes the higher stream levels as evidence of nitrogen pollution from residential areas. Of seven drinking water wells listed, four were between 0 and 0.5 mg/L of nitrate, two between 0.5 and 1, and one between 1 and 2.5.
- Health ranges from healthy to severely degraded. On the MEP's four-step scale, the upper Quashnet River is severely degraded; the lower Quashnet and southern Waquoit Bay range from significantly impaired to severely degraded; Jehu Pond, northern Waquoit Bay and both halves of Eel Pond are significantly impaired; Hamblin Pond, the Great River and Sage Lot Pond are moderately impaired; and the Little River ranges from healthy to moderately impaired.
- Monitoring stations miss their targets. Total nitrogen was 0.40 mg/L in Waquoit Bay against a 0.38 threshold, 0.65 mg/L in the Childs River against 0.38, and 0.67 mg/L in the Eel River against 0.49.
What it means for Waquoit Bay today
This summary describes our own watershed, so it applies directly: the same bay, rivers and ponds CPWB works to protect, and the same towns, Falmouth and Mashpee, that must act. It is a snapshot drawn mostly from earlier studies, with no date given in the document itself, so its numbers reflect the state's MEP work and town planning as of about 2015. For the long-term science behind where the bay's nitrogen comes from, see where Waquoit Bay's nitrogen comes from. The Research Library also holds our summaries of the Commission's 2015 Section 208 Plan, its 2017 Waquoit Bay watershed report (which gives somewhat different town shares than this one, so check which version you quote) and the state's threshold report.
The "local progress" section is a record of where planning stood then: Mashpee had been planning since 2001 and filed a final needs assessment in 2013, and Falmouth's 2014 plan proposed deferring sewers in the Waquoit Bay watershed until pilots of non-traditional methods report back. Sandwich was just starting.
Read the report
Cape Cod Commission. (2015). Waquoit Bay. In *Cape Cod Area Wide Water Quality Management Plan Update, Appendix 5B: Watershed summaries, Upper Cape* (pp. 1–4). Barnstable, MA. https://ww2.capecodcommission.org/208/appendices/Chapter%205%20Appendices/Appendix%205B:%20Watershed%20Summaries/Appendix%205B_UC_Waquoit%20Bay.pdf
License: A Cape Cod Commission publication, not openly licensed, so we link to the Commission's copy rather than host the PDF. This summary is based on the full four-page appendix, not just an abstract. The card image is the first page of the appendix, which is hidden on the post page.
Drafted with AI assistance from the linked source.
