Part one in a three-part series.

University of Massachusetts-Amherst Professor Jack Ahern and 10 graduate students — with financial support from the Barnstable Clean Water Coalition — have published a collection of site-specific landscape architecture pilot projects that are custom-designed to help clean up Mill Pond and Three Bays Watershed.

Ahern’s graduate “studio” looked holistically at a study area within the watershed, centering on the Marstons Mills River — the primary tributary of Three Bays. Providing landscape solutions for improving water quality is their goal. Their work culminated in the 67-page report published in limited edition last month and is the basis of a forthcoming book by Ahern, who owns a home in Osterville.

The U.S. Environmental Protection Agency, the Town of Barnstable, and the Association to Preserve Cape Cod have been collaborating for years on coastal watershed restoration in Three Bays, which is seen as one of the most compromised sites on Cape Cod. In 2016, a summer algal bloom caused fish kills and put the commercial oyster industry within Three Bays at risk.

According to Ahern and his students, the 12,000-acre watershed is 92 percent developed, with 7,000 residential parcels that fall within the towns of Barnstable, Sandwich, and Mashpee. Only 21 percent of the watershed is protected open space. Consequently, the water quality of the Three Bays is seriously impaired, routinely exceeding water quality standards for nitrogen.

Leading causes of pollution include septic system leaching (77 percent), stormwater discharge (13 percent), and fertilizer runoff (10 percent), the study says. Because almost 80 percent of the nitrates in the watershed are released from domestic uses, the study concludes, “landscape-based solutions to water quality degradation need to be collaborative and community-driven.”

The study says Cape Cod’s unique landscape features — specifically, its sole-source aquifer and sandy soils — also contribute to the severity of the region’s water quality concerns, exacerbating the high levels of nitrogen and bacteria in the water.

“Existing nitrogen levels are much higher in the upper areas of the Bays, especially North Bay, Prince Cove, and the mouth of the Marstons Mills River,” reads the report.

Hence, a proposed Herring Run Loop restoration and another pilot program that suggest reuse of dredged Mill Pond muck are both designed as “a conceptual toolkit.” The goals are increasing community stewardship, building upon the town’s vision for a boardwalk along Mill Pond, restoring the herring habitat, and — ultimately — re-introducing recreational boating and fishing.

Once thought to average 6- to 12-feet deep, Mill Pond is now as shallow as six inches in some places due to many years of erosion and sediment buildup, preventing it from being a functional aquatic ecosystem, the report concludes.

Immediately adjacent to the pond, a 14-acre parcel of land recently purchased by the Town of Barnstable from the Archibald family could be used as a staging area for dredging and dewatering the sediment in Mill Pond. In fact, Barnstable Town Council on Jan. 18 voted to approve a transfer order of $250,000 toward the pond’s dredging.

Although groundwater moves very slowly, says BCWA Executive Director Zenas Crocker, help is on the way for Three Bays — provided that residents are willing to change their behavior.

“The bigger picture is going to be social change,” Crocker said in a Jan. 12 interview at coalition headquarters in Osterville. “How do we motivate people to make these changes?”

Current attitudes towards lawn maintenance contribute to compromised water quality by way of lawn fertilizer and septic leeching, the report also concludes.

“Do something now,” said the usually mild-mannered Crocker, shifting gears from fact-finding to activism as he enters his second year as the coalition’s executive director. “For instance, an effective way to reduce nitrogen is to put an irrigation well next to your septic system.”

Equally important to the Cape’s water restoration, Crocker said, is using native coastal plants like bayberry, beach plum, and inkberry — along with marsh, meadow and unmowed grasses — to re-grade the topography, especially along Mill Pond and the Marstons Mills River corridor.

“Native flora has evolved with other species in the ecosystem and plays a critical role in supporting habitat for other species,” reads the report. In addition, native flora does not require extra watering or chemicals to thrive.

Landscape architecture grad students who authored the Three Bays Watershed Studio Report include: Andrew Capelluti, Allison Gramolini, Maggie Kraus, Sara Lawler, Mimi Lo, Kate O’Connor, Doug Serrill, Alysha Thompson, and Diance Tian. Contributors also include Horsley Witten Group, Barnstable Land Trust, and the Cape Cod Commission.

Upcoming articles in this series will focus on Ahern, who is vice provost of International Programs and professor of Landscape Architecture and Regional Planning at UMass/Amherst, and an emerging partnership with the Nature Conservancy.

Three Bays Watershed by the numbers

12,458 acres

7,093 parcels

92 percent developed residential lots
(approximately 1.6 acres per parcel)

Contributing towns: Barnstable,
Sandwich and Mashpee

54 freshwater ponds

Major freshwater streams:
Marstons Mills River & Little River

Source: Three-Bays Watershed: Landscape-Based Solutions to Improve Water Quality

The Barnstable Patriot – New book seeks to help Three Bays Watershed