Editor’s Note: This is the second in a three-part series.

During the 1990s, Beaver Brook Marsh, a large and ecologically rich part of the Beaver Brook watershed treasured by Milford nature-lovers, came up for sale.

Its owner, the South Central Connecticut Regional Water Authority (RWA), wanted to avoid environmental damage on this hitherto-protected raw land abutting Route 1, I-95, and the railroad, so they gave the city right of first refusal; they granted a conservation easement to the city in the marsh’s southern portion; and they imposed other conditions on development

Finally, citing zoning regulations, they expressed satisfaction that only 11 of the property’s 57 acres could be developed, saying any non-office use of the land was “unlikely” and “clearly incompatible.”

For years, environmentalists and city officials wrangled about whether Milford should acquire the marsh. No buyers materialized and the property degraded. Pollution from I-95 was most damaging. Invasive plants spread, such as phragmites, occasionally ignited by sparks from the railway

Construction of the Iroquois pipeline disturbed wildlife. Back-ups from the West Avenue sewer spilled into wetlands at the marsh. RWA built a boardwalk as an amenity. But the property was sliding down a slippery slope.

At last the marsh sold to Kingdom Life Church in 2002. Environmentalists rejoiced because church leaders wanted to preserve the land for recreation. The city rejoiced because they were off the hook for acquisition and because the church agreed to improve part of the easement, leading the city to back off on maintenance.

Soon it became clear, however, that the environment was not a priority for the congregation, nor did the church really understand its stewardship role. The slide accelerated. Water quality in the marsh’s small ponds declined, turned dangerous. Groves of white pines planted by RWA were dying. A marsh-fire torched the boardwalk. In 2013, the “For Sale” sign went up again.

“Unlikely” certainly fits the current potential buyer: Grillo, a landscaping supply firm. Already in business on Oronoque Road but unable to expand there, Grillo proposes altering 11.7 acres of the marsh’s upland along I-95 for an office, composting windrows, supply bins, and a road running east-west along the northern edge of the marsh, affording access to/from Schoolhouse Road and 1-95.

Grillo’s environmental experts argue that well-designed mitigations will not only end pollution from I-95, but actually improve the marsh’s much-impaired function as habitat for wildlife.

Would Grillo’s plan push the marsh farther down the slippery slope or pull it back up?

Inland Wetlands has approved.

PZB comes next.

We could see this moment as historical, or look back and see history happening in 2002. Either way, Milford is not alone. The city’s “lessons learned” over two decades could prove useful for open space advocates to study in an environmental drama now playing at municipalities all over Connecticut.