Clams and worms have been discovered growing in Mill Pond — the old and over-engineered economic estuary that drains the central watershed of the cape and, in the 17th century, provided the first water power for milling corn.

The finding — by surprise and accident — is cited as an "exciting" sign that restoration efforts undertaken five years ago are working.

"It's a huge recovery and payoff," said the Health Department's Max Schenk, who as the then chairman of the Conservation Commission helped organized a multi-agency recovery campaign for Mill Pond in 2003.

He said duck clams, which thrive in brackish water, and seaworms were discovered last week growing in mud beds of the pond, which is crossed by Washington Street at the site of the Richdale Market with the 17th-century mill wheel in the parking lot.

"The finding gives hope for a return of soft shell (steamer) clams when the city's new tide gate project is finally completed next year," said Barbara Warren of Salem Sound Coastwatch.

Coastwatch is part of a coalition of organizations working to restore the pond to something like its virtually prehistoric conditions, when it was the cape's only major estuary in which large volumes of fresh water flowed into a tidal basin. The flow to Mill Pond emptied from the Babson watershed, the largest on the island. The great alteration of that natural environment was the construction of the Babson Reservoir Dam in 1930, but 17th- and 18th-century drawings show multiple dams of Mill Brook along what is now Poplar Street.

Schenk said the improvement to the pond came from a decision two years ago to eliminate the tide gating effect — keeping the gate fully open all the time. That allows the tidal surges to rush through the weir and fill the pond, then empty out with the falling of the tide.

Similar conditions exist throughout the Annisquam estuary, creating clam beds and grounds for fishing for striped bass and other small game fish that are among the finest along the coast of New England.

Clammers can be seen digging at low tides from father north on Washington Street as it crosses the Goose Cove causeway at Annisquam.

The spat — seeds of the clams found in Mill Pond — and the worms were undoubtedly carried in on the tidal surges and dropped as the tides slackened.

Mill Pond has been intensely altered, first in the 17th century by the earliest settlers and later by farmers. The causeway over Mill Pond allowed the building of the first main road, Washington Street, which paralleled the Annisquam, the main transport route in the settlement before the development of the harbor.

Schenk said former Gloucester Mayor John Bell deserved credit for authorizing the first studies and efforts to restore natural conditions to the pond.

The identities of the coalition members has changed somewhat over time, but the effort has remained constant, to understand the existing ecology of the altered waterway and how to ease it back to close to what it was, Schenk said.

The next step in the process, he said, is designing a way to open the culvert even wider than today, to bring the flow closer to what it was before the first weir was constructed and the fast-moving water used to power a millstone.

"We want it flowing with regular tides," Schenk said.

The epic Mothers Day storms of 2006 ironically pushed the restoration project along. With so much floodwater flowing over the Babson Reservoir spillway, the city implemented an emergency full opening of the tide gate, which until then was utilized to keep water in the pond for much of the year.

After studying the lessons of the floods, the city decided to leave the gate open.

Richard Gaines can be reached at rgaines@gloucestertimes.com.