The North and South Rivers Watershed Association has been awarded a $22,000 grant from the Massachusetts Environmental Trust to help fund preliminary design and engineering for the removal of the Tack Factory Pond Dam in Hanover. The dam, owned by the Cardinal Cushing Center, is one of four in the Third Herring Brook system, a 5.5-mile-long tributary to the North River estuary. Other dams include the Mill Pond Dam owned by the South Shore YMCA, the Peterson Pond Dam owned by the Hanover Mall, and the Jacobs Pond Dam owned by the town of Norwell. Samantha Woods, executive director of the North and South Rivers Watershed Association, said her organization has been working with the Cardinal Cushing Center to secure grants to pay for the design and engineering study of Tack Factory Pond Dam. The study should be complete by December, Woods said, and public meetings to discuss options will then begin.