Fernwood Lake Emergency Reservoir West Dam

Six active reservoirs, one emergency reservoir and three water treatment plants provide the City of Gloucester’s drinking water. Cape Ann depends on surface drainage from its relatively small watersheds into these reservoirs. These reservoirs and treatment plants are divided into two systems, East and West, separated by the Annisquam River. There is no water connection between the East and West systems. Instead, finished water is transferred by two pipes drilled under the Annisquam River near the Water Pollution Control Facility in West Gloucester.¹ The availability of safe, clean, locally harvested drinking water is a point of civic pride, but there are ongoing concerns about the management of the watershed areas around the reservoirs.²

Fernwood Lake is part of the West Gloucester reservoir system. It is an inactive emergency reservoir that can be gravity-fed into the Wallace Reservoir.³ It is primarily used for recreation, as the reservoir requires approval from the Massachusetts Department of Environmental Protection to operate and contains high levels of organic matter that make it difficult to treat and unsafe for human consumption.⁴ The three dams surrounding Fernwood Lake — located within a FEMA-designated floodplain — were constructed in 1877 and, though they have been maintained in the past decade, are considered to be highly hazardous.⁵

Cape Ann’s water system is already vulnerable to the rising temperatures and longer, drier summers associated with climate change. The West system in Gloucester is particularly vulnerable because of the limited watershed size. An increase in fires due to a lack of maintenance and brush clearing will reduce vegetative cover and elevate turbidity in the system.⁶

During the Great Storm, the West Dam will breach, flowing into the Wallace Pond watershed and overtopping the Wallace Pond Dam. While the area between the dams is uninhabited, the discharge from Wallace Pond will send a high-velocity flood wave across Magnolia Avenue to Route 133, a key evacuation route.⁷ The drinking water supply will be contaminated with debris, dirt, salt spray, animal carcasses, and other substances.⁸ Reservoirs close to the ocean, like Flat Ledge Quarry in Rockport, will remain saltwater bays for months following the storm.⁹