Coffin Dam History
Coffin Dam, located in Smithfield, ME on the East Pond outlet stream known as the Serpentine which is located in the Kennebec River Basin, is an earthen and concrete structure. East Pond covers 1,717 acres with a mean depth of 18 ft. and maximum depth of 27 ft. (Lake Stewards of Maine, data from ME DEP, IF&W and Office of GIS). East Pond has no major inlet sources and takes 2.5+ years to flush. The Serpentine stream flows 2.86 miles through a floating bog and empties into Old Mill Stream an inlet for North Pond.
The original dam, known as Wyman Dam, was built with timber cribbing. Central Maine Power Company reconstructed the dam in 1949 to create an impoundment. The contractor was Floyd A. Baker of Oakland with E. D. Chase being the Civil Engineer who supervised the construction project which cost $790. The Dam Committee consisted of Walter Randall, E. D. Chase and Everett Coffin. The dam was dedicated as the Coffin Dam in 1949. The brass plaque is presently on display in the Groves House of the Smithfield Historical Society. The Coffin Dam is used to maintain the water level of East Pond and the residential area of the Serpentine, for fire control and for recreation.
Flowing water seriously undercut the dam so in 1953 it was reconstructed adding a concrete footing with the cost exceeding $1,500. The dam is approximately 86 ft. long and 10 ft, high with a concrete spillway flanked by earthen dikes. The concrete section, 40 ft. long, 9 ft. high and 2 ft. thick, has a central 2 ft, thick pier. The permanent portion of the spillway was topped with 2 wooden boards which were replaced with 2 side by side 1 ft. high by 10 ft. long steel flashboards each weighing about 150 lbs. The permanent spillway crest elevation is 263.0 ft. thus the elevation on the top of the flashboards is 264.0 ft. The maximum hydraulic spillway capacity with the flashboards removed is 234,000 cubic ft. per hour or 65 cubic ft. per second (cfs) at the elevation of 264.0 ft.
The East Pond Association (EPA) leased the dam from Central Maine Power Company from 1948 until 1965 for $75 per year which was the accessed taxes. During that period, the EPA paid for all repairs and the reconstruction of the dam. The EPA purchased the dam and the surrounding land from Central Maine Power Company in 1965. Additional land purchases were made as they became available in 1966 and 1967.
The boards were manually placed on the dam during the spring, removed during the fall and stored to prevent ice damage to the dam or the boards and to allow for natural fish spawning. The steel boards were heavy and difficult to handle and it took several men to maneuver their placement.
The Coffin Dam was inspected by MBP Consulting of Portland, ME on June 18, 1997 with a written report being submitted to the Maine Emergency Management Agency. There were no signs of structural instability, major deterioration of the concrete or seepage, however, Coffin Dam was classified as a high risk hazard dam because there was a potential for downstream damage.
Following the report recommendations, an arborist, Foster Tree and Landscaping Co., was hired to remove 11 trees on the earthen dike and along the downstream spillway channel costing $650. The heavy steel beams were replaced in 1998 with 10 ft. long aluminum flashboards each weighing 72 lbs. and designed by B. L. Hopkins, Jr. At each end of the boards is a 2in. wide by 5 in. long slot allowing water to flow all the time as long as there is sufficient water. It was also suggested that a lockable/mechanical device should be installed to raise and lower the flashboards. A new system with an aluminum walkway over the crest of the dam utilizing four wheels to raise and lower the two aluminum boards which slip into slots was designed by David Brown and manufactured by Pioneer Machine, Inc. of Albion, Maine.
In August of 1997 it was decided that the boards should be lowered around Memorial Day and opened around Labor Day. On July 20, 1997 debris restricting the flow of the dam was cleared and the Dam Committee of Jerry Tipper, Bryant Hopkins and John Koons continued to monitor the dam and removed debris as needed. The EPA has always maintained a functioning Dam Committee
Because of the high risk assessment, an Emergency Action Plan incorporating the services of the Smithfield Fire Chief as the primary responder was created in April of 1998. On April 24, 2009 a new Dam Inspection was done. The risk hazard was dropped to a low level thus an Emergency Plan is not required but is being updated as a precaution. There was no mandatory flow rate designated for East Pond at either Dam Inspection.
The EPA owns the land surrounding the Coffin Dam and has a deeded right of way from Route 8 thus we pay taxes annually to the town of Smithfield. We continue to have a Dam Keeper and Dam Committee that inspects the dam regularly, raises and lowers the flashboards, clears trees, floating debris and beaver construction from the dam. We work closely with North Pond representatives and dam operators always communicating when boards are adjusted.
Dam management is extremely complicated as it directly affects the residents of the camps previously known as Sunset Camps and those living on the Serpentine. There have been times when we have been asked to reduce flow to prevent flooding of the Sunset Camps. Several residents living on the Serpentine just prior to the dam have water lines in the Serpentine. When the water level drops too low, they suck mud into their water systems. We constantly monitor weather conditions as during the drought of 2021 the water dropped below the spillway, we saw rocks in the lake that we never knew existed and by the end of the summer it extremely difficult to remove boats at the public Boat Launch even though the dam boards had been closed.
In July of 2021 a highly aggressive, noxious, invasive plant was found in the ½ to mile area of the Serpentine just before the Coffin Dam. The ME DEP identified it as Curly-leaf Pondweed (CLP) a very difficult invasive to control as it drops small turions (buds) that look like a tiny pine cone which can float, drop into the sediment, grow all winter or lay dormant for 5 years. Each plant can have as many as 100 turions and the tough structure of the turion does not absorb herbicides well.
The ME DEP hired New England Milfoil, a team of commercial divers, in August of 2021 who pulled 160 gallons of CLP and 7 Lakes Alliance divers continued to pull plants well into September. The discovery of CLP certainly complicated dam issues. A seine net was placed in the Serpentine by the 7 Lake Alliance Dive Team to capture plant fragments before they flowed over the dam into Old Mill Stream and eventually into North Pond. Since the net was secured to the dam walkway, any adjustment to the boards resulted in the net being sucked into the dam often causing damage to the fragile net. CLP plants were discovered in Old Mill Stream at Sunset Camps. Those plants were pulled and no further infestation was found in North Pond. Later in the season, the net was moved into Old Mill Stream, but it was difficult to secure it at that location.
On February 4, 2022 the Maine DEP, IF&W, 7 Lakes Alliance, the North Pond Association and the East Pond Association met via zoom to discuss plans for controlling the infestation in the Serpentine. A “STOP Invasive Plants DO NOT ENTER” floating buoy was given to the EPA by the Department of Natural Resources with IF&W authorizing the placement in the Serpentine at the bend prior to the infestation area. They also banned seine fishing in that portion of the Serpentine. It was agreed that the dam should be closed after fish spawning in May.
Pulling began again in May of 2022 prior to the CLP dropping turions and divers were working in the Serpentine all summer long. Two nets were used in 2022 with one being attached to the East Pond Dam walkway and another placed in Old Mill Stream.
East Pond is the first of the seven Belgrade Lakes thus our actions directly affect North Pond (NP) and eventually most of the lakes. North Pond covers 2,531 acres with a mean depth of 13 ft. and maximum depth of 20 ft. (Lake Stewards of Maine, data from ME DEP, IF&W and Office of GIS). NP is 814 acres larger than East Pond. North Pond continued to have unprecedented low secchi disk readings, high phosphorus counts, and the absence of oxygen into November of 2022. Their nutrient rich water is ideal for the growth of invasive plants. CLP can form large masses of dead vegetation resulting in even higher phosphorus levels and possibly longer algae blooms.
The East Pond Association does not want to spread Curly-leaf Pondweed.
In 2022 the EPA was contacted as men had been seen tampering with the dam. The four walkway wheels were chained and locked, but had been manipulated and turned as far as possible as the chains were taut and the boards were raised. The boards had been lifted out of their track and were moving from side to side. Two bolts used to secure the walkway were pulled out of the middle concrete pylon and were dangling. Four different people attempted to lower the boards to reduce the flow into North Pond, but were unable to get the boards to seat properly thus a lot of water continued to flow over the dam. A more secure process was devised and the wheels were chained through the walkway shortening the locked chain. Wooden sticks were left at the dam by the trespassers so we finally installed a game camera. Three men were photographed at the dam poking something under the dam boards thus increasing the flow. The Somerset County Sheriff’s Office was notified as was the Game Warden Service in Sidney, ME. Eventually, one of the trespassers posted a video on his Facebook page showing him scraping a metal contractor’s square under our dam boards and across the surface of our 1949 concrete dam surface.
The Coffin Dam flashboards control only 12 inches of water from 263 to 264 ft, mean sea level. The Belgrade Dam Committee said that Salmon/McGraw was the only Belgrade Lake required to maintain a constant flow and the East Pond information was verified with the Maine Emergency Management Agency and the National Inventory of Dams. Five people, not members of the EPA, have inspected our dam. They all identified some major concrete projects that need attention as well as minor walkway system improvements and at present we do not know if there has been any damage to the bottom of our aluminum boards.
The East Pond Association continues to follow the advice of the Maine DEP, IF&W,
7 Lakes Alliance and scientists who have been studying East Pond for over 20 years.