Friday, March 16, 2001
ConsCom needs $13K for Greenough Dam survey
The Carlisle Conservation Commission (ConsCom) has asked the board of selectmen to include a $13,050 request for appraisal of the deteriorating Greenough Pond dam on the Warrant for Spring Town Meeting.
The ConsCom became aware of the growing threat, not only to the dam itself, but more importantly, to the town's largest and most scenic open water pond, following an inspection by the Massachusetts Department of Environmental Management (DEM) office of dam safety. Finding the dam to be in "fair to poor" condition, the DEM recommended that ConsCom employ a registered professional civil engineer experienced in dam construction and repair "at your earliest opportunity."
Volume and capacity studies
Robert Stevens of Stevens Associates, the engineering services firm chosen from a field of five to perform the preliminary survey, attended the commission's March 1 meeting to answer questions that commissioners have already heard from the public. The most frequent has been, "Why $13,050 for a preliminary study?" Stevens explained that, following the DEM's recommendations, his firm will not only evaluate the 70-year-old earthen dam, but study the hydrology and hydraulics related to its spillway capacity, prepare engineering specifications to be used by the town in seeking contract bids and deliver an operation and maintenance guide for future use.
Preliminary inspection suggests that the amount of water flowing over the dam has probably increased since 1930 and may now exceed the present capacity of the spillways. Commissioner John Lee asked whether Stevens might consider a single spillway rather than the present double one. Stevens replied that this would require replacement of the entire spillway structure. "I could do it, if the present one can't be made to work properly, but I think it will work, and I plan to pursue that option first."
Planning routine maintenance
Chair Tom Brownrigg asked what kind of ongoing maintenance would be required once the renovation is complete. Stevens's answer was reassuring. Flow boards would need to be removed at high water and later replaced. Brush and trees should be removed on a regular schedule and the roadway maintained so that it does not affect the dam. It is simple work that could be accomplished by the Department of Public Works (DPW) or by the farmhouse tenant.
Stevens told the commission the required repairs could probably be done in two stages, though that was not his recommendation. The most pressing phase would entail removal of 50 or more trees of at least six-inch girth, including roots, from the dam itself, filling in the resulting cavities and removing brush from the downstream area. DPW head Gary Davis has told the commission he has the equipment to accomplish that part of the job, under a dam engineer's direction.
Concluding the Greenough discussion, commissioner Chris Gaulden stepped down temporarily from her position as vice-chair to present an official Notice of Intent for tree removal, if and when all required town approvals are obtained. Since all the activity would have to take place within the 200-foot zone protecting Pages Brook under the state Rivers Act, she and conservation administrator Sylvia Willard had flagged the wetlands and prepared the paperwork for a "limited project," which requires local commission approval and careful subsequent perusal by the Department of Environmental Protection. The applicant, namely the Town of Carlisle, encountered scant opposition.
The board of selectmen voted on March 13 to pull the conservation commission's Greenough Dam Warrant Article. However, according to town administrator Madonna McKenzie, they are anticipating that the commission will attend the March 20 meeting to attempt to reverse the decision.
© 2001 The Carlisle Mosquito