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Dam Monitoring Program

As part of our water supply network Manchester Water Works (MWW) owns and operates 10 dams which fall under the regulatory review of the New Hampshire Department of Environmental Services, Water Division (DES). The dams range from a simple detention pond at the site of our 8.8 million-gallon tank in Derryfield Park, Manchester, to the Massabesic Lake Dam which is located off Island Pond Road, Manchester.

DES categorizes dams by the degree of damage that a potential failure could cause. The designations are AA, A, B and C, with AA signifying non-hazardous structures while C identifies a potentially high hazard dam. A summary of Manchester Water Works' dams by WRD class is listed below:

All dams are routinely inspected by experienced MWW staff on a weekly basis with an intradepartmental report filed. Monthly, a more extensive review is conducted and preventive maintenance is performed as needed. Typical areas of concern include unusual seepage, erosion of embankments and around structures, animal burrows in earthen dams, spalling and cracking of concrete surfaces, vegetation growth and security issues. Also, all MWW dams are inspected by DES personnel at regular intervals which range from 2 to 6 years depending upon the hazard classification.

Finally, MWW has in place Emergency Action Plans (EAPs) for the class B and C structures.MWW's EAPs are reviewed, tested, updated and reissued to plan holders on an annual basis as required by DES rules.

Key elements of the plan include:

  • Notification flow chart to be used in the event of an emergency
  • Monitoring assignment for MWW staff
  • Warning procedures
  • Evacuation procedures (for the defined inundation area)
  • Formal list of plan holders

For more information on MWW's dam monitoring program call 603-624-6482 ext. 208.

Class ID No. Name Location
AA 150.16 Coffer Dam Lakeshore Rd., Manchester,NH
AA 150.18 Sleggo Dam Lakeshore Rd., Manchester,NH
A 13.03 Clark Pond E. Depot Rd., Auburn, NH
A 13.09 Pingree Mill Dam Dearborn Rd., Auburn, NH
A 150.11 Deryfield Detention Pond Oak Hill Ave., Manchester, NH
A 150.10 4 MG High Reservoir Oak Hill Ave., Manchester, NH
B 150.12 20 MG Low Reservoir So. Mammoth Rd, Manchester, NH
C 13.01 Tower Hill Dam Tower Hill Rd., Auburn, NH
C 150.06 Lake Massabesic Dam Island Pond Rd., Manchester, NH
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