Sebec Dam Agreement Revisions
Lake level specifications of Operating Permit at Sebec Lake Following has been taken from the MEDEP August 17, 2005 action to reflect a change in operation of the project (Sebec Hydro, FERC No. 7253) from its present store-and-release operating mode to a run-if-the-river mode.
1. Original Approval. By order #49-8594-21180 dated July 13, 1983 the Board of Environmental Protection approved a Small Hydroelectric Generating Facilities permit and Water Quality Certification for the proposed redevelopment of the existing Sebec Dam for the purpose of generating hydroelectric power.
To address local concerns regarding long-term protection of fish and wildlife habitat and public uses the Board attached several conditions to its approval requiring that specified water levels be maintained in Sebec Lake as follows:
Condition 1: Except as irreconcilably limited by inflows to the impoundment, temporary abnormal operating conditions, by unit operation or interruption under power supply emergencies, or by order of state, local or federal authorities, where all such conditions are beyond the applicant’s control, and commencing with project construction, water levels in the impoundment shall be maintained annually: a) between 322.8 and 322.3 feet from Memorial Day to the Monday after Labor Day b) between 322.8 and 319.0 feet from Monday after Labor Day to September 30th c) between 322.8 and 317.2 feet from October 1st to the following Memorial Day. d) except that the water levels may be drawn below 310 feet during the period from the Monday after Labor day to September 10th during the construction season.
Condition 2: Water levels between October 15th and May 1st of the following year are maintained at elevations no lower than the water level achieved on October 15th.
Condition 3: An instantaneous minimum flow of 40 cubic feet per second (cfs) be maintained from the project at all times. 2. First Modification. In 1993 the ME Department of Inland Fisheries and Wildlife notified the project owner and the DEP results of a 5-year study that was conducted at Sebec Lake. Based on this study and in consultation with other interested parties, the DEP determined that holding the lake at or above elevation 322.0 feet until October 15 would benefit salmon spawning while not adversely affecting other uses of the lake.
Based on DEP’s determination, by order #L-8594-35-G-M dated July 19, 1995 the Board deleted Condition 2 and modified Condition 1 of its original approval to read as follows:
Condition 1 (revised): A. Except as temporarily modified by inflows to the project area, or by operating emergencies beyond Sebec Hydro’s control, as defined below, water levels in Sebec Lake shall be maintained annually as follows: between 322.8 and 322.3 feet Memorial Day to Monday after Labor Day between 322.8 and 322.0 feet Monday after Labor Day to October 15th* between 322.8 and 317.2 feet October 15th to following Memorial Day. * Sebec Hydro retains the authority to begin the fall drawdown before October 15th if deemed prudent in response to predicted storm events. B. Operating emergencies beyond Sebec Hydro’s control include, but may not be limited to, equipment or flashboard failure or other temporary abnormal operation condition, generating unit operation or interruption under power supply emergencies, and orders from local, state or federal law enforcement or public safety officials.
Condition 2 (eliminated): Condition 3 (as before): An instantaneous minimum flow of 40 cubic feet per second (cfs) be maintained from the project at all times. 3. Second Modification In January, 2006 the project owner, Sebec Hydro Limited Partnership, proposed to modify the operation of the approved project from its present store-and-release mode, in which lake levels are periodically drawn down to take advantage of the runoff from seasonal precipitation and snow-melt, to a run-of-river mode, in which the project would be operated on an outflow equals inflow basis and lake levels would remain stable except when a drawdown is needed to control flooding or due to operating emergencies. The DEP determined that the proposed change should “reduce the environmental impacts of fluctuating lake levels while enhancing the economic viability of the project”.
Accordingly, by Department Order #L-8594-35-H-M, dated August 17, 2005, Condition 1 of Board Order #49-8594-21180 dated July 13, 1983, as previously modified by Board Order #L-8594-35-G-M dated July 19, 1995, was further modified to read as follows:
Condition 1 (as remodified): A. Except as temporarily modified by (1) approved maintenance activities, (2) extreme hydrologic conditions as defined below, (3) emergency electrical system conditions as defined below, or (4) agreement between the applicant, appropriate state and/or federal agencies, and the Sebec Lake Association, and commencing October 1, 2005 the project shall be operated in a run-of-the river mode, with outflow approximately equal to the inflow on an instantaneous basis except during flashboard failure or replacement, and with Sebec Lake levels maintained within six inches of full pond elevation (that is between elevations 322.8 and 322.3 feet) when flashboards are in place and within three inches of spillway crest elevation (that is, between elevations 321.3 and 321.0 feet) when flashboards are not in place. B. “Extreme Hydrologic Conditions” means the occurrence of events beyond the applicant’s control, such as, but not limited to, abnormal precipitation, extreme runoff, flood conditions, ice conditions or other hydrologic conditions such as the operational restrictions and requirements contained herein are impossible to achieve or are inconsistent with safe operation of the project. C. “Emergency Electrical System Conditions” means operating emergencies beyond applicant’s control which require changes in flow regimes to eliminate such emergencies which may in some circumstances include but are not limited to equipment failure or other abnormal temporary operating condition, generating unit operation or third party mandated interruptions under power supply emergencies; and orders from local, state, or federal law enforcement or public safety authorities. D. Notwithstanding Part A of this condition, the lake level shall whenever possible be drawn down in late winter to help reduce seasonal flooding, with a target lake level of 317.8 feet on or before March 31st, and a minimum flow of 40 cfs, as established in Condition 3 of this permit, shall be maintained at all times.
Condition 2 (already eliminated) Condition 3 (contained now within Condition 1 – in Part D) RBH, 10/8/2007