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Utility director briefs Assembly on Crystal Lake (Blind Slough) dam safety; FERC plans and monitoring reviewed
Summary
Utility Director Hagerman presented the borough’s Owner’s Dam Safety Plan for Crystal Lake Dam, outlining FERC-required plans, monitoring, training and contingency measures; assembly members asked about SCADA backups, seepage monitoring and spillway erosion.
Utility Director Carl Hagerman presented the Petersburg Borough’s Owner’s Dam Safety Plan (ODSP) for the Crystal Lake (Blind Slough) dam and related facilities, describing Federal Energy Regulatory Commission (FERC) requirements, inspection and monitoring programs, training and response protocols.
Hagerman told the assembly that the Crystal Lake Dam is classified as a high-hazard dam because homes at the hatchery and recreational areas would be at risk in the event of a breach. He said the structure is “about 34 foot high, 200 foot long, rock fill dam with a concrete face on the upstream side” and described the parapet and an ungated spillway. Hagerman also said the reservoir provides roughly 5,200 acre-feet of storage and described the penstock, powerhouse and electrical interconnection.
Hagerman outlined the borough’s suite of FERC-required documents: an Emergency Action Plan (EAP), a Dam Safety Surveillance and Monitoring Plan (DSSMP), a public-safety plan for recreation areas, and the Owner’s Dam Safety Plan itself. He said the borough operates a supervisory control and data acquisition (SCADA) system and a remote camera to monitor dam conditions, maintains quarterly inspections and performs an annual unannounced dam-breach-warning and evacuation drill with documentation.
When asked about SCADA redundancy, Hagerman said there is not a second SCADA system; if fiber or communications fail, staff perform physical inspections. “If the fiber optic cable fails or is broken … we have to report that to FERC as an issue,” he said, adding that inspections would be carried out at an interval appropriate to conditions — “every few days” if stable, and daily if the lake is full and spilling.
On seepage and erosion, Hagerman said seepage is a continuous, expected feature of the rock-fill dam; the concrete/aluminum facing reduced leakage but did not eliminate seepage. He said seepage turbidity is a key monitor; he added, “I’ve never seen any turbidity in that seepage and we’re very confident the dam is stable and working as intended.” Hagerman also said riprap below the spillway mitigates erosion when the dam spills.
Hagerman described recordkeeping and auditing practices: the borough maintains inspection reports, correspondence, plans and drawings (some dating to the 1920s) and backs up documents to borough servers when possible. He said the Chief Dam Safety Engineer (a contracted licensed professional engineer) visits annually in conjunction with FERC inspections and that the ODSP is reviewed annually with a five-year independent audit requirement.
Assembly members thanked Hagerman and asked follow-up questions about reporting to FERC, inspection cadence and whether monitoring relied solely on cameras (it does not) and about erosion controls (riprap and seepage monitoring are in place). Hagerman said planned improvements and the major upgrade completed the prior year will improve safety for decades.
No formal action was required; the presentation served as the annual owner’s-dam-safety-plan briefing and informational update to the assembly.
