Mirror Pond dam to be reevaluated for risk
Jun 04, 2019
Bend resident thinks designation should be high riskBy Michael Kohn
Growing recreational use downstream from the Mirror Pond dam, known as hazard creep, could cause authorities to raise the current hazard rating of the dam from “significant” to “high.”
The Oregon Water Resources Department intends to evaluate the recreational use below the dam this summer to assess whether the rating should be raised, according to an email from Racquel Rancier, a senior policy coordinator at the department. A decision is expected later this year, she added.
Safety concerns for the 109-year-old dam have heightened amid repeated leaks — repairs for leaks have been made at least four times since 2008. The department will be assessing whether recreationalists downstream — in kayaks, casting fishing lines and ambling on pine-shaded paths — would be swept away in the event of a dam failure.
The Mirror Pond dam, which holds back the waters of Bend’s iconic Mirror Pond, will be inspected annually if the rating is increased to high, according to Rancier. Under its current rating, the safety inspection is conducted every two to three years.
“At this point, no reclassification has occurred, so we can’t know what the details and impact of that would be. It is worth noting that the hazard potential classification of a dam is not a reflection of the condition or suitability of a dam for continued operation. Rather it is solely a reflection of the potential downstream consequence if a dam should fail according to the methodologies established by the regulator,” said Tom Gauntt, media spokesman for Pacific Power, which manages the dam.
The reevaluation was prompted by a request from Bend resident Mark Davis, who frequently kayaks sections of the Deschutes River downstream from the dam. Davis, a retired dredge control officer, wrote in an email dated April 8 to the OWRD that he was concerned for public safety.
Several popular parks are located downstream from the dam, including Pacific Park, Pioneer Park, First Street Rapids Park, River View Park, Sawyer Park, Riley Ranch Nature Reserve and Tumalo State Park, wrote Davis.
“All of these parks have extensive in-water or near-water recreation,” Davis said in the email. “On any given day there can be over 100 people in the river at these parks in total.”
The number of people recreating on the river is increasing due to Bend’s fast-growing population, Davis added. He described the development and recreation increase as “hazard creep.”
“The probability of loss of life in the Deschutes River due to a dam breach at the Bend Hydro Dam should be considered a certainty and clearly this should be a reason for a high hazard rating” of the dam, Davis said.
Oregon uses a three-tiered hazard rating system, which does not reflect the condition of the dam but rather the activities downstream.
Failure of a low hazard dam is likely to result in no probable loss of human life and low economic and/or environmental loss, according to the Federal Emergency Management Agency.
The next step up, a significant hazard dam, would inflict no probable loss of human life due to failure or mis-operation, but can cause economic loss, environmental damage and disruption of lifeline facilities, according to FEMA.
Dams assigned the high hazard classification are those where failure or mis-operation will probably cause loss of human life. Owners of high hazard rated dams must prepare an emergency action plan. This includes periodic emergency response exercises and preparation of an inundation map.
Oregon is home to 74 high hazard dams and 148 significant hazard dams out of about 950 state-regulated dams, according to an OWRD report published last year.
One of the high hazard dams is the 33-foot-high North Canal Diversion Dam, located just 1.3 miles downstream from the Mirror Pond dam.
In a May email to the Bend City Council, Davis urged the city to take action due to the “extreme risk to the people of Bend” due to the age and condition of the Mirror Pond dam.
“Dams may seem placid when all is well, but that changes in an instant when they breach,” Davis told the council. “Do not underestimate the destructive power of water and continue holding public safety as a primary core value.”
— Reporter: 541-617-7818, firstname.lastname@example.org
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