Commission hears dam improvement options

By Aimee Hancock

ahancock@aimmediamidwest.com

PIQUA — The Piqua City Commission held a work session this week during which they were given an overview of possible improvements to the Piqua hydraulic canal and dam.

Rob Kirkbride, principal at Stantec Inc., gave a presentation regarding the city’s hydraulic system and requirements from the Ohio Department of Natural Resources (ODNR), along with a few alternative options for improvement to be considered by the commission and residents.

According to Kirkbride, ODNR is the governing organization for dam safety and performs evaluations every five years. Piqua’s most recent evaluation in 2019 concluded the system has several issues to be addressed, including insufficient spillway capacity to handle a design storm and ongoing maintenance of dams and hydraulic canals.

A “design storm” is the weather event that is required to determine if the structure will be suitable for safety, Kirkbride said.

“The requirements from ODNR for the design storms are based on the height of the dam, the storage volume, how much water is in the lakes and canal system, and the downstream hazards,” he said. “With the city of Piqua basically being immediately downstream of all these dams, that’s where that comes into play.”

According to Kirkbride, there are a few hundred Class I high hazard dams in Ohio, three of which are in Piqua. This includes the Frantz Pond dam, the Echo Lake dam, and Swift Run Lake dam.

The length of Piqua’s canal from Frantz Pond to Swift Run Lake is about 2 miles, with embankment heights varying from less than 5 feet to 30 feet high. The Swift Run Lake watershed is 7.42 square miles, with Echo Lake’s at 1.95 square miles and Frantz Pond at 1.05 square miles, along with 0.37 square miles of additional canal.

Kirkbride noted the system is not necessarily needed for drinking water, as the city sources from the quarry and Great Miami River with only 2% to 5% coming from Swift Run Lake, meaning the reservoir water system is mainly for recreation.

With all the dams currently classified as high hazard, they need to be able to pass the 100% probable maximum flood storm event, Kirkbride said, which is equivalent to 27 inches of stormwater over a 24-hour period. Kirkbride noted one of the largest storm events seen in the area 0ccurred in 1995 at the Lockington Dam, during which 10.75 inches of stormwater was accumulated over 48 hours.

Utilities Director Kevin Krejny said given this statistic, the ODNR requirements are “very substantial.”

“If (the probable maximum flood storm event) was to happen here, we’d have a lot of bigger issues. We’d all be out of town before it even got to 27 inches in one day,” he said.

Regardless, ODNR is still asking for these requirements to be met, Krejny said, noting that these specific requirements are the same for dams and hydraulic systems across the country.

Krejny also said the city is currently working toward reclassification for Swift Run Lake dam from a Class I to Class II, which has less stringent requirements, while reclassification will be much harder for the Frantz Pond and Echo Lake dams.

Kirkbride presented lists of alternative improvement options for each dam, highlighting the feasibility of each. Kirkbride noted that none of these options have been decided on and any potential improvements are in the very early preliminary stages, with addition discussion to take place.

Swift Run Lake dam improvement alternatives include property easements/acquisition, additional spillway capacity and/or new auxiliary/emergency spillways to allow for additional flow, overtopping protection, and re-classification of the dam. The city has already completed the acquisition of property below the dam and the majority of the property downstream is owned by the city. According to Kirkbride, all of these alternatives are feasible.

Feasible alternative options for Echo Lake and Frantz Pond dams include new spillways at alternate locations, which could include park locations; property acquisition, which may not be public friendly and includes homes near Echo Lake Dam, Fountain Park, and other downstream properties; and decommission of the dam/lower pool levels, which also may not be public friendly and would minimize or eliminate water storage.

“Potentially-feasible” alternatives presented for Echo Lake and Frantz Pond dams include new auxiliary/emergency spillways, raising the dam and canal embankments, overtopping protection, short wall installation, or to control inflow, which only solves part of the storage capacity issue.

Limited- to no-feasibility alternatives for these dams include new spillways at dam locations, which is not possible due to downstream hazards and no flow paths available through the city; a new culvert system, which requires significant capacity; and upstream lake control, which would contain only small storm events.

Alternative improvement options with potential- to total-feasibility for the hydraulic canal include widening of the canal, which would be restricted due to property boundaries; deepening of the canal; crest wall installation, which would require the removal of trees; additional flow control; overtopping protection; and property acquisition to allow for widening/deepening of the canal.

The full presentation, which includes additional details regarding each alternative, is available on the city of Piqua’s website.

Kirkbride and Krejny, along with city commission members, stressed that no decisions will be made until every option is considered and residents’ opinions are taken into account.

“From a commission standpoint, just understand that these are alternatives … and there will be more meetings that are held before any of this goes anywhere,” said Commissioner Thomas Fogt. “This is just the very beginning, and this is why we’re holding these meetings, first and foremost, to get everybody in here and everybody involved.”