WEATHERSFIELD — The Mahoning Valley Sanitary District provided its stakeholders with an update regarding the development of its Floodplain Management Plan.

Representatives from various cities, townships and organizations in the Mahoning Valley viewed a presentation last week over Zoom from Michael McNinch, chief engineer of the MVSD, which provides water to 220,000 area customers; Tony Burgoyne, a representative from OHM Advisors in Akron; Amanda Hess, the vice president of the engineering firm Gannett Fleming; and Manogya Khanal, a representative from Gannett Fleming.

The Zoom conference was a follow-up to an initial stakeholder meeting that MVSD held in person in June. MVSD has been seeking input from local influencers regarding its floodplain management plan.

The plan comes as part of the district’s pursuit of grant money from FEMA to complete renovations to the dam, which originally was constructed in 1930.

MVSD is looking to complete about $45 million worth of repairs to the dam. It is seeking $38 million in grant funds through the FEMA Building Resilient Infrastructure and Communities, or BRIC, program. As MVSD pursued the funds, the development of the floodplain management plan was suggested by FEMA.

Since June, MVSD and the consultants have evaluated stakeholder input regarding what areas of the towns, cities and organizations could be at risk within the floodplain and added that information into the floodplain management plan.

“We also asked those individuals to simply help with identifying downstream impacts that already occur today,” Burgoyne said. “Any observed flooding, specific locations that we need to further evaluate with respect to the proposed improvements that are going to be made with the dam rehabilitation.”

One focus of the study was investigating how operations at the Mineral Ridge Dam could impact the floodplain. Specifically, how the operation of the inflatable rubber dam atop the structure could impact a potential major flood event. The reservoir, which holds 10 billion gallons of water by itself, can hold an additional 1 billion because of the inflatable rubber bladder.

“That bladder is equipped with an automatic deflation mechanism,” Hess said. “So it’s inflated and then if the water rises in the reservoir to a level that’s about 6 inches above the crest, then the controls will automatically, slowly deflate the bladder and make more room for potentially more incoming floodwater.”

Hess said when the bladder is lowered, such as during a flood event, it could push additional water down stream through an already flooded Mahoning River.

“That’s why there is a potential impact on the downstream floodplain,” she said.

Hess said the majority of the study for the floodplain management plan was done using rainfall amounts that would be seen in a 10-year storm, which is an event that could be expected to be seen once every decade.

The stakeholders were tasked with submitting areas of their cities, townships or organizations that are prone to flooding.

One area of concern that was submitted to the plan after the June meeting was a section of state Route 46, suggested by the Niles Fire Department, from Rupple Road to McKees Lane.

“In this particular spot, there was a slight difference in the flooding that would be experienced if the bladder was deflated in advance of a flood event or if the automatic controls were just allowed to do their thing,” Hess said. “With the automatic controls, there is slightly more … nuisance flooding on the roadway due to the use of the automatic controls that could be avoided with the automatic deflation.”

Hess said state Route 46 was an example of an area that would be particularly vulnerable, which is why it was included in the plan.

“In this particular case … One mitigation effort would be that MVSD could continue their practice of lowering the bladder prior to storm events to avoid that potential, small additional volume of water,” Hess said. “Then another (mitigation effort) would be at this particular location, if we have low areas in the road, there is the potential for infrastructure improvement. You might be able to raise the road to eliminate some of that flooding.”

Hess said outside of the state Route 46 example, there were very few stakeholder examples that would be impacted during a 10-year storm.

“For all of the other ones, except for that Rupple Road one that we just looked at, the difference between how MVSD might operate that bladder, it made no difference,” she said.

The consultants also discussed recommendations that could be made to MVSD and the local community regarding dealing with potential floods.

For the stakeholders and local community members, it was recommended that Mahoning County and Trumbull County continue to participate in a National Flood Insurance Plan and limit development in flood prone areas; that stakeholders encourage property owners to purchase flood insurance; that stakeholders discourage the accumulation of materials in floodplains that could be washed away and contribute to flood-related debris; and that local entities identify and prioritize infrastructure improvements.

For MVSD, it was recommended that it continue to monitor weather conditions and lower the inflatable bladder prior to storm events; notify entities downstream of weather conditions that would activate the auxiliary spillway; maintain the Emergency Action Plan for the Mineral Ridge Dam; and that it continues to engage local communities and stakeholders in issues related to the dam and floodplain management.

With continuing feedback received from stakeholders, MVSD and the consultants plan to finalize the floodplain management plan and submit it to FEMA and the Ohio Department of Natural Resources before the end of the year.

McNinch said renovations to the dam have been done in the past. The first was in 1995, where two auxiliary spillways were installed. He said in 2014, a reassessment was performed on the dam.

“When that was performed, there were numerous potential areas of the construction that could be improved upon,” McNinch said. “They referred to them as potential faults and a whole redesign for the dam was done at that point. In 2021, that was completed and we are in the process of finalizing all of the funding for that.”

McNinch reminded stakeholders of what renovations MVSD plans to make to the Mineral Ridge Dam.

“We’re going to raise the core wall to uniform elevation across the whole width,” he said. “We’re going to flatten and change the slope of the earthen-side of the dam, we’re going to anchor the primary spillway into the bedrock to make sure it doesn’t shift, we’re going to demolish the two auxiliary spillways and construct a new primary spillway and we’re going to anchor that into the core wall to make sure that doesn’t shift once that’s in place.”

McNinch said the upgrades to the dam are being designed considering a “probable maximum flood” which is 19 inches of rain during a 24-hour period.

McNinch said the flood plain management plan will be a key component to getting the dam project underway.

The floodplain management plan draft, a nearly 500-page document, was provided to the stakeholders at the end of second meeting for any additional feedback.

“The last key piece of this is for us to put together this floodplain management plan,” McNinch said. “Once we have that in place, we are truly shovel-ready.”