By SUE SUCHYTA
Sunday Times Newspapers
RIVERVIEW – The city may need to spend $11 million over the next five years to upgrade its storm and wastewater sewers and other infrastructure based on a grant-funded, three-year asset survey.
The Stormwater, Asset Management and Wastewater grant inventoried all of the city’s assets, the condition and level of service, and rated the asset criticality. The results recommend operation and maintenance strategies, and a five-year capital improvement plan.
The survey identified 1,055 sanitary manholes, 742 sewer manholes, 1,017 catch basins and 49 outfalls, a place where a river, drain or sewer empties into a river or lake. All are identified by GPS location and are entered into an online database.
Only 11 sanitary manholes are damaged to the point where they need immediate replacement, with 47 being identified as critical priority and 27 as high priority.
Sewers older than 20 years and not lined in 20 years were inspected by camera. Fifteen pipe segments were found needing replacement due to cracks, fractures, broken and deformed pipes and holes. Another five pipe segments need replacement because of wrinkled or bulging liners, roots, encrustation or mineral deposits, and intruding tap connections.
The study reported 14 segments in critical condition, 34 as high priority, 50 as medium priority and 81 as low priority.
Sanitary sewer defects, lining failures and locations with a high amount of water inflow were highly concentrated along the Riverview interceptor, Williamsburg sewer and the Civic Park Drive sewer.
One of the four sanitary pump stations, Longsdorf, has motors from 1963, and has severely corroded diversion and mixing chambers. The other three sanitary pump stations are at Fordline, Greentrees and Grange Road.
The city has six storm water pump stations, at Colonial Village, Fordline and four in Valley View.
The study found that the capacity constraints of the city’s system are primarily caused by the amount of water entering the city’s system during significant rain events.
The study also looked for solutions to Huntington Meadows subdivision flooding. It was determined that during large rain events, when a large amount of water is entering the system, the Longsdorf Pump Station cannot pump the volume of water flow it receives. While the Longsdorf Pump Station is rated for 25 cubic feet per second, it is only operating at 19 cubic feet per second.
The Huntington Meadows subdivision was found to have undersized residential sewers in relation to the amount of rainwater runoff it must handle.
Senior Civil Engineer Maria Sedki, a professional engineer with Fishbeck, Thompson, Carr and Huber, said the Downriver Wastewater Treatment Facility is not backing up, and the problem is caused by the capacity of the city’s pipes.
“It can’t handle the flow it’s getting,” Sedki said. “The pipes are undersized for the amount of (inflow/infiltration) it’s receiving.
“The other issue is you can’t increase the pumping capacity of Longsdorf to resolve the issue upstream because the downstream system can’t handle it. We are stuck literally between a rock and a hard place here with Longsdorf. There is too much coming into it, and it can’t pump it.”
Recommendations are to construct a storage basin, and to relieve backups by constructing a relief sewer leading to the Downriver Regional Storage and Transport System tunnel. It was recommended that the Downriver Utility Wastewater Authority should be approached about a possible connection to the tunnel.
Sedki said the biggest expense will be tapping into the 90-inch (diameter pipe) which is 60-feet deep (below Pennsylvania Road), digging a shaft to tap into the line.
CE Raines Engineer Souheil Sabak said it is possible that if Riverview can line up with an existing manhole, DUWA could be convinced to put an internal drop connection inside the manhole at a much lesser cost.
“It has to be lined up perfectly for that to happen,” Sabak said. “Then you don’t have to excavate that deep to get to that pipe. That is something that we have to work diligently with (DUWA), to convince them that is our only affordable option, and hopefully they will sign off on it.”
City Manager Doug Drysdale said Plante Moran did a 20-year projection for water and sewer rates, and they projected that if the city were to increase the rates 2 to 4 percent each year, it can build up reserves to pay cash for the project.
“Obviously, something like Huntington Meadows you want to do sooner, and you may not have all those reserves built up right away,” Drysdale said. “But there will be some years that you are not spending a lot of capital, but you are still collecting the money and building up the reserve after the years when you do spend the money. They think we can do this without doing any bonds.”
(Sue Suchyta can be reached at [email protected].)