Corroded pipes around Dover’s Silver Lake Park to be fixed

A sewer leak spilled an estimated 84,000 gallons of untreated wastewater at Silver Lake Park in December Overflow from the leak went into the St. Jones River, but not into Silver Lake itself. (Submitted photo/Ray Parker)

DOVER — It was supposed to be a day marking yet another milestone in a slip-lining rehabilitation project of Kent County’s force main (sewer pipe), which took place under the median of U.S. 13 from Garden Lane to Denneys Road in north Dover last year.

On the morning of Dec. 19 at around 10:30, county staff, along with the contractors working on the slip-lining project, reintroduced the flow back into the rehabilitated sewer line.

However, it turned out the move had unintended consequences — a sewer leak that closed Silver Lake Park for weeks — while also causing some 1,300 feet of pipe that has been identified as needing to be replaced in the wake of the unexpected pipe failure.

Andrew Riggi, Kent County’s deputy public works director, briefed Dover City Council members on Jan. 27 on the initial findings into the leak that spilled an estimated 84,000 gallons of untreated wastewater at the park. His report said that overflow from the leak went into the St. Jones River, but not into Silver Lake itself.

“It was pretty upsetting,” said Mr. Riggi, who served as the project manager for the force main rehabilitation project on U.S. 13. “We had never had any failures downstream and we weren’t expecting this.”

County staff was notified by the city of Dover of a sewer leak in Silver Lake Park in the vicinity of Kings Highway at around 1 p.m. on Dec. 19. The location is upstream of Pump Station No. 3, located at 150 E. Water Street and downstream from the completed project.

The news soured what had been a relatively trouble-free project.

“We got it completed and got off the highway by Thanksgiving and were completed before Christmas,” said Mr. Riggi. “So, on the 19th of December we turned it on, and it wasn’t good. We had a (sewer) overflow into Silver Lake Park right behind the residents right along Lakeview Drive.

“We immediately turned it back into the bypass through the city of Dover Pump Station No. 7 and stopped the flow and it took a little while to drain down.”

Mr. Riggi said county staff cleaned and spread lime in the area of the spill at Silver Lake Park to disinfect and neutralize any harmful contaminants, while caution tape was placed around the contaminated area.

Sampling of the St. Jones River was initiated in the park and at four downstream locations. The results of the enterococcus testing indicated that all water locations returned to background levels by Dec. 23, 2019.

Four sample locations were established within the affected area for continued sampling. Salmonella was not detected in any of the soil samples. Based on soil testing, additional lime was re-applied. Soil samples were also collected from two locations outside the affected area to establish background levels of fecal coliform and salmonella.

On Jan. 12, the results from a Jan. 6 soil sample were forwarded to the city with acceptable levels below the threshold limit.

The contaminated area of the park has been top soiled, raked and seeded with matting installed on the slopes.

While the remnants of the spill have been cleaned up, Kent County is still faced with replacing at least 1,300 feet of pipe from Silver Lake Park north to Oak Lane due to severe corrosion. Mr. Riggi said investigation work should be completed by the end of March or early April.

“Right after the new year we went out there with our contractor and started digging up the area to find out what was the actual problem,” he said. “The pipe had suffered severe sulfide corrosion. There’s lot of debris in the (concrete) pipe. This is just like the ones that we just finished working on in the highway. It carries the same flow. The hydrosulfide corrosion basically ate up the concrete on the inside of the pipe.

“The concrete pipe consists of an inner concrete cylinder, a seal cylinder, some wire reinforcing with some concrete on the outside of it. Most of it (around Silver Lake Park) is gone. Our plan is to replace the damaged portions with PVC.”

As for the corroded pipes, Mr. Riggi said the county is working with the Department of Natural Resources and Environmental Control, SRF and the USDA to utilize the remainder of the funds from the U.S. 13 slip lining project for procurement of the materials and repair for the city’s pipes.

The replacement materials will be bid out, per DNREC’s requirements, near the end of February for delivery in early May with construction completion by the end of June from the park to Oak Lane. The schedule for repair of other areas identified during the investigation is still to be determined.

The investigation into the cause of the pipe failure is underway. The preliminary investigation indicated pipe failure due to sulfide corrosion. Once the extent of the damage is assessed, the intended path and next steps will be determined.

Dover City Councilman Tim Slavin told Mr. Riggi that he believed the county needed to work on providing better communication because he felt like the city of Dover took some unwarranted blame for the issue.

“Thanks for delivering bad news,” Councilman Slavin said. “I can appreciate where you’re coming from, the difficulty I have is this is a construction project that’s going to take how long? And it’s going to go through some of the most well-preserved areas that we have naturally in our city.

“Quite honestly, the city took it on the chin on this one. It didn’t matter that it was a county pipe that failed, it was, ‘There goes the city of Dover again.’ A lot of people believe this is the result of poor management on the part of the city of Dover and quite honestly, it’s not.”

Mr. Riggi said it’s simply going to take some time to fix the issue.

“Once our fittings get here in a few weeks, our hope is to open up the southern part of the park near Division Street to be able to clean that line and remove all that debris,” he said. “This is a slow process.

“We didn’t want to jump in the hole before Christmas, try and fix it, and then turn it on and have it blow up somewhere else. We made that mistake before and we don’t want to do it again.”