sewerlines griffin park

This aerial photo shows a line indicating the underground sewer pipe that leaked in Griffin Park in Pierre and fixed this week, near the lower right corner of the photo, to the left of the big tree, and the new leak recently discovered at the intersection of Missouri and Ree, in the upper left corner. The Missouri River is seen in the bottom of the photo. (Photo courtesy of City of Pierre)

City crews have repaired the broken sewer main line that caused a sinkhole to form about 25 days ago in Griffin Park just off the Missouri River.

But the remains of the sinkhole that formed on a walking trail from the leak and high groundwater collapsing the sod and dirt won’t be filled in just yet.

Utilities Director Brad Palmer told the City Commission more leakage farther up the same sewer line has been detected and needs to be repaired to avoid another possible sinkhole forming.

The main problem was a faulty decades-old 24-inch sewer pipe more than 10 feet underground that city workers had noticed in early July by some ground changes, but that became obvious about July 12 when a sinkhole gaped open on the well-used trail.

It took days just to get enough water pumped out of the gaping and enlarged hole to get at the pipe, as unusually high river and groundwater levels made what would have been a routine job difficult.

Once the crew workers got down to the problem pipe, a 50-foot section of 17-inch PVC pipe was inserted into the sewer mainline and sealed off at each end of the break with a collar and other sealing techniques.

In the meantime, a leaking problem in the same old clay pipe sewer mainline was discovered about 600 feet upstream to the north at the corner of Ree Street and Missouri Avenue, Palmer said.

That needs to be fixed now, or it could end up creating a sinkhole at that manhole, he said.

So, the hole in the walking path in Griffin Park will remain open so that cameras can be run into the sewer pipe to help monitor the repairs, he said.

“Hopefully, we will finish that up next week,” he told the Capital Journal.

To help get ‘er done, the city sought out a contractor, he said.

The unexpected big workload caused by the leak and sinkhole has cost the city not only legal tender — about $100,000, Palmer estimates — but time, also, that would have been spent on other projects already planned.

He said early last month in the sinkhole deal that a long term repair of the old clay sewer pipe line that runs at the bottom of the city’s sewer system roughly paralleling the river to the wastewater treatment plant will be needed in the next year or less.

The 24-inch old clay pipe in Griffin Park handles about two-thirds of the city’s sewage, he says.

The bypass made up of hoses and pumps around the general area of the sewer pipe repair will remain in place until the Ree Street intersection problem is fixed, Palmer said.

That means the city’s request continues for residents to reduce water use inside homes and businesses to keep the volume going into the sewer system down. Some of the reduction can mean simply avoiding the heavy use normally at early go-to-work times in the morning and readjusting some schedules of water use, he said.

That’s been a huge help, Palmer said, again thanking residents for that voluntary water restriction.

Use of water outside, which will drain into the ground or into the storm sewer system, is not a problem, he said.

Load comments