The city is asking residents to hold off on the long baths, big drinks and just overall water use to help them fix a big, old sewer line that has worn out, its final blow coming from last night’s heavy rainstorm that brought lots of water quickly, within a hour or less, in horizontal sheets.
Utilities Director Brad Palmer and other city workers have been in Griffin Park near the Missouri River since early dark Thursday morning at the sinkhole that formed over the weekend on a walking path and got bigger overnight.
“We had this sewer main in the park and have seen this sinkhole developing around it. We had plans to come in today to repair it but the storm last night caused it to collapse,” Palmer said. “We came down at midnight and started to work on it.”
The problem is more than that the oft-called Heisenberg principle that watching/measuring something changes it. It’s the basic stuff happens principle: it’s pretty hard to fix a broken pipe of stuff when the stuff is still flowing.
So the city put out a public request for people to use as little water as possible.
“We asked for a voluntary water restriction, for people to use less,” Palmer said. At the waste water treatment plant, the effects of less water use could be seen. “The flows have not been too bad and we have been able to keep up.”
To fix the broken 24-inch, decades-old clay pipe that was reinforced in the 1990s with a hard plastic liner, city workers put in a temporary pump-powered bypass taking the sewage around the sinkhole region.
The effect of the water restriction made the bypass doable, he said.
“The public has been very responsive,” Palmer said about 10:30 a.m.
The request went out before the key time when everyone is getting ready in the morning, he said.
“I heard people who said ‘I did not wash my hair this morning and the state said it would shut down its car wash operation.”
The city also closed the beach and the bathhouse at Griffin Park because of the sinkhole and the work.
The repair involves a lot of stuff.
The 24-inch pipe handles about two-thirds of the city’s sewage in its key location at the bottom of the city’s storied topography that has wastewater coming down from heights hundreds of feet above riverside level.
“It all flows downhill,” Palmer said. “This is the last pipe to go before it gets to the plant.”
About noon, while some crew workers grabbed a quick lunch of pizza or salad, others kept on trying to get enough water out of the 13-foot-deep hole dug out by a backhoe to get down to the faulty 24-inch clay pipe. But it appeared ground water, some of it perhaps rather directly coming from the Missouri River only a few feet away, was keeping water in the hole covering the pipe, foiling repair plans, said a crew chief. More pumps might be needed, he said.
Stuff is happening but it won’t be a quick fix.
“We will be here all day,” Palmer said.
The preliminary official rainfall measurement from the overnight storm in Pierre is only 0.34 inch at the automatic gauge at the Pierre Regional Airport, for the 24 hours ending at 7 a.m., Thursday, July 18, said Aaron Dye, of the National Weather Service office in Aberdeen.
It appeared that rainfall downtown during the storm was more than 0.34 inch as it came down fast and hard for more than 40 minutes.
But the wind, measured as high as 64 mph at the airport during the thunderstorm that moved west to east across Fort Pierre and Pierre, damaging some rooftops, could have interfered with the rain getting into the gauge, Dye said.
On West Elizabeth Avenue in Pierre, a trained observer reported 0.53 inch of rain from the overnight storm and another observer 12 miles north of Pierre reported 0.75 inch, Dye said.
A volunteer trained observer 25 miles west of Fort Pierre reported 1.7 inch of rain in the 24 hours ending at 8 a.m., Thursday, Dye said. In Selby, the rainfall was measured at 2.21 inches, he said.