Rapid City's flooding issues mainly on north end

Canyon Lake is in good shape, but sewers are near capacity.

By Scott Aust, Journal staff | Friday, June 06, 2008

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After flooding known trouble-prone spots, continuing stormy weather is forcing area officials and residents into a holding pattern: waiting and watching for new rising troubles.

As forecasters warned of another 2 to 3 inches of rain late Thursday into early Friday, Rapid City public works director Robert Ellis said municipal and Pennington County officials were bracing for a long campaign.

"We've got street department crews out driving around looking at our known trouble spots, making sure inlets are free of obstructions like branches, garbage or debris," Ellis said.  "Hopefully, it will spread itself out over a couple of hours. But if it really starts coming quickly, we're ready to react. We generally know where the trouble spots are so we're just waiting to see what happens."

Canyon Lake on the west side -- the epicenter of the 1972 flood -- passed inspection. The recently troubled spillway was holding up well, Ellis said Thursday afternoon. The angled concrete ramp to Rapid Creek -- the repair to seal the sinkhole that had burrowed under the spillway -- was completed about a week ago.

Ellis said the "rooster tail" that had been jetting water from the face of the spillway had been reduced to more of a "garden hose" trickle. The sinkhole has been filled, and the boil below the spillway has dissipated, he said.

"That situation appears to be under control, and we're very comfortable with that," he said.

Meanwhile, flooding north of Interstate 90 near the Meade County line Thursday prompted closing parts of Country Road, West Nike Road, 143rd Avenue, Dyess Avenue and Elk Vale Road. Ellis said Country Road and West Nike Road were reopened later.

In Pennington County, there were reports of flooding in the New Underwood, Box Elder and Wall areas. South Ellsworth Road south of Line Road was closed at 8 p.m. because of poor visibility but was expected to reopen at daylight today pending a favorable evaluation.

In the Wall area, Golf Course Road at Stone Road, and Willsie Road past the Hoffman Ranch were closed.

In the New Underwood area, 155th Avenue, 156th Avenue and 159th Avenue south of U.S. Highway 14/16 were closed, and alternate access to areas south of Highway 14/16 was available via 229th Street.

The county advised against traveling on any county road north of the Creighton area.

Pam Buck, Pennington County assistant emergency management director, said before roads are reopened they must be inspected by the county highway department.

"You put the barricades up when the water's there, and then you have to go back and take an engineering look at the road, because the stability of the road is always questionable after a force of water goes over it," Buck said. "We want to make sure we're not opening it up to additional problems. I know the public wants the road open, but it's a safety issue. We need to make sure it's not going to wash away under them."

A section of Skyline Drive remained closed from Pevans Parkway south for about 2,000 feet because of a failing retaining wall. Ellis said it appeared a little more of the wall -- about a 15-foot section -- had slid down the hill, but a full assessment of the damage hasn't been completed.

"That situation isn't improving with all this moisture," Ellis said.  

Some intersections in Rapid City experienced high water when flows overran inlets; however, no other streets have been blocked to through traffic.

One of the city's sewer lift stations in the Country Road area lost power Thursday when its electrical connection ended up under water. City crews responded quickly with a generator and got the lift station back on line before any sewer backups were reported, according to Ellis.

Ellis said the city's sanitary sewer system is running near capacity in many parts of town, possibly because people are pumping water out of flooded basements directly into the sewer system.

Ellis said the sanitary sewer system is not designed to carry this much water. In addition to high volumes of water, it is causing sewer backups in some areas. As a result, the city reminds people it is illegal to run a sump pump into the sewer. Instead, people should direct the water out into the street or into a yard.

Unfilled sandbags are available through Pennington County. Anyone who want them must provide their own transportation to pick them up. They can call the emergency management office at 394-2185.

Emergency information is also available directly through the emergency management Web page at www.co.pennington.sd.us, then click on "emergency management" or "911".

Contact Scott Aust at 394-8415 or scott.aust@rapidcityjournal.com