A deluge washed clay soils off the freshly excavated slopes of a development in Lenexa, Kansas a year ago, sending a plume of sediment racing into a stream that flowed into a nearby recreational lake. It was a clear violation of the local stormwater and sediment control ordinance.

But instead of pointing the finger-of-blame at the contractor and hitting him with hefty fines, city officials immediately implemented a collaborative plan to rectify the problem.

The Development
City Center North Village is a 68-acre, multi-use development in the central part of Lenexa, which is a suburb of Kansas City. The mix includes a variety of residential properties, from apartment buildings and condos to single family homes as well as 360,000 square feet of retail and office space.

The property is drained by a small tributary of Mill Creek which flows a half mile into Shawnee Mission Lake, a multi-use recreational body of water that sports a beach and is stocked with trout for fishing. A primary concern during the development’s review process was the protection of the lake.

Construction started in the spring of 2007. The steep slopes required a tremendous amount of excavation work - an estimated 335,000 cubic yards of cut and 230,000 cubic yards of fill - to prepare the site, according to Rob Beilfuss, Water Quality Specialist for the city.

“We were set up for disaster on this one because the contractor was unable to put in three of his main sediment ponds that were on his erosion sediment plan,” he said. Only one had been built. A delay in getting county approval to remove an existing sewer line as well as the extensive cut-and-fill excavation and the presence of shallow bedrock put off creating the others.

As interim measures, the contractor created four- and five-foot high, mulch berms around the perimeter of the development. A series of silt fences were also placed around piles of stored top soil and three rock checks were installed in the primary drainage ways.

“They were relying on perimeter controls,” Beilfuss said. “We found out quickly that that wasn’t enough.”
On the evening of March 29, 2007, Lenexa was hit with three inches of rain that proved to be too much for the BMPs.

“The mulch berms on the northern portion of the site were blown out,” Beilfuss said. “There were visible sediment plumes into the creek, and there was discoloration and solids visible all the way down into the eastern cove of Shawnee Mission Lake.”

The Plan
Several years ago, the City of Lenexa created a position, the Erosion and Sediment Control Inspector, whose job is to monitor erosion and stormwater run-off issues. He was at the job site immediately after the rainfall to see the effects of the downpour.

“We caught it first. We realized we had a problem out there,” Beilfuss said, which lead to same-day action. Digital photos were taken of the failed BMPs, sediment plumes and other effects of the heavy rain. The photos were sent via email to top city officials to show the magnitude of the problem and to bring all of them up-to-date.

A conference call was set up with city staff and the contractor and a site visit was arranged. Officials of Johnson County Parks and Recreation, which manages the lake, were also invited.

“We were all there together so we could discuss the problems and what needed to be done,” Beilfuss said. “We identified that perimeter controls had to be repaired as quickly as possible. The rock checks weren’t working, so we ordered them to be fixed and work on the sediment basins was to be done as quickly as possible.”

Over the coming days and weeks, all stakeholders were provided with regular updates on the progress to improve the site. The city contacted the county to expedite the approval to remove the old sewer line that impeded sediment basin construction. While the work on those primary BMPs got underway, the rock checks were reworked, and a more effective combination of mulch berms and terraced silt fences kept sediment from leaving the site.

The monitoring continued. Suspended clays were found to be leaving the one sediment basin that was constructed, so flocculants were added to help bind and settle out the fine clay particles that were held in suspension. At the request of the county, the city also installed rock checks on park property further down stream and before the lake to further protect the body of water.

By the summer, the site was better controlled. The remaining sediment basins were installed on all the main drainages and Faircloth Skimmers were employed to skim off and discharge cleaner water from them during rainfall events.

The Experience
Though there were those who proposed punitive action against the contractor for the sediment pollution that got into the stream and lake, no fines were levied. Lenexa officials took a different route, which is a key lesson out of this event.

“Anytime you have something that goes wrong, its human nature to point fingers and play the blame game,” Beilfuss said. They took a team approach to deal with the problem. Instead of playing the role of “regulator,” the city brought all stakeholders together from the beginning to see the problem first hand. They worked together to find ­solutions.

“We were much better off creating a ‘team’ atmosphere,” Beilfuss continued. “When you start threatening fines, you make the contractor defensive and they are not quite as willing to get something done.”

Communication was another key. As the problems were identified and solutions applied, everyone was kept updated. When it was learned that a hold up in getting county approval to remove the old sanitary sewer line was delaying the construction of the main sediment basins, the city contacted the county and asked to expedite the process. Once that was obtained, the work accelerated.

Beilfuss also said having an Erosion and Sediment Control Inspector on staff provided an early warning system for all involved. Had the sediment problem continued, it could have lead to public complaints and hefty fines from state and federal officials.

“When we discovered the problem, our city administrator caught me in the hall and said he was glad we saw it first,” he said. “Having a full time inspector really made a difference in this case, because we were able to be proactive.”

Vigilance is also important. After all involved felt that the site had been properly adapted to deal with stormwater erosions and sediment control, they ran into a problem. A machine operator who was removing sediment from one of the basins dumped it into an adjacent stream way. That brought on a directive from the city for the contractor to use a vacuum truck to clean the impacted stream.

“That was one of our lessons learned. Don’t get complacent with these sites,” Beilfuss said. “All it takes is one operator’s mistake to mess things up.” SLDT