Sustainable Land Development Today - April 2008 - (Page 36) EROSION CONTROL Pulling Together for Erosion Control City officials shun blame game in favor of team approach after blown out BMPs allow sediment to threaten recreational lake. By Steve Gaze 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-ofblame at the contractor and hitting him with hefty fines, city officials immediately implemented a collaborative plan to rectify the problem. ence 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 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 pres- 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 con- 36 April 2008 Sustainable Land Development Today
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