On Monday night, the Cassville City Council received updates on a stormwater study and the bypass elimination study currently being conducted by Olsson and Associates.
Engineer Eric Dove reported on the study of Town and Hawk Branches, which carry stormwater through Cassville to Flat Creek. According to Dove, the city's goals are to reduce flow into manholes, lower the groundwater and reduce sump pump flows during flooding events.
According to a report provided by Dove, "due to the nature of the aquifer, the flooding temporarily causes a rise in the regional water table for potentially weeks after the floodwaters recede. The elevated water table enters the sanitary sewer system through cracked pipes and leaking joints. This increased volume flows to the wastewater treatment plant and causes additional treatment costs."
In order to control the flow of stormwater into Cassville, Dove recommended the construction of three detention ponds.
A pair of detention ponds would be located on Town Branch upstream of Highway 37. The two ponds would detain a total of 2,655 acres of the upstream portion of Town Branch. The detention ponds would reduce flows by 84 percent.
Another detention pond would need to be constructed on Hawk Branch upstream of Stephens Drive. This pond would detain runoff from 508 acres of the upstream portion of Hawk Branch. The pond would reduce the flow from Hawk Branch by 73 percent.
Dove estimated that the total cost for the construction of all three ponds would be $1.5 million.
"These would be dry basins," said Dove. "We would construct berms with culverts running through them.
"The berms would maximize the available land for pasture," said Dove. "The area would be flood irrigated from time to time, which would increase vegetation in the area."
After the detention ponds are constructed, Dove also recommended that the city install twin 10-foot by six-foot culverts at County Road, Townsend Street, Main Street and East Street along Town Branch and a 42-inch twin reinforced concrete pipe on County Road and an eight-foot by four-foot reinforced concrete box on 14th Street along Hawk Branch.
Later, the city would need to dig a new drainage path down Presley Drive under 11th Street, said Dove.
"You will have some driveway culverts to deal with, but it will really just be a glorified road ditch," said Dove. "It should not be hugely costly."
The alternative to the construction of the detention ponds, would be the installation of 90-foot bridges along both waterways, said Dove. The bridges would cost around $500,000 each.
"It is five times the cost of the detention option," said Dove. "This also allows the city options to build one basin at a time and then go back and do the other improvements later.
"Just remember that drainage improvements should be completed downstream to upstream," Dove added.
Dove recommended the city review the preliminary study further while he is completing the final study of the waterways. Funding options can be researched after the final study is presented to the council.
"Most communities do these types of projects with bonds, which are supported by a sales tax," said Dove.
Dove pointed out that the city should approach the county regarding future development. Currently, the area that drains into Cassville along Town Branch is primarily agriculture land.
"If the county were to fully develop without requiring detention, there could be a large increase in flows reaching the city," said Dove. "It is recommended that the city request the county to require detention on all new development for the watersheds that flow into town."
Roger Berg, Olsson and Associates project manager, addressed the council to offer an update on the bypass elimination study.
"You have a great wastewater treatment plant," said Berg. "It is designed to process one million gallons of flow a day and offers a back-up feature that allows overflow into the old lagoon.
"If there is time between rainfalls, the treatment plant can handle the flow, but it can only handle large flows for a few days," said Berg. "You are very fortunate though. Many cities don't have the capacity that you do."
According to Berg, there is around 4,000 feet of pipe leading to the wastewater treatment plant that is currently too small. The flow to the plant each morning is currently three times larger than the pipe can handle.
Using preliminary data, Berg said he could already tell that the city will need to replace the existing 15-inch pipe with 24-inch pipe. Berg recommended the city install the new pipe along the old pipe instead of upgrading the current pipe line.
"The old pipe leaks so bad that it will not be worth the cost to repair," said Berg. "That is what you would expect from 70-year-old pipe."
The new, larger pipe will eliminate a large part of the current stormwater infiltration into the sewer lines, said Berg. He hopes to complete the entire bypass elimination study within the next two months.
"You will be able to do the improvements piece by piece and review how it has helped your problem before moving onto the next recommendation," said Berg. "The replacement of the 15-inch line will probably cost between $500,000 and $600,000."
In other business, the Cassville City Council:
* Heard that sales tax decreased 5.8 percent this month when compared to the amount of revenue the city received from sales tax in February of 2011. Revenues are currently $6,426 less than received last year.
* Discussed the city's utility payment contract, which gives residents an opportunity to enter into a contract to catch up on their utility payment and avoid disconnection of services.
* Approved the destruction of several old documents. City staff members used Missouri's records retention schedule to determine which documents should be disposed.
* Tabled the YMCA contract, which is still being reviewed by attorneys.
* Rescinded the agreement with Sprenkle and Associates, Inc., that was approved in January and approved a new contract for engineering services through the business. Changes were made to the agreement due to recommendations by the city's attorney.
* Approved a $34,310 mowing service bid from Yocks. Other bids received include: $35,500, Gregory Lawn; $36,810, Anders Lawn Service; $37,240, Go Green; $67,515, Rebar Mowing; and $88,550, Couch Excavating.
* Heard administrative reports.