It took over two weeks, but crews from the City of Muscatine and Haggerty Earthworks were able to excavate the area of a suspected sewer line leak and discovered that the problem is much bigger than first anticipated.
The leak was discovered at the intersection of Day, Birch, and Nebraska streets by Muscatine Power and Water (MPW) on October 30 and excavation began November 1. However, due to the amount of water pooling in the excavated area, the City decided to turn off the Papoose Lift Station to allow the 30-inch force main that runs to the Water Pollution Control Plant (WPCP) to empty. Turning off the lift station has allowed sewage to be discharged into the Mississippi River.
Public Works Director Brian Stineman and WPCP Director Jon Koch worked with multiple specialists at the Iowa Department of Natural Resources on repair and replacement options. Stineman informed the Muscatine City Council on Thursday, November 16 that three options were developed, with the IDNR concurring that the third option, which ends the bypass the most quickly, is the best option.
“We met with them today [November 20], and they believe our best course of action is to push a 24-inch line into the existing 30-inch line,” Koch said. “Excavation work on this project can start immediately, and pipe lining can begin as soon as material arrives in the next week or two.”
The three options that were presented to the City Council included banding the known leak, lining the entire pipe, or inserting a smaller slip-line pipe into the force main.
The first two options would involve dewatering the line, cleaning the line, and inspecting the line from Musser Park to the WPCP, which consists of 2,300 feet of 30-inch pipe. The third option does not require draining and cleaning the line, resulting in the bypass event ending sooner.
The first option centered on banding the damaged section of the pipe but that posed safety risks for crews working in the sandy soil excavation area as well as a potential risk for breaking the 16-inch water main.
The second option would have used a cured-in-place liner placed inside approximately 950 linear feet of 30-inch pipe from the Musser Park connection to a point west of Grandview Avenue. Stineman added that this option would prevent having to open cut around multiple utilities, railroad tracks, and streets. The remaining 1,400 linear feet of 30-inch pipe would be open cut and replaced from the WPCP to the junction with the lined pipe.
The third option inserts a 24-inch pipe inside the 30-inch pipe. The DNR concurs with the City’s decision to move forward with the third option, which would reduce the amount of wastewater bypassed.
Stineman asked the City Council to authorize spending up to $750,000 out of the Sewer Extension and Improvement Reserve Fund for the emergency repairs. The council passed the preauthorization on a 6-0 vote.
The city will eventually have to budget and implement a plan to open cut and place a new 30-inch force main from Musser Park to the WPCP. The current line, which is the oldest section remaining in Muscatine’s system, will be kept in place for redundancy and used as needed.
“We plan to install a new 30-inch line that will be installed by directional boring and open cutting,” Koch said. “The 24-inch slip line will remain in service as an overflow for high flow events and emergency repairs to the new line.”
The City would like to remind the public that state water quality standards for fishing and swimming may not be met in the area immediately downstream from the Papoose Creek discharge, which includes the old boat landing in Riverside Park. The landing has been closed and should not be utilized until further notice.