USACE Improves Water Quality for Atchison Residents

The City of Atchison’s aging sewer and stormwater system both sent water to the wastewater treatment plant. In the event of a flood or storm, the system would overtop and divert into a local creak. While this was once a standard practice, the outdated design was no longer in compliance with EPA standards. The City needed to separate the two, sending stormwater to the creek and sewer water to the wastewater treatment center.

To comply with the current standards, the City created a long-term plan spanning multiple phases. A local congressman worked with the United States Army Corp of Engineers (USACE) to address the issues, leveraging their expertise and funding. Following the completion of Phase 1, USACE selected our team to design improvements for the second phase.

Due to the age of the city’s infrastructure, Atchison didn’t have current, comprehensive maps of their stormwater system. To set our engineering experts up for success, our Survey Team kicked off the project. They conducted topographic and property surveys, as well as utility locates. This gave us a clear picture of the existing facilities.

Phase two focused on two sites – 15th Street and 16th Street. Going into the project, we were aware of some existing issues. There was too much water flowing across Kansas Avenue, and the current set-up didn’t meet APWA standards. Additionally, the water that used to go into the sewer system on 16th Street was overloading the system, because the outfall was undersized. To find the right solution, our Stormwater Team analyzed and modeled the area to determine where to place the inlets and how large the pipes needed to be to convey the volume of water.

Drawing on their findings, we decided to create new inlets and relocate some of the existing facilities along 15th Street. These were then connected to a new stormwater pipe that was added in the first phase. On 16th Street, we added a new stormwater system using some of the existing inlets. Water from this area will flow into a new pipe that outfalls into White Clay Creek.

One of our team’s design challenges was accommodating the steep slope from 16th Street to the creek. If left as is, the outfall would cause significant erosion problems due to the high velocity of the water. To decrease the water’s speed coming out of the stormwater pipe, we used a standard energy dissipation design from the Missouri Department of Transportation (MoDOT). This design was based on the US Bureau of Recreation (USBR) Type VI Basin design standard.

Along with these stormwater improvements, USACE will perform a full, curb to curb, replacement of pavement in the affected portion of 16th Street, as well as an intersecting alleyway. There will also be patchwork repair on 15th Street and KS Highway 7. In addition, they will patch and replace sidewalks in both areas, enhancing connectivity for pedestrians.

To minimize disruptions during construction, our Traffic Team developed a traffic control plan. This will help maintain access to homes and businesses, as well as Highway 7, Atchison’s Main Street, throughout construction.

The design for the Atchison Sewer and Stormwater Separation project is complete. Right now, USACE is preparing to solicit construction contracts. Once constructed, the design will deliver cleaner water and a safer environment for residents.