Hulse Area Drainage

The City of McPherson has been experiencing widespread drainage issues within a 360-acre watershed on the northwest side of town. The area is served by a series of undersized channels, culverts and storm sewers, which could not accommodate a 10-year rainfall event.

Benesch analyzed the capacity of the existing storm sewer system and prepared plans and specifications to alleviate the flooding by replacing eight reinforced concrete box (RCB) culverts and widening nearly a mile of the existing channel. The improvements had to be designed to safely convey runoff from a 10-year rainfall event within the system while protecting the surrounding properties for a 100-year event.

This project included multiple design and coordination challenges. As with all projects, the three issues that had to be proactively addressed included easements, utilities and permits. Given the length of the project, easements had to be acquired from 38 separate property owners. These easements were identified early in the design process and documents were quickly prepared to provide as much time as possible to negotiate and acquire each easement.

Since each culvert had to be widened to handle the design event, each crossing had to be designed around the existing utilities or coordinate their relocation. The utility that presented one of the most challenging issues was the sanitary sewer. Many of the residences in the area do not have basements, which means many of the sanitary sewers are not very deep. To accommodate the new culverts, several hundred feet of sanitary sewer had to be re-routed around or under the new RCBs.

The final challenge was obtaining a United States Army Corps of Engineers (USCAE) 404 permit for the project. Although the project included more than 300 feet of channel work below the ordinary water line, which would typically require an Individual Permit. We were able to successfully negotiate with the USACE to obtain a Nationwide Permit, which saved several months in the application process.