DNR and Utilities team up to remove aging sewer and restore trout stream

Trout anglers and River Falls citizens are benefiting from teamwork by state wastewater and fisheries staff and the city’s sewer utility to remove an aging sewer line running down the South Fork of the Kinnickinnic and restore the stream to improve its naturally reproducing brook trout population.

The project eliminates the threat that the sewer line would fail, sending raw sewage into the South Fork where it could threaten public health and a trout fishery making a strong comeback. The partnership enabled the city to tap state habitat improvement crews to help plan and carry out the complex, costly restoration more quickly and less expensively than otherwise.

In 2005, the utility replaced an aging, cement encased sewer line that had been built in 1966, right down the center of the South Fork and through several waterfalls. The pipe was deteriorating and in danger of rupturing and releasing large volumes of raw sewage directly into the river, now a Class II wild brook trout stream.

A Class II trout stream has some natural reproduction that is supplemented by stocking of brook trout. The South Fork is now being evaluated for upgrading to a Class 1 stream boasting all natural reproduction, and the potential for a sewage line break was a threat that DNR and the city wanted to eliminate.

So utility staff worked with DNR wastewater and permitting staff to secure the necessary funds and state permits for a new pipeline. A relatively new technique called directional boring was used to drill through bedrock 20-25 feet beneath and adjacent to the river. The newly drilled hole, more than 2,650 feet long, was then lined with a new 24-inch pipeline, no small task.

A joint task force was formed with utility staff and engineers, and DNR senior fishery biologists, Lower Chippewa Basin Fisheries, and Regional Field Operations. The team quickly went to work developing and finalizing work plans, obtaining permits, completing purchase orders and securing construction easements. The DNR Regional Field Operation crew mobilized equipment to the construction site in early September 2006. Some additional cement, erosion control and manhole work also had to be coordinated with a local contractor, Bettendorf Excavating.

DNR field operators ran heavy equipment, while working directly with utility and DNR representatives on the day-to-day decisions needed to complete the delicate and unpredictable work. Their goal? Restoring the riverbed, trout habitat and waterfalls to a natural and aesthetically pleasing state.

To keep costs down, most of the abandoned pipeline that remained underground was plugged and left in place. DNR crews removed remaining sections of pipe and manhole covers on or near the surface of the riverbed with a jack hammer attached to an excavator.

DNR crews then carefully restored each water cascade, and restored fish habitat in two locations, excavating and installing a series of plunge pools and boulder clusters. Access into the canyon was difficult and required building access roads and ramps to get heavy equipment and construction material in and out of the canyon and over water falls without creating damage. Special DNR equipment such as a tracked dump truck made removal of debris efficient. The project was completed in October 2006.

The cost of the directional boring exceeded $3 million, and the utility was struggling with the cost and complexity of removing the pipe and restoring the stream. Knowing that DNR staff had years of experience restoring streams, the utility asked for DNR help in planning, implementing, and constructing the abandonment and restoration portion of this important and complex project.

(Submitted by DNR with slight modifications for space allowance.)