An eroding St. Joseph River bank will be stabilized, curtailing nutrient pollution

SOUTH BEND — A 575-foot section of embankment that has significantly eroded and continues to pollute the St. Joseph River with sediment and nutrients will be stabilized starting this month, city officials said.

The $816,000 engineering project focuses on a steep, 45-foot-tall segment of the river bank alongside Riverside Drive, just south of its intersection with Angela Boulevard. Erosion is drastic at the site because the fast-moving river bends to the east. The record flood of February 2018, when the water level crested at 12.7 feet, likely sped up the process.

To restore the embankment, the slope will be graded so that its incline is more gradual. A large trench, called a rock toe, will be dug along its length and filled with large rocks up to the river's ordinary high-water mark. Above that mark, the bank will be stabilized with trees and native seed mixes, including coneflowers, black-eyed susans and New England asters.

More:Was the flood of 2018 one for the record books?

“In the end, this treatment will prevent the loss of shoreline," city engineer Kara Boyles said Friday at a press conference. "It’ll also reduce the effects of sediments and nutrients into our stream.”

Concerns have grown over the stretch of river bank because it's within 20 or so feet of Riverside Drive and even closer to a city water main, which feeds smaller pipes leading to homes and businesses in the Near Northwest Neighborhood. In the eyes of a city engineer, Boyles said, that proximity is "too close for comfort."

The project will also curtail further erosion that harms the river's ecosystem.

According to Environmental Protection Agency modeling, the project will reduce the amount of sediment eroding into the river by 569 tons a year. Nutrient pollution will decrease drastically, with 484 fewer pounds of phosphorus and 968 fewer pounds of nitrogen entering the river annually.

Nitrogen and phosphorus support the growth of algae and aquatic plants. But human activities have caused too much of the nutrients to pour into streams and rivers feeding large bodies of water such as the Great Lakes, according to the EPA.

The overload has caused illnesses and deaths in Great Lakes fish and other aquatic wildlife. In the case of harmful algal blooms, which are most common in Lake Erie, Green Bay and Saginaw Bay, humans can also become sick.

"Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle," the EPA states. "Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive."

The stabilization project was paid for in part with a $200,000 grant from the Great Lakes Sediment and Nutrient Reduction program and a $90,000 grant from the Indiana Division of Natural Resources. The work is expected to be finished by this fall, officials said.

Contact South Bend Tribune city reporter Jordan Smith at 574-235-6480 or JTsmith@gannett.com. Follow him on Twitter: @jordantsmith09