Over the past 3 years, FRWA has been involved in two very special fish passage projects with the Connecticut Department of Environmental Protection (CTDEP) Fisheries program. Both projects were funded by the U. S. Fish & Wildlife Service with labor being provided by CT DEP Fisheries and logistical support by FRWA. We are thankful to CT DOT for allowing the Nod Brook work in one of their culverts and for Anchor Management who permitted us to temporarily store equipment on their property near Nod Brook in Avon.
Nod Brook – Route 10 Culvert – August 2005
Nod Brook, an important tributary of the Farmington River should be home to more fish, particularly trout and Atlantic Salmon. The long box culvert under Route 10, just south of the Avon Wellness Center/Healthtrax building, is seen by few of the commuters and neighbors who travel over it by the thousands daily. It may be out of sight but it has been identified by Steve Gephard, a fish passage expert with the CT DEP Diadromous Fish Program, as a key impediment to fish passage. It is for that reason that the Nod Brook culvert under Route 10 was chosen for this special retrofitting.
The key to reversing Nod Brook’s fish fortune was to improve the ability of fish to navigate through a long, in this case over 200 feet, flat-bottomed double-box culvert that spread low flows over too wide a surface area. These wide, long and dark passageways are too shallow and their flow too uniform to allow fish migration, especially at times of low flow that occur in the summer. DEP Fisheries installed specially designed small concrete baffles that deepened and improved streamflow for fish migrating through a long box culvert running under Route 10 in Avon. (see photos) Now, commuters and fish can take comfort that even during low flows, fish are migrating through the culvert. Indeed, immediately upon the completion of the project, fish could be seen swimming through the culvert.
Sandy Brook – August 2006, September 2007
A bridge over Sandy Brook includes a complete bank-to-bank concrete apron to stabilize its footings. It covers the native streambed, prevents the creation of a low flow channel, blocks interstitial flow, and downcutting below its downstream lip presents a challenge to passage by migratory fish. The flows on the apron are shallow due to the large width and high velocity due to the lack of streambed structure. Sandy Brook has valuable upstream habitat for fish moving up from the lower Brook and from the Farmington River. Atlantic salmon are stocked in this Brook.
In this project, rebar cribs welded together to form a grid were installed in the apron to help modify the overly laminar flow in the streambed. One half of the stream bank was blocked off so that flow could be concentrated and modified for optimal fish passage flows. Although the rebar cribs and rock ladder were established in August 2006, additional rock was added in September 2007 to compensate for rock that was washed out of the structure in the heavy spring floods of April, 2007.