Representative Projects



FY14 Frankenmuth Fish Passage

Location: City of Frankenmuth, Michigan
Client: USACE Detroit District
Project Description

From the City of Frankenmuth, the Cass River extends 73 miles upstream and encompasses 908 square miles of Michigan’s largest watershed, Saginaw Bay. The Frankenmuth Dam, located on the Cass River, was originally constructed for milling purposes in the early 1840’s for one of the world’s early sources of hydro-electric “power”. Through a collaborative effort guided by the U.S. Fish & Wildlife Service, various studies indicated that certain sporting fish species such as the walleye and the endangered lake sturgeon were unable to progress past the dam, thereby limiting their spawning habitat since the original dam was constructed prior to the Civil War.

In a joint effort between the USACE Detroit District and the City of Frankenmuth, funds were appropriated to address the problem under a sole-source construction contract awarded to CTI in September, 2014. The FY14 Frankenmuth Fish Passage project included the demolition of a water control structure (concrete and timber cribbing dam) that was 235-feet wide and 13-feet high, in addition to the construction of a new, eco-friendly rock ramp fish passage extending over 330 feet in length with stone step-pool rapids designed to create a gradual slope easily navigable for fish. The project included 14 stone “arch” weirs with intervening pools and 5 stone vanes to reduce bank erosion.

The field work began in the late fall of 2014, with a focus on completing the out-of-river work including: site clearing; stone deliveries; a compensatory excavation of over 8,000 CY of soil at the adjacent Fortress Golf Course to provide flood plain equalization; and reconstruction of the north river bank to raise the levee embankment to the 100-year flood plain elevation. Activities associated with the levee earthwork also included demolition and re-construction of a retaining wall structure, concrete sidewalk, and asphalt pavement.

CTI strategically scheduled the fish passage work for the summer of 2015 to coincide with the historical low-flow conditions of the Cass River. Stone deliveries and staging continued in June, 2015 with each weir stone individually inspected upon delivery to assure adherence to strict design specifications. Construction of the haul road began in July, 2015 along the south river embankment, followed by commencement of the in-river work with placement of over 6,000 tons of recycled concrete into a deep scour hole that formed over many years at the base of the dam.

Placement of the rock ramp base material followed, including over 10,000 tons of 2-feet diameter stones blended with small riprap at a grade of 3 percent. Each weir placed over the ramp stone base consisted of a 3-feet diameter “footer” stone and a 5-feet diameter “header” stone with individual stone weights exceeding 10,000 pounds. The weirs were built with very tight survey tolerances, and each stone placed individually to form an arch configuration the full width of the river to serve as the new hydrological barrier, ultimately allowing for the same post construction river profile upstream. In total, 24,873 tons of stone were placed in the river and bank armoring encompassing approximately 5 acres.

This monumental project was completed in early October 2015, and proved to be a great success for all stakeholders. The City of Frankenmuth held a ribbon-cutting ceremony with a special congratulations given to CTI on their dedication, expertise, and ability to deliver the finished product in accordance with a sensitive completion schedule.

Project Highlights
  • Earthwork / Embankment Construction
  • Dam Removal / Demolition
  • Construction Quality Control
  • Geotechnical Testing
  • Geological Quality Analysis
  • Placement of 24,000 tons of Large Stone & Heavy Rip-Rap
  • Individual Stone Weights Exceeding 10,000 lbs.
  • Work completed during active river conditions with water flows exceeding 500 CFS

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