Otter Creek Lake and Park Restoration Project

Otter Creek Lake 4 - Houston Engineering INC. | Otter Creek
Otter Creek Lake and Park Restoration Project

Overview

Background

Otter Creek Lake and Park is in Tama County, IA. FYRA Engineering (now part of Houston Engineering, Inc., [HEI]), was hired to complete Phase 1 planning, conceptual design, and construction cost estimation for a variety of alternatives to improve publicly owned land adjacent to the lake and restore Otter Creek Lake. Prioritization and selection of dredging methods, zones, and spoils containment sites were major elements of the Phase 1 plan.

The Project

The design phases (Phase 2 and Phase 3) each focused on specific elements identified and prioritized in the Phase 1 plan.

Phase 2

Phase 2 included design and construction of three watershed sediment and phosphorus retention basin best management practices (BMPs) as well as a detailed cut and cover operation for the implementation of a low-level drawdown pipe in the main lake.
This included a time-sensitive sequencing plan to excavate the existing dam embankment, which includes a controlled dam breach to drawdown the water in the lake. Segments of the drawdown pipe will be placed, and portions of the embankment will be strategically backfilled to maintain the flood protection that the dam provides to reduce the risk of damage from a flood event to the embankment while under construction.

A 32-foot concrete outlet control structure that houses the knife gate valve used to manage future lake drawdown was constructed when the lake was drained. It was then backfilled around and above the new pipe as the rest of the embankment material was put back in place. This process required geotechnical evaluation and a thorough understanding of risk and construction sequencing. Construction started in mid-June 2021 and was completed in November 2021.

Phase 3

Phase 3 of the design includes the design of mechanical dredging and spoils containment, shoreline and jetty improvements, and a large sediment basin on the main tributary directly above the lake selected from the Phase 1 plan. This sediment retention structure is on the main stem directly upstream of lake and is large enough to meet dam safety criteria. Through coordination with the Iowa Department of Natural Resources Dam Safety, the team was able to reduce the size of the structure to a low-hazard dam by performing breach modeling and designing downstream modifications to ensure the safety of the campground located downstream in the event of a dam breach. Due to space limitations, a large articulated concrete block weir outlet structure was designed to reduce the top of dam embankment elevation, eliminating the need for an off-site easement. Construction began in December 2021

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Project Highlights

  • This project showcases our team’s expertise in rehabilitating old watershed dams, constructing new ones, and performing dam rehabilitation services on the four major dams in this lake complex.
  • Coordinated with the Iowa Department of Natural Resource Dam Safety to ensure safety of the dam and development a design that would avoid the need for an off-site easement.
Project Details

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Client: Tama County Conservation Board

Location: Tama County, Iowa

Project Highlights

Project Highlights

  • This project showcases our team’s expertise in rehabilitating old watershed dams, constructing new ones, and performing dam rehabilitation services on the four major dams in this lake complex.
  • Coordinated with the Iowa Department of Natural Resource Dam Safety to ensure safety of the dam and development a design that would avoid the need for an off-site easement.
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