The Saylorville Lake Project, Johnston, Iowa, also includes the Big Creek Remedial Works.
The Big Creek Remedial Works Project was awarded the 1976 Chief of Engineers Distinguished Design Award. Originally Polk City was to be protected with a system of tall levees, but placing dams both above and below the city eliminated the need for those levees. The Iowa Department of Natural Resources manages the ponding area behind the Barrier Dam as an inviolate refuge during a portion of the year to protect waterfowl. The Big Creek Remedial Works provides protection for parts of Polk City Iowa and adjacent Big Creek Valley which are below the full flood pool level. This flood protection system consists of:
- Barrier Dam: It protects Polk City from rising water in Saylorville Lake.
- Pump Stations: Excess water can be drained into Saylorville Lake via gravity flow through a conduit in the Barrier Dam or pumped when Saylorville Lake levels rise. There are three pumps with 350 h.p. motors which are each capable of pumping 17,000 gallons per minute and three 500 h.p. pumps capable of pumping 29,940 gallons per minute when Saylorville Lake level is high with 50’ of water head pressure above the pumps.
- Diversion Dam: It formed the 880-acre Big Creek Lake and protects Polk City from floodwaters within Big Creek Watershed. A minimum 3 cfs water quality release is maintained from the Diversion Dam through Polk City into the Ponding Area.
- Diversion Channel & Terminal Dam/Spillway: Diverts floodwater from Big Creek Lake into Saylorville Lake. The spillway with a crest elevation of 920.0 NGVD keeps the lake level relatively stable at that elevation.
Project in Operation
OM – Operations and Maintenance
Flood Control Act of 1958
Summarized Project Costs: Not applicable
Major Work Item Prior Fiscal Year
FY 2023: Project was in operation. Construction of Supplemental Pump Station (funded in FY18) was substantially complete.
Major Work Item Current Year
FY 2024: Project is in operation. Complete efforts associated with construction of Supplemental Pump Station. Contract extended one year due to insufficient water levels on main pool to conduct the wet test of the pumps which requires the Saylorville Lake elevation to be approximately 16’ above conservation pool. The current estimated project completion date is November 2023.