EX O&M - 26149 2004 Operations and Maintenance Plan.pdf

Shiawassee River State Game Area Sections 34 and 35, T.11N, R.3E, Saginaw County Dam ID #1819 Operations and Maintenance Plan

The following recommendations for operations and maintenance of Dam ID#1819 are the result of an inspection made in September 1998 by Paul Wessel, P.E. from DEQ- LWMD Dam Safety Program. Updates were added after another inspection in November 2003.

Dam ID#1819 consists of an embankment that is 15,000 feet long, 12 feet high, has a crest width of 12 feet, and 2:1 side slopes. The embankment creates a wildlife flooding approximately 1600 acres in surface area. One water control structure is present and ftinctions as a spillway; a radial gate structure with two 20-foot radial gates (Radial Gates). Formerly, impoundment levels were controlled by a stoplog controlled overflow weir structure outletting to seven 36-inch corrugated metal pipes (7 Tubes Structure).

This structure was removed in 2001, based upon concerns over the condition of the riser frame support and the corrugated metal outlet pipes. The weir and the six bays of timber stoplogs were removed and the CMPs were filled with flowable fill. Additionally, a 900-foot auxiliary spillway is present to take high streamflows. Wildlife impoundment levels are controlled by operation of the Radial Gates. In addition to providing important wetland habitat for wildlife, the impoundment provides a fall water supply for adjacent diked cropland units flooded for waterfowl use and hunting opportunity. .

The Radial Gates remain open except from September through late November/early December. Water levels are closely monitored at the Radial Gates and must be frequently adjusted to maintain desired water levels during the fall.

Routine maintenance of structures located on the Shiawassee River State Game Area is, and will continue to be, standard practice. Inspections of the dike, water control structures, and auxiliary spillway will be performed monthly except during those times of the year when ice and snow restrict access to the dike. Inspections will also be made as necessary after high water flows and flood conditions. Any problems that are encountered will be reported and repairs made as necessary.

During inspections of the embankment, presence of animal burrows, erosion problems, and encroaching vegetation will be noted and monitored. Animal burrows will be filled as needed, mowing or burning of the embankment will be done annually as needed, and brush growth on the embankment will be monitored and removed as necessary. Any erosion problems encountered will be repaired as necessary.

Inspections performed on the Radial Gates will address the following items:

condition and functional operation of structures (e.g., cracks and seepage in concrete), sedimentation, and condition of bridge. During inspections on the Radial Gates, the following will also be monitored: efflorescence on abutment walls, minor leakage of the radial gates, and debris near gates. Problems will be reported as needed and repairs made

Revised 1/27/04 as necessary. The bridge deck over the Radial Gates was replaced in 1999; condition will be monitored and maintenance performed as necessary.

There is currently substantial erosion on both of the channel banks immediately downstream of the Radial Gates. This is the result of high velocity releases from the Radial Gates when they are opened in late November/early December. Attempts to armor the banks with 5A rip rap have failed and the rock now lies in the middle of the channel, blocking boat access. Methods have been attempted to reduce velocity through the gates by gradual dewatering of the impoundment, however these actions have not worked. Requests for funding of installation of rock-filled gabion structures to reduce erosion were denied. Currently, there are plans to dredge out the channel downstream of the Radial Gates and to reshape both banks so that there is a very gradual slope down to the channel. Erosion appears to have increased after the 7 Tubes overflow structure was removed. Therefore, plans are also being considered to install an overflow structure near the location of the 7 Tubes. After removal of the 7 Tubes in 2001, it was determined that an overflow structure is needed to address water flows into the river system, flooding concerns, and increased erosion at the Radial Gates. All of these proposed plans will continue to be evaluated. Regular monitoring of erosion at the Radial Gates structure will continue.

Although the 7 Tubes structure was removed, inspections of the 7 CMPs will continue on a regular basis to monitor seepage

The auxiliary spillway will be monitored for erosion problems and action taken as necessary.

Responsible parties for the operations and management of the dike, water control structures, and spillway include: DNR Saginaw Bay Wildlife Management Unit (989 684-9141), Shiawassee River State Game Area, Wildlife Biologist at St. Charles field office (989-865-6211), and the Wildlife Technician at St. Charles field office (same phone number as Wildlife Biologist). Inspections and monitoring will be the responsibility of the Wildlife Biologist and Wildlife Technician at St. Charles. The Wildlife Management Unit Supervisor will receive reports of regular inspections and problems encountered during monitoring.

Revised 1/27/04