TOLNA COULEE CONTROL STRUCTURE PLANS

  • TOLNA COULEE CONTROL STRUCTUREThe Tolna Coulee Control Structure was built in 2012 by the U.S. Army  Corps of Engineers.
  • “The North Dakota State Water Commission (NDSWC) is the owner and operating agency.” (p. 1)
  • The Tolna Coulee Control Structure (TCCS)  is 12′ tall and 120′ long.
  • The TCCS will encourage drainage from Devils Lake into the Sheyenne River.
  • Water will begin flowing  from Devils Lake sooner than it would have and in a narrower channel.
  • The Operating Plan allows drainage to begin as soon as Devils Lake rises to 1456 feet above mean sea level, not 1457 or 1458 feet msl.
  • Water will begin to flow through a 40′ opening in the Control Structure.
  • If the Tolna Coulee erodes wider and deeper, the Control Structure will also widen and deepen.
  • The Tolna Coulee could erode down to 1446 feet msl, where the base of the structure prevents further erosion.
  • This process could go on forever, as there is no limitation on how long the Control Structure will operate.
  • If the Tolna Coulee does not erode, water will still overflow from Devils Lake through the structure if the lake rises and overflows.
  • All of the water draining into the Tolna Coulee will flow into the Sheyenne.
  • Flow rates through the Tolna Coulee will meet or exceed 3,000 cubic feet per second.
  • If the Tolna Coulee erodes, more logs will be removed to allow more erosion to continue.
  • If all of the stop logs are removed, there will be no control over the amount of water to be released into the Sheyenne River.
  • Once the stop logs are removed, “they will not be replaced.” (p. 2)
  • Once erosion of the Tolna Coulee occurs, all of the water in Devils Lake above that elevation will flow into the Sheyenne River without any control.
  • The Devils Lake watershed will be added to the Sheyenne River watershed.
  • Outflows “will be conducted in a manner of discharge not to exceed 3,000 cfs.” (p. 3)

EXCEPT: In “High Hydrometerological Conditions: Conditions become high if discharge exceeds 3,000 cfs.” (p. 4) [Repeated 4 times]

CONCLUSIONS

  1. Once Devils Lake rises to overflow elevation, there is no method of preventing water from draining into the Sheyenne.
  2. When will water retention in  the upper Devils Lake Basin be considered?
  3. How will the Sheyenne River react to Devils Lake water if up to 7,500 cfs are already in the river and 3,000 cfs are added from Devils Lake?
  4. Will the flood prevention methods used in Valley City, Fort Ransom, Lisbon and along the river be adequate if Devils Lake water is added to the Sheyenne?
  5. How much will flood insurance cost in those cities and along the river once Devils Lake water is added to the river?
  6. How will the Operating Plan be interpreted when statements made are  vague and contradictory?
Outlet To Sheyenne
Outlet
Location
  Discharge
Volume
Cumulative
Subtotal Adding to Sheyenne River

1.

West Bay
100 cfs
(plus increase requested to 250 cfs)

100 cfs -up to 250 cfs

250 cfs

2.
West Bay
(add’l proposed)

Adding
100 cfs

100 cfs

350 cfs

3.

East Devils Lake
(proposed)

Adding 250-350 cfs

250-350 cfs

600-700 cfs
Potential Total
         


January 24, 2011, North Dakota Govenor’s website.

Dalrymple Moves Up Devils Lake Flood Control Timetable
BISMARCK, ND – Gov. Jack Dalrymple today ordered an emergency waiver that allows for the immediate design and construction of a water control structure at Devils Lakes’ Tolna Coulee.
Dalrymple’s order shortens by about two months the State Water Commission’s prescribed timetable in selecting a design and contractor to build a control structure at Tolna Coulee. State law holds that the governor has authority to waive certain agency procedures when necessary to minimize or avert the effects of a disaster or emergency.
“Building a control structure at Tolna Coulee is a critical element in our strategy to alleviate flooding at Devils Lake and protect downstream communities,” Dalrymple said. “We will proceed expeditiously at Tolna Coulee and with plans for additional outlet capacity.”
State officials plan to expand the lake’s west-end outlet to increase water discharges from 250 cubic feet per second (cfs) to 350 cfs; build an east-end outlet with a discharge capacity of 250 cfs; and build a control structure at Tolna Coulee.
According to the National Weather Service, water levels in the Devils Lake region are currently at 1451.6, with a 90 percent chance they will rise to 1453.5 and a 50 percent chance they will rise to 1454.6. Greater than average precipitation and heavy snowpack suggest Devils Lake and Stump Lake will rise to record levels this spring and summer.

05058500 SHEYENNE RIVER AT VALLEY CITY, ND USGS
http://nd.water.usgs.gov/floodtracking/charts/05058500_09020204.html
Flood Tracking Charts for North Dakota and Selected Tributaries (USGS)
http://nd.water.usgs.gov/floodtracking/index.html