Biggest Wetland Project in State Awaits First Spring Flush
Jan 17, 2020
To Prevent Floods, Remove Nitrate
January 17, 2020 (Storm Lake, Iowa) – The largest wetland project undertaken by the Iowa Department of Agriculture and Land Stewardship sits east of Storm Lake waiting for spring to come so it can perform its duty. It was built last summer not only to prevent flooding, but to remove nitrate from primarily tile-drained land in five Buena Vista County drainage districts.
Those who drove east out of Storm Lake on C49 last spring could see the problem. Nine miles east of Walmart – straight north of Newell – a drainage ditch runs north to south under the blacktop eventually emptying into the Raccoon River. Floodwaters lapped up on both sides of C49, almost up to road level. Round bales lay submerged to the right. Up a small rise is Haahr Turkey Farm.
During the summer things dried up and grading equipment moved in on the north side of C49. Workers created a berm, or a big earthen basin. Floodwater and tile drainage from 5,548 acres to the north will collect in the pool.
The pool is shallow to encourage denitrification, a microbial process that converts nitrate to nitrogen gas (most of the air we breathe).
The wetland pool (year-round standing water) will be approximately 56 acres.
When the water in the pool reaches a certain level it flows over a weir – a dam-like structure – made of sheet pile. Long metal posts – the longest a whopping 34 feet long – were driven vertically into the ground side by side. The crest of the weir is 50 feet wide.
The wetland includes at the east end Grau Wildlife area where trees are planted and a pond attracts waterfowl.
The construction of the wetland is part of the Iowa Conservation Reserve Enhancement Program (CREP).
All that needs to be done to finish the project is some tile work and seeding which will happen next spring, says Bethany Brittenham, an ISG engineer who was part of the effort.
The total easement for this large development is 75 acres. Originally five landowners were involved. Now two are, since the others sold land to the DNR, says Brittenham.
While the outlet channels will be the responsibility of the drainage district, the grassland will be the responsibility of the landowner.
The remaining cost, development, acquisition and maintenance of the wetland itself is the responsibility of IDALS.
“That’s why I like this project. Farmers can do it,” she says. “And it improves water quality.”
The cost per year of nitrate removal is an average of $0.26/lb. “That makes wetlands one of the more efficient and cost effective practices for nitrate removal,” she says
When the final steps of the project are complete the total cost will become public.
To read original article from The Storm Lake Times, click here.