HomeMy WebLinkAboutA011 - Resolution approving preliminary plans & specifications for 2023/24 Story County Edge of Field Project, setting January 7, 2026, as the bid due date & January 13, 2026, as the date of Public HearingITEM #:11
DATE:11-18-25
DEPT:W&PC
SUBJECT:FY 2023/24 STORY COUNTY EDGE OF FIELD PROJECT
COUNCIL ACTION FORM
BACKGROUND:
The Water Pollution Control (WPC) Facility is being converted to implement nutrient removal
treatment technology over a period of 20 years. Separate from the work occurring at the
treatment plant, watershed-based improvements performed by the City can be
“banked” as credit toward any future, more stringent nutrient reduction regulations
imposed on the WPC Facility. On February 24, 2021, staff executed a Memorandum of
Understanding (MOU) with the Iowa Department of Natural Resources to allow these off-site
nutrient reductions to be registered and banked through the Iowa Nutrient Reduction
Exchange.
Over the past several years, staff has developed a partnership with multiple entities to bundle
several Edge-of-Field (EOF) practices into a single bid package. The FY 2023/24 project will
construct EOF practices across Story County, consisting of seven saturated buffers
and twelve bioreactors that will intercept and treat 22 agricultural tile outlets. These
practices promote the natural removal of nitrogen from subsurface drainage before it
enters streams and other surface waters. Additional background information about these
practices is shown in the attachment.
In addition to the nutrient reduction benefits, these practices also provide a modest degree of
resilience to droughts and floods by holding water on the landscape for longer durations.
On March 28, 2023 and July 8, 2025, City Council approved two separate agreements that
outlined the funding arrangements and project management duties for the EOF project. The
City of Ames is acting as the fiscal agent for the project, and the Iowa Department of
Agricultural and Land Stewardship (IDALS) and Story County/Story County Conservation are
acting as funding partners. Project funding consists of 75% from IDALS and a 25% local
match that is split equally between the City and Story County. The City’s share will be
funded from the $100,000 budgeted annually in the Watershed Based Nutrient
Reduction capital improvements project.
The final design is complete, and all participating landowners have submitted the
necessary documentation. Staff is now prepared to issue a Notice to Bidders for the
EOF project. The engineer ’s estimate of probable construction costs is $354,337, with
the City’s estimated contribution being $44,295.
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ALTERNATIVES:
1. Approve the preliminary plans and specifications and issue a Notice to Bidders for the
FY 2023/24 Story County Edge of Field Project, and establish January 7, 2026 as the bid
due date and January 13, 2026, as the date of public hearing and award.
2. Do not approve the plans and specifications and Notice to Bidders, thereby delaying the
completion of this project.
CITY MANAGER'S RECOMMENDED ACTION:
The Ames Water Pollution Control Facility will be converted to a nutrient removal
treatment technology over a period of 20 years. To mitigate future investment beyond
what is already planned for, watershed-based projects can be performed, and the
resulting nutrient reduction credits can be banked. Following project completion, the
City will register each of these practices and receive annual nutrient reduction credit for
the lifespan of each practice. Therefore, it is the recommendation of the City Manager that
the City Council adopt Alternative No. 1, as described above.
ATTACHMENT(S):
About_Saturated_Buffers_and_Nitrifying_Bioreactors.pdf
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About Saturated Buffers and Nitrifying Bioreactors
Saturated Buffers
A saturated buffer is an area of perennial vegetation between agricultural
fields and waterways where tile outlets drain. Tile lines connect to a
control structure, which distributes water laterally along the buffer. As
water drains into the buffer, the living roots of perennial vegetation
absorb water and nutrients, like nitrogen. According to the Iowa Nutrient
Reduction Strategy, a saturated buffer has the potential to remove 50%
of nitrogen from water that is diverted through the buffer.
Bioreactors
A bioreactor is a buried trench on the edge of a farm field that is
traditionally filled with woodchips. Drainage tiles outlet into the
woodchips where bacteria convert nitrogen in tile water into nitrogen gas.
According to the Iowa Nutrient Reduction Strategy, a bioreactor, on
average, removes 43% of nitrogen from water diverted through it.
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