Dubuque Flood Gate Replacement and Pump Station Project Paused Due to 2020 Gavilon Fertilizer Spill

As required before beginning the project, the City of Dubuque conducted an environmental review for the project site in 2019. Such reviews are standard and the City knows the importance of this step because, as the oldest city in Iowa, there are several contaminated sites in the community, some of which are very near the 16th Street Detention Basin. This environmental review for the project resulted in a "Finding of No Significant Impact (FNSI)" for the site. This review and approval, along with others received from the U.S. Economic Development Administration and U.S. Army Corps of Engineers, were required for the project to proceed.

In 2020, after completion of that environmental review, a fertilizer spill occurred at the Gavilon Grain site near 12th Street and Kerper Boulevard. The IDNR was notified of the spill and monitored Gavilon's clean-up efforts. The spill created an underground chemical plume (body of contaminated groundwater) containing nitrate and ammonia, according to an IDNR consent decree with Gavilon related to the spill. The City of Dubuque was aware that the IDNR was monitoring the Gavilon clean-up, and the City had no indications from the IDNR that this incident could impact the City's project.

In October 2021, as the City prepared to proceed with the project, the IDNR issued a Reaffirmation of the 2019 Finding of No Significant Impact, reaffirming the environmental review was successfully completed and allowing the City to proceed with the project. The IDNR also issued a Local Flood Plain Permit in July 2020, another requirement for the work to begin, stating the IDNR reviewed the project and had no objection to the granting of the permit.

Recently, the project contractor applied for a permit for dewatering work on the project. As part of that application process, the IDNR determined the City must conduct further environmental studies before the IDNR issues a permit allowing the discharge of water to the Mississippi River from 10 dewatering wells at the project site necessary for the construction. The IDNR's concern involves the possibility that the dewatering wells on the project site could draw contaminants from the Gavilon spill site. The IDNR is requiring an environmental study to determine concentration levels of the chemicals and identify treatment options, if necessary, before the water can be discharged to the river.

Work on the construction of the pump station and flood gate replacement will be paused until the necessary permits are secured. The City has hired HDR Engineering and Terracon Consultants to expedite and assist with the environmental study at an estimated cost of $240,000. This funding will come from the project's contingency budget. The estimated timeline to complete the first phase of the environmental study was three months. Now that phase one is nearing completion, the City will enter the second and third phases of the study, which are estimated to take approximately seven months, followed by an implementation phase of the study results, which could take up to an additional seven months.

The $28.2 million project is the next major phase of the Bee Branch Watershed Flood Mitigation Project. It involves the construction of a new stormwater pumping station on Kerper Blvd. and the decommissioning of the existing pump station system installed as part of the John C. Culver Floodwall/Levee system. The new facility will include a new flood gate, four new 100,000 gallon per minute pumps (double the pumping capacity of the existing facility), new electrical service, and the installation of back-up generators. The improvements will greatly enhance the system that conveys stormwater from the Bee Branch Watershed to the Mississippi River and protects over 1,300 properties from flooding during high river levels. The project also adds additional resiliency options as rainstorms increase in both rainfall and intensity. It builds upon the flood protection established through earlier phases of the Bee Branch Project, which currently safeguards against storms as severe as a 500-year event.