7th Avenue Creek Flood Reduction and Stream Restoration

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  • St. Charles, Illinois

The 7th Avenue Creek Flood Reduction and Stream Restoration Project is located within the City of St. Charles, Illinois. The 7th Avenue Creek Watershed is a tributary to the Lower Fox River Watershed. The Fox River in this area is on the Section 303(d) impaired waterway list. The Creek traverses from east to west through the heart of the City and provides an amenity to the residents that live along the creek. However, the condition of the watershed and the creek has deteriorated significantly as a result of urbanization and lack of best management practices which has caused impacts on water quality. As noted in the approved Watershed Plan, approximately 77% of the stream is highly channelized; 87% of the stream is noted as being moderately to severely eroded; and approximately 77% of the riparian areas were in poor condition.

The 7th Avenue Creek also experiences flooding along its banks due to constricted floodplain and sedimentation that has reduced the overall capacity of the channel. In some cases, the steep and eroding banks of the creek are protected by the failing structural measures, creating hazards for human health and safety and impacting water quality and floodplain connectivity.

The 2008 flood event far exceeded the mapped flood boundaries of the regulatory Flood Insurance Rate Maps (FIRM). As a result, FEMA, in partnership with the City, did a restudy of the 7th Avenue Creek watershed hydrology and hydraulics and determined that the flows along 7th Avenue Creek were approximately 250% greater than the Flood Insurance Study (FIS). FEMA started a remapping process and provided City with preliminary revised floodplain maps. The maps showed that the Base Flood Elevations (BFE’s) were approximately 3 feet higher than the regulatory FIRM. The mapped flood risks were far greater than what was shown on the regulatory FIRM. Approximately 118 properties (residential and commercial) were impacted by the preliminary revised floodplain maps. While many of the properties saw increases in floodway and floodplain limits on their property, approximately 49 properties were newly mapped in the floodplain. The FEMA maps have now become effective.

During the remapping study, the City started the concurrent planning process for mitigating the impacts of the preliminary revised FEMA floodplain maps. The City was aware that many residents and businesses would be impacted by high food insurance premiums once the new maps become effective. Three distinct alternatives were prepared.

  1. Alternative 1 was “Do Nothing”
  2. Alternative 2 included channel and culvert conveyance improvement, to the extent practical, within the available creek footprint
  3. Alternative 3 included a more holistic and strategic approach to opening the creek by buying out targeted properties for improving conveyance and floodplain storage; installing meanders, pools, and riffles grade control structures; and native vegetation to improve water quality, floodplain function and habitat, aesthetics, and quality of life. This approach was also supportive of a sustainable strategy to address climate change (increased flows) and resiliency (reduced depth and duration of flooding and improved safety) for long-term community benefit.

The City Council adopted the Master Plan with Alternative 3 as the preferred implementation strategy. The project was phased and Phase 1 (this project) of the master plan was implemented and completed in October 2021. While Alternative 3 required significant capital investments, it also allowed the City to leverage funding sources that support this approach. For example, the City was able to secure grants from EPA Section 319 (h) and Illinois EPA Green Infrastructure Grant Opportunity (GIGO) for the Phase I portion of the project. The total project construction costs (per awarded contract) for the 7th Avenue Phase I Project was $3,588,540. Through creative funding strategies, the City will receive $2,090,667 in approved grant funding with its local share of only $201,767 (or 9.6% of the approved grant). The total grant dollars received for this project reduced the City’s portion of the costs for the project to $1,699,640 or 47.4% of the total project construction costs of $3,588,540).  The City plans to secure additional grant monies for future phases.

The 7th Avenue Creek Phase I project was completed in a single-family residential neighborhood, with the creek aligned on private property in many instances. Approximately 40 properties abutted the project limits for this phase of the project prior to the start of the master plan. The City began preparing for the project by purchasing a total of 12 parcels of land adjacent to the project limits. Land acquisition began in 2016 as the project’s conceptual planning came together. In 2021, City staff obtained 10 temporary/permanent easements, as well as 2 partial parcel acquisitions. The remaining 28 properties will benefit from reduced flood elevations and buildings removed from the floodplain. The Phase I provided the greatest return on investment in regard to impacting the greatest number of properties.

The project includes conveyance, water quality, and stream restoration improvements along the creek. These include the following:

  1. Approximately 1,870 linear feet of a meandering two-stage ditch by grading an artificial floodplain bench just above the bank full height and restoration with native vegetation
  2. Removal of one (1) culvert and opening of the creek and closing roadway access through this area
  3. Removal and replacement of three (3) culverts
  4. Installation of nine (9) stream meanders
  5. Installation of twelve (12) grade stabilization structures
  6. Approximately 4.9 acres of urban filter strip along the full stream corridor and replanting with native vegetation

Since the 7th Avenue Creek project is located primarily within the residential and commercial area, public engagement was a critical component to help build consensus and vision for the project. At the onset of the master plan, a survey questionnaire was sent to each property within the project area. Subsequently, a number of public information meetings were held during the planning phase. Simultaneously, a dedicated project website was created where residents and stakeholders can access the planning document and comment. Before and after renderings of the proposed improvements helped the public comprehend the vision and impacts of the proposed improvements.

The project was fully completed ahead of the EPA grant schedule of November 2021 and within budget. The project was completed with no reports of accidents or injury, as well as no lost time during construction. Approximately 28 properties will benefit from a reduced floodplain. The proposed BMPs will help remove approximately 314 tons/year of sediments, 17,758 lbs./year of TSS, 287 lbs./year of Phosphorous, and 715 lbs./year of nitrogen. The proposed improvements and project outcome reflect City Staff and City Council’s leadership and vision to address many challenges, build consensus and adopt an alternative that supports sustainability, resiliency, and long-term community benefits.

Awards

APWA Public Works 2022 Project of the Year Fox Valley Branch and Chicago Metro Chapter

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