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Stormwater Alternatives Study

Village Council Approves Memorandum of Understanding for Wetlands Stormwater Project (8/1/17 update)

After the Willow Road Tunnel Project was set aside due to cost concerns, the Village engaged Strand Associates to re-examine alternatives to alleviate flood risk in western Winnetka. After an extensive evaluation, Strand recommended a multi-phase approach that would provide significant flood risk reduction to over 400 homes against a 100-year flood event, as well as improve stormwater quality. The lynchpin of the vision is a stormwater management wetlands project on land owned by the Forest Preserves of Cook County (FPCC), at the northwest corner of Hibbard Road and Winnetka Avenue.

When the Village Council discussed Strand’s proposed vision in June, 2016, the Council agreed the most important task was to secure FPCC permission to use their land. For over a year, Village and FPCC staff negotiated to reach agreement on a draft Memorandum of Understanding (MOU) to delineate key project parameters in sufficient detail to gain project approval. FPCC staff presented this draft to the FPCC Board of Commissioners at their July 20, 2017 meeting, and it was unanimously approved. This agreement provides the Village with a high degree of certainty that the license agreement necessary for the project will ultimately be approved by the FPCC Board of Commissioners.

At the August 1, 2017 Regular Council meeting, the Village Council voted unanimously to approve the MOU with the FPCC and move ahead with engineering tasks and intergovernmental negotiations with other local agency stakeholders. Several FPCC issues are addressed in the MOU: (i) the wetlands detention project can only be a part of an overall flood reduction program, not the only solution; (ii) stormwater quality must be improved before it is released to FPCC property; (iii) tree removal should be minimized, and the Village must comply with FPCC tree mitigation and license fees; (iv) Winnetka will assume long-term maintenance of the project; and (v) Winnetka will provide off-site benefits to further the goals of the FPCC.

The original proposal for the wetlands project was revised over the course of the FPCC negotiations, resulting in an iteration that costs less than the original plan, removes fewer trees, and is more in keeping with FPCC goals.  The MOU provides agreement on the following key points:  (i) the wetland project aligns with FPCC goals and benefits both Winnetka and the FPCC; (ii) the size and scope of the project is fixed, along with the preliminary design; (iii) a water quality program is specified to clean the stormwater currently being sent through the FPCC land to the Skokie River; (iv) all fees associated for the project are fixed; and (v) a long-term maintenance plan is established, to be administered by Winnetka.

With approval of the MOU, the Village will continue discussions about other potential stormwater storage projects with Winnetka agencies, including New Trier High School District 203, Winnetka District 36, and Winnetka Park District – who already demonstrated their commitment with letters of support for the MOU.  Most importantly, the Village can start substantive work on engineering tasks without fear that these dollars are wasted on a project that will never be approved.

To see the agenda report, click here.
To see Mr. Saunders’ presentation, click here.

Below are links to the MOU and its exhibits:

  1. Memorandum of Understanding

Strand Study Approach

In October 2015, the Council hired Strand Associates to complete a stormwater management evaluation to uncover and evaluate a series of creative, holistic, technically and scientifically sound, sustainable, feasible, and cost-effective improvements to provide flood risk reduction for areas of southern and western Winnetka for appropriate levels of protection up to a 100-year event, including Area L (South of Willow Road), Areas J & G (North of Willow Road – the “Tree Streets”), and Area H (Provident Study Area). Strand has a proven track record of finding creative stormwater solutions for its clients that the Village believes is critical to identifying potential flood risk reduction solutions.  

Importantly, Strand Associates was selected in part based on the firm's commitment to engaging the community.   Strand partnered with the Village and implemented a proactive public outreach strategy to ensure that its work incorporates ideas, input, and suggestions from members of the community, environmental stakeholders, other agencies, and government decision makers. 

Strand Associates undertook a watershed based approach to evaluation of stormwater management and flood control in the western and southwestern areas of Winnetka.  The watershed based approach considers the relationship of stormwater among natural systems, the environment, infrastructure (sewers, transportation, parks and open space), the economy, and the community in order to integrate stormwater and flood control solutions into the broader vision for the community as a whole. The result often delivers tremendous added value to the community by providing tangible and visible amenities beyond just stormwater management and flooding control.

Over the course of the study, the following specific activities were performed:

  • Data gathering and review
    • Comprehensive evaluation of available data characterizing the conditions of the watershed such as topography, density of homes and development, impervious ground cover and soil conditions, roadway network, utilities, frequency of flooding and historical extents of flooding, property ownership, neighborhood and community character, and various plans for improvements or changes in the watershed.
  • Evaluate hydrologic and hydraulic modeling for verification of existing conditions and historical flooding
    • Verify the computer models used in the study accurately reflect the conditions Winnetka experiences during various rainfall events to determine whether potential stormwater management alternatives are realistic, appropriate, and feasible to provide the level of protection expected by the community. 
  • Alternatives development
    • Identify the many potential stormwater management and flood control opportunities within the watershed and carefully considering the feasibility, practicality, cost, benefit, and measure of protection of each opportunity; a wide spectrum of stormwater management solutions will be considered, which includes many traditional stormwater management controls as well as a selection of more innovative and creative solutions that may not have been previously considered.
  • Stakeholder engagement
    • Create a commuinity effort around the planning and implementation, as there are critical community entities in the watershed that will be integral to successful and sustainable stormwater and flood mitigation improvements; explore partnerships and collaborative opportunities with stakeholders whose goals and objectives are directly impacted by stormwater issues and will also benefit from the Village’s stormwater management efforts.
  • Public participation
    • Conduct an extensive public participation effort will be directed towards gaining valuable input from the community; inform and involve the public throughout the planning and design processes to understand the needs, desires, and opportunities addressed by the identified alternatives.

Strand's Initial Watershed Findings

In our study of the west and southwest watershed area of Winnetka, it was critical for our team to investigate and understand the course of events that have lead up to the current stormwater and flood control issues the Village is experiencing.  Our investigations revealed the following important points:

  • The watershed was historically a lowland marsh environment.
  • The area was historically the flood plain for the Skokie River.
  • pw-skokie-river-floodplain-img-20190501In 1938, a levee system was constructed along the east edge of the Skokie River resulting in the following drainage features:
    • The levee system protects Winnetka from flooding due to the Skokie River.
    • The levee system blocks natural stormwater runoff to the Skokie River.
    • The levee system creates a “bathtub” effect in west and southwest Winnetka.
    • The Village is dependent on pumping to drain the watershed.
  • None of the west and southwest watershed runs off to the Skokie Lagoons.
  • Other features within the watershed like Hibbard Road and Willow Road create bathtubs within bathtubs requiring a series of pumping stations into pumping stations.
  • The vast majority of the watershed is ultimately pumped into the Skokie River at a pump station on Winnetka Avenue.
  • A newer and more powerful computer modeling system has been created to better understand the complicated drainage system serving the west and southwest watershed.
  • This modeling system provides a real-time perspective of what happens in the watershed during various rainfall events.
  • The real-time effects of the July 2011 storm event can be seen here.
  • This model will be used to evaluation various stormwater management and flood control strategies.
  • A wide range of strategies will be considered:
  • pw-stmw-mgmt-strategies-img-20190501Each strategy provides a different level of protection.
    • Most green infrastructure is effective on a homeowner-level and provides protection for less intense, more frequent rainfall events.
    • More expansive green infrastructure, local stormwater storage, and conventional conveyance are effective on a neighborhood-level and provide protection for more intense rainfall events.
    • Large scale watershed-level stormwater conveyance, storage, and pumping infrastructure is required to handle significant rainfall events and historic levels of flooding.
    • Each alternative also has a different level of investment to implement.
  • Moving forward our goal will be to find the right balance of stormwater and flood protection, investment, and benefit.

Public Meeting Highlights

The first Public Open Houses (Awareness Phase) were held on January 21 and 23, 2016. The second Open Houses (Exploration Phase) were held on March 3 and 5, 2016. The fifth public meeting for the study was held on April 12, 2016. 

Summaries, study findings to-date, and presentation materials are available on the Public Meeting Highlights page.

On June 7, 2016, Strand Associates presented their Final Concept Report on the Stormwater Alternatives Study to the Village Council.

Stay engaged with Strand's study:

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