WINNETKA – Consultants Strand Associates presented a four-phase, $57.7 million plan at a community meeting that attempts to address stormwater issues that plague western and southwestern portions of Winnetka.
Strand’s proposal includes conveying stormwater to various storage sites throughout the village on both school and Park District property, as well as on Cook County Forest Preserve property.
After abandoning a plan for a stormwater tunnel in the fall of 2015 — primarily due to run-away costs — the village hired Strand to study the area and propose alternative solutions. Winnetka Engineer Steve Saunders described Strand’s proposal as a “holistic, no stone unturned” approach.
At the workshop on April 12 residents had an opportunity to hear Strand’s proposal and provide the consultants with feedback. “We really want to hear from you tonight,” said Michael Waldron, municipal engineering coordinator for Strand.
Waldron began the presentation by providing the historical backdrop. Prior to the development of the Skokie Lagoons in the 1930s, western Winnetka was a low wetland area that was part of the flood plain of the Skokie River.
At the same time the lagoons were developed, a levee system was constructed near the lagoons, which protects western Winnetka from flooding. “The flooding you experience is not from the Skokie River,” Waldron said. Rather, Waldron said that water trapped behind the levee functions like a bathtub without an outlet, which relies on pump stations to pump the water into the Skokie River. However, when severe storms hit the area the pump stations are unable to pump the stormwater quickly enough and flooding occurs.
Strand’s proposal targets a 100-year storm event, which he defined as 4.85 inches of rain occurring over a three-hour time period. Most recently, the area experienced this event in both 2008 and 2011, which caused roughly 1,000 Winnetka homes to flood, according to a village survey. Waldron explained that a 100-year storm event is one that has a 1% chance of occurring any given year.
After studying the area, Strand has concluded that 150 acre-feet of water — the equivalent of filling Soldier Field to a depth of 35 feet — needs to be removed and stored to adequately address a 100-year storm event.
A portion of Phase I of Strand’s plan would require an intergovernmental agreement between Winnetka and Cook County Forest Preserve, permitting the village to store stormwater on Forest Preserve land at Hibbard Road, between Willow Road and Winnetka Avenue. This site would hold 120 acre-feet of water — about 3/4 of the volume of water that needs to be stored — and is essentially the lynchpin of the entire plan.
“This is a critical point for us in this project,” Waldron explained.
While the Cook County Forest Preserve’s default stance is typically not to allow stormwater storage on its property, Saunders said it has been open to this proposal. However, the Forest Preserve will only consider the proposal if the village exhausts other options and the water is clean before it arrives at the Forest Preserve for storage.
Waldron said the village’s stormwater is not high quality — it contains pollutants such as oil, salt and fertilizers — but proposes to filter out some of the contaminants by implementing green infrastructure throughout the village. Describing it as a “treatment train,” the plan includes such solutions as rain barrels and rain gardens.
Phase I of the plan would also include storing water underground at Duke-Childs play field. The plan includes making the landfill a playing field — using soil from dredging the Duke-Childs field — where soccer and lacrosse can be played.
The second phase of the plan, and most controversial, includes storing water at Crow Island Woods, which is owned by the Winnetka Park District. The stormwater would be conveyed through pipes along Sunset Road and Mount Pleasant Street and then deposited into a five-foot pool of standing water.
“It is not intended to be a clear cut. It is intended to work with this property to provide storage,” Waldron said.
But many residents at the meeting questioned whether standing water would cause an increase in mosquitos and whether it was safe to have a five-foot deep pond of contaminated water so close to Crow Island Elementary School. Others worried that the development would destroy pathways and old growth trees.
“It is not our intention to ruin the pathway system so that people can continue to use it,” Waldron said.
He also noted that the permanent pool would be designed to function as a balanced wetland, which data shows should reduce the number of mosquitos. Waldron also said that the green infrastructure would help to treat the water and capture contaminants before flowing into the Crow Island storage area.
“The goal here is to use natural processes to break down the pollutants as much as possible,” Waldron said. He further noted that the proposal was in line with Environmental Protection Agency recommendations.
The Crow Island storage area would hold about 10% to 12% of the total volume of stormwater the plan aims to address.
Finally, Phase 3 of the plan would store stormwater underground at Skokie Washburn play fields, and convey stormwater on Oak Street and Elm Street. The final phase, which Waldron said could be held off for a while into the future, proposes improvements along Willow Road, Provident Avenue and an area north of Pine Street, as well as creating some storage at the Park District’s golf course and the forest preserve between the golf course and Forest Way.
The Forest Preserve portion of the plan is by far the most important, given its holding capacity, but it is also the lengthiest to implement — Saunders projected that it would take about four years. The other plans are estimated at about 2 to 2 1/2 years to implement.