Darren Olsen of Christopher Burke Engineering told the Community High School District 218 Board of Education on July 15, 2025, that the Polaris Park stormwater storage basin project will begin this fall and use a grassed-slope basin to store and release large stormwater flows to reduce neighborhood flooding.

The presentation explained why engineers moved away from a retaining-wall design: subsurface geotechnical work found poor organic soils under the park, which raised construction risk and cost. "We got away from the retaining walls and we now are going with more grassed slopes," Olsen said, adding the slope will be a 4-to-1 grade designed to be traversable by pedestrians and maintenance equipment.

The project will excavate to about 7 feet at the deepest point and return three ball fields and a football field to the site. Engineers plan more than a mile of perforated underdrains, placed roughly 12 to 15 inches below the playing surface, and a system of surface inlets around the field perimeter to move water into the underdrain network. Water entering the park will come from a new large-diameter inflow sewer tied to the village storm sewer; an outlet sewer will return treated flows to the village system after storms.

Why it matters: the basin is designed to capture severe storm events that otherwise would flood streets and basements in adjacent neighborhoods. The presenters said smaller storms mainly drain overland and will not trigger the park inflow; the system is sized to accept very large storms. According to the presentation, inflow from the storm sewer will begin to fill the park in events of about 1 inch of rain per hour but the basin is designed to reach its maximum (about 7 feet) only in extreme storms such as roughly 4.5 inches in an hour or about 7.5 inches over 12 hours; after such events the basin is expected to drain in roughly 30 hours.

Design and community-access features include two staircases and an ADA-compliant ramp on each side of the park, a concrete vehicle access ramp at the northeast corner sized for maintenance trucks and emergency vehicles, and perimeter fences during construction. Engineers recommended restoring the playing surfaces with seed and erosion blanket rather than sod; they said seed saved roughly $600,000 on a similar project and establishes within a year when contractors meet contract requirements.

Contract and schedule details: Lee Fell of Christopher Burke Engineering outlined the procurement and construction timeline. The village will advertise the job for bids next month, evaluate bids in August/September, and present a recommended low bidder to the village board for award in September. A pre-construction open house for residents is planned for October; construction of the park excavation is slated to begin November 2025. Roadway and utility work is expected to follow in March 2026, with the storm sewer and roadway work targeted for completion by October 2026. The park construction is scheduled to finish in 2026 and the district and village expect the park to be ready for community use in spring 2027. Fell said the contractor will be responsible for establishment and maintenance of the turf until final acceptance, a period the presenters described as roughly one growing season after construction is complete.

Board discussion and resident impacts: board members asked for a copy of the intergovernmental agreement (IGA) between the village and CHSD 218 that governs field repairs and long-term maintenance; a board member requested the district re-share that IGA with members who joined the board after it was first approved. Presenters said the village and the district will perform a joint punch-list walkthrough with the resident engineer before accepting the work.

Construction mitigation: presenters said the contractor will phase street openings so only a limited number of blocks are open at any time and that roads will be reopened at the end of each workday. Residents who require driveway access will receive advance notice when concrete pours or curb work require temporary closures. The village will publish project updates and email notices via a project page and a sign-up on the village website.

Background and precedent: the consultants showed photographs from similar regional projects (Libertyville, Tinley Park) to illustrate the finished appearance and slope traversability. Presenters said seed-and-blanket restoration on a comparable project established in under a year while saving the district and village a substantial amount versus installing sod.

Next steps: the village and district will provide the board a copy of the IGA and residents can sign up for project updates on the Village of Oak Lawn project page. The presenters encouraged board members and residents to attend an October pre-construction open house with the contractor and resident engineer.