Ravinia Festival South Parking Lot

Challenge

Designers had to manage stormwater to keep the south parking area accessible, keep adjacent neighbors’ basements dry, and control the outflow of water to the municipal storm sewer. Heavy clay soils eliminated infiltration as a treatment option. Preserving the many large oak trees around the parking area was necessary to maintain site character and meet Highland Park’s tree preservation ordinance. Due to the seasonal use of Ravinia’s grounds, all construction had to be completed during winter months, when weather could cause significant delay.

Solution

The design uses permeable pavers and underground vaults to quickly remove large volumes of water from the surface and release it at a controlled rate into city storm sewers, eliminating flooding in the parking area and adjacent residences without major changes to surface grade and visual character. The pavement edge was designed to avoid removing existing oaks and impacting critical root zones. Construction was able to proceed during good weather days in the winter; however, ensuring all permits were in place earlier would have expedited the process.

• Permeable pavers allow stormwater to drain quickly from the surface of the lot into an underground detention area, solving the frequent flooding problem and allowing year-round access to the parking area.
• Replacing the compacted gravel lot with 27,473 sf of permeable concrete pavers increased permeable area on the site from 38% to 81%.
• The underground detention system vaults store more than 249,000 gallons of stormwater and release it slowly into the municipal storm sewer system.
• By eliminating the pooling of water on the surface, maintenance work required to clean up the parking area after storms was reduced.
• The pavement edge was designed to avoid existing trees and their critical root zones.
• The project and process improved relationships with residential neighbors of the Ravinia Festival.

• Installing 27,000 sf of permeable concrete unit pavers instead of traditional poured concrete saved over $35,000 in construction costs.
• Using detention vaults installed under the parking lot avoided the need to purchase three adjacent lots at a cost of $1.8 million to accommodate above-ground stormwater detention.

• Completing a successful sustainably-designed project can increase acceptance of the non-standard methods used. The success of this project encouraged the client to choose similar sustainable methods on subsequent projects.
• The City and the owner/client must be on the same page about scheduling, design, and permitting. Due to the heavy use of the Festival grounds in the summer and fall, improvements needed to be completed in a timely fashion during the off-season. Ensuring that all the necessary permits were in place allowed for efficient work that took advantage of as many good weather days as possible.
• A StormTrap system should be orderd as early as possible in the process. The contractor was delayed because of the long lead time required to manufacture the units. For a similar project in the north parking lot at Ravinia, manufacturing time was built into the design and permit time frame so the units could be delivered on schedule.
• The extent of the site excavation must be considered when designing a StormTrap system. Due to the depth of excavation required to install the underground detention vaults, certain benching specifications were needed to open the site up. This required excavating 15 ft beyond the limits shown on the plans, putting the proposed excavating area in tree root zones. The design and placement of the vault system had to be altered to avoid certain root zones because of strict OSHA conformance.
• Getting a full existing utility survey rather than just a topographical survey can prevent problems down the line. The topographical survey did not record utility information with 100% accuracy, leading to several unforeseen conflicts.
• It is importatnt to coordinate with the general contractor to agree upon sequencing, construction methodology, and fully buildable contract documents. Anticipating the methods and sequencing of a contractor may not be accurate due to site constraints.

Project Team

Owner/Client: Ravinia Festival
Owner’s Representative: AT Group, Inc.
Landscape Architect: JJR, LLC
Civil Engineer and Stormwater Management: JJR, LLC
Forester: City of Highland Park
General Contractor: W.B. Olson, Inc.
Paving Contractor: LPS Underground
Utility Contractor: PirTano Construction

Role of the Landscape Architect

Served as the prime design coordinator for all the design disciplines involved in the project. Assisted the owner/client through the project process as a trusted advisor and confidant. Supplied master planning services as the owner/client looked forward to future needs of the Festival. Met the daily coordination needs required of the prime consultant between the owner, design team, and general contractor.