Description

1) Wilmette Neighborhood Storage Project - The Largest Capital Project in the Village's History
Darren Olson, PE, CFM, D.WRE, Christopher B. Burke Engineering, Ltd., dolson@cbbel.com
Co-presenters: Brigitte Berger-Raish, P.E, bergerb@wilmette.com; Matt Moffitt, PE, CFM, mmoffitt@baxterwoodman.com

Abstract: The Village of Wilmette is a northern suburb of Chicago and is located adjacent to Lake Michigan. There is a major watershed divide within the Village; one watershed drains east to Lake Michigan and the other west to the North Branch of the Chicago River. Runoff in the western watershed is collected by regional trunk line storm sewers that outfall to a large stormwater pumping station at the River. The historic storm sewer conveyance system is undersized compared to modern standards and the western portion of the Village regularly experiences widespread urban (non-riverine) flooding. The Village developed a Stormwater Management Plan from 2013-2015 to assess the significant flooding experienced in the western portion of the Village, analyzing several improvement options. Primary alternatives included several miles of large diameter storm sewer to increase conveyance capacity to the River, and three localized neighborhood underground stormwater storage basins, among others. After years of study, public participation, an independent value-engineering review and deliberation, the Village Board decided to move forward with the neighborhood storage option. The overall program was divided into 4 construction projects totaling nearly $64M. The project included a combined 40+ acre-ft of underground stormwater storage at three prominent parks with sports fields (one of them shared with two adjacent schools) within the Village and nearly five miles of large diameter storm sewers in dense residential neighborhoods with mature trees. In addition to the complex engineering, the project required significant coordination with residents, the park district, and the school district. The presentation will discuss the project, beginning in 2013, through completion of the final phase of construction in November 2022; including the public engagement, Park District Intergovernmental Agreement, scheduling, safety-sensitive construction and other unique features of what was the largest capital project in the Village’s history.

2) Digging Deep for Long-term Flood Relief: Phase 2 Tunnel Feasibility Study
Jason Becker, PE, CFM, Halff Associates, jbecker@halff.com
Co-presenters: Sam Hinojosa, PE, CFM, shinojosa@halff.com

Abstract: Harris County has experienced several major storm events within the last decade that have resulted in catastrophic flooding. The Harris County Flood Control District explored the use of deep, large diameter tunnels for stormwater conveyance to address existing flooding issues and reduce future flood risk. Based on the recommendations of the Phase 1 Study, the Flood Control District authorized a Phase 2 Study to perform a more detailed evaluation of the potential benefits, costs, and implementation challenges of tunnels as a major flood risk reduction solution. A key component of the Phase 2 Study was the watershed assessment and hydrologic & hydraulic (H&H) analysis completed to support the development of tunnel concepts and estimate benefits to compare tunnel alternatives. This presentation will discuss the methodologies and results of the Phase 2 Study evaluation and highlight the preliminary watershed screening, creation of proposed tunnel modeling, calculation of flooded structures and instances of flooding benefits, and evaluation of traditional solutions. Finally, a path forward will be presented that focuses on refinement of tunnel alternatives, additional data collection and engineering analysis, and updated H&H modeling to more accurately estimate impacts and benefits. The Phase 2 Study represents an important step in the continued investigation of stormwater tunnels as an innovative and effective long-term, regional flood risk reduction solution.

3) No Stranger to the Rain: Economically Sizing Storm Structures in a Changing Midwest
Chris Shultz, PE , JEO Consulting Group, cshultz@jeo.com
Co-presenters: Patrick Hartman, JEO Consulting Group, phartman@jeo.com, Allison Atkinson, aatkinson@jeo.com

Abstract: The combination of changing weather patterns, limited financial resources for storm sewer implementation, and spatial constraints in cluttered urban areas creates an impetus for evaluating our stormwater design methodology. Properly sizing stormwater infrastructure begins with predicting appropriate and accurate flow rates, a challenge bounded by both stagnant municipal regulations, advancements in stormwater modeling, and growing public concerns about climate change. The City of Lawrence, Kansas, has taken a progressive approach to storm selection and rainfall distribution for their upcoming infrastructure projects. The City has partnered with JEO Consulting Group to model deficiencies and design improvements for a major stormwater trunkline in the Jayhawk Watershed in historic Old West Lawrence. Simultaneously, the City is evaluating appropriate NOAA Atlas 14 rainfall distributions to use as a future stormwater standards. This presentation examines the effects that different rainfall distributions have on CIP recommendations and the resulting economic impact to a municipal stormwater program. It examines the variations in deficiency identification based on different MSE distributions vs. SCS distributions, and how those differences correlate to real world observations from area residents. Observations imply that while choosing rainfall distribution standards based on economics may be appropriate for minor stormwater infrastructure, more conservative approaches should be considered for high-expenditure trunk lines