A Confluence of Expertise
Sometimes, a project has unique parameters that engage and entwine the expertise of a unique combination of disciplines. About 10 years ago, Berkeley had begun experiencing an increase in urban flooding, including areas that had never flooded previously. Civiltech provided hydrologic and hydraulic model analysis to develop an improvement recommendation that involved adding new sections of relief storm sewer and a detention basin for additional stormwater storage. The detention basin included a new pump station.
This project Incorporated the Following:
- Community engagement
- Hydrologic and hydraulic modeling
- Stormwater analysis and control
- Stormwater storage
- Cross discipline coordination
- Procurement of funding
Hydrologic and Hydraulic Modeling
In the field of water resources engineering, hydrologic and hydraulic modeling is a tool commonly used for engineering analysis and to evaluate the benefits of proposed improvements. Hydrology represents the quantity of water (runoff) generated from a specific area or watershed. Hydraulics deals with the physical properties of water, such as calculating the depth of flow in a pipe or open channel. A combined hydrologic/hydraulic model allows us to evaluate the impacts of various improvement scenarios and the benefits that would be achieved. Civiltech was initially retained by Berkeley to provide an existing and proposed condition hydrologic/hydraulic model analysis to determine the cause of the flooding and to develop and evaluate potential engineering design solutions.
Scope of Services
- SWMM Hydrologic and Hydraulic Analysis
- Analysis of Design Alternatives
- Technical Report
- Cost Estimates
- Pump Station Hydraulic Report
- Preparation of Contract Plans, Specifications, and Estimate
- Agency Permitting (IDOT, Cook County, and MWRD)
- Multi-agency (IDOT EDP Grant, MWRD Local Projects Grant, CDBG through Cook County)
Hydrologic and Hydraulic Analysis
The existing and proposed hydrologic/hydraulic analysis was developed using the Environmental Protection Agency – Stormwater Management Model (EPA-SWMM) analysis software. EPA-SWMM is a public domain software that combines hydrology and hydraulics, allowing a detailed and complex analysis. The model simulates dynamic rainfall runoff routing, transporting the runoff through storm sewers, channels, and pumps.
For the hydrologic analysis, the Village was divided into four major watersheds. The northern sub-watershed, which experienced the majority of the flooding, was modeled in the most detail. The hydrographs developed for each sub-watershed were then used in the storm sewer hydraulic analysis.
The existing hydraulic analysis looked at the storm sewer pipe sizes, rims, and invert elevations taken from the Village’s storm sewer utility atlas. The results of the existing condition, 100-year analysis showed flooding in the areas where the computed hydraulic grade line is above the manhole rim elevations. The flooding generally occurred in the lowest geographic areas since the storm sewer had limited capacity and was overwhelmed during the modeled 100-year storm. The results of the model verified the flooding conditions that had been historically observed by the Village.
The EPA-SWMM model allowed an analysis of alternative design solutions. An alternative was developed that included adding two relief sewers and expanding an existing Village stormwater detention basin. The proposed relief storm sewers would divert stormwater at two critical locations where a majority of the existing flooding occurs. The proposed condition hydraulic model demonstrated significant improvements to the existing condition. The lowering of the existing basin required a stormwater pump station to be installed, that was also incorporated in the model. The proposed detention basin improvements provided an additional 34.6 acre-feet of storage having significant impact at existing locations during flooding events and providing benefits to downstream communities.
The engineering and hydrologic/hydraulic model analysis of the proposed Village of Berkeley Flood Control Project is an example of the significant benefits that can be achieved as a result of the proposed improvements, including:
- The proposed relief sewer is able to divert a significant amount of stormwater to the detention basin such that the 100-year hydraulic grade line is reduced by several feet in areas of chronic flooding.
- The proposed flood control project will directly benefit approximately 800 homes.
- The proposed improvement will provide an additional 34.6 acre-feet of detention storage during the 100-year 24 hour design storm event.
By developing the SWMM model, Civiltech was able to identify problem areas through simulation and to evaluate the benefits of specific solutions.
The cost of these critical improvements came with a big price tag. As a result, the team began to work on the Phase II plans and specifications as well as assist in procuring funding for the project. The funding efforts were a success as the project received funding from Metropolitan Water Reclamation District (MWRD), through a Cook County Community Development Block Grant and from IDOT under the Economic Development Program (EDP). But with this robust funding came new challenges for Phase III. Each funding source had unique conditions including stipulations regarding the subcontracting companies used and special documentation requirements.
In addition to the atypical requirements placed on the contractor from the funding sources, the design of the storm water pump station created additional challenges. The pump station involved four additional and unique subcontractors with specialized work to be coordinated, as well as a complex set of specifications.