Keeping Up With the Falls
Revisiting the village of Menomonee Falls stormwater management plan nine years later
Tuesday, November 01, 2011
By Kurt A. Peot
In 2002, Stormwater magazine featured an article about a stormwater management plan for the village of Menomonee Falls, WI (“A Stormwater Management System Plan for Menomonee Falls” by Michael F. Campbell, November/December 2002 issue). The simultaneous completion of both a stormwater management plan and a sanitary sewerage system plan was to identify storm and sanitary sewer capacity problems in existing developed areas and to serve as a roadmap for future projects, so that environmental, economic, and construction concerns could be addressed in concert with each other. Nine years after the village started working with these plans, how are things going? Has this holistic approach paid off for the village? What identified projects have been completed, and what are the results? Are the plans still the driving force behind future projects?
First, a little refresher course about the village in is order. In 2002, Menomonee Falls was the third-fastest-growing community in southeastern Wisconsin and the largest village in the state of Wisconsin. About half of the village was urbanized, and continued urban growth was assumed to be the norm. The stormwater management plan and a sanitary sewerage system plan were prepared concurrently, with both plans focusing on complementary objectives. The plans were designed to provide adequate facilities for major storms up to the 100-year event by providing overland flow paths in swales and street rights of way without flooding homes or businesses in the 33-square-mile area. The studies highlighted multiple alternative plans for both existing and future development scenarios, with consideration of water-quality objectives and critical land uses. Advantages and disadvantages of all the alternatives were clearly outlined so that village officials could make informed decisions that meshed with necessary repairs and upgrades. A comprehensive list of capital improvements and annual operating and maintenance costs, and rankings by priority based on previous flooding, were the real heart and soul of the studies.
The plans recommended the installation of 10,115 linear feet of new culverts ranging in size from 12-inch-diameter circular pipes to 5-foot by 10-foot reinforced concrete box culverts, the installation of 90,863 linear feet of new 18- to 102-inch-diameter concrete storm sewer, the elevation of roadway grades at 38 locations, the construction of five wet stormwater quantity and quality control detention ponds, the construction of two wet stormwater quality control detention ponds, the retrofitting of seven existing dry ponds with permanent pools of water for quality control, and increased street sweeping. The projects placed in the high-priority classification were those that would assist in minimizing sanitary sewer backups and the related property damages and hazards to public health by adding capacity. Generally, these projects were located in areas for which sanitary sewer system improvements were recommended in the village sanitary sewerage system plan companion to the stormwater management system plan.
One of the first things that happened as a result of the studies was the establishment of a Sanitary Sewer Automated Emergency Operation System (AEOS). The AEOS is a system of sanitary sewer relays and 10 diversion pump stations that convey flows around system bottlenecks to the main village interceptor at two location where inline storage can be constructed if necessary. The sanitary sewer study found that the existing sanitary sewer system was adequate for full buildout of the sewershed. However, one of the criteria requested by the village was that the existing sewers should be adequate to convey sanitary flows that occur for at least a 10-year recurrence interval event. The village also asked that a system be developed to address the flows experienced in a June 1997 flood event that had an estimated recurrence interval of more than 500 years. The AEOS was recommended to meet that criterion. The AEOS is intended to operate only during extreme events. The village has had six of these events in the last 11 years, including three very recent heavy rainfalls. On May 21, 2009, 6.30 inches of rain fell in one weekend. On July 14–15, 2010, 4.4 inches fell, and on July 22, 2010, 6.06 inches, including an atypical 4.27 inches in one hour!
The concept behind the AOES is that when an extreme event happens and high groundwater becomes an issue, flows are conveyed past local system restrictions to a downstream location where more sewer system capacity exists. The village has already constructed several portions of the AOES that have resulted in reducing the occurrence of sanitary sewer overflows within the village from an annual event at multiple locations to only two occurrences over the last six years.
Priority Projects Tackled First
The completed studies allowed the village to identify projects that would have the greatest immediate impact on localized basements backups and bypassing. Jeff Nettesheim, P.E., village director of utilities, worked with consulting engineering firm Ruekert & Mielke Inc. of Waukesha, WI, to move forward with several large projects.
In 2003, the Shady Lane and Appleton Avenue diversion pumping station was constructed. The project was designed to alleviate recurrent bypass pumping in the heavily commercial Appleton Avenue and Shady Lane area of the village. As a part of the project, provisions in the design accounted for the potential for three separate pump stations to manifold into one force main. This required additional hydraulic analysis to ensure that the pumping stations had adequate capacity to pump against the head caused by each other and the ability to throttle down to the capacity of the system when pumping alone. The hydraulic analysis included provisions for multiple speed pumping to address the varying flows and head conditions in the system.
Approximately 1,600 feet of 12- to 15-inch-diameter sanitary sewer relay was installed in the project area. A diversion pumping station was built on village right-of-way property, 2,200 feet of 16-inch diameter force main was installed, and a diversion outlet and controls were located on village property. Another feature gave the village the ability to bypass flows in the event of a catastrophic weather event that flooded out the system. SCADA telemetry was installed to report status and log volumes of flows associated with the pumping station and diversion/bypassing of flow.
The Appleton Avenue, Arthur Avenue, and Menomonee River Parkway relay and relief sewers were constructed from 2000 to 2003, with more than 5,400 feet of new gravity sewer ranging in size from 12-inch to 30-inch diameter. Improvements were also made at Shady Lane and Menomonee Avenue as preparation for a new force main and lift stations. The location of these relay and relief sewers was designed to function with no labor or electricity costs. This enabled the village to eliminate chronic basement backups without bypass pumping. The approach not only was less costly for design and construction, but also eliminated future operation and maintenance costs.
Consistent Approach to Projects Continued
The projects completed in 2000 through 2004 addressed some major problem areas. Using the companion studies as a roadmap, the village continued to identify and plan for additional projects that kept the momentum going. Another priority project that was identified in the 2001 studies was one that would address flooding along Menomonee Avenue due to high water levels in an adjacent nature preserve area. A new sewer will be constructed that will connect all four undersized storm sewer systems together and redirect runoff away from the preserve to aid in abating the flooding reported along Menomonee Avenue.
In 2010, two wet-weather submersible lift stations were constructed in conjunction with the previously constructed force main. The lift stations and force main reduce the sewage level in the gravity sewer system, preventing surcharging and basement backups in the area adjacent to Menomonee Avenue. During and after wet weather, excess flows in the sewer system are routed over a longitudinal weir to the lift station wet wells. From there, the sewage is pumped approximately 9,000 feet to an area of the gravity sewer system that has much more capacity. The design includes a system to monitor the level of sewage in the receiving sewer. If the receiving sewer is at capacity, which can be expected during a major weather event, a valve automatically closes, directing the flow to the Menomonee River.
Previously, the village had to use a manual operation with a series of portable trash pumps to reduce surcharging in the trunk sewer along Menomonee Avenue. This system was labor intensive, directed all sewage pumped to the storm sewer system, and still resulted in basement backups. The new system includes two lift stations, a force main, a diversion manhole, and an outlet manhole. Only weeks after the completion of the project, 6.06 inches of rain fell in Menomonee Falls. The lift station and force main system performed as designed, and no basement backups took place in this area during or after this heavy rain event. This major rainfall did result in the village having to bypass 1.2 million gallons of sewage. But there was no bypassing in any of the areas where projects were completed. This clearly illustrated that the solutions identified in the sanitary sewer study, and the resultant completed projects, were spot on in their ability to eliminate basement backups and bypassing.
The village worked with the Milwaukee Metropolitan Sewerage District (MMSD) to devise a system that wouldn’t exacerbate problems downstream. If flow exceeds available system capacity at the downstream ends of these AEOS projects, controls divert sewage to the Menomonee River. If the frequency and amount of bypassing exceeds acceptable levels set by the Wisconsin Department of Natural Resources or MMSD, the village has land available at each discharge point to construct inline storage.
Both the stormwater management plan and a sanitary sewerage system plan anticipated these scenarios. The improvements made to date direct bypass flows from the AEOS projects to two key locations where the village already owns land. Because of this advanced planning, storage facilities can be constructed relatively inexpensively and easily in the future and the village doesn’t have to worry about land acquisitions or expensive modifications to existing infrastructure.
Unfinished Business
Ideally, all of the recommendations made in the stormwater management plan would be implemented. But in real life, the economics of completing the various recommended projects make that goal hard to achieve. The study suggested a 20-year implementation cycle. At the halfway point, a number of the larger projects have been completed.
On the stormwater side of things, 12% of the total recommendations have been implemented, of which 35% were highly recommended by the study. An additional 12% are included in the 5-year capital improvement plan and will be constructed or are already under construction.
On the storm sewer side of things, many of the recommended plan improvements have been accomplished as part of routine street maintenance projects. In particular, culvert improvements are always included as part of any street project. Nettesheim says, “The studies are always used both to evaluate the priority of the project and to serve as a vehicle to move our entire stormwater management and sanitary sewer plans forward. I can’t imagine working without the plan. It also helps our elected officials in the budgeting process.”
The simultaneous completion of both a stormwater management plan and a sanitary sewerage system plan has put Menomonee Falls in a position to be proactive for years to come. The impressive reduction in basement backups and surface water flooding confirm that these companion studies, used as dynamic, working documents, are having a positive impact in the village.
Author's Bio: Kurt A. Peot, P.E., is a principal and a supervisor in the Civil/Municipal Department at Ruekert and Mielke Inc., a multidisciplinary municipal engineering firm with offices in Waukesha, Kenosha, and Madison, WI. He has served as a consulting engineer to the village of Menomonee Falls for over 25 years. |
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