Postition Statement: MMSD Floodwater Detention Basins at the Milwaukee County Grounds

Date: April 26, 2006
 
Background:
 
The Milwaukee County Grounds is a 1,000 acre property owned by Milwaukee County located entirely within the City of Wauwatosa.  While a large portion of the County Grounds has been developed, the County Grounds still contain approximately 235 acres of large undeveloped tracts of open space featuring a rolling topography with forests, open fields, and the confluence of Underwood Creek with the Menomonee River, as well as historically designated institutional buildings (Eschweiler Builders), a 19th century cemetery, and important wildlife habitat, especially for birds and the State threatened Butler Garter Snake. 
 
Friends of Milwaukee's Rivers has been advocating for the protection of the County Grounds since our inception in 1995.  The County Grounds has faced various threats during the last decade, including proposals to sell off all or portions of the land to private developers.  Although citizens have been unable to save the entire County Grounds, and portions of the land have been designated for economic development and for playing fields for Wisconsin Lutheran College, citizen efforts have been vital to the preservation of a 65 acre State Forest on the site and to obtaining some legal protections in the form of conservation easements for the remaining natural areas of the property and City of Wauwatosa zoning designation as “conservancy” during summer 2004. 
 
Now the County Grounds faces a new threat.  The Milwaukee Metropolitan Sewerage District (MMSD) has applied to the Wisconsin Department of Natural Resources for permits to construct a flood-control project on the grounds.  The project includes the creation of a 91-acre floodwater detention basin by excavating about 2 million cubic yards of material (about enough to fill the Mayfair Mall), a floodwater diversion structure at Underwood Creek, an underground tunnel, and an outlet/spillway structure to divert water from the basin back to the Menomonee River.  This project includes destruction of 4.69 acres of wetlands, and considerable effects to the hydrology, habitat, and ecological functioning of both the Menomonee River and Underwood Creek.  In addition, over 50 additional acres will be impacted by grading and fill activities, as soil from the basins will be now be dumped on the uplands instead of being trucked off site as originally planned.  The project also includes removal of concrete and rehabilitation of a portion of Underwood Creek, from USH 100 to its confluence with the Menomonee River, and the construction of a bridge to carry Swan Boulevard over the basin.
 
Position:
 
FMR has stated from the beginning that we felt that the County Grounds option, which was considered as part of a Menomonee River watershed-wide flood management strategy, is not the best way to manage floodwaters caused by increasing development and storm water runoff.  Although we understand that flooding is a serious concern that needs to be managed, FMR has advocated for a more regional or sub-regional strategy that included incorporation of smaller, low-lying areas along both Underwood Creek and the Menomonee River, which could be designed to store floodwater as well as provide improved wildlife habitat, aesthetics, and recreational opportunities for local residents.  This approach would also have distributed the true “costs” and inconvenience of flood management to the entire causative region as opposed to placing a disproportionate cost on local residents around the County Grounds.  In addition, this option also permanently changes one of our last great public spaces in Milwaukee County.  However, these regional and more “environmentally sustainable” alternatives were discounted because they would be more costly to build and maintain over the long term—essentially one large basin would be easier to manage and maintain than many smaller basins. 
 
FMR has also not been convinced that these basins will significantly minimize future flooding events similar to the 1997-1998 storms that devastated portions of the Milwaukee area, and feel that at best such basins would serve as “speed bumps” or delay the inevitable flooding that would occur under such extreme rain events.  The Environmental Assessment for this project states that the detention basins would fill up with water in 4 hours and that water would take 4 days to drain via a low-level outlet to the Menomonee River following a one percent probability event (essentially an extreme storm with a one percent probability of happening in any year – or a “100 year” flood).  Furthermore, high flows greater than the one percent probability event would be passed with an emergency overflow spillway located within the same outfall/spillway structure. Presumably during such situations, water will exit the basins much more quickly to minimize back-waters and upstream flooding.  Since these basins are being built essentially to address “extreme storms”, it begs the question of whether the projected $84 million price tag is warranted for this slow down of water, and to address approximately $100 million in flood damage during the last 8 years as stated in the Environmental Assessment (EA).   
 
FMR has advocated for an Environmental Impact Statement (EIS) from the early days of this project to identify whether the benefits of this project warrant the costs, and even though the Wisconsin Department of Natural Resources has decided that MMSD does not need to prepare an EIS, FMR feels that the costs and benefits of this project have still not been adequately addressed.  However, if this project continues to go forward as seems apparent, FMR urges the public and the responsible public agencies to ensure that the following issues are addressed:
 
  • Wetland impacts are minimized to the greatest extent possible, and wetland mitigation should take place on-site or in the Underwood Creek watershed, where it can provide benefit for local flood management, wildlife, and human populations, as opposed to off-site mitigation that does none of the above.
  • The use of rip rap is minimized to the greatest extent possible, instead relying on bioengineering and the incorporation of native plants and natural stabilization materials such as coir matting, biologs, etc.
  •   Landscaping on the site uses native plants as described in the “Landscape and Ecological Plan for the Milwaukee County Grounds” by HNTB, and furthermore, that landscaping projects, trails, and amenities (e.g. soccer fields, tennis courts, etc.) described in that report are carried out to completion and adequately funded to re-create and improve upon what is lost.
  • Fish entrapment is minimized as a result of the design of the detention basins, the diversion tunnel/structure from Underwood Creek to the basins, and the spillway from the basins to the Menomonee River.  In addition, effects on fish of drawdown of Underwood Creek during storm events exceeding the 25% probability events should also be assessed.
  • Ecological benefits of the project should exceed the costs.  Although FMR does concede that certain components of this project, in particular, the removal of concrete lining along a portion of Underwood Creek are positive, we remain concerned that the positive water quality and wildlife habitat impacts of concrete removal will be negated by other components such as the creation of an underground concrete-lined tunnel having a 17-foot inner diameter to connect water from the diversion structure at Underwood Creek to the detention basins. 
  • An adequate maintenance plan for the detention basin area should be created by MMSD.  This plan should be accessible to the public and should deal with how public concerns will be addressed, when the basins will be dredged, what will be done to remediate upstream sewage overflows that contaminate the basins in the future, what will be done to address effects of stormwater runoff, algae, etc.
  • Agencies should ensure that MMSD provides adequate funds to Milwaukee County Parks for planting and future maintenance of the uplands portion of the site, which includes pruning, invasive plant species removal, and other land management activities.  MMSD states that this project allows for “development of an upland open space area” as if there is not an existing open space that has been used by local residents for generations.  This is not a “new” amenity—it is a solution to “save” MMSD and taxpayers money by not shipping fill off-site, and having to naturalize an “unnatural” topography as a result. 
  •   Agencies should ensure that MMSD complies with storm water management regulations during construction, and that they provide funds in the form of bonds or other suitable vehicle to help the DNR with oversight and enforcement of this massive construction project.  These funds would also serve as a “security deposit” so that any violations could be suitably remediated by DNR staff if necessary as quickly as possible or after the project is terminated.  If there are no violations, money could be returned at the end of construction.
  • Water quality impacts from the constructed detention basin should be examined and regulated if possible via a WPDES discharge permit.  Potential impacts to water quality could include thermal impacts, as well as flushes of sediment and other contaminants.  Without some sort of regulatory authority or permit, it will be very difficult for the DNR or citizens to require any changes in the future to ameliorate water quality concerns. Likewise, DNR should require regular water quality monitoring by MMSD to ensure that there are no water quality problems associated with this flood management basin of extraordinary size.
  • Agencies should insure that safety impacts from these detention basins are minimized. The Environmental Assessment states that because of the degree of water diversion involved, the Milwaukee County Grounds facility would be regulated as a dam and assigned a high hazard rating due to the potential effects on downstream structures should it fail.  It goes on to state that should the basins fail, that flood waters could flow over Swan Blvd to the Menomonee River directly, and or breach the embankment on the eastern side of the basins, which would be addressed through berm construction.  DNR should ensure that these basins are protective of downstream structures and communities, as well as assure that there is a plan to educate the public to minimize potential safety concerns (e.g. drownings) as well as effects on recreational users such as paddlers. 
  • Agencies should ensure that there is a plan (and funding contingencies) to deal with downstream erosion and scour caused in the future by diverted water entering the Menomonee River from the emergency and low-flow spillways. 
  • Impacts on the Butler’s Garter Snake and its habitat should be minimized, and habitat destroyed should be mitigated for on-site.