The Smith Pond Drainage District is approximately 1,770 acres and is located south of I-494 and west of TH-77 (Cedar Avenue). The District generally discharges east to the Airport South Drainage District, Cedar Avenue, and to a regional storm water treatment basin (Pond C) within the Minnesota Valley National Wildlife Refuge. Storm water runoff eventually drains to the Long Meadow Lake and ultimately to the Minnesota River.

The City of Bloomington retained SRF to update and calibrate XP-SWMM and P-8 models for the District.  The project approach assimilated existing resources with additional information obtained through this study in an effort to develop encompassing hydrologic, hydraulic and water quality models.  Significant GIS resources were incorporated into the analysis, including land use, soils and infrastructure into the models. 

The existing XP-SWMM and P8 models will function as the basis or backbone from which more refined models will be created. The detail added to the XP-SWMM and P8 models include refined drainage areas, calibrated hydrologic and hydraulic parameters, storage volume relationships within flood areas, and overland flow paths. Ultimately, the XPSWMM and P8 models will be calibrated to ensure proper representation of the study area.

The reconstruction of Cedar Avenue to accommodate bus rapid transit (BRT) offered the cities of Apple Valley and Lakeville an opportunity to identify and solve drainage problems associated with the trunk storm sewer system that had been constructed over numerous decades. 

This 3.8 mile construction project involved analysis of existing storm sewer infrastructure and design of new systems that meet local and State Aid design criteria. The corridor consists of 104 acres of drainage, and conveys additional runoff from the adjacent 388 acres. Much of the offsite runoff is routed through existing storm water ponds prior to, or after, entering the corridor. Likewise, some of the offsite runoff enters and exits the corridor more than one time.

SRF staff used existing hydrologic information and GIS based information to construct an XP-SWMM model to evaluate the existing systems and suggest alternatives to solve flooding problems within the Cedar Avenue corridor as well as meet the requirements of the various regulatory agencies.

The final report guided the cities and Dakota County to deciding which segments of the trunk system should be replaced or augmented, saving the project significant costs and assisting in staging the construction on this very busy commuter route.

Purgatory Creek is an urban stream located along a picturesque route through the City of Eden Prairie. As is typical with many urban streams, Purgatory Creek has, over the years, experienced a significant increase in flow and volume due to increases in impervious surface within its watershed. As flow rates and volumes increased, so did stream bank erosion. In particular two reaches, totaling approximately 420 feet, located just below Riverview Road in the Minnesota River floodplain, experienced extensive erosion and streambank deterioration. A small wetland located along the creek’s overbank in Reach 1, fed by groundwater from a perched pond, together with the embankment that separates the pond from the Creek were being threatened. Reach 2 was threatening to consume a large part of a property owner’s land as it tried to create an oxbow.

Implemented by the City with 50 percent matching funding from the Lower Minnesota River Watershed District (LMRWD), this project began with determining the Creek’s characteristics such as entrenchment ratio (6), width to depth ratio (7), sinuosity (1.3) and slope (1.0%). Based on these parameters, a Rosgen’s classification of E5 was determined. Bankfull discharge based on the 1.5 year flow recurrence was computed. Then velocities and, finally, streambank shear stress values were calculated for this condition plus several other flow regimes.

These values were compared to permissible values based on geotechnical analysis of soils properties. Highest shear stress zones were then identified and a bioengineered solution selected. Based on the relatively high velocities and shear stresses that would be experienced through these two reaches, a vegetated geogrid system that involves the construction geotextile wrapped “pillows” of soil and/or suitable backfill, and a riprap toe was selected. Watershed district and DNR permits were obtained, and final designs were completed.

The project commenced in 2008 and was completed in 2009. A three-year monitoring period is currently underway. SRF also provided construction administration services.

The Kimmes - Tobin Wetland Mitigation Site, constructed in 1993, has provided 168 acres of wetland mitigation for the Wisconsin Department of Transportation (WisDOT). The site is situated on an elevated plateau between Mud Creek and Clear Creek, both tributaries of the Nemadji River. Since construction, excess surface hydrology and subsequent wave action and muskrat activity at the Kimmes-Tobin Site has resulted in berm deterioration and erosion.

SRF was retained by WisDOT to study viable methods to strengthen berms that impound the 17-celled site. The Phase I Study recommended a surface water drawdown of one to two feet in several of the basins, berm repairs, and installation of several new water level control structures. These modifications have the potential to promote plant community succession; some wetlands may convert to other wetland types, and some drier type wetlands (e.g., wet meadows) may convert to uplands.

SRF submitted a Technical Memorandum, which described post-engineering scenarios of plant community succession and summarized a plan to monitor these vegetation changes. Plant community succession scenarios discussed included Natural Passive Succession, Guided Succession (intensive planting of native seed mixes, plugs, and whips), and Natural Passive Succession with Limited Pilot Studies.

Severe congestion, delays caused by operation of the historic Stillwater Lift Bridge, and the condition and maintenance of the bridge have prompted discussions and study of a new bridge over the St. Croix River near Stillwater for many years. Although a preferred alternative was selected as part of the 1995 Final EIS, the alternative was not allowed to proceed because of its impact on the St. Croix River, which is part of the National Wild and Scenic River system. SRF recently worked with MnDOT to complete a supplemental EIS for the project.

Successful completion of the environmental review required balancing transportation needs, impacts to the pristine Lower St. Croix National Scenic Riverway, and impacts to cultural resources including the Stillwater Lift Bridge and the Downtown Commercial Historic District. The project included extensive agency coordination meetings to identify key issues, assess project impacts and coordinate appropriate mitigation strategies. Broad public involvement, including numerous public information meetings and newsletters, was also critical.

Since the St. Croix River is a National Scenic Riverway, water resources issues, including in-river, point source and non-point source pollutant loadings are of great concern. These issues are currently being studied by the St. Croix Basin Water Resources Planning Team that is comprised of a number of Minnesota and Wisconsin organizations, agencies and non-profit groups. In order to address the many concerns that Team members have expressed, a Water Resources Group was formed under the auspices of the St. Croix River Crossing Supplemental EIS project that included key Team members such as the WisDNR, MnDNR and the National Park Service plus WisDOT, MnDOT and interested non-profits.

As the convener and coordinator, SRF provided leadership, research, information, stormwater quality modeling results and analysis of issues addressed by the Water Resources Group. Two white papers were produced by SRF for the Water Resources Group: “Effects of Stormwater Discharge on Fresh Water Mussels” and “Analysis of Highway Stormwater Runoff Impacts to Potable Groundwater Aquifers.” A comprehensive stormwater quality model was developed that was used for analysis of phosphorus loading from the St. Croix River Crossing project to the river.

Water quality analysis was performed using P-8 to assess various mitigation strategies to obtain the overall goal of 20 percent phosphorous reduction to the St. Croix. Compiled with SWMM hydrologic modeling, the models demonstrated how the proposed project would lessen the impact of stormwater runoff on this valued resource.