Current Water Resource Projects
NE Penn Drainage Area Improvement Project
In November 2010, the City hired Barr Engineering to complete a feasibility study to examine the existing conditions and causes of temporary flooding within the NE Penn Drainage Area without causing increased flooding at other locations. The study yielded ten alternatives that the City Council evaluated. On November 15, 2011 Public Works hosted two public open houses to provide information on the proposed project to the public and take comments.
On January 3, 2012, the City Council ordered the NE Penn Drainage Area Improvement Project based on the earlier feasibility report and public input. The solution chosen by the City Council was Alternative 10 from that feasibility report, which consists of constructing new, larger storm sewer pipe and inlet capacity in the approximate location shown below. The construction methods proposed were to be a combination of open trench and tunneling methods. Through the early stages of design a revised estimate was developed that exceeds the current project budget. Therefore, on October 8, 2012, the City Council will consider cancelling the project as ordered.
Engineering staff will continue to seek more feasible alternatives to meet the goals of the original project.
Storm Sewer Color TV Inspection
Work includes closed circuit television inspection of storm sewer mainline pipe at locations of future reconstruction and overlay projects. Inspection results are used to determine necessary repairs in conjunction with future roadway projects. Inspection records also provide information to minimize long-term maintenance costs and traffic interruptions, and reduce erosion.
Pond Maintenance Project
The 2015-905 Pond Maintenance Project is currently under consideration including St. Edward Pond, Kingsdale Pond and Hyland Hills Ponds North and South. Sediment samples are being analyzed for sediment disposal requirements. Construction is anticipated for early winter 2015/2016. Nearby residents will be notified of the work.
Sediment removal, bank stabilization and minor storm sewer maintenance are regularly completed during the winter months to provide better access to equipment and crews, minimize risks of problems with rain, and reduce damage to the environment. Final restoration typically begins in the spring and is completed by early summer.
Sediment accumulates in lakes and ponds from erosion, winter ice control and other sources. Phosphorus and other nutrients attach to the soil particles and contribute to algae blooms and excess aquatic vegetation. Sediment removal from lakes and ponds connected to the City's storm sewer system provides water quality benefits by reducing nutrients and increasing the normal water volume and storage capacity. Lakes and ponds are excavated to similar size and shape as originally constructed or adopted as storm water retention/detention ponds.
Permits are typically required from the MnDNR, MPCA, watershed districts and other water authorities.
The 2013-902 Pond Maintenance Project included sediment excavation at Barthel's Pond and Marsh Lake near Hillcrest School. Excavated sediment from Barthel's Pond was used for fill off-site at the contractors option, but higher PAH levels at Marsh Lake required landfill disposal. Work was completed in January 2014 with final restoration in the spring. The Nine Mile Creek Watershed District requires buffer signs, which will be installed in 2015, as a condition of their permit.
The 2012-902 Pond Maintenance Project was successfully concluded at Wrights Lake (E. 86th St & Old Cedar Ave.) in March 2013. The excavated sediment was disposed in certified landfills due to polycyclic aromatic hydrocarbons (PAHs), which must be disposed according to Minnesota Pollution Control Agency guidelines.
Oxboro Lake Update: The pond maintenance at Oxboro Lake will be delayed pending budgeting for several other projects that involve flood mitigation and stepped up replacement of aging storm sewer pipes.
The NE Penn Project is currently being further analyzed to mitigate temporary flooding in the Knox/American Blvd. area, the project planning initially included tunneling new storm sewer piping to Upper Penn Lake, but following preliminary construction estimates to be too expensive.
The City has stepped up inspections of aging corrugated steel pipes, especially critical outfalls, in an effort to avoid dangerous sinkholes and failures that could cause erosion of the Minnesota River bluff. The expected design life for most steel storm sewer pipe can exceed 50 years, but many factors such as soil characteristics, water levels, chlorides, abrasion and others can reduce the serviceability. As the pipes age, corrosion can create holes that allow the surrounding soil to flow into the pipe. This can often result in a sinkhole, which depending on the location can be a safety or environmental problem. As many of these pipes were installed in the late 1950's and early 60's their serviceable life is coming due. When it is determined that pipe replacement is required various options of pipe materials, project timing and trenchless alternatives are considered depending on the location and impacts to the public (i.e. traffic) and the environment.
For additional information or questions regarding this project, please contact:
Steve Segar, PE
Lower Penn Lake Management Plan
The City of Bloomington Engineering Division has been working with the Department of Natural Resources (DNR), Nine Mile Creek Watershed District, and Public to gather information to ultimately develop a management plan for Lower Penn Lake. The goal of the plan is to outline detailed actions to preserve, maintain, or achieve desired attainable uses for the lake.
Follow the link below to visit the project web page.
Long Meadow Lake Outfall Project
The 2012-904 Long Meadow Lake Outfall Project includes removing and replacing a failing metal storm sewer pipe with a high-density polyethylene pipe from East Old Shakopee Road near 34th Ave. S. to Long Meadow Lake. The existing pipe was installed in 1966, and due to corrosion had leaks, separated joints and was causing erosion along the Minnesota River bluff. Work will begin in mid-December and is expected to be completed by early March 2013. Performing this work in the winter will reduce the conflicts with wildlife, reduce the potential for erosion and allow the soft soils to freeze and reduce disturbance from the heavy construction equipment. The work requires permits and reporting to several agencies including the Minnesota DNR, Minnesota Board of Water and Soil Resources, US Army Corps of Engineers, US Fish and Wildlife Service (as the work extends partially onto the Wildlife Refuge) and the Lower Minnesota River Watershed District.
Parking lots can be designed with the environment in mind.
Harrison Park Regional Infiltration Project
The City of Bloomington recently constructed an Infiltration Demonstration Project at Harrison Park. The Project consists of a permeable asphalt parking lot and two rainwater gardens. This location was selected for several reasons, including; the deteriorated parking surfacing, proximity to Nine Mile Creek, central location, good infiltration capacity of the existing soils and high public profile.
Project Design Objectives:
- Improve water quality
- Reduce quantity of storm water runoff
- Reduce flash flows during intense rain events
- Reduce impervious land coverage
- Provide retention, infiltration and cooling of storm water
- Minimize erosion
- Increase Creek base flows during low flow periods
- Bind heavy metals and toxins coming off parking lot
- Pervious Pavement
Construction of the permeable asphalt parking lot and rainwater gardens was completed in early October 2008. The asphalt differs from standard asphalt in that it contains very little fine aggregate that would lead to dense impervious pavement. The pavement looks very coarse, since it has high void content, and is slightly more difficult for construction workers to get a "polished smooth" surface. A preliminary test with a flush truck confirmed that water flowed right thru the pavement. The porous asphalt and crushed granite rock base layers are designed to infiltrate storm water and minimize runoff to nearby Nine Mile Creek, reducing annual runoff by 90%. A monitoring plan is planned to confirm this anticipated performance.
How to keep the water flowing thru the pavement? Twice a year the parking lot will be swept by a special vacuum type street sweeper. Keeping sand, grit and other particles from clogging the pours is key to maintaining the infiltration capabilities of the pavement. And when the snow flies, sand and salt are not required for winter maintenance, just plow the snow off as usual, and solar energy will melt the remaining snow right into the porous pavement.
Two rainwater water gardens were also constructed to demonstrate alternative methods of treating storm water. One rainwater garden will be in the center parking median, containing native trees and plants that can tolerate drier conditions, as this area will not get much runoff. The other rainwater garden will be located west of the access to Nine Mile Creek. This rainwater garden is designed to capture runoff from the adjacent trail, apartment parking lot and the park area, and is designed with native flowers, grasses and shrubs that can tolerate more frequent wet conditions. These garden areas will require little maintenance after the establishment period, and offer natural beauty and infiltration of storm water runoff.
The project was designed by the Engineering and Park Maintenance Divisions of Public Works. Public Works staff has been monitoring and maintaining the parking lot for one year. We are seeing continued infiltration and good performance. Several areas of concern: snow plows have scraped some surface rocks, flow from the standard asphalt may be carrying extra fines and overloading the pervious pavement causing some plugging, and the rainwater garden shared with the Woodland Apartments is undersized (but that was all the space available). Engineering staff will continue to monitor the parking lot performance for the coming years.
The following presentation is available for download. We respectfully request that any use other than personal should include credit to the City of Bloomington.