Project Background and Overview
Phases 5 and 6 of the Lower Badger Mill Creek Interceptor (LBMCI) will complete a regional sanitary sewer interceptor that was more than 20 years in the making. Representatives from the District, Town of Verona, City of Verona, and City of Madison met in 2001 to discuss planning for sewerage service in the Lower Badger Mill Creek drainage basin. This basin includes parts of the far west side of Madison, the town of Middleton, the town of Verona, and the City of Verona. It was determined that the best way to serve the basin was with a regional gravity sanitary sewer interceptor pipe.
The initial design of the entire 39,000 feet of interceptor pipe was started in 2004 and completed in 2006. Phase 1 included 8,000 feet of pipe at the downstream end of the sewershed and was constructed from Pump Station 17 to Edward Street by the City of Verona and the District in 2006. Phases 2, 3, and 4 of the LBMCI from Edward Street to County Highway PD included approximately 10,000 feet of pipe that was built from 2008 to 2018. The upper 12,000 feet of the regional interceptor was constructed by the City of Madison in 2012, 2015, and 2016. Phases 5 & 6 will complete the final 9,000 feet of interceptor pipe and will connect the District Phase 4 pipe north of County Highway PD to the pipe installed by the City of Madison in 2012 at Midtown Road. When complete the new Phase 5 & 6 interceptor pipe will convey an average sewage flow of approximately 3 million gallons per day and enable the decommissioning of a temporary City of Madison sanitary sewage pump station (also called a lift station) at Midtown Road. The Phase 5 & 6 designs use the initial 2006 design as a starting point and incorporate deviations from the initial design as appropriate.
Final design of Phase 5 is complete, the project has been bid and awarded, and construction has begun as described below. Final design of Phase 6 continues as described below with construction scheduled to begin in 2024.
What are interceptors and pump stations?
An interceptor is a sewer pipe that receives wastewater from smaller local sewer pipes that serve neighborhoods or municipalities. Interceptors are the largest pipes in the sewage system and convey wastewater by gravity to pump stations or treatment facilities.
A pump station sits at a low point within a sewer service area basin (or drainage basin). Wastewater flows by gravity to the pump station and from there it is pumped through a pressurized pipe called a force main over hills and ridges to a higher elevation where it can again flow by gravity on its way toward the regional treatment plant.
LBMCI Phase 5
Phase 5 of the Lower Badger Mill Creek Interceptor (LBMCI) is currently under construction north of County Highway PD between Shady Oak Lane and Country View Road. The Phase 5 project will include 3,550 feet of new 30-inch diameter sanitary sewer interceptor pipe and 10 new manholes. The project is being constructed in coordination with the widening of County Highway PD and with the Ardent Glen development on the Marty Farm property.
The construction contract for Phase 5 was advertised for bids on June 15, 2023 and bids were opened on July 13, 2023. The construction project was awarded to Integrity Grading and Excavating (IGE) on July 27,2023. IGE began construction on October 10, 2023. Construction will take place in the Phase 1 area of the Ardent Glen development and in the Marty Farm corn fields.
The soils underlying the Marty Farm topsoil are mostly sand and gravel outwash from the Johnstown Moraine. This terminal moraine marks the furthest extent of the Laurentide Ice Sheet - Green Bay Lobe between approximately 30,000 and 20,000 years ago. The 30-inch diameter interceptor pipe will be installed between 13 to 18 feet below the ground surface.
Several of the interceptor manholes will be temporarily left from 3 to 7 feet above the existing ground surface. The 6-foot diameter manholes are being left elevated to match the planned surface elevation of future paved paths and roads in the Ardent Glen neighborhood. As the Ardent Glen neighborhood continues to develop, fill will be placed around the manholes and the manhole castings and covers will be adjusted so that only the cover is visible. Until then the manholes sticking up out of the ground will look rather odd. Phase 5 will end near the shoulder of Shady Oak Lane approximately 500 feet northwest of the Marty Farm silos.
LBMCI Phase 6
Phase 6 of the Lower Badger Mill Creek Interceptor (LBMCI) will be approximately 5,300 feet long starting where Phase 5 left off at the downstream end. The pipe will run up Shady Oak Lane approximately 1,200 feet to the bridge between Shady Hill Drive (no street sign) and Nor-Del-Hill Road. East of the bridge, on the Shady Hill Drive side, the interceptor will veer north through private property and up a ravine that cuts through the Johnstown Moraine. A Guide to the Glacial Landscapes of Dane County, Wisconsin, Mickelson, 1983 (page 40 - mile 17) describes the ravine as follows (driving towards Midtown Road):
“Meltwater cut through the moraine to your right at this location and water flowed through this channel as the glacier margin retreated from the Johnstown Moraine. Richardson Cave, a small cave in the Platteville-Galena dolomite is present a few hundred yards up this drainageway. Continuing on Shady Oak Lane, you now climb onto the Johnstown Moraine.”
The depth of the pipe along the initial 2006 proposed alignment in the ravine ranged from 8 to 25 feet below ground surface (bgs). With input from private property owners, our design consultant raSmith, and the District project engineer, the proposed alignment has been updated to follow the channel of the ephemeral stream that runs along the bottom of the ravine. The depth to the bottom of the pipe along the new proposed alignment will range from 8 to 15 feet bgs.
Glacial meltwater rushing through the ravine 20,000 to 30,000 years ago carried lighter soil particles such as clay, silt, sand, and gravel to the outwash plain below the moraine. Larger cobbles and boulders settled out of the meltwater earlier and it is likely that many were left in the ravine. In fact, several very large boulders are visible on the surface of the ravine bottom today. Excavating large cobbles and boulders is more difficult than excavating smaller, more uniform soil particles. Another potential issue is the depth to bedrock in the channel. Soil borings and a seismic survey along the original proposed alignment during the initial design effort in 2006 determined that bedrock is likely below the bottom of the proposed pipe. The bedrock profile may be different along the new proposed pipe alignment in the ravine.
The Wisconsin Geological and Natural History Survey (WGNHS) has been hired by the District, through our consultant raSmith, to perform a geophysical investigation along the entire proposed alignment of Phases 5 and 6. The last fieldwork for the study will take place in the ravine and is nearly complete. The results of the geophysical investigation in the ravine will inform the District’s decision regarding the feasibility of the new proposed route along the channel. Data from the geophysical investigation will be shared when it is available.
The proposed alignment exits the ravine approximately 250 feet southwest from an impoundment of the ephemeral stream. The purpose of the impoundment is to prevent upstream stormwater runoff from entering nearby Richardson’s Cave. After exiting the ravine, the pipe will run east and then north in farmland up to Midtown Road. Any manholes in active farm fields will be left several feet bgs so that farming may continue on the land above. At Midtown Road the pipe will cross to the north side of the road and then run east to the City of Madison Midtown Lift Station. Once connected to existing pipe installed in 2012 by the City of Madison, the entire Lower Badger Mill Creek Interceptor will be complete. Assuming improvements to the District’s Pump Station 17 and associated force main are complete, gravity sewer flow from the entire Badger Mill Creek sewershed will be possible and the temporary Midtown Lift Station can be abandoned.
Hydrogeology and Private Wells
The District and our consultant have gathered publicly available well records within and beyond a 1,000 foot corridor along the proposed pipe alignment. A 3-dimensional visualization model was created from these well records and other existing regional information. Review of this data indicates that the shallow bedrock layer is a dolomite karst formation. Karst formations are characterized by interconnected solution cavities and crevices that can allow rapid transmission of water similar to pipe flow. Therefore, groundwater in karst formations is susceptible to impacts from sources and activities at the surface. Because the construction of Phase 6 will disturb the ground surface, local impacts in the karst formation may occur as the new pipe is installed. Private well owners in the area have expressed concerns about possible construction impacts on their well water and the integrity of their wells. Recognizing these concerns, the District, with assistance from raSmith and AECOM, is developing a plan to address potential risks and impacts that may occur during construction.
Private well capture areas are relatively small. Based on the local hydrogeology and typical well use, the potential for impacts to private wells more than 500 feet away from the construction is expected to be limited. In addition, private wells cased through the karst formation that draw water from the underlying deep sandstone formations are much less likely to be impacted by surface activities. Deep sandstone formations have slower groundwater flow and provide more filtration, whereas the shallow karst formation, with its interconnected cavities and crevices, has faster groundwater flow with less filtering capability.
The plan that the District is developing is focused on private wells located within a 1,000 foot corridor, 500 feet on each side of the proposed pipe. Existing well records are being reviewed to assess the susceptibility of those private wells to impacts based on the depth of their casing and the bedrock from which the well is drawing its water. Owners of wells within 500 feet of the proposed pipe alignment will receive letters to confirm information on their private wells and to establish communications regarding the planned construction, potential impacts, and steps to take if their wells are impacted during construction. More details on the District’s plan will be made available once the private well information is confirmed.
- Newsletter 1: June 7, 2005
- Newsletter 2: February 7, 2006
- Newsletter 3: February 23, 2006
- Newsletter 4: November 23, 2022
The District will coordinate with private and government stakeholders and will hold public information meetings for this project.
Meeting #2, In-Person - Open House & Formal Presentation:
- December 7, 2023, 5:30-7:30 pm
- Town of Verona Town Hall, 7669 County Highway PD
- Open House format from 5:30-6:00 p.m. followed by a formal presentation and Q&A.
Public Information Meeting (PIM) #1 was held almost exactly one year prior on December 8, 2022. The meeting was an open house format held at the Town of Verona Town Hall. Since PIM #1, the proposed alignment of Phase 5 was changed based on coordination with the Ardent Glen development and the proposed alignment of Phase 6 was changed based on input from private property owners.