What are the documented locations and maps of Minneapolis stormwater and sewer tunnels?
Executive summary
stormwater-network">Minneapolis contains a large, multilayered underground sewer and stormwater network: roughly 830 miles of sanitary sewers, 509 miles of storm pipes, about 12 miles of deep storm tunnels, and about 31 miles of sanitary main and interceptor tunnels, all mapped and managed by city and regional agencies [1]. Publicly accessible maps and GIS layers exist but are fragmented across City of Minneapolis project maps, Metropolitan Council/State GIS collections, the Minnesota Natural Resources Atlas, and local watershed monitoring groups [2] [3] [4] [5].
1. What the inventory looks like: miles, manholes and tunnels
The City of Minneapolis quantifies the system in linear miles and access points: 830 miles of sanitary sewer, 509 miles of storm pipes, approximately 12 miles of deep storm tunnels and 31 miles of sanitary interceptor tunnels, with roughly 18,000 storm manholes and 32,000 sanitary manholes that provide access for maintenance and inspection [1] [6]. The city also reports nearly 29,000 storm drain inlets and a portfolio of at least 20 stormwater ponds and man-made wetlands tied into the system, indicating the scale and complexity of conveyance and outfall locations across the municipal footprint [6] [1].
2. Documented deep tunnels and named projects
Not all tunnels are nameless corridors; the Central City Tunnel System is a documented deep storm tunnel built into Minneapolis’ sandstone, with a newly constructed segment under Washington Ave. S. between Nicollet Mall and Chicago Ave running parallel to an existing tunnel under Chicago Ave—specific locational descriptions the city publishes for that project [7]. The Como Stormwater Tunnel improvement project lists street‑level intersections where work occurred (Como Ave at 19th–24th Aves), demonstrating that tunnel improvements and known tunnel alignments are often published as project maps [8].
3. Outfalls, monitoring sites and specific pipe details
Watershed and monitoring organizations publish point locations tied to tunnels and outfalls: the Mississippi River outfall for the 2NNBC (Old Bassett Creek Tunnel) drains to the west bank at river mile 854.8 and is tracked by the Mississippi Watershed Management Organization, which also documents a concrete 4.5‑foot diameter storm pipe accessed through a manhole near New Brighton Boulevard (Highway 88) that drains parts of northeast Minneapolis and adjacent cities [5]. These monitoring sites provide concrete locational anchor points where subterranean infrastructure connects to surface waters [5].
4. Where to find maps and raw GIS data
Comprehensive public mapping requires stitching multiple sources: the City of Minneapolis offers project‑level maps and a sewer pipe‑lining project map showing locations of active work [2] [9], the Minnesota Geospatial Information Office links to Metropolitan Council datasets including sewersheds and sewer interceptor systems for the Twin Cities [3], and the Minnesota Natural Resources Atlas hosts an MS4 layer that displays publicly owned stormwater infrastructure such as pipes, ditches and retention ponds [4]. Independent map visualizations also exist—e.g., a 2014 CARTO map of Minneapolis and St. Paul storm drains created from municipal datasets [10].
5. Public access, limitations and how to obtain more precise maps
The city provides neighborhood‑level resources (custom GIS maps for storm drain stenciling, project maps for construction work) and directs operational inquiries to 311, but it does not centralize a single public “tunnel map” covering every deep interceptor and storm tunnel with granular alignments in a one‑stop portal—users must request or download separate GIS layers from the City, Metropolitan Council, or state GIS portals and consult watershed monitoring reports for outfall coordinates [11] [2] [3] [4]. The city also notes recent inventory and condition assessment studies for storm tunnels, signaling that detailed inspection data exist though they may be published as project or report documents rather than a continuous public map [6].
6. Takeaway and recommended next steps for researchers
For a working map of Minneapolis stormwater and sewer tunnels, combine City of Minneapolis project maps (for named tunnel projects and lining work), Metropolitan Council/State GIS sewer datasets (for sewersheds and interceptors), the MS4 layer in the Minnesota Natural Resources Atlas (for storm infrastructure), and watershed monitoring reports (for outfalls and monitoring stations)—this blended approach reconstructs the documented locations described in municipal and regional sources [2] [3] [4] [5]. If precise alignments or engineering drawings are required, submit data requests to Minneapolis Public Works and the Metropolitan Council, and consult the inventory/condition assessment studies the city references for deeper technical detail [6] [12].