Stormwater Improvements for a Historic Stream
Swede Hollow on the City of Saint Paul’s East Side is a historic immigrant neighborhood dating back to the 19th century. This lowland valley includes a portion of a stream from Phalen Creek to the Mississippi River. After housing was removed following the turn of the century, the city created Swede Hollow Park and placed some of the stream flow in a storm sewer pipe to complete its path to the river.
By the late 1980s, the City of Saint Paul had decided to daylight the stream into a small channel system, which at the time included clearwater flows from the nearby Hamm’s brewery and 3M manufacturing plant. As nearby manufacturing declined in the early 1990s, the stream was left with only neighborhood stormwater drainage and groundwater seepage as a base flow source. Stormwater drainage deposited large amounts of sediment in an adjacent pond.
“Swede Hollow is one of the most unique natural spaces in CRWD and Saint Paul. Thanks to the partnership with the city and community stakeholders, we are excited to make changes that will increase base flow in the stream and improve trail access for the community to enjoy.”-Nate Zwonitzer, Water Resource Project Manager
In 2011, the City of Saint Paul Department of Parks and Recreation received a grant from CRWD to conduct a stream restoration feasibility study for the water resources in Swede Hollow Park. The study recommended several improvements to the stream’s function and aesthetic, including groundwater harvesting, removing sediment from the pond, and structural changes to increase streamflow.
An additional CRWD grant awarded in 2015 provided funds to complete the following improvements:
Surface groundwater harvesting to protect trails and add flow to the stream. After industrial sources of stream flow were cut off, it was found that groundwater seeps could support a small base flow. Project improvements will intercept this groundwater and direct it to the stream. This will also protect the existing trail from flooding and ice.
Reconstruction of the lower pond outlet structure to raise the outlet elevation and provide greater pond depth. The pond will also be dredged to remove the sediment that has built up over the years.
Replacement of a storm sewer structure to increase water flow. A current structure intercepts stream flow part way through the channel, and replacing this structure will maintain flow in the stream.
The project was completed in 2019 and the new storm sewer structures are keeping more water flowing in the stream. Though most of the groundwater harvesting work was successful in preventing water from flowing over the path, the record-setting precipitation likely contributed to increased groundwater flow. This made it difficult to capture all of the groundwater in a couple locations. Some water over the walking path is still occurring but may vary with weather patterns. Rather than make additional attempts to capture groundwater in those areas, future modifications to the path will be considered as identified in the City of Saint Paul’s Swede Hollow Park Master Plan.
The potential for improved wildlife habitat, educational programs, and trail connections will contribute to the public enjoyment of Swede Hollow Park for many years.