POPLAR RIVER MANAGEMENT BOARD AND PROJECT PARTNER INVESTMENTS
In collaboration with the Cook County SWCD, the PRMB has invested over $2.5 million in grants and private funds in conservation projects and other initiatives to improve water quality and to reduce sediment to the River.
One of the first steps was to commission a scientific study, at our cost, to map the principal sources of sediment to the River so that the highest sediment-producing sources would be addressed first by projects. This study, and others that followed, highlighted the large contribution of sediment made by slumps, landsides, gullies and ravines. Armed with this data, PRMB partners began implementing a series of projects to reduce sediment from both natural and manmade causes.
With the significant contributors of sediment identified and projects underway, the board, in 2012, put in motion a second phase of scientific research and data collection to target the next round of projects needed to further reduce sediment and move toward their goal.
This new research and design guidelines for erosion control on ski runs could be used as a model for ski resorts across the country. Utilizing this new data, the Cook County SWCD was successful in securing an $829,000 2014 Targeted Watershed Grant from the Clean Water Legacy Fund.
The $829,000 grant will be used for in-stream stabilization, upland runoff erosion control, and implementation of water bars on ski slopes and native grass and forbs plantings. This new work will build on the accomplishments of past efforts and provide benefits in sediment reduction to the Poplar River for decades to come.
Poplar River Management Board Investments:
- Brule Tightline -- $156,272
- Eagle Mountain Stormwater system -- $83,871
- Elimination & Revegetation of 50% of trails, roads -- $42,650
- Stormwater improvements to remaining roads -- $54,265
- PRMB Contributions -- $98,330
- GLC Grant match; Ullr Tightline fall 2011, others 2012-13 -- $147,000
Total PRMB: $582,388
Public Investments in Poplar River:
- 2006 Coastal Program Grant - Megaslump Study $30,000
- 2007 CWL Grant - Megaslump & other projects - $350,000
- 2009 GLC Grant - Ullr Tightline $30,000
- 2010 GLC Grant - $687,000
- 2014 CWL Targeted Watershed Grant - $829,000
Total Public = $1,926,000
TOTAL PUBLIC AND PRIVATE INVESTMENTS: $2,508,388
SEDIMENT REDUCTION PROJECT DETAILS
Megaslump. Initial studies showed that the largest single source of sediment was the Megaslump: a large unstable bank located on the outside corner of a 180-degree bend in the River. The energy of the River has caused mass-wasting events from this bank for decades, and the Megaslump is clearly visible in aerial photographs taken before the ski area was opened in 1948. With very little development proximate to the Megaslump since 1948, the sediment produced by the Megaslump is believed to be a largely natural phenomenon. The first TMDL study identified the Megaslump as contributing 26% (or 20% if sediment from the Upper Watershed is included) or 522 tons/year of sediment annually to the River. This was therefore identified as a high-priority project.
Design on the Megaslump was carried out in 2007 and construction in 2008. Since construction, the Megaslump has become increasingly stable and no mass wasting events have been observed. In addition, the constructed structures have held up after repeated high-flow events.
Brule Tightline. (A \"tightline\" is a pipe that conveys water through a steep or erosion-sensitive area, to eliminate the potential for erosion in that area.) The valley between Ullr and Eagle Mountains is a steep and erosion-prone area, especially the area immediately above the Poplar River where the landslope becomes very steep. Various surface-constructed solutions were implemented over the years with only temporary success. Engineers recommended a tightline to pass the water through the sensitive area adjacent to the River. This was constructed in 2005-6. Construction included the restoration of gullies that had developed from uncontrolled surface flows. This system also includes a second pipe that collects surface flow along the slope through drop-inlets located at water bars. This system has worked as designed, the area has completely stabilized, and thick vegetation has taken hold. This system has exceeded expectations, and helps minimize sediment runoff.
Eagle Mountain Stormwater System. Eagle Mountain is the most developed of the four mountains at the ski resort, and includes the ski resort\'s base area buildings, roads, sidewalks and parking areas in addition to ski runs. Engineers recommended, as a next-step BMP, a stormwater system be constructed to intercept all stormwater on Eagle Mountain before it reaches the Poplar River. Such a system was designed by engineers constructed in 2006-7. This system includes a sediment basin located immediately adjacent to the Poplar River, treating the water before discharge. This system continues in operation and has performed as anticipated.
Elimination of Work Roads. The TMDL study identified the extent to which unvegetated roads contribute to sediment in the River. As a result, Lutsen Mountains reviewed all trails and roads with the goal of minimizing the square-footage of these areas. Since 2007, 50% of our roads and trails that existed prior to 2007 have been closed. Signage was purchased and is re-installed each spring to ensure that vehicles stay on designated routes and stay off sensitive areas.
Moose-Mystery Stream Project. A culvert carrying a small tributary under a ski run failed during a 5\" rain event in June 2008. Considerable erosion was taking place at the site, aggravated by very fine soils. The proximity of the project to the River made it a high-priority project to reduce sediment. A design was developed by SWCD engineers, and construction took place late fall 2008. The new culvert was placed at the original stream elevation, the upstream channel was restored, and weirs were added to the stream channel to control flow. Today, the area is well vegetated and the culvert and stream channel are functioning properly, and with a significant reduction in erosion in and around the site.
Ullr Gully Project. A large historical gully was noted in the TMDL on a steep slope between end of County Road 5 and the Poplar River. Because of the size of the gully and its proximity to the River, it was identified as a high-priority project. The project was completed in 2012. This tightline will accept all flows from the adjacent County Road and ski runs and send them to the River without degrading the steep slope below the County Road. The tightline was placed inside the gully and measures were taken to ensure that water landing on top of the tightline (i.e. the old gully) would be transported to the bottom without causing further erosion.
Caribou Highlands Flowpath. The area between Caribou Highlands Lodge and the Poplar River was identified in the TMDL as an area of concern, due to its proximity to the River (the resort follows the River along a bluff), the steep slopes between the resort and the River, and the ski trails and roads that intercepted this flowpath before getting to the River. The project was completed in 2013.
Mystery Mountain Flowpath, Eagle Mountain Road. These are both areas of concern in the TMDL, and are both immediately adjacent to the River and therefore have the potential for high levels of sediment delivery to the River. Funding is in place for both of these projects. The Eagle Mountain Road project was completed in 2013 and the Mystery Mountain Flow Path was completed in 2014.
County Road Stormwater Improvements. After years of planning with state and local officials, improvements are completed along the County Road in the heart of Lutsen Mountains ski area. This roadway section has never had stormwater infrastructure, and as a result, stormwater flows frequently overtopped the road and caused erosion damage on the steep slopes between the road and the Poplar River. These roadway improvements include an engineered stormsewer system that will intercept the stormwater flows and direct them to either the Brule Tightline or to the newly constructed Ullr Tightline. All of these flows therefore will be transported to the River without doing any damage to the adjacent slopes and without delivering additional sediment to the River. This is the last piece of a comprehensive system of stormwater infrastructure that spans across the entire length of the ski resort on the side of the River most susceptible to erosion due to the combination of (i) the high incidence of steep slopes immediately above the River, (ii) the large size of the watersheds draining into this side of the River, (iii) the presence of the only two 180-degree bends of the River in the Lower Watershed, and (iv) the presence of the County Road and most of the ski resort\'s buildings and parking areas.
Moose Mountain Stormwater Basin. A water collection system will be engineered and was constructed in 2014. This project will control runoff from the hillslope areas of Moose Mountain. A sediment basin structure will serve to settle out sediment and reduce flow velocity before getting to the River.
PRMB is near their goal of eliminating or offsetting all manmade sediment in the Lower Poplar River.
This track record of more than ten conservation projects and measures implemented to date, and including funded projects planned through 2013, have eliminated an estimated 835 tons or 42% of the median sediment load of 1,985 tons/year calculated by RTI under the TMDL (32% if sediment from the Upper Watershed is included).
This is a significant accomplishment, and possibly unprecedented, for a listed water body prior to completion of a TMDL.