Kingston Wetland Feasibility Study and Restoration Project

The Kingston Wetland was constructed back in the mid-1980s to provide treatment of water from the Clearwater River as part of the Clearwater River Chain of Lakes (1980) Restoration Project. As part of the District's TMDL Implementation efforts, the Kingston Wetland Feasibility Study and Restoration Project was designed and implemented to extend the original project's useful life and provide on-going water quality benefits to downstream waters. The restoration project seeks to:

Address a dissolved oxygen (DO) impairment in this section of the Clearwater River
Restore natural ecology and hydrology in the wetland and river
Maintain the wetland's particular phosphorus treatment capacity while addressing the exportation of soluble phosphorus from the wetland during low-flow conditions

A grant of $404,000 was received for this project from the Minnesota Pollution Control Agency through a Grant from the United States Environmental Protection Agency, Section 319 Nonpoint Source Management Fund. The project was constructed in late winter - early spring of 2013. Major project components include: a restored low-flow meandered channel, a rock riffle pool, and a limestone filter berm.
Results of Project:

DO: Pre-restoration 59% of samples collected at all times of day violated the DO standard. Post-restoration only 27% of samples violated DO standards.
Total Phosphorus (TP): Pre-restoration (2001-2012) avg TP concentration at monitoring station below Kingston Wetland Complex was 308 ug/L. Post-restoration (2013-current) was 199 ug/L (arithmetic mean). TP load reductions are estimated to be 1,955 lbs. annually
Soluble Phosphorus (OP): Pre-restoration (2001-2012) avg OP concentration at monitoring station below Kingston Wetland Complex was 156 ug/L. Post-restoration (2013-current) was 100 ug/L (arithmetic mean).
Hilsenhoff Biotic Index (HBI) scores, which is used to track ecological functions, greatly improved in the Clearwater River post-restoration as compared to pre-restoration (8.26 in 2012, 6.08 in 2014). Over the same time period, percentage of intolerant macroinvertebrates species increasing from 0.00% to 1.59% of total sampled, pollution tolerant species decreased from 35.22% to 18.73%, and super-tolerant species decreased from 55.66% to 6.03%. (For comparison, HBI scores from other low gradient streams in MN ranged from 5.8 to 8.8; the best achievable goal for the Clearwater River in this section is 5.8).
Approximately 6,100 lineal feet of the Clearwater River's channel was restored to a meandering low-flow channel from its previously-ditch state. During high flows, the river accesses the wetland complex via an existing diversion channel around the edge of the wetland, along with overtopping the low-flow channel. This maintains the particulate phosphorus capacity, while addressing the sediment oxygen demand in the wetland during low-flow conditions that was a large driver of the dissolved oxygen impairment in the Clearwater River below the wetland.
A limestone filter berm was installed at the outlet of the wetland to remove soluble phosphorus during low flow conditions.