5.8.2 Marsh/Wasserman Lake Wetland Restoration and Stream Stabilization

ProjectMarsh/Wasserman Lake Wetland Restoration and Stream Stabilization
DescriptionRestoration of 1,500 feet of stream and 30 acres of wetland along Six Mile Creek and riparian wetlands between Marsh Lake and Wasserman Lake
Need

A TMDL study including a phosphorus reduction plan is currently being developed for Wasserman Lake. Proposed reductions include control of external sources of phosphorus through various efforts in the watershed and internal load management. The TMDL identified a need to reduce external loading by 383 pounds annually.

The TMDL identified two improvements to the corridor between Marsh and Wasserman Lakes as potential means to reduce phosphorus load to Wasserman Lake: stabilization of eroded portions of the stream connecting Marsh Lake and Wasserman Lake, and restoration of the wetland complex through which that stream flows. The Upper Watershed Stream Assessment identified the Marsh Lake Road culvert crossing as in need of improvement and stabilization, and streambank erosion was noted just downstream of the culvert.

The TMDL is not yet final as of this writing and details of the specific improvements have not been developed. However, there is a potential to restore approximately 1500 linear feet of Six Mile Creek channel, and potentially 30 or more acres of riparian wetland. This Preserve classification wetland is identified in the MCWD 2003 Functional Assessment of Wetlands as providing significant downstream water quality and flood storage benefits. The wetland currently exhibits moderate wildlife habitat and low vegetative diversity, being primarily cattails with reed canary grass and buckthorn in areas.

Stream restoration could repair existing eroded sites and improve streambank stability using bioengineering techniques. This restoration would also reduce sediment-bound phosphorus contributions to downstream Wasserman Lake. Wetland restoration could provide the opportunity to replace the invasive vegetative species with more diverse species to enhance wildlife habitat. Creating a more defined channel meandering through the wetland could reduce internal loading of phosphorus from wetland sediments, and the flushing of particulate matter from the wetland. The TMDL estimated a 99 pound phosphorus load reduction could be achievable through these restorations.

There are two distinct wetland areas in the corridor (see Figure 20). The wetland area between Marsh Lake Road and a local private road, the Marsh Lake Road culvert repair and downstream stream restoration are here designated “Phase I.” The wetland and stream restoration north of the local private road and Wasserman Lake are “Phase II.” These wetlands are located within the Key Conservation Area identified for this subwatershed.

OutcomeReduction in phosphorus load from external sources estimated at 99 pounds annually; improved water clarity in Wasserman Lake; more diverse wetland vegetation community; improved habitat in Six Mile Creek; streambank stabilization and reduced sediment transport from eroding streambanks
Estimated Cost and Funding
Phase I: Culvert repair, stream restoration
and wetland restoration.  Source of funding
is the District capital levy.

 

Phase II: Stream and wetland restoration.
Source of funding is the District capital levy.
$67,600 Design, easmnt
$653,700 Construction
$721,300 Total

$73,600 Design, easmnt
$613,900 Construction
$687,500 Total
Schedule

2013 Fish, vegetation, and zooplankton surveys, development of management plans

2014 Implementation of strategies