Wetland Mitigation

Since the beginning of the U.S. Army Corps of Engineers (COE) Section 404 regulatory permitting process, MoDOT has constructed or has been responsible for constructing approximately 69 mitigation sites composed of over 600 acres (excluding mitigation bank sites).  These sites are distributed statewide, and many times are located within MoDOT right-of-way (ROW) or immediately adjacent to ROW.  Generally speaking, MoDOT must monitor these sites for at least five years following their completion to ensure their success before the COE will formally grant a release.  Once these sites are released, MoDOT typically retains them in its realty inventory.  The ultimate intent is to relinquish these properties to a trust or non-profit organization so that they can perform any long-term maintenance and protection.

Wetland Banks

A wetland mitigation bank can be defined as an area of land where all three wetland components---hydric soils, wetland hydrology, and hydrophytic plants---have been restored and protected to provide compensation for wetland impacts.  A bank site can be created by a government agency, nonprofit organization, or corporation, which acts as the bank sponsor and undertakes these activities under formal agreement with the COE.  The formal agreement specifies the proposed restoration plan that will be undertaken and the number of environmental credits that the bank may potentially generate.  The Section 404 permit conditions will define the required mitigation ratios.  Typically, replacement ratios will be 1.5:1; however, rare wetland types and special aquatic sites can be mitigated at up to 5:1.

To enable a banker to use the credits generated from the restoration efforts at a bank site, the banker must first receive approval from the COE on the geographic service area that the bank will serve.  The primary service areas that MoDOT has adopted for its bank sites are defined as ecological drainage units (EDUs).  The EDU concept was developed by the Missouri Resource & Assessment Partnership (MoRAP).  EDUs consist of grouped watersheds within their larger regional setting.  The regional distinctions primarily consist of variations in climate, geology, soil, landform, and stream character.  The taxonomic composition (i.e., species & genetics) between EDUs is relatively distinct; however, within the same regional context, like species among different EDUs may have similar physiological tolerances and reproductive and foraging strategies. 

The COE compensatory mitigation rule was approved in 2008.  The rule establishes a preference hierarchy for mitigation options (i.e., mitigation bank credits, in-lieu fee program credits, and permittee-responsible mitigation projects).  The permittee may use any of these three options to mitigate for project impacts; however, the COE preference is the use of mitigation banks. 

Bootheel Bank

MoDOT’s first wetland bank site was established in 2003, near Dexter inStoddard County, Missouri.  This site was constructed by a private farmer, who designed and developed it in conjunction with his agricultural wetland bank site.  The two banks are only separated by an earthen berm.  Since that time, MoDOT has developed four additional wetland mitigation bank sites throughout the state.

Mari-Osa Bank

The Mari-Osa Delta Bank site in Osage County is one of two wetland bank sites in central Missouri (the other is Blue Springs Bank; see below).  It was developed in 2006 and is located approximately 12 miles east of Jefferson City, immediately north of the Route 63/50 interchange.  The approximately 30-acre bank primarily consists of emergent and forested wetland types.  The majority of Mari-Osa Bank’s hydrologic input is from the Maries River, whose confluence with the Osage River is west of the site.

Blue Springs Bank

The Blue Springs Bank site in Jackson County is one of two wetland bank sites in central Missouri (the other is Mari-Osa; see above).  The site is in Fleming County Park, on COE operations land for Blue Springs Lake.  The 30-acre site was completed in 2009 as a cooperative effort between MoDOT and the COE. 

Blue Springs Bank consists of four cells containing 24 acres of emergent, scrub/shrub, and forested wetland habitat.  Some enhancements of existing wetland features at the site were also made.  The hydrology of the cells can be manipulated through the use of water inflow from the lake through piping; this allows for greater management of water in and through the system to better achieve targeted restoration goals.  This site is accessible to the public for bird and wildlife observation.

North Fork Spring River Bank

Construction of the North Fork Spring River Bank was completed in 2010.  The site is located in Barton County, Missouri, approximately six miles south of Lamar in the southwest corner of Routes 71 and 126.  MoDOT purchased and partially used the 76-acre site for borrow in the 1970’s when additional Route 71 lanes were constructed.  MoDOT’s development proposal included a plan to enhance the existing 33 acres of forested wetland and nine acres of emergent/scrub/shrub wetland, as well as the creation of 14-acre and three-acre wetland cells in the old-agricultural-field portion of the site.

A primary function of the Bank is to provide wildlife habitat, particularly for wetland-dependent species.  The marsh and forested wetlands of the bank provide habitat for shorebirds, waterfowl, water birds, and wading birds.  The remnant shrubs and woods remain as habitat for neotropical migrant birds and local upland mammals.  The Bank also provides amphibian and reptile breeding habitat.

The upper North Fork Spring River is on the 303d list as an impaired water body (ID # 3188).  The 303d listed waters are state-identified waters that do not meet state water quality standards.  The primary pollutant in upper North Fork Spring River is sediment, with the section closest to the city of Lamar identified as having low dissolved oxygen levels.  It is unlikely the Bank will contribute toward significant improvement in mitigating low dissolved oxygen, however, the Bank may provide sediment retention benefits and increased flood storage capacity.

Bear Creek Bank

The 50-acre Bear Creek Bank was constructed in November 2011.  The Bank is located in northeast Macon County, off of Mesquite Street and adjacent to Bear Creek.  It is situated directly across from a previously developed 52-acre wetland and stream mitigation site, which was constructed as project-specific mitigation for the expansion of Highway 36 to a four-lane facility between Macon and Shelbina.

The Bank consists of 10 constructed wetland pools and a section of a preserved remnant oxbow of Bear Creek, which bisects the site.  The Bank was designed for passive hydrologic control, meaning there are no water management controls installed to manipulate water levels within the constructed wetland pools.  Eight of the 10 constructed pools were created by shallow excavation.  Hydrologic detention within the other two pools was achieved through construction of low profile berms.

The primary focus of this Bank is to restore wetland and wildlife habitat along Bear Creek in a highly agricultural area.  Most of this site consists of restored emergent wetland, but scrub-shrub and forested wetland components are also present.