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April 06, 2015 2:27:02 PM CST
Harris County Flood Control District Expanding Greens Bayou Wetlands Mitigation Bank
Additional Protected Acreage Offers Mitigation for Wetland Losses in Harris County
The Harris County Flood Control District has begun construction on a project that is quadrupling the protected habitat at its Greens Bayou Wetlands Mitigation Bank (Greens WetBank) in northeast Harris County. The project will restore and enhance grassy and forested wetlands contained in 675 additional acres, and – over time – provide valuable credits for environmental mitigation.
On January 6, 2015, Harris County Commissioners Court awarded a $519,656 construction contract to low bidder UFL Inc. to perform the necessary construction, which includes clearing and restoring 41 acres of historically grassy wetlands and constructing low earthen berms (or mounds of soil) to encourage more wetlands formation throughout the site. The wetlands expansion plan is outlined in a new Mitigation Banking Instrument (MBI) approved by Harris County Commissioners and signed in late September 2014 by the U.S. Army Corps of Engineers. Construction began in March and is expected to be completed in late 2015.
Mitigation banks are consolidated, permanently protected areas where wetlands or other natural resources are created, enhanced or preserved – and then banked as “credits.” Federally permitted projects that have unavoidable wetland impacts elsewhere help pay for and maintain the mitigation bank’s new or improved natural resources by purchasing the “credits” in compensation for the “debits” of wetlands that their project will destroy or impact.
Wetlands are environmentally important areas that are saturated or covered with water most of the year. Mitigation banks are authorized under provisions of the federal Clean Water Act to prevent the net loss of wetlands nationwide. Mitigation banks are considered preferable to project-by-project environmental mitigation because the bank’s consolidated acreage offers superior benefits in the form of wildlife habitat, water quality enhancement and other natural biological functions.
Greens WetBank was the first of its kind in Harris County when it was created in 1995 near the confluence of Greens and Garners bayous. Approximately 225 acres of Greens WetBank – referred to as Subdivisions A and B – have already been developed for wetlands mitigation since that time. With the additional acreage to be enhanced this year – Subdivision C – the area for wetlands mitigation will total approximately 900 acres, and will be part of a larger tract of Flood Control District properties totaling 1,450 acres.
A portion of the already-developed areas of the mitigation bank include a backup water supply and pump to circulate some water through a portion of the site, and to capture and purify some runoff from the Sam Houston Tollway Northeast. Plans for the new section include a more low-tech approach that works with natural runoff to restore and enhance wetlands. Approximately 3,150 linear feet of strategically placed earthen berms will be added to hold back and direct the flow of rainwater, while nine low-water crossings on existing maintenance trails will also serve to distribute rainfall around the forested site. Those maintenance trails also will be raised slightly to help encourage water to pool behind them. Over a period of several years, the work will enhance existing wetlands and encourage new wetlands to form – resulting in wetlands mitigation credits that can be sold to help sustain the mitigation bank.
In one area of the mitigation bank, 41 acres of native prairie that were overtaken by trees and vegetation since grazing leases ended in the 1980s will be cleared and allowed to revegetate as grassy wetlands. Historic photos show this area was originally wetlands, and contains a “seed bank” of grassy wetland species. Plans call for additional wetlands planting, if needed. This work will add to Texas’ coastal prairies and wetlands, which have shrunk to a small fraction of their historic range. A forested buffer will remain along Greens and Garners bayous, as well as along Sam Houston Tollway Northeast.
For more about the Greens Bayou Wetlands Mitigation Bank, a new website includes history, photographs and other information about credit availability, at www.greenswetbank.org.
ABOUT THE HARRIS COUNTY FLOOD CONTROL DISTRICT
The Harris County Flood Control District provides flood damage reduction projects that work, with appropriate regard for community and natural values. With more than 1,500 bayous and creeks totaling approximately 2,500 miles in length, the Flood Control District accomplishes its mission by devising flood damage reduction plans, implementing the plans and maintaining the infrastructure.