08-21-2002 Committee Meeting - Laserfiche WebLink

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Port of Houston Authority Wetland Mitigation Plan This wetland project will be considered a success, and the project will be considered complete, when all of the performance standards listed below have been achieved. Wetland Hydrology Site hydrology is an important factor contributing to the success of the proposed wetlands. Existing hydrology, south of the drainage canal, will be modified slightly to allow surface water to be impounded on the 70.8-acre wetland site. The proposed wetland design will use low earthen levees to divert a portion of the stormwater runoff flowing across the property, from south to north, and east to west, into the wetlands. Site hydrology outside of the watershed formed by the levees will not be adversely impacted. Water that passes through the created wetlands will be discharged into the Harris County drainage canal at an existing discharge point. During periods with median levels of rainfall (based on TWQB and NWS data for 1954-2000) the size of the flooded zone will remain relatively constant. By design, the size of the flooded area will vary as a result of the amount of rainfall received in the watershed and the rate of evapotranspiration. The size of the flooded zone will decrease during periods of low rainfall and peak evapotranspiration (June -September), but will not typically fall below 40 acres. During periods with less than median levels of rainfall, the flooded zone may be significantly reduced or completely lost. A hydrologic model developed for the wetlands indicates that there may be little or no standing water in the wetlands from June through September during years with less than median levels of rainfall or years with less than normal levels of rainfall during summer. Performance Standards a. Hydrology in the proposed wetlands will be evaluated during each monitoring period and results will be reported in the monitoring reports. The footprint of hydrophytic vegetation will vary depending on the water level in the system. When measured at full pool, the combined wetlands should contain 70.8 acres of flooded habitat. During Phase I, the wetland footprints will be measured at full pool at least once each year. The achievement of full pool will demonstrate that site hydrology is appropriate for wetland development. The footprint of hydrophytic vegetation will be used to provide supportive evidence of success. Benchmark Ecological Services, Inc. June 2002 y4 LA 6+ S LA