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<br />!.UVv <br /> <br />e <br /> <br />e <br />Port of Houston Authority No. 21520(Revised) <br />Galveston Bay, along the Bayport Ship Channel, <br />City of Pasadena, Harris County, Texas. <br />Attachment 1, Sheet jo of J'l:(Revised May 2003) <br /> <br />. <br /> <br />Port of Houston Authority <br />Wetland Mitigation Plan <br /> <br />Wetland Hydrology <br /> <br />Site hydrology is an important factor contributing to the success of the proposed wetlands. <br />Existing hydrology, south of the drainage canal, will be modified slightly to allow surface water to <br />be impounded on the 70.8-acre wetland site. The proposed wetland design will use low earthen <br />levees to divert a portion of the stormwater runoff flowing across the prop~~, from south to <br />north, and east to west, into the wetlands. Site hydrology outside of the watershed formed by <br />the levees will not be adversely impacted. Water that passes through the created wetlands will <br />be discharged into the Harris County drainage canal at an existing discharge point. <br /> <br />During periods with median levels of rainfall (based on TWaB and NWS data for 1954-2000) <br />the size of the flooded zone will remain relatively constant. By design, the size of the flooded <br />area will vary as a result of the amount of rainfall received in the watershed and the rate of <br />evapotranspiration. The size of the flooded zone will decrease during periods of low rainfall and <br />peak evapotranspiration (June-September), but will not typically fall below 40 acres. <br /> <br />During periods with less than median levels of rainfall, the flooded zone may be significantly <br />reduced or completely lost. A hydrologic model developed for the wetlands indicates that there <br />may be little or no standing water in the weUands from June through September during years <br />with less than median levels of rainfall or years with less than normal levels of rainfall during <br />summer. <br /> <br />. <br /> <br />Performance Standards <br /> <br />8. Hydrology in the proposed wetlands will be evaluated during each monitoring period <br />and results will be reported in the monitoring reports. The footprint of hydrophytic <br />vegetation will vary depending on the water level in the system. When measured at <br />full pool, the combined wetlands should contain 70.8 acres of flooded habitat. During <br />Phase I, the wetland footprints will be measured at full pool at least once each year. <br />The achievement of full pool will demonstrate that site hydrology is appropriate for <br />weUand development. The footprint of hydrophytic vegetation will be used to provide <br />supportive evidence of success. <br /> <br />. <br /> <br />Benchmark Ecological Services, Inc. <br /> <br />May 2003 <br />