Full Public Notice Project Plans Mitigation Plans
Department of the Army Permit SWG-2007-00850, issued to the applicant on 12 February 2010, authorized permanent excavation of 0.31 acres of open water (Taylors Bayou), permanent excavation of 0.21 acres of adjacent herbaceous wetlands (Taylors Bayou), and permanent fill of 0.037 acres of open water (Alligator Bayou), during construction of a new low-flow pump station. Approximately 970 linear feet of temporary steel sheet pile cofferdam was authorized, and the permit required sediment analyses of material to be excavated (58,500 cubic yards) in accordance with Texas Commission on Environmental Quality (TCEQ) criteria prior to construction, placement of contaminated material in a confined upland site approved for the contaminant of concern, and placement of uncontaminated material on uplands of hurricane protection levees near the project site, stabilized by seeding with grass. Compensatory mitigation consisted of enhancement and permanent preservation of a 3-acre forested upland/wetland complex containing 1.75 acres of forested wetlands and 1.25 acres of uplands; the area would be placed in a conservation easement held by a qualified third-party 501(c) (3) land trust. The authorized project has not been constructed, and the applicant proposes a modified project in which the new pump station would be constructed approximately 200 feet east of its originally-permitted location, with modified dimensions of some project features, modified impacts to waters of the U.S., and modified compensatory mitigation. The need for the adjusted project location was brought about by a 33 USC Section 408 review by the Corps, and to decrease steepness of the access road so that heavy machinery can travel from the existing pump station to the proposed pump station.
For the modified project, approximately 1,400 linear feet of temporary steel sheet pile cofferdam would initially be constructed around the construction site to allow excavation and construction in the dry. Construction of the cofferdam would result in 0.82 acre of temporary impact to waters of the U.S. (0.07 acre of estuarine emergent wetland and 0.75 acre of open water). The areas to be excavated consist mostly of man-made levee and access road with small herbaceous wetlands present at the lower ends of the levee toe slope on both ends of the proposed excavation area. The applicant conducted sediment sampling in the portions of Alligator and Taylors Bayous that would be excavated for construction of the pump station expansion and determined that the excavated materials could be disposed of on nearby levees utilizing appropriate best management practices for erosion and sedimentation control as specified in the Sampling Protocol. The new pump station, concrete wing walls, concrete slab, access road, and pumping machinery would then be constructed within the newly excavated area, with a bottom elevation at approximately 4.5 feet below sea level. Excavation and fill activities would permanently impact approximately 1.30 acre of waters of the U.S. (0.76 acre of herbaceous/shrub wetlands and 0.54 acre of open water habitat). Total excavation is estimated at 127,000 cubic yards (cy): 12,650 cy from Taylors Bayou (open water and adjacent wetlands), 7,454 cy from Alligator Bayou (open water and adjacent wetlands), and 106,896 cy from existing upland levee. Approximately 6,000 cy would be reused for fill in the construction of the new pump station, and 121,000 cy would be stockpiled in two proposed excavated material placement areas for future use in levee repairs. These two placement areas would be permanently stabilized with concrete barriers and silt fence, and revegetated to prevent erosion into alligator Bayou or off-site.
Existing PS 16 is one of the main components of the Jefferson County Drainage District No. 7 system, serving approximately 90,000 residents in the cities of Port Arthur, Port Neches, Groves, Nederland, and unincorporated areas of the county. The drainage area flowing to PS 16 is estimated to be 37.6 square miles (24,083 acres), which includes Main A, Main B, Main C, West Port Arthur Road, Pear Ridge, Central, El Vista, Vista Village, and Montrose drainage areas contained within the hurricane protection levees for these communities. In turn, PS 16 pumps water out of the contained system into Taylors Bayou. However, more flow is actually generated within the main outfall system than PS 16 can remove in a peak flow situation or major storm event. The applicant proposes to add the new low-flow pump station to the existing PS16 in order to relieve shallow flooding within the drainage area, and thereby prevent structure and road flooding. The project would allow PS 16 to pump water from surrounding drainages within the contained basin into Taylors Bayou more quickly, adding 1 million gallons per minute (gpm) of pumping capacity to the existing 2.6 million gpm capacity at PS 16, and from a lower elevation. The proposed improvements to PS 16 would maintain continuous low flow, reduce flooding incidents, and provide backup capacity in the event that one or more of the existing pumps should become non-operational.