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ST9905DR-CS040408JAMES L ALTSTAETTER, RE JEFFREY E CAFFEY. RE STEPHEN j COONAN, RE PEGGy~V GLASS Ph D DAVID A GUDAL ~E A. LEE HEAD IlL RE BETTY L JORDAN RE CLETU$ R MARTIN, RE LORETTA E. MOKRY MARK A PERKINS RE ALAN H PLUMMER JR, RE. DEE RICHARD H SMITH, RE ALAN R TUCKER, RE. R JONATHAN YOUNG, Ph D, RE 84i WEST MITCHELL ARLINGTON,TEXAS 76013-2506 816-0201 April 8, 2004 Mr. Presley Hatcher U.S. Army Corps of Engineers CESWF-PER-R 819 Taylor Street P.O. Box 17300 Fort Worth, Texas 76102-0300 RE: Request for Section 404 Permit Coverage Review for the proposed Modification of Tributary G-1 from Freeport Parkway through Coppell Road South in Coppell, Dallas County, Texas Dear Mr. Hatcher: The City of Coppell proposes to modify the channel of approximately 1,900 linear feet of an ephemeral headwater tributary to Grapevine Creek designated as Tributary G-I. The proposed project includes the modification of the Tributary G-1 channel, which starts at Freeport Parkway, to create a 35' wide earthen bottom width with meandering 5' wide base flow channel and 1:1 side slopes armored with stepped gabion basket retaining wall for a top width of 50' within the existing 60' drainage easement. The proposed channel modification will be conducted in conjunction with proposed roadway improvements to Bethel Road West. The construction of the improved Bethel Road West roadway will include the construction of four 10' x 7' box culverts to convey flows under the roadway. A 1' thick gabion mattress will be installed downstream of the Bethel Road West culverts between the headwalls to dissipate erosive flow velocities. Stream flow will then continue downstream through a modified channel of same design as upstream of Bethel Road. Flows will be conveyed under Coppell Road South through four 10' x 8' box culverts, then the modified tributary channel will transition back to the natural channel approximately 300 linear feet downstream of Coppell Road South. The proposed project includes planting native herbaceous species along the meandering base flow channel and on the channel banks in addition to the planting of a mixture of native canopy trees, small trees, and shrubs to establish a diverse riparian corridor that will be contiguous with native areas downstream of the proposed project area. The proposed modifications to Tributary G-I are needed to accommodate drainage from developed and developing urban areas upstream of the Bethel Road crossing and to provide protection from flooding and erosion that is currently threatening the structural integrity of adjacent private properties. The improved drainage will also Mr. Presley Hatcher Page 2 April 8, 2004 increase traffic safety on Bethel Road and Coppell Road by facilitating drainage from these roadways. Enclosed for your review are individual 404 permit application form ENG4345 with attachments, proposed Mitigation Plan dated April 8, 2004, Texas Commission on Environmental Quality Tier II Certification Questionnaire, and Tier II Alternatives Analysis. Should you have any questions or comments concerning this project, please call Jason Voight or myself at (817) 461-1491. Very truly yours, ALAN PLUMMER ASSOCIATES, INC. Loretta E. Mokry Project Manager LEM:JCV cc: Ms. Suzan Taylor, City of Coppell Mr. Craig Bond, TranSystems Corporation Mr. Chris Moorman, Freese and Nichols, Inc. II. Tier II 401 Certification Questionnaire Impacts to surface water in the state, including wetlands A. What is the area of surface water in the state, including wetlands, that will be disturbed, altered or destroyed by the proposed activity? The proposed activity will impact approximately 1900 linear feet (LF) of an ephemeral tributary (G-1) to Grapevine Creek between Freeport Parkway through approximately 300 LF downstream of Coppell Road South. No wetlands will be disturbed, altered or destroyed by the proposed activity. Is compensatory mitigation proposed? lf yes, submit a copy of the mitigation plan. If no, explain why not. A plan to provide compensatory mitigation on-site as part of the project design is proposed. A copy of the proposed mitigation plan is included with this submittal. Disposal of waste materials A. Describe the methods for disposing of materials recovered from the removal or destruction of existing structures. The existing stmctures to be removed as part of the proposed project will be the box culverts at the Bethel Road and Coppell Road South crossings. The contractor selected shall be responsible for locating suitable disposal sites for removed materials on the project. The City does not allow stockpiling, dumping, or disposal of excess material in floodplains or below the 100-year elevation of drainage ways. Describe the methods for disposing of sewage generated during construction. If the proposed work establishes a business or subdivision, describe the method for disposing of sewage after completing the project. No sewage will be generated at the site of the proposed activity. Construction crews will be provided with a temporary contained restroom facility on-site through the duration of constmction which will be removed from the site upon completion of the project. For marinas, describe plans for collecting and disposing of sewage from marine sanitation devices. Also, discuss provisions for the disposing of sewage generated from day-to-day activities. Not applicable. III. Water Quality impacts Describe the methods to minimize the short-term and long-term turbidity and suspended solids in the waters being dredged and/or filled. Also, describe the type of sediment (sand, clay, etc.) that will be dredged or used for fill. No waters will be dredged with the proposed project. Proposed methods for construction of the modified channel with gabion reinforced side slopes are described below. Topsoil from on-site will be used as back fill and final grading above the gabions prior to planting of specified mitigation planting plan. Describe measures that will be used to stabilize disturbed soil areas, including: dredge material mounds, new levees or berm& building sites, and construction work areas. The description should address both short-term (construction related) and long-term (normal operation or maintenance) measures. Typical measures might include containment structures, drainage modifications, sediment fences, or vegetative cover. Special construction techniques intended to minimize soil or sediment disruption should also be described. Multiple actions will be taken during construction to protect water quality within tributary G1 and downstream receiving waters including Grapevine Creek and associated buffer zones adjacent to the project area. These actions include but are not limited to: confining construction materials and debris to the construction site; stabilizing disturbed areas at the earliest possible date with the use of permanent or temporary vegetation, blankets, or matting, mulch, or sod; isolating the project area from downstream segments by using and maintaining sand bag berms, silt fencing, triangular filter dikes, rock berms, or hay bale dikes below the downstream portion of the project area; protecting vegetation from unnecessary damage; and performing all proposed construction activities within the reaches of the stream channel during low flow conditions to minimize sediment introduction into downstream reaches including Tributary G 1 and Grapevine Creek. The contractor selected for the project will not be directed by city inspector and will ultimately determine the constmction methods used for the channel. Based on city inspector's knowledge and experience with channel and gabion wire basket construction, the proposed improvements will generally be constructed as follows: All construction will be in accordance with the City of Coppell Standard Specifications. The contractor shall obtain a Texas Pollution Discharges Elimination System general construction permit and furnish a site-specific Storm Water Pollution Prevention Plan (SWP3) prepared by a Texas Licensed Professional Engineer prior to commencement of construction. The contractor shall prevent excavated or disturbed material from flowing into the Stream G1 outside of the work limits. A pay item for the preparation and implementation of the SWP3 will be included in the bid proposal. The line and grade of the proposed channel will be staked and a trackhoe may be used to excavate the channel. The excess material will be removed with a front-end loader and loaded onto dump trucks for disposal. The topsoil shall be removed and stockpiled on- site for use on the project. The contractor shall be responsible for locating suitable disposal sites for removal items. This will be stated in the pay item descriptions for all removal material on the project. The City does not allow stockpiling, dumping, or disposal of excess material in floodplains or below the 100-year elevation of drainage ways. A bulldozer and/or grade-all type machinery may be used to establish the finished subgrades for the channel bottom and side slopes as shown in the plans. The excavation and constmction of the proposed channel will be conducted in two phases. First excavation of the east/south side of the proposed channel to the subgrade elevation will be conducted and gabions, box culverts, and headwall installed while conveyance of storm flows is maintained in the existing undisturbed stream channel to the west/north. The existing stream channel will be protected from construction activities during this first phase. After completion of installation of gabion baskets and box culverts on the east/south side, the modified stream channel will be planted with the permanent vegetation specified in the mitigation plan. Storm flows will then be routed to the modified side of the proposed stream channel and phase two construction will begin on the west/north side of the proposed channel. Excavation of the west/north side of the proposed channel and construction activities for installation of the gabion baskets, box culverts, and headwall will be isolated from storm flows in the east/south side of the modified channel. Follow completion of construction, the west/north side of the proposed channel will also be planted with the permanent vegetation specified in the mitigation plan and flows will be rerouted to a meandering base flow channel in the bottom of the modified channel. The gabion wire baskets shall be prefabricated to the size called for in the plans and shall consist of galvanized wire with additional PVC coating. The stone used to fill the baskets shall be clean, and shall be stored and handled in a manner to prevent contamination. Any required geotextile fabric behind the gabion wall will be placed by hand. Any crushed stone required behind the gabion wall will be placed with a backhoe. The contractor will start with the bottom layer of gabion wire baskets. The bottom and four sides of the wire baskets will be assembled by hand and moved into place. Wire baskets will be tied in accordance with gabion technical specifications. The stone material will be placed into the wire baskets with a front-end loader or trackhoe. The top layer of stone will be hand finished to allow for the placement and tying of the wire basket top. Backfill behind the gabion wall will be placed with a backhoe and mechanically tamped to the required density. The contractor will then proceed with the next layer of wire baskets until the channel sides are to the required height. The prefabricated box culverts will be placed with a trackhoe. Backfill behind the boxes will be placed with a backhoe and mechanically tamped to the required density. Finished elevations for the channel bottom, pilot channel, and slopes behind the gabion walls may be established with a bulldozer and/or grade-all type machinery. Topsoil will be placed with a backhoe in those areas designated for vegetation or grass. Upon completion of final grading, the bottom of the modified channel will be seeded with the native grass, legume, and wildflower mixture specified in the mitigation plan. Appropriate erosion control measures will be employed to enable the seeding mixture to germinate and become established in the desired areas. These measures may include but are not limited to the use of a bonded fiber matrix hydromulch or erosion control blanket material. The specified mitigation planting along the upper bank of the modified channel will also be conducted which includes canopy trees, small trees and shrubs, and seeding of herbaceous species including native grasses, legumes, and wildflowers. Erosion control devices will be removed as the vegetation becomes established and provides stabilization of the modified channel. Discuss how hydraulically dredged materials will be handled to ensure maximum settling of solids before discharging the decant water. Plans should include a calculation of minimum settling times with supporting data. (Reference: Technical Report, DS-7810, Dredge Material Research Program, GUIDELINES FOR DESIGNING, OPERATING, AND MAINTAINING DREDGE MATERIAL CONTAINMENT AREAS) If future maintenance dredging will be required, the disposal site should be designed to accommodate additional dredged materials. If not, please include plans for periodically removing the dried sediments from the disposal area. No hydraulically dredging materials will be produced by the proposed activity. Modification of the ephemeral tributary channel will be conducted by excavation during dry conditions. All materials removed by excavation will be removed from the site and disposed of at an upland site. Describe any methods used to test the sediments for contamination, especially when dredging in an area known or likely to be contaminated, such as downstream of municipal or industrial wastewater discharges. Not applicable. Tier II Alternatives Analysis Alternatives A. How could you satisfy your needs in ways which do not affect surface water in the state? The proposed modifications to Tributary G-I are needed to accommodate drainage from developed and developing urban areas upstream of the Bethel Road crossing and to address stream bank erosion downstream of Bethel Road which imperils two private residences. Detention facilities have been required by city ordinance for recent developments within the drainage basin to restrict flows from developed land to pre-development runoff volumes. However, a significant portion of the drainage area is owned by the DFW Airport and lies outside the City of Coppell's jurisdiction and attempts to get commitment from DFW for installation of detention facilities in conjunction with development of this area have not been successful. Requesting and being granted a variance to the City's ordinance requiring drainage capacity to accommodate the 100-year ultimate developed runoff along Bethel Road achieved minimization of impacts resulting from increasing the drainage capacity of Tributary G-1 upstream of Coppell Road and Bethel Road. The reduction of design criteria for drainage capacity and requirement for detention within the upstream drainage area (where possible), results in minimization of impacts to downstream reaches of Tributary G-1 and Grapevine Creek. The reduction in design criteria also reduces the overall width of impact for the modified channel so that high quality hard mast trees (pecans) within the riparian corridor may be preserved. Although efforts to reduce requirements and therefore, minimize impacts of the proposed project have been implemented and achieved, the drainage needs for the area still require modification of the existing degraded ephemeral tributary. channel. B. How could the project be re-designed to fit the site without affecting surface water in the state? The nature of the project does not allow for an alternative design that would not affect surface water in the state. C. How could the project be made smaller and still meet your needs ? As presented above in I.A. and discussed in detail in the proposed mitigation plan dated March 18, 2004, the design criteria have been reduced to allow minimization of impacts to downstream reaches of the ephemeral tributary G-1 and Grapevine Creek. What other sites were considered? 1. What geographical area was searched for alternative sites ? 2. How did you determine whether other non-wetland sites are available for development in the area ? 3. In recent years, have you sold or leased any lands located within the vicinity of the project? If so, why were they unsuitable for the project? The proposed project is to address drainage issues from developed and developing urban areas upstream of the Bethel Road crossing within the drainage basin of Tributary G-I. Therefore, no alternative sites were considered. An alternative design to convey storm runoff flows through a system of box culverts aligned with Bethel Road was evaluated and deemed not practical due to concerns regarding increased erosion potential in reaches of Tributary G-1 downstream of Bethel Road and Coppell Road South as a result of the discharges from the box culverts. The proposed project to modify the reach of Tributary G-1 from Freeport Parkway through Coppell Road South to accommodate drainage from this drainage basin but with a variance from the ordinance-required 100-year storm event capacity in anticipation of construction of additional on-site detention facilities was chosen as the most practicable alternative with the least adverse impacts to downstream receiving waters. E. What are the consequences of not building the project? The consequences of not building the project include potential flooding of roadways and private property and continued threat to the structural integrity of two private residences from existing erosion problems along the channel downstream of Bethel Road. II. Comparison of alternatives A. How do the costs compare for the alternatives considered above ? Detailed description of alternative components and associated costs found in Section lb of Mitigation Plan dated April 8, 2004. Alternative Brief description Costs Alternative 1 No Action Loss of private property due to erosion impacts; Flooding potential of major roadways and adjacent private and public properties Alternative 2 Upgraded box culverts; $5,876,351 Concrete lined open channel Alternative 3 Concrete lined open $4,556,872 channels Alternative 4 Precast stone lined $4,479, 362 channels Alternative 5 Earthen bottom channel $5,691,020 with gabion reinforced side slopes B. Are there logistical (location, access, transportation, etc.) reasons that limit the alternatives considered? The proposed project is to address drainage issues from the developed and developing tracts within the drainage basin of Tributary G-1. Therefore, the alternatives considered were limited to this drainage basin and specifically the drainage basin upstream of Coppell Road South. C. Are there technological limitations for the alternatives considered? Drainage has to be provided within the 60'-wide drainage easement area. D. Are there other reasons certain alternatives are not feasible? Conveyance of the storm runoff from the developed and developing tracts within the drainage basin through a series of box culverts separate from the stream channel were considered, but due to potential adverse impacts from increased erosion potential resulting from the storm culverted discharge to downstream reaches of Tributary G-1 and Grapevine Creek, this option was not considered feasible. III. If you have not chosen an alternative which would avoid impacts to surface water in the state, explain: A. Why your alternative was selected, and The proposed project is to address drainage issues from developed and developing urban areas upstream of the Bethel Road crossing within the drainage basin of Tributary G-1. The proposed project is needed to protect public and private property from potential flooding, to control existing erosion problems that currently threaten the structural integrity of private residences, and to protect public safety. The proposed project alternative was selected because it addresses the described issues and provides protection from accelerated erosion of downstream reaches of the unnamed tributary. Other measures (i.e. detention basins and rerouting of flows) to control storm runoff from developed properties have already been implemented. Conveyance of existing runoff from the urban watershed through a system of box culverts to bypass the natural channel would result in significant erosion potential to the downstream reaches of the channel at the discharge of the box culverts. The proposed project will result in less adverse impacts overall to the tributary system. B. What you plan to do to minimize adverse effects on the surface water in the state impacted. The excavation and construction of gabions, box culverts, and headwalls will be conducted in two phases for the proposed channel, each side of the channel being constructed separately, to provide conveyance and isolation of storm flows during construction. Multiple actions will be taken during construction to protect water quality and minimize adverse effects within tributary G1 and downstream receiving waters including Grapevine Creek and associated buffer zones adjacent to the project area. These actions include but are not limited to: confining construction materials and debris to the construction site; stabilizing disturbed areas at the earliest possible date with the use of permanent or temporary vegetation, blankets, or matting, mulch, or sod; isolating the project area from downstream segments by using and maintaining sand bag berms, silt fencing, triangular filter dikes, rock herms, or hay bale dikes below the downstream portion of the project area; protecting vegetation from unnecessary damage; and performing all proposed construction activities within the reaches of the stream channel during low flow conditions to minimize sediment introduction into downstream reaches including Tributary G1 and Grapevine Creek. Upon completion of final grading, the bottom of the modified channel will be seeded with the native grass, legume, and wildflower mixture specified in the mitigation plan. Appropriate erosion control measures will be employed to enable the seeding mixture to germinate and become established in the desired areas. These measures may include but are not limited to the use of a bonded fiber matrix hydromulch or erosion control blanket material to protect the seeding. The specified mitigation planting along the upper bank of the modified channel will also be conducted which includes canopy trees, small trees and shrubs, and seeding of herbaceous species including native grasses, legumes, and wildflowers. Please provide a comparison of each criteria (from Part ID for each site evaluation in the alternatives analysis. Alternative Costs Logistics Technical Other Limitations 1 Erosion and Limited to Restricted Does not flood impacts drainage area for address City's to public and basin for design responsibilities private Tributary G- to property 1 appropriately protect safety and property 2 $5,876,351 Limited to Restricted Limits drainage area for opportunity for basin for design on-site Tributary G- mitigation 1 3 $4,556,872 Limited to Restricted Limits drainage area for opportunity for basin for design on-site Tributary G- mitigation 1 4 $4,479,362 Limited to Restricted Limits drainage area for opportunity for basin for design on-site Tributary G- mitigation 1 5 $5,691,020 Limited to Restricted Provides drainage area for opportunity for basin for design on-site Tributary G- mitigation 1