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ST9905DR-CS041007 T H £ C I T Y 0 F COPPEL£ October 7, 2004 Ms. Jessica Napier US Army Corps of Engineers Fort Worth District - Regulatory Branch 819 Taylor Street, Room 3A37 P.O. Box 17300 Fort Worth, Texas 76102-0300 Bethel Road I / ST 99-05 USACE Project No. 200400181 Tributary G-1 Modification Dear Ms. Napier: The City of Coppell in conjunction with the firm of Alan Plummer Associates, Inc., (APAI) submitted an application for an individual 404 permit and 401 Water Quality Certification for the uppermost section of Stream G-l, between Freeport Parkway and Coppell Road, in April 2004. You provided comments and revisions to the permit during the April 29, on-site meeting with APA1. The city was directed to restore the section of stream with a natural channel design that contained features such as pools, riffles, and vegetated buffer strips in accordance with the Stream Management manual by I. Craig Fischenich and Hollis Allen. The proposed modifications to Stream G-1 are a part of the Bethel Road I and Bethel Road II projects curremly under design by the engineering firms of TranSystems, Inc., and Freese and Nichols, respectively. Construction of the Bethel Road I project is scheduled to start in early 2005. The city will proceed on schedule with construction of the roadway and drainage improvements and hold off on construction of the channel modifications to Stream G-1. There are several matters we want to present to the Corps of Engineers for consideration prior to proceeding with the 404 permit application and construction of the channel modifications. 1. HISTORICAL USE TranSystems directed the firm of Integrated Environmental Solutions, Inc., (IES) to perform a survey for potential jurisdictional waters of the United States within the project limits of Bethel Road I. The focus was on the ephemeral drainage channel located south of Bethel Road between Freeport Parkway and Loch Lane. lES concluded that the channel south of Bethel Road was the beginning of Stream G-I, and identified the section of Stream G-1 from Freeport Parkway to Coppell Road as jurisdictional waters of the U.S. They based their decision on the presence of the current ordinary high water mark, drainage patterns on the USGS Map, and the hydrologic connection to larger jurisdictional waters. Following the submittal of the permit, the city researched the historical use of the channel south of Bethel Road. The city maintains that this portion of the stream is a drainage channel that was constructed and is still utilized as part of the storm drain system for the drainage area. The Bethel Road I & Il roadway, drainage, and channel improvements are a continuation of the existing storm dram system. The following exhibits provide information on the historical use and existing condition of the channel. Sequence of Development Exhibit 'A' The USGS Map for the Grapevine Quadrangle shows Stream G-I beginning north of Bethel Road and extending northeast to Coppell Road. The FIRM Flood Insurance Rate Map No. 48113C135 $ agrees with the quadrangle map. In addition, the IES delineation study stated that the soil survey shows the channel starting 1500 feet east of Coppell Road. Exhibit 'A-I' 1979 - The Minyards parcel is approximately 35 acres. Detention was constructed with the development and the storm dram system discharged directly into the channel. 1980 - The Coppell Commerce parcel is approximately 32 acres. Burns and Hammond streets were constructed with storm drain systems that discharged into the channel. In addition a flume was constructed at the cul-de-sac on Hammond Street that discharged into the channel. Exhibit 'A-2' 1981 - The existing +-20-foot wide ditch was realigned and replaced with a 20-foot bottom width and 40- foot overall width earthen channel with a flow line of +0.30%. The 60-foot drainage easement was acquired for the construction of the earthen channel. Esters Road was reconstructed with a storm dram system that discharged into the channel. 1987-88 - The U.S. Post Office parcel is approximately 75 acres. No detention was constructed with the development. The reinforced concrete pilot channel and the 8' x 4' and 8' x 5' box culverts were constructed with the Royal Lane Drainage Improvements. The original design for the Bethel Road drainage improvements called for the construction of 2 - 10' x 5' box culverts, but only one box culvert was constructed. The improved storm drainage system for all of the above referenced improvements discharged into the channel. Exhibit 'A-3' 1996 - Minyards constructed an additional building. 2001 - The Koll parcel is approximately 19 acres. Detention was constructed with the development and the storm drain system discharged into the channel. Exhibit 'A-4' The aerial photograph from 1986 does not show a tree corridor on either side of the channel on the south side of Bethel Road. There is a wide tree corridor on either side of the stream from the north side of Bethel Road to the stream's confluence with Grapevine Creek. Existing Conditions Exhibit 'B' TranSystems prepared the contour map in 2004 as part of the jurisdictional delineation of Stream G-1. The contours on the south side of Bethel Road reflect the 40-foot wide earthen channel that was constructed in 1981. The 20-foot wide bottom and 3:1 side slopes are still evident throughout the length of the channel. The contours on the north side of Bethel Road reflect a natural stream channel. The channel is narrower and the side slopes are much steeper. Exhibits 'C' & 'C-I' The cross sections illustrate the differences in the width and side slopes of channel from south of Bethel Road to north of Bethel Road. The depth of the channel is approximately the same on both sides of Bethel Road. 2 Exhibits 'D', 'D-I', 'D-2' & 'D-Y The photographs of the existing channel were taken six days after a 2.28" rainfall event. There are areas of standing water but the majority of the channel is dry. The earthen channel that was constructed in 1981 is still evident in many of the photographs and there is no presence of the current ordinary high water mark in many of the photographs. The city is requesting the Corps to reconsider including the channel south of Bethel Road as pan of the jurisdictional waters of the U.S. There is conflicting data on where the headwaters of Stream G-1 historically initiated and none of the resources have the stream starting at Freeport Parkway. Prior to development in the area, the sheet flow from the surrounding drainage area probably lacked sufficient hydraulic erosion to initiate and maintain a clearly defined channel upstream of Bethel Road. The city acquired a 60-foot drainage easement at the time the channel was constructed for access and maintenance purposes, and for the construction of future storm drain improvements. The city does not have drainage easements on any other section of Stream G-1. The cross sections and photographs illustrate the differences in the bottom width and the side slopes on the man-made channel south of Bethel Road and the natural stream channel north of Bethel Road. 2. EROSION AND FLOODING PROBLEMS Stream G-1 runs parallel to Loch Lane between Coppell Road and Bethel Road causing erosion and flooding problems. The voluntary purchase of the homes in the flood prone areas around Loch Lane is not an option for the city since many of the residents do not want to relocate. The home located at 620 Loch Lane is within the 100-year flood plain and has severe erosion problems that need to be addressed. Exhibits 'E' through 'E-Y illustrate these erosion problems. Exhibit 'E' TranSystems prepared the contour map in 2004 as part of the jurisdictional delineation of Stream G-1. The contours on the north side of Bethel Road show the extent of the erosion and the proximity of the erosion to the driveway and foundation of the house. Exhibits 'E-I', 'E-2' & 'E-Y The photographs show the structures that am impacted by the erosion. The foundation under the brick wall is exposed and the slab north of the brick wall has fallen. The area under the concrete driveway where the 36-inch pipe is located is being undermined and the driveway is cracking and settling as a result. One of the primary objectives in the design of the channel modifications for the Bethel I & II projects was to alleviate the flooding and erosion problems along Loch Lane. The channel was originally designed with a concrete bottom and concrete side slopes but was changed to a grass bottom with gabion basket side slopes to meet the requirements of the permit. The change increased the overall width of the channel and moved the side slope closer to the house at 602 Loch Lane. The stream bank adjacent to the house must be stabilized to prevent the potential failure of the brick wall, driveway and house fouadaf/o~, however the gabion baskets require construction space that is not available. The city would prefer to extend the wall of the box culvert for the stream bank stabilization in this area. If this option is not acceptable, the city is agreeable to discussing other viable options with the Corps. 3. CONSTRAINTS There are many constraints that limit the restoration of Stream G-1 to a natural channel design that contains features such as pools, riffles, and vegetated buffer strips. The overall width of the ehannel within the existing or proposed 60~foot drainage easement leaves very narrow buffer strips on either side of the channel. On the north side of Bethel Road the channel is located between two houses that are 3 approximately 100 foot apart. Them is no tolerance for movement of the channel and there is not enough area along the north side of Bethel Road to acquire a drainage easement any larger than 60 foot. The city will preserve existing riparian trees where possible and restrict construction in the surrounding 100-year flood plain, but the buffer strips will be insufficient for water quality protection, riparian habitat, or stream stabilization. The city has to take the citizen's needs into consideration in the design of a channel. There have been numerous complaints about standing water in the channel from the residents who live along Loch Lane. The standing water is mused by the accumulation of sediment in the streambed. Stream G-1 is an ephemeral stream and the city is unsure whether drop pools or other features that have standing water would be of benefit to the residents. The city also needs to construct a channel that can be maintained. In early 2004, the city established a Mumcipal Drainage Utility System that included fees for various zoning classifications. The fees will be used for Phase II compliance, including the maintenance of storm dram systems. The channel design must protect the existing infrastructure, including a 12-inch samtary sewer main that is located under, and parallel to Bethel Road. The existing sewer can not be lowered due to the flatness of the existing grade. There is approximately six inches between the bottom of the proposed box culvert over Bethel Road and the top of the existing sewer. The center box can not be lowered for the pilot channel. Your review and consideration of these items is appreciated. Once a determination has been made, the city will proceed as necessary to stay in compliance with the USACE regulations for roadway and channel construction. Sincerely, lot inator Department Phone: 972-304-7019 Fax: 972-304-3570 Attachments 4