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Lakewood A-CS 950505 e Specialists in Gabion Construction, Craig Olden, Inc. Soil Stabilization and Erosion Control Structures C~nersi Contractors For ~ Decades ...... May 5, 1995 City o~ Coppell P. O. Box 478 Coppell TX 75019 FAX# 393-3673 Attention: Mr. Ken Griffin, P.E. ~ -_'/ City Eng~ ~l RE: 216 Hollywood COppell, Texas RFQ# 1398 Dear Mr. Griffin, In accordance with your request, we have visited the above ref~ site to determine the extent of the erosion and estimated costs for a solution. This particular site is located on the cut-bank or outside curve of the creek. Higher water velocities occur along the outside of the curve which will have a tendency to be more erosive than for other straighter sections of the creek. In ~_ition, it was observed that the soils are sandy clays which are more prc~e to erosion. This particular reach of the creek appears to have a normal water surface level of approximately 6' above the flow line of the creek with an additional 6 to 9 feet of embankment above the normal water surface. ~_refore, the overall height is approximately 15 feet. At the time of our visit, the water surface was several feet above normal and we were unable to determine the exact heights. In our examination of this site and the adjacent property, it appears that this is not simply an erosion problem, but is also one of soil st~_bility. As we know frc~ previous work upstream, the area in general has a tendency to incur shallow to deeper slides due to the particular soils that exist along the creek. Generally speaking, most of the slides examined appear to have been precipitated by erosional ~cour at the toe of the slope which when combined with other factors cause a slide to occur. Therefore, erosion protection is nece-~y to prevent slides from occurring. However, an erosion control system in many locations must also be designed as an earth retention system due to the inherent soil inst~_bility and the This particular site b~ evidence of an older, apparently deep failure on the North end. The existing topographical features are consistent with what would be expected for an older failure, and is also typical of many similar locations upstream. Based on this visual evidence, we would conclude that the site in question will probably need to be addressed as a soil st~_bility problem and not just an erosion problem. C~ recycled paper P.O. Box 1500 *Little Elm, Texas 75068 Dallas Metro 214/294-5000 *D/FW Metro 214/691-1815 ,1-800-GABIONS · FAX 214/294-2664 PAGE2 May 5, 1995 City of Coppell RE: 216 Hollywood, COppell, It is our ~rstand/z~ that the objective for the proposed work would be to eliminate further loss of the bank includLng the large specimen trees present at the site. The two methods that oould be used to st_~_bilize the bank would be to slope the e~bmnk~t to a se~ble angle and add an erosion oontrol system, or build a vertical wall at the edge of the existing bank. It costs less to slope the ~mbankment. In consideration of the trees, however, sloping of the embankment is not poesible. ~herefore, a vertical structure (wall) fi-c~-.~ 12 to 15 feet in height would be rec~i~ed along the creek bank. Based on the limited sound/rigs below the water, it appears that the Eagle Ford shale formation is present at the flow line in the creek and would provide an accepts_hie bearing and anchoring surface for a wall. We believe a composite anchored gabion wall or a pier foumded gabion wall beginning at the shale approximately 6 to 7 feet below the water surface would be the most cost effective solution. This wall would be similar in many respects to the work recently performed upstream. Assuming a length of 200 feet and a 15' wall height, the estimated cost would be approximately $110,000.00 _+, including geotechnical and stl-actur~l engineering. It is suggested that additional field work be performed in order to verify the embankment heights and depths to shale. This would best be performed when the water surface is closer to the normal level. This additional field work would refine the estimated costs we have given. In order to determine an exact cost, it will be nece~.~y to perform a topographical survey with cross sections of the creek and geotechnical engineering. Either of thmse services could be performed or coordinated by our firm. It is our understand/r~ that tb~ City is being requested more frequently to with some of these situations oocurring in this particular reach of the creek. The estimate for the cost of the 216 Hollywood site should not be used to extrapolate costs for larger areas of the creek as cc~diti~ vary greatly from location to location. We suggest that the City consider an evaluation by a qualified firm to determine the extent of tb~ erosion/soil stability problems, prioritization of the various areas, and estimated costs for different solution alternatives. We have noted that geological conditions vary up and down the creek considerably, and a number of different solutions may be required for different types of conditions. It has been our observation that many engineering firms are not necessarily familiar with this type of evaluation and we suggest that a consultant be chosen carefully. Our firm could coordinate or perform this work, or we could suggest some firms we believe would be appropriate to perform this study. If we can answer any questions or furnish adO~tional information, please do not Sincerely, /s/ craig Craig Olden, President CRAIG OLDEN, INC. March 2 I, 1995 Mr. Jim Witt City. Manager City. of Coppell Coppell, TX 75019 Dear Jim, Thank you for taking the time to meet with the Churches and me this past Monday. The abiliw to interact with the leaders of the community, is one of the many reasons my wife and I moved to a smaller town like Coppell. At issue is the state of erosion along the banks of the creek bordering the houses on Holl~vood Drive in Lakewood Estates. The erosion appears to be concentrated at a bend in the creek behind our house and the houses along either side. We purchased the lot nine months ago and since that time we have lost approximately 12 inches of soil. At this rate we ~vill lose not only the large 60 foot ~- oak trees bordering the creek, but within a few years the creek ~vill be well into our back yard. My neighbors and I would like to pursue the possibility of the ciw putting in a retaining wall to halt the erosion. We feel this project lends itself to the public arena for several reasons, a) The erosion has greatly increased due to the extensive building in Coppell. b) The cost is prohibitive to the individual homeowners, but relatively inexpensive by public works standards, e) The area behind the houses are mandated to be left open by our homeowners agreement. The eroding banks pose a significant hazard to children in the community fishing on the banks of the creek. d) The cit3' has initiated many worthwhile programs to maintain and enhance the natural beauty of the area. The banks along the creek are lined with some the largest and most dramatic trees found an~vhere in Texas. These trees will be lost if something is not done quickly. I truly hope that you are successful in convincing the Finance Committee of the worthiness of this project. If there is an~hing I can do please do not hesitate to call. Your attention in this matter is greatly appreciated. Ty McAden 208 Holl~vood Coppell, Texas 75019 Home 304-0642 Office 706-3759 6688 N. Central Expy. · Suite 800 · Dallas, Texas 75206 * (214) 750-5809 · Fax (214) 750-5842 March 20, 1995 Jim Witt City Manager City of Coppell Coppell, Texas 75019 RE: Erosion of Denton Creek banks on our property Dear Mr. Witt; We are writing you to ask your help in finding an answer to the erosion of the banks along the back of our property at 204 Hollywood Drive. Since moving into our house last June, we have seen the edge of our property along the banks become more and more eroded as the level of the water rises and falls. When the creek is full, especially when the waters from Grapevine lake area are let out via the dam, the water rises to the very edge of our lot. Then as the water level drops, crucial topsoil around the trees that line the bank is washed away. We have two trees that now are undercut by the water's rise and fall. One of them is now starting to lean towards the center of the creek, and will without something being done, fall into the creek. Not only will we lose a tree, but it will block the flow of the creek as all our trees are huge like the one that the city already had to remove two doors down at the Church's. Both our trees and the crucial soil around the edge of the creek area can be saved if the city will do something now. If nothing is done soon, the edge bank along the back of our lot and the trees that line it, are going to suffer irreversible damage from this continuing erosion problem. We want the trees saved by shoring the bank area up as the city has done on other projects in the city. The back edge of our lot now has areas underneath it that are not held up by any soil, and anyone stepping near the edge will fall in the creek. We are especially concerned about this due to the number of children in our area. With the Spring rainy season almost upon us, we urge the City of Coppell to take action now to shore up the bank of Denton Creek. Every time the creek rises and falls, more of the bank is lost forever. More importantly, the danger to others increases as this continues to happen. We are enclosing a number of pictures that were taken last weekend to allow you to see what we are talking about. We will be more than happy to supply you with any other information that may help you reach a decision in this matter. We urge the City to take immediate action. We will be more than happy to show you the area we are concerned about if someone from the City will come out to our address. We thank you in advance for your help. Sam and Mardi Crowley 204 Hollywood Drive Coppell, Texas 75017 Phone Number 304-0644 cc: Engineering Dept. City of CopDell Tom Morton, Mayor of Coppell Lakes of Coppell Homeowner's Association PS. I am also enclosing a picture of the backup of debris and trash that is located under the power lines by the concrete bridge off of Sandy Lake Road. This dirt road leads to the gun range and while located, I believe, in Carrollton is causing Denton Creek to backup. Therefore, it does affect the Coppell area especially homeowners along the creek. March 21, 1994 Mr. Jim Witt City Manager City of Coppell Coppell, TX 75019 Dear Jim, First, let me express on behalf of my husband and myself, just how pleased we are that you have taken time to meet with us and our neighbor, Ty McAden and assess our situation in person. As per our conversations at those meetings on March 13, 1994 and March 20, 1994, I would like to reiterate just how serious the situation is concerning Denton Creek. We live at 212 Hollywood Dr., Lakewood Estates, with the rear of our property on Denton Creek. We are experiencing a full blown erosion problem, along with our immediate neighbors to the south, Susan and Ty McAden at 208 Hollywood and Mardi and Sam Crowley at 204 Hollywood. Our properties seem to be feeling the brunt of the erosion problem in this area due to our properties being on a bend in the creek. We purchased this home less that one year ago, and in that time have witnessed a sizable amount of ground give way and wash down the creek. As I write this letter there is one area that poses an immediate threat. The ground is cracked and having been eroded from the underside could cave in at any time, especially if someone were to step on it. Jim, it is my sincere opinion, that this little creek with it's Eco System intact, existed without threat until just recently. With the burst of development and building in the last three or so years, not only in Coppell, but in surrounding areas, ie:, Grapevine, Flower Mound, Lewisville, etc., this creek is just unable to handle the load, if you will. With the runoff from the frequent storms we experience and considering there is just so much more concrete and so much less ground to saturate, it is no wonder that the creek cannot handle the load. It is amazing to me that a environmental impact study was not made of the area before all of this development was ever started. However, the result is that this creek is suffering from the growing pains of the area. At jeopardy is our properties, as well as, the many, many trees which have lined this creek bed, some I am sure, for hundreds of years. Our homes, the ground soil, and these beautiful trees are all threatened if something is not done and done very soon. I would like to submit to you that this is a very dangerous situation: A) Erosion: Causing undermining of the bank where a wandering child could easily walk on insecure ground which might give way and toss that child into the creek. B) Erosion: Causing the undermining of the bank and loss of valuable topsoil washed away in sizable chunks with every storm and every time Lake Grapevine, via the dam, releases water. Within a short amount of time, Denton Creek will not only be seen from our backyard, but will indeed be our backyard. C) Erosion: Causing loss of soil around the tree roots... putting these huge trees at risk of falling. Enclosed, you will find photos illustrating what happens when a tree falls. Debris starts collecting, the creek starts to damn diverting the water flow and causing threat of flood. We need help to solve this crucial and potentially dangerous situation. We are aware that a dam of wire and rock might be the solution to our problem. We would appreciate an opportunity to stand before the appropriate committee so that we might speak to them of the urgency of this situation. We truly appreciate your time and effort on our behalf. cerely, /~ C~pp~ll, TX, 75019 (1~) 304-0617 CC: Tom Morton, Mayor Kenneth Griffin, City Engineer Lakes of Coppell Homeowner's Association