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DR9306-CS 931215December 15, 1993 Mr. Ken Griffin, P.E. City Engineer City of Coppell P.O. Box 478 Coppell, Texas 75019 RE: Design of Channel Improvements for Stream G-6, Tributary to Grapevine Creek, Coppell, Texas Dear Ken: The following will serve as O'Brien Engineering's proposal for services relative to the referenced project, for a reach of creek approximately 2,800 feet in length. The reach begins at a point nearly 1700 feet upstream of the culvert at Bethel School Road and ends at the creek's confluence with Grapevine Creek. I. OVERVIEW The "City-Wide Storm Management Study" (Management Study), dated January 1991, indicates that three houses lie within the 100 year flood plain under fully developed conditions. The Management Study also indicates that the creek channel is subjected to severe erosion in some areas, and wet, marshy conditions in other areas. The recommended solution for the subject area consists of several parts, which are described in the Management Study as follows: 1) Increase the capacity of the culvert under Bethel School Road by adding a 6 x 10 box to the existing structure. 2) Construct a 12' wide concrete pilot channel 300' long immediately upstream of Bethel School Road. Also construct 4' high retaining walls on both sides of the pilot channel and place rock rip-rap along a 50' long existing vertical wall. 3) For a distance of approximately 900' upstream of the end of the proposed pilot channel clear debris, and grade and re-grass the channel. 4) Increase the channel bottom width to 20' for a distance of 30' downstream of Bethel School Road. Regrade the channel downstream to it's confluence with Grapevine Creek, to provide positive drainage. o'brien engineering p.o. box 334 coppell, texas 75019 phone: (214) 241-0336 fax: (214) 241-0370 Mr. Ken Griffin, P.F-' December 15, 1993 Page 2 II. BASIC SERVICES The following scope of services, defines work to be performed toward the engineering of the above solution with three modifications or clarifications: 1) grading and re-grassing of the channel upstream of the end of the proposed pilot channel will extend 1400' rather than the 900' indicated, 2) the culvert improvements, pilot channel, and retaining walls will be recalculated using a hydraulic model revised with current topography and field conditions, and 3) the work downstream of Bethel School Road to the confluence with Grapevine Creek will consist only of minimal grading in the bottom of the existing channel so as to achieve a positive slope. A. Data Gathering 1. Utilities - Contact utility companies with facilities in the project area and request that all underground utilities be probed and identified with flagging. Obtain "as-built" drawings of drainage, water and sewer facilities in the area. 2. Deed Research - Obtain copies of City records of easements and rights-of-way in the study area. Research county deed records as may be necessary if the City records are lacking. 3. Studies - Obtain copies of soil surveys or boring logs conducted for other facilities in the area. 4. Wetlands Jurisdictional Determination - Prepare a letter to the US Army Corps of Engineers (COE) requesting a jurisdictional determination of the area based on the proposed improvements. Accompany the COE on it's field trip to assess the area. B. Surveying - Conduct a topographic design survey of the area sufficient to produce mapping at a scale of 1"=20' with a contour interval of 1' Obtain dimensions, locations and elevations of culverts, manholes, utility flagging, drainage structures, driveways, trees in excess of 3" in diameter, fences, retaining walls, pools and other physical features which potentially may affect, or be affected by, the proposed improvements. The City will supply a recent aerial photo of the area to assist in identifying features which should be surveyed. Finished floor elevations of the three houses identified as inundated in the Management Study will be surveyed to verify proximity to adjacent 100 year water surface elevations. Mr. Ken Griffin, P.E. December 15, 1993 Page 3 C. Hydraulic Modeling Verification - Use data from the completed topographic survey to verify the hydraulic model used in the Management Study. Typical information to be compared will include channel and culvert geometry and elevations, roughness coefficients, house locations and elevations, and the like. The model will be adjusted to correct minor inconsistencies. The proposed facilities will be tested in the revised model to assure that the projected results concur with those of the Management Study. D. Meet with the City to review topo and modeling results. E. Soils Investigation - Coordinate with a soils testing laboratory to obtain soil samples and conduct standard tests for design purposes. F. Preliminary Design - Based on surveyed information and required drainage capacity, calculate the dimensions, alignment and sizes of the channel and culvert. Prepare preliminary plans to include plan/profile drawings of the pilot channel and retaining walls, earthen channel, and culvert (at a scale of l"=5'v, l"=20'h), details and utility adjustments. Utility adjustments may include relocation of water and adjusting ditch connections within the right-of-way or easement. Gas, electrical, and TV cable line relocations, if any, are to be performed by the appropriate utility company. G. Meet with the City to review proposed configuration and facilities. A set of preliminary plans will be sent to each utility company with facilities in the area for their comments. Final Design - Complete plans, incorporating final utility company considerations and City comments. I. Forward a copy of the final plans to utility companies. Obtain possible further considerations and begin arrangements for any necessary adjustments. J. Engineer's Estimate - Based on completed plans, prepare an engineer's estimate of the cost of construction. Meet with the City to review plans, easement requirements and cost estimate. K. Specifications and Bid Documents - The City will prepare specifications and bid documents for the proposed facilities. O'Brien Engineering will review the draft set of specifications and bid documents and make comments to the City. Mr. Ken Griffin, P.E. December 15, 1993 Page 4 L. Assist the City in presenting the proposed improvements by attending a City Council meeting and homeowner meeting. M. Construction Services 1. The City will prepare the advertisement for bids and any addendums which may be necessary. The City will conduct the pre-bid meeting and the bid opening, and will check contractors' qualifications and bonds. The City will also prepare the bid tabulation. 2. Perform one-time construction staking of line and grade for the following: l) channel grading and grade to drain; 2) pilot channel and retaining wall; and, 3) culvert at Bethel School Road. 3. Construction Administration - O'Brien Engineering will make occasional visits to the site during construction to observe that the work is in general conformance with plans and design intent. The City will conduct inspections, direct the Contractor with any special instructions, prepare routine change orders, review Contractor's pay requests, and coordinate with soils testing laboratory for testing of the concrete in the culvert, retaining walls, and pilot channel. 4. As-Builts - Construction inspection is to be performed by the City. O'Brien Engineering will perform a final "as- built" survey, to include measuring of critical dimensions and elevations, and using the City inspector's "as-built" mark-ups and survey information, prepare "as- built" plans. III. ADDITIONAL SERVICES If additional services, beyond those described are required, these services will be provided as requested by the City. Additional services may include but not be limited to the following: A. Representing Client at city council meetings or P & Z meetings, and at staff meetings beyond those indicated in basic services. B. Preparing special surveys, studies and submissions (other than those identified under basic services) required for approval by any agency having authority over the project or immediate area. C. NOI - At this point it appears that an area significantly less than 5 acres will be disturbed by the proposed improvements. Mr. Ken Griffin, P.E. December 15, 1993 Page 5 In the event that the disturbed area will exceed 5 acres, we will provide a proposal for submitting a Notice of Intent to EPA and for preparing a storm water pollution prevention plan at the request of the City. D. Making revisions to the plans and/or hydraulic model as a result of changes to the basic plan, configuration or location, or as a result of errors in modeling by other parties. E. Request for Map Revision - Stream G-6 has not been included in the study area of FEMA's effective 100 year flood plain. Consequently, no effective flood plain has been delineated. If it becomes necessary to make a request to FEMA to obtain approval of the project, or to prepare a submittal declaring the limits of the flood plain, we will provide a proposal for these services at the request of the City. F. Wetlands Mitigation - It appears that the total jurisdictional wetlands in the project area is less than one acre, which will allow for nationwide permitting under the section 404 permitting process. If mitigation is required, however, whether as a result of more than one acre involvement or by requirement of COE, we will provide a proposal for the necessary services at the City's request. G. Services associated with preparation of easements required by the proposed construction. Construction staking beyond one-time staking. I. Construction inspection. J. Assistance to Client as an expert witness in any litigation with third parties. K. Additional copies of Plans and Specifications beyond 25 sets. IV. COMPENSATION Compensation to O'Brien Engineering for the above described services shall be according to the following schedule. Billings will be on a monthly basis and payment is due within 10 days of the date of the invoice. 1. Basic Services Items I.A.1. through I.M.4., for a lump sum fee of $28,700. 2. Additional Services - on an hourly basis as requested by the Client. A separate proposal will be provided on any Mr. Ken Griffin, P.E. December 15, 1993 Page 6 additional services item at the Client's request. 3. In addition to compensation for specified services, O'Brien Engineering will be reimbursed for direct project expenses incurred during the course of the project such as permitting fees or items which are requested by the Client, such as blue prints beyond 12 sets, photographs, printing, expenses for travel outside the metroplex, messenger services and the like. The Client may terminate this contract, if done so in writing. The Client agrees, in such case to compensate O'Brien Engineering for reasonable expenses incurred and for services completed through the time of termination, on an hourly basis at our hourly rates (copy of the rate schedule is attached). O'Brien Engineering appreciates the opportunity to submit this proposal. The estimated time for completion of design surveying and engineering services is eight (8) weeks form the date of the order to proceed. The required time for services related to construction is dependent upon numerous outside factors. We are prepared to begin work immediately. The terms of the contract shall be valid for a period of 18 months from the date of this proposal. If the proposal meets with your approval, please sign and return one copy for our files. Sincerely, ACCEPTED: O'BRIEN ENGINEERING CITY OF COPPELL O'Brien, P.E. incipal Title Date HOURLY RATES November 1993 SENIOR HYDROLOGIST $ 75.00 SENIOR ENGINEER $ 65.00 GRADUATE ENGINEER $ 55.00 SENIOR TECHNICIAN $ 45.00 TECHNICIAN $ 35.00 THREE PERSON SURVEY CREW $ 70.00 DRAF?SPERSON $ 25.00 COMPUTER TERMINAL $ 8.50 o'brien engineering p.o. box 334 coppell, texas 75019 phone: (214} 241-0336 fax: (214) 241-0370