REPORT TO COUNCIL DORWICK DITCH PETITION REHABILITATION PROJECT JUNE 8, 2016

Transcription

1 REPORT TO COUNCIL DORWICK DITCH PETITION REHABILITATION PROJECT JUNE 8, 2016 Based on a preliminary study by Euthenics, Inc. 1

2 SECTION I GENERAL INFORMATION AND EXISTING CONDITIONS Property owner complaints have been registered for a number of years due to the deteriorating condition of Dorwick Ditch and its tributaries. As a result, the Summit County Engineer commissioned a study to evaluate drainage conditions in the area and determine the costs that may be anticipated should the drainage system be upgraded and placed under County maintenance in accord with the Ditch Petition provisions of ORC 6133 and On April 4, 2016 a petition for improvement of this ditch was received by Summit County Council. A Public Viewing of this proposed improvement took place Friday June 3 rd, 2016 at 2:00 p.m. A Public Hearing is scheduled for Monday, June 20 th 2016 at 4:30 p.m. This document shall serve as the Engineer s Report to County Council required to be submitted on or before the date of the Public Hearing. Field visits were made in the fall of 2014 of the Dorwick Ditch located in Northfield Center Township by the consulting engineering firm of Euthenics, Inc. The ditch runs primarily along the back and side property lines. During the field visit, three main deficiencies that prevent the ditch from functioning effectively were identified. Those deficiencies are as follows: Ditch clogged with debris and overgrown vegetation. (Picture 1) Ditch width is inconsistent. (Picture 2) Ditch has a variable flowline profile and sag areas with ponding. (Pictures 3 and 4) Picture 1 (Dorwick Ditch, Looking North) The side slopes of the ditch are overgrown with vegetation. Over time, various amounts of debris have accumulated along this vegetation and continually decreased the effective channel cross section. Picture 2 (Dorwick Ditch, Looking North) The ditch varies between 15 feet and 25 feet wide. 2

3 Picture 3 (Dorwick Ditch, Looking Northwest There was standing water throughout the length of the ditch. The upper portion of the ditch, parallel with Dorwick Drive, had significantly more standing water due to the lack of a continuous grade along the existing flowline profile. Picture 4 (Marwyck Drive culvert outlet, Looking Northwest) A foot deep pool of standing water at the Marwyck Drive culvert outlet. Roughly half of each existing 20 pipe is submerged. The ditch, much of which was constructed during the development of the residential subdivisions in the 50 s and 60 s runs primarily alongside and back parcel lines. The ditch cross section varies in width as it meanders its way southeast but it is primarily a wide, nonchannelized section (as shown in the picture). Overall, the ditch is in poor condition and does not function well. There are a large number of trees within the potential ditch widening construction limits. A tree survey study should be carried out to determine which trees are within existing and proposed drainage easements. There are a number of fences (wooden, chain link, etc.) and landscaping within the potential ditch widening construction limits. Each item will need to be located to determine whether it can be saved or if it is an encroachment. A number of privately built / owned footbridges are located along Dorwick Ditch and its tributaries. Each structure needs to be inspected to determine if it is located outside of the estimated flow and whether it can be removed and reinstalled. 3

4 The condition of pipe inlets and outlets were observed at: Bayberry Drive - Dorwick Ditch (Northern Extension) Dorwick Drive - Marwyck / Kenwick Ditch Dorwick Drive - Kenwick / Pickwick Ditch Dorwick Drive Beacon Hills Ditch All locations appear to be in good to fair working condition. *Note: The condition of pipes shown for replacement in the Marwyck Drive Storm Sewer Improvement plans was not determined. SECTION II PROJECT NARRATIVE The Dorwick Ditch Rehabilitation Project consists of a number of rear yard ditches and will consist of replacing culverts and cleaning and reconstructing ditch flowline profile to provide a more consistent grade to eliminate ponding and standing water. A map showing the areas to be improved is attached as Exhibit A. All ditches will be re-channelized to provide uniform bottom and side slope. Permit and Regulatory Requirements After consultation with the Ohio EPA Division of Surface Water and the U.S. Army Corps of Engineers, The project is categorized as a routine maintenance project and has an Earth Disturbed Area (EDA) of less than one acre. Such projects are exempt from the NOI permit so long as it has an EDA of less than 5 acres. According to the Flood Insurance Rate Map (FIRM) from the Federal Emergency Management Agency (FEMA), the Dorwick Ditch is not defined as a water of the State and is not in a delineated flood plain area. The map has been included as part of this study. It is anticipated that the ditch rehabilitation will not require any FEMA or Ohio EPA involvement. One concern our office has in clearing the ditch is possible wetlands involvement. A wetlands scientist should investigate the project area to determine the magnitude of any wetlands deconstruction. Cost Estimate Rehabilitation Project The Rehabilitation Project is estimated to cost $505,575. A more in-depth cost estimate will be developed once the detailed plans are completed. The overall costs of the project are as follows: Project Construction: $405,475 Additional Expenses: Surveying, Inspection, 21% $84,500 Advertising and Mailing $3,500 Interest to Finance 3% $12,100 Total Estimated Cost of Project: $505,575. 4

5 SECTION III ASSESSMENT PROCEDURE Cost Estimate Permanent Maintenance As part of Dorwick Ditch Rehabilitation Project, a permanent maintenance program will be initiated. Although a yearly cost for the anticipated maintenance can be determined, the interval at which the maintenance is performed is left to the discretion of the Summit County Engineer. The Ohio Drainage Laws Petition Procedure, which outlines the provisions for the ditch petition process, has been utilized as part of this study. Although the Procedure does not specifically designate a methodology it does state that the assessments are levied on each parcel of land benefited, to pay the cost of construction and maintenance of improvements. After researching various options available to calculate assessments, it appears that the impervious areas method may be best suited for the project. This method takes into account the impact that the runoff from the impervious areas within each parcel has on the overall drainage area. Runoff coefficients established by the Ohio Department of Transportation were used to create the Parcel Benefit Factor. Parcel Benefit Factor = ODOT Runoff Coefficient x Parcel Drainage Area Project Drainage Area Assessments to cover the construction costs are assumed to be collected over 10 years. The annual assessment rate for each parcel is calculated as below: Annual Assessment per Parcel = Parcel Benefit Factor X Project Costs X 20% 10 The perpetual maintenance will be collected annually and will be computed by taking 20% of the construction costs, and then dividing by eight, as shown below: Annual Maintenance Assessment per Parcel = Parcel Benefit Factor X Project Costs X 20% 8 ODOT Runoff Coefficients: Impervious Areas (House, Driveway, Sidewalk, Etc.): 0.90* Grass Covered Areas: 0.50 Woods Covered Areas: 0.20 Grass and Woods Areas: 0.35 * Note: For all parcels that have a house, an impervious area of 3,600 S.F. may be used to represent the house and driveway footprint. The annual assessment per parcel for construction costs, to be paid over 10 years, is as follows: MAX: $1,115, MIN: $3.13, AVG: $179.20*. 5

6 The annual assessment per parcel for maintenance, to be paid in perpetuity, is as follows: MAX: $278., MIN: $0.79, AVG: $44.80*. * Note: The AVG. cost will be applicable to most parcels. SECTION IV PROJECT ASSUMPTIONS Property and Drainage Area Map The Property and Drainage Area Map was created using GIS Data available from the Summit County Fiscal Office and Ohio Statewide Imagery Project (OSIP). All parcel areas used to determine the individual property assessment costs were taken from CAD areas as shown by the parcel line data available from the Summit County Fiscal Office. For precise actual values, the recorded parcel areas established by the Summit County Fiscal Office must be used. All existing drainage structures, ditches, and conduits shown were established from drainage data available from the Summit County Fiscal Office and field visits made during the project. Further investigation will be needed to establish the physical location of these items to construct an accurate drainage area map. All drainage attributes used to determine the individual runoff coefficients and Parcel Benefit Factor were established with the following assumptions: All parcels with a house (including the house footprint and driveway) were estimated with an impervious runoff coefficient of 0.90 for 3,600 square feet. All remaining areas were characterized as grass with a runoff coefficient of 0.50, woods with a runoff coefficient of 0.20, or a combination of grass and woods with a runoff coefficient of Drainage attributes are denoted with a X under the following runoff coefficients: H for house, G for grass, W for woods, and G/W for grass and woods. The existing right of way for any roadway was not included within the drainage areas. Additional investigation of work with the right of way will be performed in the design phase to determine if any right of way area costs will be attributed to Northfield Center Township or Summit County. All improvements within and crossing public street right-of-ways are to be paid by the public entity responsible for roadway maintenance and such costs shall be excluded from the estimate of assessable costs. Existing Site Conditions No drainage calculations or pipe sizing has been performed at this time. All existing conduit is assumed to be of the correct size and grade. The conditions of specific conduits were noted during the field visits as shown in this study. Any conduits not specifically field verified were assumed to be in a fair to good working condition. More detailed analysis will be performed during the design phase of the improvement. 6

7 SECTION V PROJECT RECOMMENDATIONS The entire drainage system consisting of the Dorwick Ditch, its outlet and its tributaries should be rehabilitated, and placed under public maintenance to ensure that the system will properly function in the future. The County Ditch Petition that has been filed under the provisions of ORC 6131 & 6137 will provide the needed rehabilitation and future maintenance. Upon viewing the proposed improvement and studying the drainage area it is the opinion of the County Engineer that the cost of the proposed improvement is not unreasonable and the benefits of the improvement would be greater than the cost incurred. 7