Township of McNab/Braeside Reconstruction/Rehabilitation of Goshen Road

Transcription

1 Township of McNab/Braeside Reconstruction/Rehabilitation of Goshen Road Prepared for: Mr. Ryan Frew, P. Eng. Township of McNab/Braeside 2508 Russett Drive Arnprior, ON K7S 3G8 Prepared by: McIntosh Perry Consulting Engineers Ltd. 115 Walgreen Road Carp, ON K0A 1L0 December 9, 2015

2 Table of Contents 1.0 BACKGROUND Project Scope Classification and Existing Data Design Criteria Scope of Engineering Services PUBLIC CONSULTATION Environmental Assessment Public Consultation SURFACE AND SUBSURFACE Existing Surface and Drainage Subsurface Conditions GEOTECHNICAL RECOMMENDATIONS Pavement Rehabilitation ROAD GEOMETRICS Horizontal Alignment Vertical Alignment Road Allowance Utility Relocations Culvert Replacements Canaan Road Intersection DESIGN OPTIONS AND COST ESTIMATES Option 1: Road Rehabilitation Only No Geometry Improvements Option 2: Road Rehabilitation 60km/hr Design Speed Option 3: Road Rehabilitation 70km/hr Design Speed Option 4: Road Rehabilitation 60km/hr Design Speed Using Comfort Control Recommendation CLOSURE...8 i

3 1.0 BACKGROUND The Corporation of the Township of McNab/Braeside is looking for a cost effective option to reconstruct/rehabilitate Goshen Road. The limits of reconstruction/rehabilitation are from 350m south of Highway 17 to Calabogie Road (County Road 508). The total length of construction is approximately 4.1km. Goshen Road is classified as a rural collector road with a posted speed of 70km/h. The right-of-way (ROW) width is approximately 20 meters and the Average Annual Daily Traffic (AADT) is 211. Safety improvements are necessary on Goshen Road in order to meet current provincial design standards. One of the challenges on this project will be the design of profile improvements in order to have the vertical curves compliant with the posted speed limit. McIntosh Perry recognizes that this is a low volume road and that a balance must be reached between maintaining public safety and limiting capital costs for improvements. Changes to the road profile may require costly utility relocations, which McIntosh Perry avoids with the preferred option. Changes to the profile will also affect adjacent properties and could have adverse effects on driveway slopes and may even require land acquisition. Subgrade conditions will be reviewed for inclusion in the options analysis as corrections to the profile will require rock excavation at the crests and embankment construction on soft soils in the sags, both of which can escalate project costs. McIntosh Perry has investigated the existing conditions and developed options in order to meet the desirable design standards. Current conditions such as posted speed limit, lane widths, shoulder widths, road safety, load restrictions, and road gradient been be reviewed and optimized to minimize costs and meet all provincial and Township standards. It is recognized that some of the safety improvements require large capital costs and that the Township has to prioritize the capital investment in their road network while still maintaining due regard for public safety. Alternatives to avoid high construction costs such as warning signage and decreased speed limits have been considered. A road cost-benefit analysis has been conducted in order to achieve the best road design possible during the preliminary design phase. 2

4 1.1 Project Scope To reconstruct/rehabilitate Goshen Road from 350m (the limits of reconstruction for future Hwy 417 expansion) south of Highway 17 to Calabogie Road (County Road 508). The total length of construction is approximately 4.1km. See Figure 1 for the key map of the project limits. Figure 1 Key Map 1.2 Classification and Existing Data Goshen Road is classified as a rural collector road with a posted speed of 70km/h. The right-of-way (ROW) width is approximately 20 meters and the Average Annual Daily Traffic (AADT) is 211. There have been no recent accidents or flooding reported along this section of roadway. The current access from Goshen Road onto Highway 17 is to be removed in the future with the Highway 417 Expansion Project. The schedule for this expansion and the effect it will have on the traffic volume have not been confirmed, therefore McIntosh Perry will design the road for its current conditions. 1.3 Design Criteria Township has identified the following as their target road design standards: Design Speed: 80 km/h 1 Lane Width: 3.00 to 3.25m with a 3% cross fall Shoulder Width: 1.0m + 0.5m rounding with a 6% cross fall Pavement Structure: Surface Treatment or Hot Mix Surface Maximum grade: 10% 2 Right-of-Way Width: 20m 1 The design speed may be reduced to 60 km/h to address existing severe geometric constraints. 2 The slope may be slightly higher in select locations in order to reduce large fills. 3

5 1.4 Scope of Engineering Services The County has retained the services of a professional engineering firm to assist the County with the detailed design and construction supervision. The scope of the engineering services includes: Geotechnical investigation Topographic Survey Assessment of optimum design criteria Confirm Municipal Class Environmental Assessment Schedule Prepare preliminary and detailed designs with cost estimates Prepare notices and presentation materials for public meeting Coordinate approvals with agencies and utilities Prepare tender document, assist with tendering and award 2.0 PUBLIC CONSULTATION 2.1 Environmental Assessment The Project Schedule(s) in the Municipal Class Environmental Assessment (EA) can be currently classified as an A+ undertaking as per Paragraphs 19 and 24, Appendix 1: 19. Reconstruction where reconstructed road or other linear paved facilities (e.g. HOV lanes) will be for the same purpose, use, capacity and at the same location as the facility being reconstructed (e.g. no change in the number of lanes), and 24. Reconstruction of a water crossing where the reconstructed facility will be for the same purpose, use, capacity and the same location. (Capacity refers to either hydraulic or road capacity.) This includes ferry docks. The Schedule A+ activities are pre-approved however, the public is to be advised prior to project implementation. If during the design process it is determined that the Schedule has changed then the consultation will be adjusted to meet the EA requirements. 2.2 Public Consultation The Public will be consulted once the preliminary design is completed. An Open House and Presentation is tentatively planned for January The purpose of this point of contact is to present the public with design recommendations and to incorporate feedback into the final design. No further design consultation is planned, however meetings with individual property owners may be necessary in order to resolve localized design issues. The public will be notified of construction timing which is currently scheduled for

6 3.0 SURFACE AND SUBSURFACE 3.1 Existing Surface and Drainage While there are poorly performing areas within the limits, typically as shown by extensive pothole patching, the road exhibits generally good drainage conditions, with a good ride condition. Major distortions and wheel track rutting are not evident. Multiple longitudinal and edge of pavement cracking are evident and in areas this has advanced to slight alligatoring and further to areas of extensive potholing as above. 3.2 Subsurface Conditions In general the site stratigraphy consists of approximately 100 mm to 800 mm of pavement structure consisting of an average of 20mm thick surface treatment followed by 180mm to 780mm of sandy gravel (granular fill). The granular pavement fill is underlain by silt, silty sand and sand, which extends to the depth of investigation in all boreholes with the exception of borehole BH15-23 in which the silty sand was underlain by a layer of sandy silty clay before reverting back to silty sand. In boreholes BH15-25 and BH15-26 the pavement structure was underlain by a layer of sandy silty clay deposit. For classification purposes, the soils encountered at this site can be divided into the following three distinct zones. a) Sandy Gravel to Gravelly Sand (Pavement structure, Granular Fill) b) Silt, Silty Sand and Sand c) Sandy Silty Clay 4.0 GEOTECHNICAL RECOMMENDATIONS 4.1 Pavement Rehabilitation The most cost effective alternative for the rehabilitation of the road is to pulverize the existing surface treatment, mix it with the underlying granular materials, add 150mm of granular A material, and then apply a double surface treatment on the entire road. A couple of isolated areas of subexcavation may still be required. In the case of a major grade raise (i.e. Greater than 300mm), it would be recommended to use 150mm or more of Granular B-Type 1 followed by 150 mm of Granular A. 5.0 ROAD GEOMETRICS The following sections are to be read in conjunction with the design drawings. 5.1 Horizontal Alignment Within the limits of construction, Goshen road is a relatively straight road. The profile does shift slightly from the centre of the right-of-way in a few locations to avoid steep embankments and expensive rock excavation. It would not be economical to move the road to the centre of the right-of-way and therefore only minor adjustments will be made to create a more consistent alignment. 5

7 5.2 Vertical Alignment The existing road has several poor vertical curves with two crest curves with a design speed of 40 km/hr and two more at 50 km/hr. There are two sag curves with a design speed of 50km/hr and one at 70km/hr. All the remaining curves have a design speed of 80km/hr or higher. The cost to design the road with a design speed of 80 or even 70 km/hr is prohibitive with several cuts exceeding 1 metre and fills exceeding 1 to 2 metres. Several driveways would be affected and would create situations where the driveway would be greater than 10%. The amount of land acquisitions increases greatly between the 60km/hr and 70km/hr design speed, which will cause a lot of extra coordination and budget prior to construction. Therefore, McIntosh Perry is recommending that the road be designed for a design speed of 60 km/hr. The final design may need to consider a couple of vertical curves at 60 km/hr due to geometric constraints and functionality of adjacent driveways. These sections of road would be signed to caution motorists of recommended driving speed or hidden driveways. 5.3 Road Allowance Goshen Road has a Road Allowance of 20m. With respect to the extent of some of the cuts and fills, this is a narrow right-or-way. Land acquisition or temporary limited interest agreements are required in select locations in order to maintain the 60km/hr design speed profile with the minimum 2:1 embankments slopes. 5.4 Utility Relocations It was made known during the project start-up meeting that utility pole relocations should be avoided if possible. The hydro transmission line is a major overhead line that had recently been installed. 5.5 Culvert Replacements After a hydraulic analysis of the two main cross culverts (the first is 750m south of Canaan Rd. and the second 175m north of Calabogie Rd.), It has been determined that both do not meet the current standards. The first one also does not meet the length requirements in order to build 2:1 sloping from the edge of shoulder. For this reason, we recommend replacing the 1800mmØ culvert with an 18m long 2000mmØ galvanized CSP. The second culvert close to Calabogie Rd. has a sufficient length but needs to be increased from an 800mmØ to a 1400mmØ to cost effectively improve the risk of flooding. 6

8 5.6 Canaan Road Intersection The Canaan Road intersection has been reviewed and improvements have been determined. Keeping the costs in mind, tree removal to increase sight lines would not be suggested because few trees are within the right of way and the low traffic at this intersection. Furthermore, to reduce the amount of gravel being tracked across the road we would recommend fully paving the shoulders. 6.0 DESIGN OPTIONS AND COST ESTIMATES 6.1 Option 1: Road Rehabilitation Only No Geometry Improvements This option would only reconstruct the road, without improvements to the vertical or horizontal geometry. This would require reduced speed warning signs at many crest and sag curves locations. The minimum work to be done is as follows: In-Place full depth reclamation of bituminous pavement and underlying granular base. Place 150mm of Granular A. Remove and replace select driveway culverts that are either buried or have collapsed. Increase lanes to 3.0m and shoulders to 1.0m. Minor ditching. Double surface treatment applied throughout project limits. Construction cost estimate: $1,150, Option 2: Road Rehabilitation 60km/hr Design Speed This option would reconstruct the road, with improvements to the geometry to attain a 60km/hr design speed. This would require reduced speed limit on the entire road or at a minimum warning signs at select curve locations. The scope of ditching would be increased and all the culverts would require replacement. Land acquisition would be required in a few locations. Construction cost estimate: $1,800, Option 3: Road Rehabilitation 70km/hr Design Speed This option would reconstruct the road, with improvements to the geometry to attain a 70km/hr design speed. The existing 70km/hr posted speed can be maintained as long as the Township accepts a posted speed that is the same as the design speed. This option would further increase the extent of ditching and number of locations where land acquisition is required. Utility pole relocation would also be required at one location. Construction cost estimate: $2,220,000 7

9 6.4 Option 4: Road Rehabilitation 60km/hr Design Speed Using Comfort Control (Preferred Option) This option would reconstruct the road, with improvements to the geometry to attain a 60km/hr design speed. Comfort control rather than headlight control values for sag curves will be used even though there is no street lighting along Goshen Road. During the Options Review Meeting with the Township, this was considered acceptable due to the low traffic volumes, no known accident history, limited construction budget, and only significant modification to two vertical curves within the project limits. This would require reduced speed limit on the entire road or at a minimum warning signs at select curve locations. The scope of ditching would be to improve drainage and lower the ditch centre beneath the road structure. Most of the culverts would require replacement to achieve this. Land acquisition would be only be required at one location and likely could be taken care of with a temporary limited interest agreement since only grading of the ditch back slope on their property would be required. Construction cost estimate: $1,360, Recommendation Option 1 is the most economical solution but does not address safety concerns, the speed limit would have to be decreased significantly, and the poor ditching would not be improved. Options 2 and 3 are costly and outside the Township s budget due to the extent of cuts and fills, land acquisition, utility relocation, and far-reaching driveway reinstatement. Option 4 is a more cost effective solution which is only slightly higher than the budget while still increasing the roadway safety and drainage. Therefore, McIntosh Perry recommends that the road be designed according to Option 4 with a posted speed of 60km/h at an estimate cost of $1,360, CLOSURE We trust that this report suffices the requirements of this project. Please contact the undersigned should you have any questions or concerns. Jordan Stewart, EIT Municipal Engineering Intern Denton Byers, P. Eng. Senior Transportation Engineer 8