5 ALTERNATIVE SOLUTIONS AND EVALUATION

Transcription

1 Page 23 5 ALTERNATIVE SOLUTIONS AND EVALUATION The process used for the assessment and evaluation of the alternatives follows the procedures of the Municipal Class EA, as described below: Identify a reasonable range of alternative solutions for addressing the Problem Identify the criteria to be used for the evaluation of the alternative solutions Using the evaluation criteria, rank the alternatives in terms of positive and negative effects Select the Technically Preferred Alternative Present the Alternative Solutions and the Technically Preferred Alternative at the Public Information Centre Confirm the Preferred Solution 5.1 Alternatives Considered The following Alternatives were considered during the Class EA process: Do Nothing Rehabilitate the Bridge Replace the Bridge No improvements to the bridge or approaches Repair the existing bridge to acceptable structural and safety conditions Replace the existing bridge with a new bridge that meets geometric, structural, and safety standards. Additional details on the alternatives are presented in Table 5.1. Table 5.1 Alternative Solutions No. Description Work included 1 Do Nothing No work on the bridge 2 Rehabilitate the existing bridge Concrete patch repairs to abutment walls; replace barrier system; patch repairs to girders; patch repairs to deck underside; patch repairs to deck; new waterproofing and pavement 3 Replace bridge with single lane bridge Remove existing structure; replace with new structure (abutments and superstructure) 4 Replace bridge with two-lane bridge of equal span 5 Replace bridge with two-lane bridge of longer span Remove existing structure; replace with new structure (abutments and superstructure) Remove existing structure; replace with new structure (abutments and superstructure)

2 Page Evaluation Criteria The alternative solutions were assessed using four factors, namely transportation; social, economic, and cultural environments; natural environment; and cost. The Factors and the Criteria used are summarized in Table 5.2. Factor Transportation Social, Economic, Cultural Environments Natural Environment Cost Table 5.2 Evaluation Criteria Criteria Operations and Snow Clearance Geometric Design Criteria Safety Property Noise Aesthetics Archaeology and Heritage Fisheries Terrestrial Habitat Surface water and flooding Groundwater Construction Life Cycle Cost 5.3 Evaluation of Alternative Solutions To enable the comparison of the various alternatives, comparative cost estimates and life cycle costs were prepared for each alternative, as summarized in Table 5.3. Table 5.3 Alternative Solutions - Life Cycle Costs No. Description Work included Estimated Cost Approx. Useful Life Estimated Life Cycle Cost 1 Do Nothing No work on the bridge <10 $813,000 2 Rehabilitate the existing bridge, Span = 11.9 m 3 Replace bridge with single lane bridge Span = 11.9 m Deck Width = 5.0m Concrete patch repairs to abutment walls; replace barrier system; patch repairs to girders; patch repairs to deck underside; patch repairs to deck; new waterproofing and pavement Remove existing structure; replace with new structure (abutments and superstructure) $230, $914,000 $713, $770,000

3 Page 25 Table 5.3 Alternative Solutions - Life Cycle Costs No. Description Work included Estimated Cost 4 Replace bridge with two-lane bridge Span = 11.9 m Deck Width = 8.5m Remove existing structure; replace with new structure (abutments and superstructure) Approx. Estimated Life Useful Life Cycle Cost $914, $1,014,000 5 Replace bridge with two-lane bridge Span = 16.1 m Deck Width = 8.5m Remove existing structure; replace with new structure (abutments and superstructure) $1,076, $1,215,000 Each criterion was assigned a score between -5.0 and +5.0, depending on the extent of impact or improvement relative to existing conditions, that is, the Do Nothing alternative. Table 5.4 presents a description of the positive and negative effects of each alternative, and Table 5.5 presents the scores that were assigned to each criterion for each alternative. The scoring for Construction Cost was calculated by prorating the score of 5 by a factor equal to one minus the ratio of the Construction cost of the Alternative to the Highest construction cost, i.e. where C = Cost and HC is Highest Cost. =5 1 The score for Life Cycle Cost was calculated based on prorating the score of 5 by a factor equal to the ratio of the Lowest Life Cycle cost to the Life Cycle Cost of the Alternative, i.e. =5 where C = Cost and LC is Lowest Cost. The evaluation was carried assuming that each factor and criterion would have the same importance. The results of the evaluation are presented in Table 5.6. It is possible to assign different importance values to each one of the Factors. For instance, given that the site and the alternatives will have a relatively minor positive or negative effect on the Social, Economic, and Cultural and the Natural Environments, it is reasonable to provide each of these two factors with 15% of the importance and the Transportation and Cost Factors with 35%. The results are also presented in Table 5.6.

4 Page 26 Table 5.4 Positive and Negative Effects No. Description of Criteria Group Positive Effects Negative Effects Alternative 1 Do Nothing Transportation None Narrow bridge is a concern for snowplow operation Does not meet current geometric design standards Unsafe due to narrowing of road from two lanes to one lane Social, Economic and Cultural None None Environments Natural Environment None None immediate, but could result in pieces of concrete falling into creek 2 Rehabilitate the existing bridge 3 Replace bridge with single lane bridge Cost No capital cost in the near term Bridge will require replacement or closure in about 5 years Cost of maintenance is highest of the alternatives Transportation None Narrow bridge is a concern for snowplow operation Does not meet current geometric design standards Unsafe due to narrowing of road from two lanes to one lane Social, Economic and Cultural None None Environments Natural Environment None None Cost Relatively mid-level capital cost in the near term Bridge will require replacement or closure in about 10 years Life cycle cost Transportation None Does not meet current geometric design standards Unsafe due to narrowing of road from two lanes to one lane Social, Economic and Cultural None None Environments Natural Environment None None Cost Eliminates need to spend funds in rehabilitation Cost of replacing bridge in Replace bridge with two-lane bridge, 11.9 m Span Transportation Width of bridge will be sufficient for snow clearing operations None Meets current geometric design criteria Improves safety at crossing Social, Economic and Cultural None None Environments Natural Environment None if weir not eliminated; some if weir removed Minor effect on fish habitat; however, effects can be mitigated Cost Eliminates need to spend funds in rehabilitation Cost of replacing bridge in Replace bridge with two-lane bridge, 16.1 m span Transportation Width of bridge will be sufficient for snow clearing operations None Meets current geometric design criteria Improves safety at crossing Social, Economic and Cultural None None Environments Natural Environment None None Cost Eliminates need to spend funds in rehabilitation Cost of replacing bridge in 2012

5 Page 27 Table 5.5 Scoring of Alternatives Evaluation Criteria Group Transportation Social, Economic, Cultural Environments Natural Environment Cost Weight Criteria Operations and Snow Clearance Geometric Design Criteria Safety Property Noise Aesthetics Archaeology and Heritage Fisheries Terrestrial Habitat Surface water and flooding Groundwater Construction Life Cycle No. Description of Alternative 1 Do Nothing Rehabilitate the existing bridge Replace bridge with single lane bridge 4 Replace bridge with two-lane bridge of equal span 5 Replace bridge with two-lane bridge of longer span

6 Page 28 Table 5.6 Results of Evaluation of Alternative Solutions No. Description of Alternative Score with No Score with Weights Weights 1 Do Nothing Rehabilitate the existing bridge Replace bridge with single lane bridge Replace bridge with two-lane bridge of equal span Replace bridge with two-lane bridge of longer span On the basis of the results of the evaluation, it can be concluded that alternatives 1, 2 and 3 score substantially lower than Alternatives 4 and 5. Alternative 4 received the highest score when no weights are applied, and when weights are applied. Therefore, it was concluded that Alternative 4 is the Technically Preferred Alternative. This Alternative was carried forward for public input, and was confirmed as the Preferred Solution based on the input received. It should be noted that the structure presented to the public is a structure with a span of 14.0 m, which is longer than the existing, but is shorter than the 16.0 m span examined in the evaluation of alternatives. The reason for the longer span is that the foundations recommended by the geotechnical engineering sub-consultant consist of pile foundations, which necessitated the longer span to enable driving the piles without interference with the existing foundations. Examination of Table 5.6 shows that Alternatives 4 and 5 had scores that are quite similar.

7 Page Construction Options At the Public Information Centre on November 1, 2011, the various Alternatives as discussed above were presented to the public for information. Two Construction Options are available for implementation of the Technically Preferred Alternative, namely Road Closed During Construction or Road Open Staged Construction. Below is a description of the two construction options, their advantages and disadvantages, and their evaluation using evaluation criteria Road Closed During Construction In this Construction Option, the road will be closed to traffic (both pedestrian and vehicular) at the bridge, for a distance of 30 m north and south of Parks Creek. The advantages of this Construction Option are Faster Construction It is the safest for road users and construction workers Requires no additional cost Results in the least disruption to the watercourse and the fisheries Results in the least ecological impacts The disadvantage of this option is that it requires a detour. The estimated maximum additional travel time required is 5 minutes, based on starting on the south side of the bridge, travelling south to Thrashers Road, west to Hwy 37, north to Plainfield, and south to the north side of the bridge. This is the longest detour Road Open Staged Construction In this construction option, the road would remain open to traffic during construction. One lane of traffic would be maintained on the existing bridge while half of the new bridge is constructed adjacent to it. Upon completion of half of the new bridge, traffic would be diverted on to the completed portion of the new bridge and the existing bridge would be removed and the new bridge completed. This is illustrated in Figure 5-1 on the next page. To facilitate staged construction Bronk Road would have to be realigned locally to accommodate the shift in the road alignment which would increase the scope of the bridge replacement project, as the approach road works would have to be extended at least 100 m on each side of the bridge. Realignment to the west would encroach on the Victoria Cemetery property and the existing Water Survey of Canada concrete weir prevents realignment to the east. The introduction of a horizontal curve to accommodate the realignment would not be desirable due to the rural nature of the road and the lack of illumination. Additionally the potential effects on the Parks Creek fish habitat would be substantial and would likely require

8 Page 30 Authorization from the Department of Fisheries and Oceans. For these reasons, staging using the existing bridge is not feasible. Figure 5-1 Staged Construction Using Existing Bridge If the bridge is constructed aligned with the existing Bronk Road centre line, which is the most appropriate design, it will be necessary to provide a temporary crossing to accommodate traffic during construction. This would require construction of a temporary creek bridge and approaches. Figures 5-2 to 5-5 show four possible temporary crossing configurations. It is estimated that the additional cost of the temporary bridge and approaches will increase the cost of the project by about $150,000. In the options where it is necessary to stage the construction of the bridge (Figures 5-3 and 5-4), the cost of construction of the structure could be higher by about $30,000 than the cost of construction of the structure in one operation.

9 Page 31 The staging configuration in Figure 5-2 would encroach on the Victoria Cemetery property and would require placement of fill on the existing creek channel. This is not considered a feasible option. Figure 5-2 Temporary Crossing West of Bridge, New Bridge Constructed in One Stage

10 Page 32 In the staging option shown on Figure 5-3 the temporary bridge and approaches would be entirely within the existing road allowance, but would require installation of road protection structures to permit work on the new bridge. In addition, construction of the new bridge would need to be in two stages. Once the east half of the new bridge is completed, traffic would be diverted to it and construction of the west half could proceed. Figure 5-3 Temporary Crossing West of Bridge, New Bridge Constructed in Two Stages

11 Page 33 The staging option illustrated in Figure 5-4 is similar to the one shown in Figure 5-3, but reversed. The biggest constraints on this option are the existing water level gauge and weir, and the overhead wires, which will have to be relocated during construction. Figure 5-4 Temporary Crossing East of Bridge, New Bridge Constructed in Two Stages

12 Page 34 The staging option illustrated in Figure 5-5 is similar to the one shown in Figure 5-2, but reversed. The biggest constraints on this option are the existing water level gauge and weir and the overhead wires, which will have to be relocated during construction. Figure 5-5 Temporary Crossing East of Bridge, New Bridge Constructed in One Stage

13 Page Evaluation of Construction Options The two Construction Options were evaluated using the following evaluation criteria, similar to the criteria used for the evaluation of the main alternatives. Traffic Safety Property Noise Aesthetics Archaeology and Heritage Fisheries Terrestrial Habitat Surface water and flooding Groundwater Construction The summary of the evaluation is presented in Table 5.7. On the basis of the evaluation of the Construction Options, it was concluded that the most appropriate one is to close the road during construction and implement a detour.

14 Page 36 Table 5.7 Construction Option Evaluation Evaluation Criteria Alternative Solutions Transportation Social, Economic, Cultural Environments Natural Environment Cost Overall Rating Weight No. Description Work included Traffic Safety Property Noise Aesthetics Archaeology and Heritage Fisheries Terrestrial Habitat Construction No Weights Weights 1 Staged Construction 2 Bridge Closed Bridge constructed in two stages. One lane of traffic Road closed during construction Estimated duration = 3 months