Shannon County Route 19: Spring Valley Bridge Alternatives

Bridge J0420 carries Route 19 over Spring Valley, just south of Round Spring. The bridge is almost 523 feet long carrying two traffic lanes on a 20-foot roadway. The current bridge condition ratings from the last available official inspection in October 2019 indicate the bridge is in satisfactory to poor condition.

The following alternatives were explored.

S-1

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Description:

  • New bridge on existing alignment.
  • A grated two-lane temporary bridge will be built prior to construction of the new bridge and will be removed after the new bridge is constructed.

Advantages:

  • Matches location of existing bridge.
  • Less permanent roadway work.
  • Avoids retaining walls or reinforced slopes.

Disadvantages:

  • Additional cost for temporary bridge.
  • Builds two bridges over the channel during construction.
  • Extensive formwork in the channel.
  • Longer construction period than new bridge on new alignment.

S-2

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Description:

  • New bridge upstream (northwest) of the existing bridge.
  • No temporary bridge required.

Advantages:

  • Shorter construction period than new bridge on existing alignment or rehabilitated bridge.
  • No temporary bridge required; cost savings.

Disadvantages:

  • More permanent roadway work.
  • May need retaining walls or reinforced slopes.

S-3

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Description:

  • Single phase rehabilitation of the existing bridge.
  • A grated two-lane temporary bridge will be built prior to the rehabilitation of the existing bridge and will be removed after the existing bridge is rehabilitated.

Advantages:

  • Matches location of existing bridge.
  • Less permanent roadway work.
  • Avoids retaining walls or reinforced slopes.

Disadvantages:

  • Additional cost for temporary bridge.
  • Remediated concrete of the existing bridge is buried in the structure, possibly requiring further rehabilitation in the future.
  • Shorter life expectancy compared to a new bridge.
  • Extensive formwork in the channel.

No-Build Alternative

Cost: Variable depending on inspection results

Description:

  • This alternative leaves the bridge in place. Routine maintenance of the bridge would continue, but no major rehabilitation would be done. Without a major rehabilitation or replacement project, the bridge would likely be closed in the next 10 years.
  • This alternative is required to be carried forward in the environmental assessment process as a baseline for comparison purposes.

Advantages

  • Little to no environmental concerns

Disadvantages

  • High maintenance costs
  • Doesn't meet current design standards
  • The deck, substructure, and superstructure wouldn't be improved
  • Shorter life span