QnA_4.12.19_clarification_4_12_19.pdf

Questions and Answers during Advertisement for WY TIG US212(9) Beartooth Highway

April 10, 2019

Questions Answers

1 Plan sheets H15 and H16 call out 18” max vertical spacing between reinforcements. Will CFL accept 24” lifts for the MSE wall on the referenced project?

The preliminary design is based on the GRS concept presented in FHWA- HRT-17-080 “Design and Construction Guideline for Geosynthetic Reinforced Soil Abutments and Integrated Bridge Systems”, which employs closer reinforcement spacing than is typical for MSE walls. The spacing depicted on sheets H15 and H16 is 225 mm (9-inch) to meet the GRS requirements. A spacing of 205 mm (8-inch or 3 reinforcements per basket) will likely be suitable. The contractor should evaluate the internal stability for this spacing and submit with the shop drawings in accordance with Section 257.

Added 4/12/2019 – Will CFL accept 24” lifts for the MSE wall on the referenced project? YES, 24” baskets are acceptable for use on the project

2 Plan sheets H15 and H16 call out reinforcements as geogrid or geotextile. With the ‘Contractor-Designed Retaining Walls’ section included in the spec, will CFL accept inextensible, steel soil reinforcements per 720.01(h) for the MSE wall on this project?

The GRS concept is based on the use of extensible reinforcements to form a composite material. Metallic reinforcements have not been studied for this application, and therefore, are excluded from this application.

Added for clarification 4/12/2019 – NO, metallic reinforcements are not permitted.

3 Plan sheet H15 notes a 62% base to height ratio for the reinforcement lengths. We typically don’t supply anything less than 70% B/H, per AASHTO design standards. Is the 62% base to height ratio for the MSE wall on this project correct?

The GRS design methodology does not require the typical 70% minimum base width. The minimum base width provided in the plans is based on preliminary external analysis. Per subsection 257.04(k), the contractor provides final design analysis of the walls, including minimum reinforcement lengths. We recommend that the contractor review the GRS guidelines referenced previously prior to developing their design.

Contractor analysis may determine that additional reinforcement lengths are required. If this is the case, additional shoring may also be required, and should be discussed between the contractor and appropriate sub-contractors.

4 Will stay in place deck forms such as steel pan decking be allowed for forming the bridge deck going over beartooth ravine?

No, cast in-place deck forms such as steel pan decking is not allowed for deck forming on the Beartooth Ravine bridge.

5 Plan sheet G3 foundation plan indicates “anticipated limits of disturbance” at Beartooth Ravine Bridge. Are these limits “anticipated limits”, or are they “hard” limits of disturbance? Will contractors be allowed to propose alternate access/shoring plans that would potentially encroach beyond these limits?

The limits are “Anticipated Limits of Disturbance.” Contractor will be allowed to propose alternate access/shoring plans that would potentially encroach beyond these limits but will have to restore areas used at the completion of the project.