Statement of Work_Low Volumn Bridge Design Criteria.docx

STATEMENT OF WORK

LOW VOLUME BRIDGE DESIGN AND SPECIFICATIONS CRITERIA

MAINE NRCS

INTRODUCTION

The Maine Natural Resources Conservation Service (NRCS) requires the services of an Architect-Engineer (A-E) firm to develop bridge design criteria according to the current American Association of State Highway and Transportation Officials (AASHTO) Load Resistance Factor Design (LRFD) Bridge Design Specifications for low volume road applications in Maine.

BACKGROUND AND JUSTIFICATION

The Maine NRCS are replacing failing, undersized culverts with “stream smart” structures that will allow for aquatic organism passage while still allowing landowners access to farm and forest land. Typical bridge designs completed by the Maine NRCS are for local and privately owned roads with low traffic volumes and low speeds. Occasionally bridges are designed for pedestrian and/or livestock crossing only.

All bridge design loads shall be designed in accordance with the current AASHTO LRFD design specifications with a minimum design vehicle load of HL-93. Bridges will be used by farm equipment, logging equipment and road vehicles; logging equipment on privately owned roads will typically be considered overloaded vehicles.

Typical bridges are built for a single landowner in remote areas. Therefore, these bridges can be considered low speeds and low volume use. Bridges are built by local small contractors with light equipment to include excavators up to 30 ton. Consider building bridges from locally available materials including sawn lumber. The proposed bridge design procedure will accommodate bridge designs for various sizes, loads and materials to custom fit any application in Maine.

C. SCOPE OF WORK

The proposed bridge design procedure shall be designed in accordance with current standards and specifications. The following are design conditions that shall be included in the analysis and design procedure:

Bridge Superstructure Base design on current AASHTO LRFD Bridge Design Specifications and AASHTO Guidelines for Geometric Design of Low Volume Roads.

Design valid for bridges with inside abutment spans of 16 ft. to 60 ft.

Consider bridges to be for one-way traffic only.

Consider bridges to be low volume and low speed.

Bridge railing can be attached to outside steel stringers or to top of bridge deck.

Minimum design vehicle load of HL-93 and maximum design vehicle load up to HS-30 equivalent loading.

Consider that bridges are built with light equipment in remote areas with limited access.

Consider bridges to be built with locally sourced materials.

Typical bridge decks are composed of precast concrete panels or sawn lumber.

Bridge Substructure Typical stringers are composed of either steel or timber.

Height range: 4 ft. to 10 ft.

Abutments are typically placed on the following soil types: GW, GP, GM, SW, SP, SM Abutment are typically made from precast or prefabricated products from locally sourced materials.

Consider that abutments are built with light equipment in remote areas with limited access and roads cannot be closed for long periods of time.

Abutments may need to be skewed to the road to allow for appropriate channel alignment; proposed inside abutment span up to 60 ft.

The following are design services that are required for the Maine NRCS in the development of a bridge design criteria for up to 60 ft. inside span bridges:

1. Bridge Superstructure: Provide a design procedure guidance document and spreadsheet that is applicable to the typical bridges used by NRCS in Maine.

a. Written report outlining the design procedure and assumptions for the bridge superstructures with inside abutment spans up to 60 ft. (Note: total bridge length will exceed 60 ft.)

b. The design tool for the bridge superstructure shall be an Excel spreadsheet. Requests to develop and provide a design procedure in a format other than Excel shall be submitted to the Maine NRCS technical point-of-contact for approval. Design tool shall include a detailed user guide that can be used for bridge superstructure designs by NRCS engineers.

c. Typical drawings for bridge superstructures showing pertinent details in AutoCAD format.

d. Virtual training on the use of the design spreadsheets.

2. Bridge Substructure

a. Written report outlining the design procedure and assumptions for the bridge substructures to support the above bridge superstructures for abutments heights of 4-10 ft. using locally sourced precast or prefabricated materials.

b. An abutment design tool shall be an Excel spreadsheet. Requests to develop and provide a design procedure in a format other than Excel shall be submitted to NRCS technical point-of-contact for approval. Design tool shall include a detailed user guide that can be used for bridge substructure designs by NRCS engineers.

c. Typical drawings for bridge substructures showing pertinent details in AutoCAD format.

d. Virtual training on the use of the design spreadsheets.

All work on this project will be performed in English units. All worked performed by the A-E firm will be designed in accordance with NRCS standards and specifications (see Section D. Applicable Documents for additional information). Final submittals of plans and specifications will be made in both reproducible hard copy originals and electronic files. The submittal must include all necessary substantiating data including calculations, design constraints and limitations. All plans will be stamped by a professional engineer licensed in the State of Maine and will include the following certification on all drawings: To the best of my professional knowledge, judgment and belief, these plans meet applicable NRCS standards.

A proposed schedule shall be submitted by the A-E firm with the cost proposal to include, but is not limited to the following items:

1. Bridge Design Progress Reports

a. A preliminary design report including all items listed in the Scope of Work shall be submitted within 60 days of the Notice to Proceed.

b. The Maine NRCS will provide comments within two weeks of receiving the preliminary report.

c. At a minimum, monthly meetings (teleconference or virtual meeting) with the NRCS and the A-E firm to discuss project status.

2. Final Bridge Design

a. Draft design report and tools to be updated based on comments received from the NRCS within 30 days of receipt and resubmitted to the Maine NRCS for review.

b. The final design report, tools and drawings shall be submitted to NRCS no later than 30 days from receipt of Maine NRCS final comments.

c. Virtual training on the use of the design spreadsheets and drawings.

D. APPLICABLE DOCUMENTS

All work shall conform to all NRCS policy documents and technical guidelines and references. NRCS Policy documents will include the General Manual (GM), National Engineering Manual (NEM), NRCS technical material will include all the sections in, but not limited to, the National Engineering Handbook (NEH), National Handbook of Conservation Practices (NHCP), Technical Releases (TR), and Technical Notes (TN).

Following is a list of current design standards and specifications used by NRCS Maine for the design and installation of bridges for various applications:

1. Maine NRCS Field Office Technical Guide (eFOTG), Section IV, Conservation Practice Standard (CPS) 396 Aquatic Organism Passage

2. Maine NRCS Field Office Technical Guide (eFOTG), Section IV, Conservation Practice Standard (CPS) 578 Stream Crossing

3. Title 210, National Engineering Manual (NEM), Part 503, Safety, Natural Resources Conservation Service (NRCS), June 2017

4. Title 210, NEM, Part 511, Design

5. Title 210, NEM, Part 536, Structural Engineering, NRCS, June 2017

6. Title 210, National Engineering Handbook (NEH), Section 6, Structural Design, NRCS, May 2008

7. American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications, 9th Edition, 2020

8. AASHTO Guidelines for Geometric Design of Low-Volume Roads, 2nd Edition, 2019

9. Steel Construction Manual, American Institute of Steel Construction, Fourteenth Edition.