Attachment 11 SP1 FSH 7709.56b.pdf

WO AMENDMENT 7709.56b-2014-1

EFFECTIVE DATE: 11/24/2014

DURATION: This amendment is effective until superseded or removed.

7709.56b_zero_code

FSH 7709.56b - TRANSPORTATION STRUCTURES HANDBOOK

Table of Contents

02 - OBJECTIVE

03 - POLICY

05 - DEFINITIONS

09 - REFERENCES

DURATION: This amendment is effective until superseded or removed.

02 - OBJECTIVE

Plan, locate, survey, design, construct, operate, and maintain road and trail bridges and other engineered structures in a cost-effective, safe, and efficient manner, consistent with road and trail management objectives. This Handbook is intended for use by Engineers and Technicians who perform transportation program activity and management at all levels of the Forest Service.

03 - POLICY

Plan, locate, survey, design, construct, operate, and maintain road and trail bridges and other engineered structures in accordance with applicable provisions of Title 23, Code of Federal

Regulations (23 CFR), Executive Orders, direction in the FSM 7700 series, and this Handbook.

Ensure that the above listed activities are performed and checked by qualified individuals.

05 - DEFINITIONS

In addition to definitions in FSM 7705, FSM 7720.5, FSM 7722.05, FSM 7723.05, FSM 7730.5, FSM 7736.05, FSM 7737.05, and the NBIS, the following definitions apply:

Annual Peak Flow. The maximum discharge that occurs during each year of record.

Bankfull Discharge. The flow of a stream at bankful stream width which occurs on average every 1-3 years.

Bankfull Stream Width (Bankfull). The width of a stream’s surface when water has risen to a point where the banks are beginning to be overtopped and water is beginning to overflow onto the floodplain.

Clear Span. The distance between abutment faces of bridges, or between the inside of culvert corrugations, measure parallel to the centerline of the roadway.

Flow States:

1. Steady or Unsteady Flow. Indicates whether flow parameters such as discharge, depth, and velocity change with time at any cross-section.

2. Uniform or Non-uniform Flow. Indicates whether there are velocity or depth changes along the length of the channel. Non-uniform flow can be subdivided into gradually varied and rapidly varied flow.

3. Subcritical or Supercritical Flow. Indicates whether the flow at a particular cross-section is controlled by downstream conditions (subcritical low-flow velocity and high depth) or by upstream conditions (supercritical high-flow velocity and low depth).

DURATION: This amendment is effective until superseded or removed.

Ford. A paved or unpaved stream crossing where the road profile has been dropped to near the stream channel bottom and all stream flow crosses over the riding surface of the crossing.

Geomorphic Design. A channel design that addresses the average bankfull channel dimensions, natural stream gradient, bedform, and planform of a stream; attempts to replicate them through a structure; reconnects the stream within the structure to the upstream and downstream channels; and meets most fish and other aquatic organism movement and habitat needs.

Hydraulic Capacity Design. A design that accommodates the maximum design flood, but which does not necessarily take into account the effects of debris and sediment transported in the flood water.

Hydrograph. A graph of flow versus time that gives the base flow of a stream prior to a rainfall event and also shows the increased flows over time, including the maximum peak flow, that result from the rainfall event.

Low-Water Structure. A structure, including a low-water bridge or a vented ford, designed to pass floods of a selected frequency over a traveled route.

Recurrence Interval. The number of years before there is a 50 percent chance a particular flood flow will have occurred.

Stream Simulation. A design approach where the stream channel through the crossing simulates the dimensions, character, and processes of the adjacent natural channel, ideally presenting no more of an obstacle to movement of organisms than the natural channel.

09 - REFERENCES

The following Forest Service Handbooks are available at http://www.fs.fed.us/cgi-bin/Directives/get_dirs/fsh. Reference these Handbooks to plan, design, construct, operate or maintain transportation structures:

1. Road Preconstruction Handbook, FSH 7709.56.

2. Road Construction Handbook, FSH 7709.57.

3. Road Maintenance Handbook, FSH 7709.58.

4. Trails Management Handbook, FSH 2309.18.

http://www.fs.fed.us/cgi-bin/Directives/get_dirs/fsh http://www.fs.fed.us/cgi-bin/Directives/get_dirs/fsh

DURATION: This amendment is effective until superseded or removed.

7709.56b_10

CHAPTER 10 - PLANNING

10.2 - Objectives

11 - PRELIMINARY PLANNING

11.1 - Travel Analysis

11.2 - Travel Management Decisions

11.3 - Road and Trail Management Objectives

11.4 - Alternatives

11.5 - Project Development Process

12 - PROJECT FUNDING

13 - REQUIRED DESIGN INFORMATION

14 - PROJECT ENGINEERING REPORT

14.1 - Report Contents

14.2 - Report Preparation, Review, and Approval

DURATION: This amendment is effective until superseded or removed.

10.2 - Objectives

To prepare and submit environmental documents, feasibility studies, and engineering reports necessary to design bridges and other engineered structures in a timely manner in order to provide road and trail access to meet land and resource management plan objectives.

11 - PRELIMINARY PLANNING

11.1 - Travel Analysis

Travel analysis assesses the current forest transportation system and identifies issues and assesses benefits, problems, and risks to inform decisions related to identification of the minimum road system per 36 CFR Part 212.5(b)(1); designation of roads, trails and areas for motor vehicle use per 36 CFR Part 212.51; and development of transportation facilities. Travel analysis is done at various scales. It is the Forest Service’s process for the identification of issues and concerns involving cumulative effects and connected actions that may be associated with transportation developments.

Travel analysis is documented in a report. The report may contain information on concerns identified in the travel analysis process about cumulative effects and connected actions as well as recommendations for alternative projects to be considered through environmental analysis and decision making to best accomplish management objectives while mitigating concerns.

Bridge engineering expertise may be necessary to conduct a proper travel analysis. This is particularly true in developing costs for stream crossing structures, and where cumulative watershed effects have been identified or where concerns regarding passage of aquatic species have been identified.

Further direction on travel analysis is found in FSM 7712 and FSH 7709.55, chapter 20.

11.2 - Travel Management Decisions

Travel management decisions include adding a route to or removing a route from the forest transportation system, constructing a National Forest System (NFS) road or NFS trail, acquiring an NFS route through a land purchase or exchange, decommissioning a route, approving an area for motor vehicle use, or changing allowed motor vehicle classes or time of year for motor vehicle use. This includes decisions to construct or reconstruct bridges and other structures.

Travel management decisions involve environmental analysis and decision making, including appropriate public comment and involvement. Decisions are documented in accordance with the

Forest Service’s NEPA regulations at 36 CFR part 220 and NEPA procedures at FSH 1909.15, where applicable.

DURATION: This amendment is effective until superseded or removed.

Professional bridge engineering expertise may be necessary in decision making. The expertise provides advice to decision makers and the public on the relative costs involved in alternatives, constructability of alternatives, temporary environmental impacts during construction, and long-term environmental impacts and benefits once structures are in place.

Further direction on travel management decisions is found in FSM 7715.

11.3 - Road and Trail Management Objectives

Road and Trail Management Objectives (RMOs and TMOs) document the intended purpose of an individual road or trail in providing access to implement a land and resource management plan as well as decisions about applicable standards for the facility. RMOs and TMOs should be based on management area direction and access management objectives. RMOs and TMOs contain design criteria, operation criteria, and maintenance criteria.

Further direction on RMOs is found in FSM 7714 and FSH 7709.59, chapter 10. Further direction on TMOs is found in FSM 2353.

11.4 - Alternatives

Alternatives for design of a particular bridge or structure must be based on the travel management decision and the applicable RMOs or TMOs. Within the limitations of the decision and applicable RMOs or TMOs, it is appropriate to consider several alternative designs and select the one that best meets the RMOs or TMOs and minimizes costs over the life of the structure.

11.5 - Project Development Process

Each organizational unit having authority to approve structural designs and plans should develop a method for displaying authorities, responsibilities, and the anticipated sequence of activities for each project. The following considerations should be addressed for each project:

1. Establish a timeframe for each sequential phase of the work.

2. Assign coordination responsibilities and approval points, and delegate required authority (FSM 7722.04 and FSM 7723.04).

3. Establish a timeframe for completion and determine the steps required to complete within that timeframe. Document the sequence of activities and time requirements associated with each step. Designate individuals or staffs responsible for completing each step and those who shall provide input or be contacted to coordinate the project work.

DURATION: This amendment is effective until superseded or removed.

4. Give each project an appropriate name and number and determine tentative coordination, field work, and design needs. Establish the project scope by identifying the preferred structure type and estimating the size, cost, and projected completion date.

5. Include Engineering personnel responsible for transportation structure preconstruction work (FSM 7722.04) to provide needed technical input in planning activities.

6. Identify specific work and coordination needed for meeting the following:

a. Forest Plan requirements (FSM 7712).

b. Environmental requirements (FSM 7721.12).

c. Requirements of Executive Orders 11988 (Floodplain Management) and 11990

(Protection of Wetlands) (FSM 7701.4).

d. Requirements for Resource Specialist input found in the travel management decision and RMOs/TMOs.

e. Requirements of cooperative agreements relative to road jurisdiction and maintenance (FSM 7730).

f. Hydraulic (sec. 34 and sec. 60), hydrologic (sec. 50), geotechnical (sec. 31), structural design (secs. 70 and 80), and construction engineering requirements

(FSM 7721.3).

g. Site surveying requirements (sec. 32).

h. Contract administration requirements (FSM 7722.41 and FSM 7723.31).

i. Wild and Scenic River requirements (36 CFR part 297).

j. U.S. Army, Corps of Engineers 404 general permit requirements (33 CFR part

330).

k. U.S. Coast Guard permits for activity in navigable waterways (33 CFR parts 114 and 115).

l. Power withdrawals (FSM 5520).

m. Fish and wildlife protection (36 CFR part 241 and FSM 2610).

n. Biological Evaluations for Threatened and Endangered Species (FSM 2670).

DURATION: This amendment is effective until superseded or removed.

o. Archeological and cultural resource preservation requirements (36 CFR 296 and

FSM 2360).

p. Local and State laws and regulations related to transportation planning

(FSM 7712.1).

q. Water quality (FSM 2532) and/or water rights (FSM 2541).

r. Wilderness protection and management requirements (36 CFR part 293 and

FSM 2320).

12 - PROJECT FUNDING

Ensure that funding for the project has been secured and approved in accordance with Regional procedures for implementing an annual program of work, such as the capital investment program or the timber sale program (36 CFR 212.2(c)).

13 - REQUIRED DESIGN INFORMATION

The following documents and information should be developed and included with the Project

Engineering Report (sec. 14).

1. Topographic map (sec. 32).

2. Road and trail design information (sec. 33).

3. Foundation investigation data (sec. 31.3).

4. Stream channel survey data (sec. 34).

5. Information on existing structures and photographs (sec. 35).

6. Hydrologic data and stream hydraulic analysis (secs. 50 and 60).

7. Inspection reports for existing structures (sec. 81).

8. Evaluation of the load-carrying capacity of existing structures (sec. 83).

DURATION: This amendment is effective until superseded or removed.

14 - PROJECT ENGINEERING REPORT

The project engineering report should contain the project description and background; the documentation and display of the applicable travel management decisions, documentation, and display of the RMOs/TMOs; project and management requirements; and basic engineering data needed to design the structure.

14.1 - Report Contents

Develop a written report for each project that includes the following:

1. Identify the project name, number, and location.

2. Discuss the preliminary planning process outlined in section 11.

3. Identification of the RMOs/TMOs (sec. 11.3). Include resources to be served, type and amount of traffic, safety, and environmental considerations, whether the road is a public road (FSM 7720.5), and restrictions on road use. Identify environmental or other site-specific constraints.

4. Include design information and documents listed in section 13.

5. Include road design elements and standards (FSM 7720.05 and FSH 7709.56, sec. 42).

Include the number of lanes, roadway width, shoulder width, curve widening, clearances, design speed, and sight distance. Also include the road maintenance level (FSH 7709.59, sec. 60) and the vehicle for which the structure is to be designed.

6. Discuss the alternatives to a bridge, culvert, or low-water structure that were considered (sec. 11.4).

7. Recommend structural alternatives that the designer should consider. Display the reasoning and the associated costs such as the following:

a. New structure.

b. Replacement structure.

c. Rehabilitation.

d. Reduced design loading.

e. Alternative structure types, such as low-water structures.

DURATION: This amendment is effective until superseded or removed.

8. List project management requirements and other information needed by Project

Engineers (preconstruction and construction) for preparing the design and contract documents and for administering the construction contract. As a minimum, include the following:

a. Identify source of technical assistance for interpretation of the road or trail design and contract plans. Describe coordination between resource management areas if needed.

b. Identify timeframe for preconstruction work remaining to be completed.

Coordinate with the design office the time requirements for project design and completion of construction plans, specifications, and estimates. Where outside design services are used, include the time needed for contract award and review.

c. Determine funding source(s) (sec. 12) and the amount programmed for design, construction, and construction engineering.

d. List all other project management concerns that may affect structure design or construction, such as personnel qualified and available to perform construction inspection (FSH 7109.17), environmental constraints, time limitations, provisions of cooperative or cost share agreements, right-of-way acquisition, coordination with the

Corps of Engineers, State, county, or other local government officials, and esthetic requirements (color, type of material).

9. List design requirements established for the structure type and size. List all criteria regarding site conditions, such as road alignment, vehicle and pedestrian use, and stream conditions that will affect the design or construction of the structure. Include the following:

a. Design criteria.

(1) Design loading and frequency (sec. 72.2).

(2) Utilities to be incorporated in the structure or to be considered in design.

(3) Navigation within the stream or clearances for underpasses and overpasses.

(4) Road template and right-of-way limits. Include curve or slough widening, superelevation or crown, curve radii, fill and cut slope ratios, and so forth.

(5) Bridge and approach railing (need, type, and finish) (sec. 72.3).

(6) Sidewalk requirements, if applicable.

DURATION: This amendment is effective until superseded or removed.

(7) Special signing requirements.

(8) Availability of material sources, such as aggregate and riprap.

(9) Foundation conditions (sec. 31.3).

(10) Hydrology (sec. 50). The report should contain observations, calculations, and recommendations for the site from the Forest Staff Officer for hydrology studies.

The following data are to be included:

(a) Drainage area used on a U.S. Geological Survey (USGS) map (or copy) along with a terrain description, discussion on soil type(s), vegetative cover, and surface storage.

(b) Stream flow records including location of gauge(s) date of peak recorded flow, quantity of peak recorded flow, and flood frequency interval of that flow. Discuss the probable cause of the flow (if known), such as snow melt, snow melt and precipitation, precipitation only, or other causes.

(c) Other historical information, such as performance of existing structures during past flows (state structure length, type, and elevation), water levels observed by markings on the channel banks or eyewitness accounts, debris or ice problems, and scour or deposition problems.

(d) Calculations supporting the design discharge at the selected frequency. The design discharge frequencies for bridges and major culverts should be the 100- year flood, or as established by Regional guidance (sec. 50).

(11) Hydraulics. See sections 50 and 60 for additional direction. A description of hydraulic conditions should discuss analyses made and the results of the analyses in the form of recommendations. Items to be discussed should include:

(a) Manning's "n" value (channel roughness factor) determined and used in the analysis based on stream characteristics, photographs, and references used for comparison.

(b) Stream gradient, stream cross-section, and velocity used in calculations.

(c) Recommendations should be based on calculations, including high-water elevations for design, desirable stream cross-section, and maximum allowable velocities for limiting fisheries impact and scour potential.

(d) Comments on debris and ice hazards at the site.

DURATION: This amendment is effective until superseded or removed.

(e) Recommendations on scour potential and use of riprap or other measures for protection from scour. Include extent of riprap coverage and class of riprap needed.

(f) Comments relative to fisheries' concerns (maximum velocities, baffles needed, estimated length of time of construction work in stream).

(g) Minimum freeboard for ice and debris.

(12) Recommended bridge deck wearing surface, if any.

(13) Vehicle design speed.

(14) Soil and water corrosion potential.

b. Construction considerations.

(1) Construction seasonal limitations.

(2) Stream access requirements and constraints.

(3) Construction and traffic bypass limitations (location, loading, volume, and speed).

(4) Road access limitations for construction components and equipment (girders and cranes).

14.2 - Report Preparation, Review, and Approval

Prepare the project engineering report to fully display and document the needed project information. The size and complexity of the report will vary with the project scope and complexity. Use project data sheet(s) developed by the Bridge Program Manager for routine data included in the report.

The project engineering report should be signed and dated by the individual assigned responsibility for its completion, and reviewed and approved by the Forest Engineer.

Submit the report to the Regional Bridge Engineer.

DURATION: This amendment is effective until superseded or removed.

7709.56b_20

CHAPTER 20 - STRUCTURE LOCATION

20.2 - Objectives

20.3 - Policy

21 - RECONNAISSANCE

22 - SITE SELECTION

23 - FITTING THE STRUCTURE TO THE SITE

DURATION: This amendment is effective until superseded or removed.

20.2 - Objectives

To place bridges and culverts in locations that will be cost-effective and best meet road management objectives (RMOs) for roads and trail management objectives (TMOs) for trails.

20.3 - Policy

Locate roadway alignments and fit structure sites in accordance with preliminary studies that have been coordinated with RMOs, TMOs, and travel management decisions.

21 - RECONNAISSANCE

Make a reconnaissance of the area to determine the most promising structure site(s) that meet overall transportation needs (FSH 7709.56, sec. 22). Involve Resource Specialists as needed.

Use information about topography, soils, geology, hydrology, and vegetation to identify sites for field review. Visit each proposed site to gather specific information for evaluating each site.

22 - SITE SELECTION

Conduct detailed studies of the most promising sites. Select an appropriate site where the road or trail and drainage structure will achieve the RMOs or TMOs. Also consider the following:

1. Avoid sites where changes in hydraulic characteristics affect the adjacent resources and downstream non-Forest Service owned lands.

2. Place the crossing on a straight stretch of stream. However, in valleys where stream channels meander, do not rule out sharp bends as possible structure sites; because they often indicate the presence of erosion resistant material and a stable point in the stream reach.

3. Use a 90-degree crossing where possible.

4. Avoid curves and steep grades in road or trail alignment.

5. Cross at a narrow stream channel section.

6. Select sites with stable soils and slopes.

7. Select sites where rock is at or near the surface.

8. Avoid locations that require a channel change.

9. Avoid stream crossings where channels are subject to channel degradation, shifting, aggradations, or excessive scour. For example, determine if the following conditions apply:

DURATION: This amendment is effective until superseded or removed.

a. The stream banks and streambed are erodible. Also determine the depth of erodible material.

b. The stream reach at the site location has been stable in both the horizontal and vertical direction in recent history.

c. Any upstream or downstream manmade structures are planned that might affect stream stability.

d. The crossing is in an alluvial fan, as they are subject to aggradation and sudden shifts in alignment. Preferably, cross near the apex or head of the fan.

10. Avoid locations downstream from slope failures, debris jams, and ice jams.

23 - FITTING THE STRUCTURE TO THE SITE

Fit structures to proposed sites during preliminary design. Prepare conceptual plans of each site being considered. Study and compare the various road alignments, gradients, possible locations for abutments and piers, height of bridge decks, clearances, the possible outline of the toe of approach fills, and any other factors pertinent to the specific design. Prepare a rough cost estimate for each alternative site to assist in making a final selection.

Obtain an appropriate balance between the bridge cost and the road cost. Include construction, maintenance, and user costs.

Align the structure with the road so that earthwork is balanced and cuts and fills are minimized.

Consider the following criteria:

1. Locate bridges and culverts consistent with RMOs/TMOs, stream degradation effects, and esthetics.

2. Use straight approaches to bridges of at least 50 to 100 feet if possible.

3. Minimize curvature of the approaches. Limit any curves entering or leaving a road bridge to a minimum radius of 100 feet if possible, or at least within the horizontal curve criteria established for the design speed of the road. Remember that widening to accommodate off-tracking of large trucks on curves near a structure will require wider roadway widths than necessary on a straight alignment (FSH 7709.56, ch. 40, sec. 42.45).

4. Design the structure and approaches on a constant gradient where possible. Sudden changes in grade at a bridge can increase the live load impact forces on the bridge.

5. Place bridges on a slight grade where the road or trail geometry permits. Avoid bridge deck profile grades greater than 5 percent.

DURATION: This amendment is effective until superseded or removed.

6. Ensure adequate clearance under a bridge to allow flood waters, floating ice, or debris to pass during high runoff.

7. Locate bridge substructures out of stream channels where possible. This will tend to lower costs and reduce potential for scour and damage from debris.

8. Avoid constricting waterways with approach fills, abutments, or piers. This will mitigate potential failures that may result from scour during floods.

9. Protect fish habitat and fish passage by minimizing streambed disturbance and limiting changes in water velocity and depth.

10. Evaluate the advisability and cost of using longer span bridges with less costly abutments, such as spill-through and stub abutments, in lieu of shorter structures that use retaining wall abutments. Cantilever wall type abutments reduce superstructure costs but are significantly offset by increased abutment costs.

11. Consider construction access in bridge location decisions. A contractor will generally need equipment on both sides of a stream to build a bridge. Providing such access can have significant cost and environmental impacts.

12. When replacing an existing bridge, consider any requirements in the travel management decision and the RMOs/TMOs regarding maintenance of traffic during construction. The cost and environmental effects of any necessary temporary crossings for public access and the costs of any necessary detours must be considered.

DURATION: This amendment is effective until superseded or removed.

7709.56b_30

CHAPTER 30 - SITE SURVEYS

30.2 - Objectives

30.3 - Policy

31 - FOUNDATION INVESTIGATIONS

31.1 - Field Reconnaissance

31.2 - Preliminary Investigation

31.3 - Foundation Investigation Report

31.4 - Final Investigation

32 - GUIDELINES FOR PREPARING TOPOGRAPHIC MAPS

32.1 - Use of Photogrammetry

33 - ROUTE DESIGN INFORMATION

34 - STREAM CHANNEL SURVEY

35 - ADDITIONAL DATA

35.1 - Information on Existing Structure

35.2 - Information on Nearby Structures

35.3 - Photographs

35.4 - Staging Area Information

DURATION: This amendment is effective until superseded or removed.

30.2 - Objectives

To conduct site surveys, including foundation investigations, site reconnaissance, preparation of topographic maps, and stream channel surveys, and to secure other pertinent data related to preparing adequate structure design information.

30.3 - Policy

Conduct a site survey for all bridges, arches, and long span arches. Conduct a site survey for large culverts as needed. Make the site survey commensurate with the complexity of the site and the proposed structure.

31 - FOUNDATION INVESTIGATIONS

Conduct a foundation investigation for all structures. Vary the amount and type of investigation effort dependent upon a number of factors, such as structure type; site characteristics, including foundation conditions; access; availability of equipment; economics; and available time.

Consider structure type and foundation conditions as the primary elements that determine the type and degree of foundation investigative effort needed. Coordinate the evaluation of these factors for each site with the geotechnical personnel who will conduct or coordinate the investigation effort and with involved project and Forest Management personnel.

Consider a variety of methods for foundation investigation work, dependent upon the conditions outlined above. Investigations may range from visual observation of site conditions and mapping of geological conditions to test pits or extensive soil borings over several alternate sites.

Where necessary, supplement these investigations with other geophysical or remote sensing techniques.

Where rock outcrops are present and drilling is not necessary to determine the extent of rock or its quality, perform limited geologic mapping of abutment and pier footing sites to describe and display foundation conditions. Where appropriate, for sites that will use relatively shallow footing depths, excavate properly logged test pits.

Where time permits and conditions warrant, conduct the bridge foundation investigation effort in three phases:

Phase 1. Conduct field reconnaissance work to identify geotechnical investigation needs and to assist in selecting the specific crossing site and/or the bridge type.

Phase 2. Conduct preliminary investigation work to identify subsurface conditions at the crossing site.

Phase 3. Conduct final investigation work to obtain data for specific abutment and/or pier designs. At less complex sites, only phases 1 and 2 may be appropriate.

DURATION: This amendment is effective until superseded or removed.

31.1 - Field Reconnaissance

Coordinate with the Regional Bridge Engineer and the Regional or Forest Geotechnical Engineer to determine project scope and complexity.

Review known or recorded information for the structure site, such as previous designs, available soil and geological studies, and aerial photographs.

Conduct a site visit with appropriate personnel to classify soil and rock types, to determine their condition and stability, and to obtain information on topographic features, natural flora and fauna, evidence of subsurface water, and any manmade features. Inspect natural lakes and adjacent slopes in the area and study the natural drainage patterns.

Develop a soil profile (field cross section) that depicts the anticipated subsurface conditions, including the distance to bedrock for use in the preliminary design and planning and in conducting the investigation.

31.2 - Preliminary Investigation

Conduct a foundation investigation based on the recommendations of the designer and the materials and Geotechnical Engineering Specialists. Use a preliminary design drawing, depicting bridge location and tentative substructure locations and types, as a guide for the investigation and location of drill sites at the proposed location of piers and abutments.

Use seismic or resistivity investigations only in conjunction with borings or test piles, or where subsurface conditions are predictable, based on knowledge of local geology and adjacent structures.

Perform borings or dig test holes to locate ground water.

Investigate sites for short, simple structures, generally those less than 20 feet long, and trail bridge sites thoroughly enough to determine the capacity of soils for design of the abutments.

Investigate the general area around the proposed bridge site to determine the need for subsurface drainage systems.

DURATION: This amendment is effective until superseded or removed.

31.3 - Foundation Investigation Report

The Geotechnical Engineer should analyze the information obtained from the field investigations and summarize all findings in a report that includes the following:

1. Description of the field investigation procedures, location of test borings, and other tests performed. Provide a log of the test borings.

2. Narrative of laboratory tests and results.

3. Analysis and description of soil and site conditions.

4. Analysis of channel stability conditions.

5. Recommended design parameters for the foundation types, including soil capacities and recommended bridge substructure type(s).

6. Recommended stream bank protection measures.

7. Recommended excavation and dewatering requirements at the site during construction.

Maintain a copy of the foundation investigation report in the permanent bridge design file.

31.4 - Final Investigation

Conduct additional investigation work at specific abutment and/or pier sites when the foundation data from the preliminary investigation is incomplete or insufficient for performing an adequate bridge design. Coordinate with the Design Office to determine the specific data that are needed before initiating final investigation efforts.

32 - GUIDELINES FOR PREPARING TOPOGRAPHIC MAPS

Prepare the topographic map using either conventional, on-the-ground survey and mapping procedures or photogrammetric methods, as appropriate. Make sure the area covered in the topographic map is sufficient to design and detail the structure, the approaches, and related improvements such as dikes, channel improvements, bank protection measures, detour structures, and flood stage overflow channels. Generally, this work encompasses the total width of the flood plain.

DURATION: This amendment is effective until superseded or removed.

Follow these guidelines for preparing the map:

1. Establish a horizontal and vertical geometric control point commensurate with the structure. For most bridges and culverts do the following:

a. Use the same horizontal and vertical geometric control point for the bridge site survey as used for the overall road project. Do not use different elevation datum, especially where two structures are affected by the same storm flow and interact in passing that flow.

b. Show bench mark locations, descriptions, and elevations. Establish vertical geometric control by using primary bench marks, intermediate bench marks, and elevations of appropriate stakes/hubs and traverse stations. Temporary bench marks used for obtaining contours and cross sections should be to the nearest 0.1 foot.

Establish elevations of all construction bench marks to 0.01 foot. Close all level circuits for accuracy checks.

c. Establish horizontal geometric control by using preliminary (P) or final (L) line survey points and stationing. Install reference points and run traverses along the stream to establish base lines for dikes or channel changes. Measure the centerline of any existing bridge and substructure units to 0.01 foot. For existing structures, show elevations to the nearest 0.01 foot at both ends of all bridge seats, including piers.

Measure angles to the nearest 30 seconds. Obtain closure across the stream for all sites either by direct measurement or by triangulation.

d. When Global Positioning System (GPS)/Global Navigation Satellite System (GNSS) equipment is available, collect and record latitude and longitude data at a point on each end of the proposed structure.

2. Prepare the site survey map on a reproducible material that is durable and dimensionally stable. Alternatively, use electronic media or computer software to transmit site survey data in a suitable format, with electronic data showing a real world (1:1) scale.

3. Use a scale of either 1 inch = 10 feet or 1 inch = 20 feet and a maximum contour interval of 2 feet to display site survey data on a site plan. Use a dimensionless ratio for scale when using metric measurements.

4. Show the location and identify all subsurface explorations, such as drill holes and test pits.

5. Show true "north" arrow and road data, including the road name and number and distance to the nearest town. Indicate existing roads and structures with dashed lines.

Orient the map so that road stationing is from left to right.

DURATION: This amendment is effective until superseded or removed.

6. Identify section corners, land lines, and right-of-way limits if they are within the area of the topographic map. Give the Forest and Ranger District name and legal land survey description as is customary for legal land descriptions in the State where the project is located. In areas with the Public Land Survey System (PLSS), provide the legal land subdivision part (such as NW1/4SE1/4…), the land parcel (such as section or protraction block) number, township number, range number, and principal meridian name, as well as the State and local governmental unit name (county, township, parish, borough) In States without a PLSS, provide a legal land description consistent with State land surveying and land description standards and requirements.

7. Show GPS/GNSS coordinate information when available.

8. Show stream name and direction of flow.

9. Locate and identify stream banks, types of ground cover in the approach areas, edge of stream, islands, rock outcrops, large boulders, gravel and sand bars, debris jams, overflow channels, side streams, old channels, scour areas, backwater areas, high-water marks (date, where possible), ground water elevation, and other items important to the location of the structure.

10. Locate existing constructed features such as buildings, fences, ditches, pipelines, and utility lines. Indicate vertical clearances of overhead facilities.

11. Provide a title block on the map for names or initials of individuals preparing the map and checking it. Include survey date, map completion date, Forest, District, road number and name, bridge number and name, and related data.

32.1 - Use of Photogrammetry

Consider using photogrammetry in developing topographic maps for sites that are in relatively open country (less than 50 percent crown cover). Specify aerial photography that will provide photogrammetric measurements at a reasonable level of accuracy, indicated by the root-mean-square error method for geometric control. Contact the Geometronics staff for specific information.

Consider using existing resource photography and using high-altitude photo data as the geometric control.

Consider ground-based photography where there are overhangs that cannot be mapped with vertical photography or where sites are too hazardous to map with ground methods. This method may also be used for small sites for which aerial photography may not be economical.

DURATION: This amendment is effective until superseded or removed.

33 - ROUTE DESIGN INFORMATION

Obtain the plan and profile sheet for the section of road or trail encompassing the bridge site.

Show stations and angle of intersection between the centerline of the proposed route and the centerline of any intersecting roads, railroads, or trails at the bridge site.

Plot the ground profile along the proposed roadway centerline using the same scale as the topographic map. Do not exaggerate the vertical scale. Extend the profile 100 to 150 feet beyond the extreme limits of the proposed bridge or to the limits of the flood plain, whichever is greater. Make sure the ground profile agrees with the topographic map.

Prepare a typical cross-section sheet showing sections of the proposed route and any existing roads or trails that will remain in place or that will be reconstructed. Show the relationship of the ground profile to the centerline and edges of the proposed route on the cross-sections. Consider the need for additional width to permit proper installation of guardrails on the approaches to bridges.

34 - STREAM CHANNEL SURVEY

See U.S. Department of Agriculture, Forest Service. Stream Simulation: An Ecological Approach to Providing Passage for Aquatic Organisms at Road-Stream Crossings (sec. 60.8).

Include survey data, description of stream and physical ground characteristics, estimates of engineering data needed for hydraulic design, and photographs of the site.

Establish a base line and a beginning cross-section location for the drainage channel.

Show the stream survey geometric control line, including traverse stations, elevations, and cross-section locations on the topographic map. Extend the geometric control line an adequate distance up and downstream especially where data will be used to perform in-depth hydraulic analyses using hydraulic engineering software. Provide cross-sections taken at 25-50 foot intervals and at all angle points along the geometric control line.

Include stream cross-sections taken at all critical stream sections, such as locations of stream ends, sand and gravel bars, debris points, rapids, points of stream gradient changes, points where the channel is restricted, and at the intersection of the road and stream centerlines. Show on the stream cross-section, locations of stream bottom, water's edge, high water mark (if visible or known), top of bank, breaks in the ground, and location of significant vegetation. Length of cross-sections should include the entire flood plain.

Obtain dates of previous floods and information on drift, ice conditions, and other pertinent events.

Classify streambed material by the percentages and sizes of sand, gravel, cobbles, and/or boulders, and specify vegetative cover for hydraulic calculations. Include an estimate of Manning's "n" value (channel roughness factor), a description of any debris and/or ice problems, DURATION: This amendment is effective until superseded or removed.

bank cutting, scour or stream degradation or aggradations. Take photographs to indicate the streambed conditions and materials. Make an estimate ("straw test") of the velocity of the stream when possible. Include records from stream gauges near the site when available.

35 - ADDITIONAL DATA

35.1 - Information on Existing Structure

If a replacement structure is involved, recommend whether elements of the existing substructure can be considered for use in the new structure, or whether they may serve as false work during construction of the new structure. If so, include measurements of the existing substructure and copies of the original or as-built plans, if available.

35.2 - Information on Nearby Structures

Obtain information on any existing structure(s) in the vicinity of the proposed structure, including foundation type, waterway opening, overtopping, and flood damage history. Include upstream and downstream distances from the proposed structure to the existing structure(s).

35.3 - Photographs

Provide photographs that accurately depict all pertinent site conditions, including road or trail approach views, views of the flood plain, upstream and downstream views, streambed material and condition, rock outcrops, foundation material, and existing facilities. Show the centerline and stationing of the traveled way. Indicate on the topographic map the point and direction from which the photographs were taken.

35.4 - Staging Area Information

Locate areas near the bridge site that may be suitable for staging of manpower, equipment, and materials during construction. Provide photographs and measurements of these sites and measurements of the distance from the sites to the bridge location. Include estimates of any mitigation measures that may be necessary for use of the sites to meet resource management objectives and environmental protection requirements.

DURATION: This amendment is effective until superseded or removed.

7709.56b_40

CHAPTER 40 - PRELIMINARY DESIGN

40.2 - Objectives

40.3 - Policy

40.6 - References

41 - PRELIMINARY DESIGN PROCESS

42 - SELECTING ALTERNATIVE STRUCTURE TYPES

43 - DESIGN CONSIDERATIONS

43.1 - Appearance

43.2 - Waterways

43.3 - Long Term vs. Short Term Structures

43.4 - Modular, Portable Bridges

43.5 - Use of Previously Used Material

44 - ECONOMIC ANALYSIS OF ALTERNATIVES

45 - SELECTING THE ALTERNATIVE FOR FINAL DESIGN

45.1 - Documentation

DURATION: This amendment is effective until superseded or removed.

40.2 - Objectives

To develop preliminary structure designs for bridges, trail bridges, and major and minor culverts that include the following:

1. Development and evaluation of bridge and major culvert alternatives that meet the road management objectives (RMOs - FSM 7714).

2. Development and evaluation of trail bridge alternatives that meet the trail management objectives (TMOs).

40.3 - Policy

Develop preliminary designs for each bridge and major culvert and for trail bridges when the size and scope of the project are appropriate.

40.6 - References

1. American Association of State Highway and Transportation Officials (AASHTO).

“The Manual for Bridge Evaluation. Current edition.” The web address to order this publication is: https://bookstore.transportation.org/browse_bookstore.aspx

2. U.S. Department of Agriculture, Forest Service (USDA-FS). The Least Total

Expected Cost--An Economic Analysis Method for Selection of Culverts and Other

Transportation Structures, EM-7700-9. The web address to order this publication is:

http://www.fs.fed.us/eng/techdev/sdtdc.htm

3. U.S. Department of Transportation. Federal Highway Administration (FHWA).

Hydraulic Design of Bridges with Risk Analysis, FHWA-TS-80-226. March 1980.

The web address to order this publication is: http://flh.fhwa.dot.gov/resources/pse/specs/

4. U.S. Department of Transportation. FHWA. Hydrology, Hydraulic Engineering

Circular No. 19 (HEC-19), FHWA-IP-84-15. October 1984. The web address to order this publication is: http://www.fhwa.dot.gov/bridge/elibrary.htm

5. U.S. Department of Transportation. FHWA. The Design of Encroachments on Flood

Plains Using Risk Analysis, Hydraulic Engineering Circular No. 17 (HEC-17), FHWA-

EPD-86-112. 1981. The web address to order this publication is:

http://flh.fhwa.dot.gov/resources/pse/specs/ https://bookstore.transportation.org/browse_bookstore.aspx http://www.fs.fed.us/eng/techdev/sdtdc.htm http://flh.fhwa.dot.gov/resources/pse/specs/ http://www.fhwa.dot.gov/bridge/elibrary.htm http://flh.fhwa.dot.gov/resources/pse/specs/

DURATION: This amendment is effective until superseded or removed.

41 - PRELIMINARY DESIGN PROCESS

Complete the following preliminary design steps:

1. Select structure types for analysis and comparison.

2. Analyze the alternatives.

a. Develop information needed for conducting the analysis.

b. Conduct an economic analysis (sec. 44).

3. Select an alternative for the final design.

42 - SELECTING ALTERNATIVE STRUCTURE TYPES

Select tentative alternative structure types for analysis.

1. Each alternative should meet criteria and limitations specified in the following:

a. The Project Engineering Report (sec. 14).

b. The RMOs or TMOs (sec. 11.3).

c. The road design criteria (sec. 14.1).

d. The foundation investigation (sec. 31).

2. Also consider the following factors:

a. Stream channel alignment, cross-section, stability, need for protective measures, and channel modifications.

b. The availability of structural components.

c. Resource protection needs, including fisheries.

d. Lowering approach embankments, where possible, so that they are overtopped before the structure itself is overtopped or breached. This may save on construction costs and will reduce the possibility of damage to the structure. Allowing for more damage to the approaches may permit the structure to be made smaller and will normally result in less total cost to repair.

DURATION: This amendment is effective until superseded or removed.

43 - DESIGN CONSIDERATIONS

43.1 - Appearance

Design structures to be compatible with the natural surroundings and to meet visual quality objectives in form, color, and texture.

Locate surface drainage features to avoid causing discoloration of structure components. Use materials compatible with the surrounding environment. Miter large culverts consistent with structural adequacy and safety and bevel inlets to increase flow efficiency. Utilize the input of architects and landscape architects in planning and design activity when appropriate.

43.2 - Waterways

Maintain natural stream conditions at waterway crossings. Ensure that desirable streambed conditions and fish habitat is protected when selecting structure type. When fish use the streams for habitat, spawning, or migration, consider using arches or bridges rather than culverts.

43.3 - Long Term vs. Short Term Structures

Match structure design life with the structure service life identified in the RMOs or TMOs.

When service life is relatively short, consider using modular portable bridge superstructures or other appropriate short-term facilities.

Avoid the following:

1. Replacing a component of a structure with materials that would have a design life less than, or significantly longer than, the remaining service life of the structure of which it will become a part.

2. Repeated disturbance of the streambed and stream banks when a structure is replaced.

3. Inadequate hydraulic capability for the structure design life.

Do not use short-term structures for long-term facilities without the Responsible Official making a travel management decision to do so. Any such travel management decision should be advised by an economic analysis that considers future replacement costs, costs of environmental consequences due to repeated construction activities, management requirements, and long-term maintenance/repair needs.

Use long-term structures for short-term facilities only if structures are designed for relocation and reuse at other sites.

DURATION: This amendment is effective until superseded or removed.

43.4 - Modular, Portable Bridges

Design modular, portable, or reusable bridge superstructures to meet the same criteria used for short-term and long-term structures. Consider site safety requirements, abutment construction and hydraulic design needs, and total life-cycle costs before using a modular portable bridge.

Do not use modular bridges for long-term facilities except where permitted by Regional guidance and when cost analyses indicate lower life cycle costs.

43.5 - Use of Previously Used Material

Do not incorporate structural elements made from previously used materials into structures unless a registered professional engineer certifies in writing that the capacity and remaining life of the material is adequate for the intended use. Consider previously used materials only when a thorough inspection and structural analysis indicates an economic advantage for their use and a level of risk is acceptable.

Obtain approval from the Regional Director of Engineering before using any previously used materials in any road or trail bridge (FSM 7722.04c).

Do not use railroad car body units for permanent or temporary road or trail bridges on National

Forest System roads, trails, or lands.

44 - ECONOMIC ANALYSIS OF ALTERNATIVES

Make an economic analysis of alternatives as part of the preliminary design activity. Economic analysis may be performed in accordance with professionally acceptable procedures such as analyses that consider costs incurred during the entire life of the structure.

45 - SELECTING THE ALTERNATIVE FOR FINAL DESIGN

In addition to…