A1_Appendix_A__Bridges_BMPs_2012_5_Pages.pdf

Appendix A – Best Management Practices

By conforming to the resource protection measures, Roads BMPs and other design criteria discussed in this section, the project would also be in conformance with the BMPs established in the Forest Service BMP handbook (USDA Forest service, 2012). Additional relevant BMPs can be found in the Caltrans BMP Manual.

BMP 2.8 - Stream Crossings

References: FSM 7720 – Transportation System – Development FSH 7709.56 – chapter 10 – Preconstruction Decisions FP-03 – Section 107 – Legal Relations and Responsibility to the Public FP-03 – Section 157 – Soil Erosion Control FP-03 – Division 200 – Earthwork FP-03 – Division 550 – Bridge Construction FP-03 – Division 600 – Incidental Construction

Objective: Minimize water, aquatic, and riparian resource disturbances and related sediment production when constructing, reconstructing, or maintaining temporary and permanent water crossings.

Explanation: Stream crossings present the highest risk to water quality associated with roads. Forest management activities often occur in areas that require surface waters to be crossed. Depending on the activity type and duration, crossings may be needed permanently or temporarily. Permanent crossings are designed to meet applicable standards while also protecting water, aquatic, and riparian resources.

Examples of crossings include culverts, bridges, arched pipes, low water crossings, fords, vented fords, and permeable fills. Crossing materials and construction will vary, based on the type of access required and volume of use expected. Optimally, crossings should be designed and installed to provide passage for the flow of water plus anticipated sediment and debris, provide for desired aquatic organism passage, and minimize disturbance to the surface and shallow groundwater resources. Sizing is based on a weighed balance between providing for larger storm events, and cost feasibility, while still meeting other resource objectives.

Construction, reconstruction, and maintenance of a water crossing usually requires heavy equipment to be in and near streams, lakes, and other aquatic habitats to install or remove culverts, fords and bridges and their associated fills, abutments, piles, and cribbing. Such disturbance near the waterbody can increase the potential for accelerated erosion and sedimentation from destabilization of streambanks or shorelines, vegetation and ground cover removal, and soil exposure or compaction. In addition, heavy equipment has potential for contamination of the surface water from vehicle fluids.

Permits may be required for in-stream work associated with stream crossing construction and maintenance projects. There are specific requirements for such projects under the Clean Water Act and implementing regulations. State and local entities may also provide guidance and regulations such as the Forest Practices Act and others.

The risk from construction, reconstruction or maintenance of stream crossings can be managed by using the appropriate techniques from the following list adapted as needed to local site conditions.

Techniques:

Enforcement of the techniques is the responsibility of the inspector and contracting officer’s representative for public works contracts, the inspector and engineering representative for timber sale roads, and the permit administrator for stream crossings constructed or reconstructed under administrative operations (for example, Road Use Permit, Special Use Permit). If stream crossings are constructed, reconstructed, or maintained by force account crews, the project manager and foreman are responsible for adherence to project drawings, specifications, and Erosion Control Plan. The forest hydrologist works in conjunction with engineering and administrative personnel to provide additional monitoring and evaluation during implementation, as needed.

Location and Design

• Locate roads in an interdisciplinary manner with a hydrologist, soils scientist, and geologist if necessary.

• Plan and locate surface water crossings to limit the number and extent required to service the activity.

• Design the stream crossing to pass the 100-year flood flow plus associated sediment and debris; armor to withstand design flows and to provide desired passage of fish and other aquatic organisms.

• Locate and design crossings to minimize disturbance to the waterbody.

• Use structures appropriate to the site conditions and traffic levels:

Favor bridges, bottomless arches, or buried pipe-arches for those streams with identifiable floodplains and elevated road prisms, instead of pipe culverts. Place bridge and arch footings below the scour depth for the 100-year flood flow plus the appropriate factor of safety. Favor armored fords for those streams where vehicle traffic is either seasonal or temporary, or the ford design maintains the channel pattern, profile and dimension. For perennial streams, use vented fords, so that the crossing can pass low flows.

See BMP 2.2: General Guidelines for the Location and Design of Roads, for further guidance.

Construction and Reconstruction – Permanent and Temporary Crossings

• Implement the approved erosion control plan that covers all disturbed areas, including borrow areas, stockpiles, stream diversions, etc. used during stream crossing construction or reconstruction (see BMP 2.13– Erosion Control Plan).

•Use temporary filters, berms, barriers, conveyances or other materials to collect sediment and prevent it from entering surface waters.

• Set the minimum construction limits needed for the project and confine disturbance to within this area.

• Accurately establish and preserve vertical control through design invert and outlet elevations on site for each crossing, to assure that the constructed stream-crossing structure will perform as intended, and promote effective drainage without damage or impact to water, aquatic, or riparian resources.

• Accurately establish and preserve horizontal alignment for each stream-crossing structure, to assure that flows do not erode stream banks or shoreline.

•Install stream crossings according to project design specifications and drawings. Design should sustain bankfull dimensions of width, depth and slope, and maintain streambed and bank resiliency.

• Minimize streambank and riparian area excavation during construction:

•Stabilize adjacent areas disturbed during construction using surface cover (mulch), retaining structures, and or mechanical stabilization materials.

•Keep excavated materials out of channels, floodplains, wetlands, and lakes.

•Install silt fences or other sediment- and debris-retention barriers between the water body and construction material stockpiles and wastes.

• Bypass roads for use during construction are considered temporary roads, and are subject to the all relevant BMPs. •Decommissioning and stabilization of the bypass roads are inherent in the project plan.

• Ensure imported fill materials meet project specifications, and are free of toxins and invasive aquatic or riparian species.

• To the extent possible, conduct operations during the least critical periods for water and aquatic resources: when streams are dry; during low-water conditions; in compliance with spawning and breeding season restrictions.

• Divert or dewater stream flow for all live streams or standing waterbodies during crossing installation and invasive maintenance:

•Return clean flows to channel or water body downstream of the activity.

•Restore flows to their natural stream course as soon as possible after construction or prior to seasonal closures.

• Install downstream collection basins, retention facilities, or filtering systems as needed to capture and retain turbid water.

•Remove collected sediment as needed to maintain their design capacity during the life of the project.

• Construct diversion prevention dips to accommodate overtopping of runoff if diversion potential exists, when shown on project drawings and specifications. Locate diversion prevention dips downslope of the crossing rather than directly over crossing fill; if designed, armor diversion prevention dips based on soil characteristics and potential risk.

• Install cross drains (for example, rolling dips; waterbars) to hydrologically disconnect the road above the crossing and to dissipate concentrated flows.

• Remove all project debris from the water body in a manner that will cause the least disturbance.

• Dispose of unsuitable material in approved waste areas outside of the SMZ.

• Clean equipment used for instream work prior to entering the water body:

•Remove external oil, grease, dirt and mud from the equipment and repair leaks prior to arriving at the project site.

•Inspect all equipment before unloading at site.

•Inspect equipment daily for leaks or accumulations of grease, and correct identified problems before entering streams or areas that drain directly to waterbodies.

•Remove all dirt and plant parts to ensure that noxious weeds and aquatic invasive species are not brought to the site.

• Fuel and service equipment used for in-stream or riparian work (including chainsaws and other hand power tools) only in designated areas (see BMP Road-10).

• Fully suspend logs, pipes, posts and other transported materials when crossing waterbodies and SMZs.

• Restore the original surface of the streambed, lake bottom, or wetland upon completing the crossing construction or maintenance. Construct the surface of the streambed according to project specifications and drawings for aquatic passage projects.

•Stockpile materials by strata or as indicated by specified design criteria when extensive dredging or excavation of these substrates is required.

• Stabilize streambanks, shorelines, cut and fill slopes, turnouts, and other disturbed areas adjacent to the water resource following crossing installation or maintenance:

•Use riprap or rock, wood, vegetation, and other native materials as appropriate.

•Install riprap or other slope protection to prevent erosion from water movement.

•Size rock slope protection for the 100-year flood flow event.

•Use appropriate construction techniques (keying in riprap) and underlayments (filter blankets or other geotextile) to prevent undermining.

•Ensure stone used for riprap is free of weakly structured rock, soil, organic material, and other material not resistant to erosive water action.

•Place stable materials below drainage outlets on erodible soils to dissipate energy.

• Provide effective soil cover (mulch, woody debris, rock, vegetation, blankets) on exposed soil surfaces for both short- and long-term recovery.

• Revegetate disturbed areas.

• Stabilize temporary crossings that must remain in place during high-runoff seasons.

• Remove temporary crossings and restore the waterbody profile and substrate when the need for the crossing no longer exists.

Maintenance

• Implement the approved erosion control plan that covers all disturbed areas, including borrow areas, stockpiles, stream diversions used during stream-crossing maintenance and culvert cleaning (see BMP 2.13– Erosion Control Plan).

•Use temporary filters, berms, barriers, conveyances, or other materials to collect sediment and prevent it from entering surface waters.

• Remove all project debris from the stream or creek in a manner that will cause the least disturbance.

• Dispose of unsuitable material in approved waste areas outside of the SMZ.

• Clean equipment used for instream work prior to entering the stream/creek:

•Remove external oil, grease, dirt and mud from the equipment, and repair leaks prior to arriving at the project site.

•Inspect all equipment before unloading at site.

•Inspect equipment daily for leaks or accumulations of grease, and correct identified problems before entering streams or areas that drain directly to waterbodies.

•Remove all dirt and plant parts to ensure that noxious weeds and aquatic invasive species are not brought to the site.

• Fuel and service equipment used for in-stream or riparian work (including chainsaws and other hand power tools) only in designated areas (see BMP 2.10).

• Maintain and remove buildup of sediment and debris in diversion prevention dips, rolling dips, and waterbars to ensure they are functioning properly, and do not contribute to the hydrological connectivity of the road.

• Ensure that inside ditches are maintained properly, and are relieved at regular intervals to eliminate hydrological connectivity. See BMP 2.4, Road Maintenance and Operations.