BRIDGE SURVEYS April 24, 2018 - PowerPoint Presentation

BRIDGE SURVEYS April 24, 2018

Bridge Survey Location Request(EPG 747.1) Districts (designer) should request guidance for survey activities related to hydraulics for Bridge designed structures as early in the design process as possible using the Bridge Survey Location Request Form .A form should be submitted for each structure location and preferably in groups rather than individually.

Horizontal and Vertical Control(EPG 238.3.36.1.1 & 238.3.36.1.2) Benchmarks A benchmark is set on each end of the proposed structure. Preferably on opposite corners of the structure.  Referenced Points (Horizontal Control Points)Referenced points are set neareach end of proposed bridge. Preferably, near the top of the stream bank on stream crossings.

Centerline and Offset Profiles( EPG 238.3.36.1.3) Bridge Division will provide this information in the Bridge Survey Location Request form. The three lines of ground profiles provide critical information used in the layout of structures. Existing ground profiles are to be parallel to the roadway . One profile at the centerline of the roadway and the other two offset beyond the outer extents of the roadway fill and ditch lines on each side .

Centerline and Offset Profiles( EPG 238.3.36.1.3) Length Stream Crossings. Centerline and offset profiles for the crossing shall extend 5 ft. above the limits of extreme high water on each side of the channel or as defined by Bridge Division. Grade Crossings. Centerline and offset profiles for the crossing shall extend sufficiently beyond the limits of the proposed structure. See EPG 747.2.3.4.4 Additional Information for Grade Separations and EPG 747.2.3.4.5 Additional Information for Railroad Crossings for minimum extents.

Widening Existing Bridge (EPG 238.3.36.1.4) Bridge surveys for widening existing bridges include the same survey information as that required for new structures. Existing structure not constructed by the state, the bridge survey includes complete details of the existing structure. If the existing structure was constructed by the state, these details are not necessary. Accurate ties to the existing bridge from the survey centerline. Multiple box culverts, classified as bridges, the bridge survey includes the flow line elevation and the top slab elevation for the existing structure.

Widening Existing Bridge (cont.)( EPG 238.3.36.1.4) Span type structures, the bridge survey includes elevations along the existing bridge floor at 5 ft. intervals along the centerline and curb lines on each side, along with elevations of the bridge seats at all bents, and, if practical, the elevation of the top of the footings. Deck replacement on steel beam or girder bridges, bottom of top flange elevations for each stringer or girder for each substructure unit are required. Locations where elevations are taken on existing bridges must be clearly described on the bridge survey sheets . Stationing at existing bridge ends and at the centerline of each intermediate bent or pier is also required.

Grade Separation (EPG 238.3.36.2) Highway Surveys for grade separation structures, both railroad and highway, include offset profiles to beyond the limits of the structure along the centerline on which the structure is to be constructed. Structures crossing existing pavements, the survey includes profiles along the existing pavement at the centerline and at the edges of pavement for at least 50 ft. outside the structure.

Grade Separation (cont.) Highway (cont.) Profile elevations are obtained at intervals not exceeding 25 ft. Cross-sections may be obtained at interval not exceeding 25 ft. along the existing pavement in lieu of the profiles. Contours are required for grade separation structures only where the natural ground elevation differs by more than 10 ft. within the limits of the proposed structure and the bridge skew angle exceeds 50 degrees. Contours and/or cross sections are obtained by photogrammetry on photogrammetric surveys. All other information is obtained by field methods.

Grade Separation (cont.) RAILROAD Profile of the top of rail or rails to at least 200 ft. from the survey centerline measured normal (perpendicular) to the survey centerline. Top of rail profile elevations are obtained at intervals not exceeding 50 ft. Profiles are required for each railroad track at multiple track crossings. Profiles are required for each rail where the top of rail elevation differs.

Stream Crossings (EPG 238.3.36.3) Stream meander, man-made features, and contours extending at least 1000 ft. up and down the valley from the proposed bridge location; Centerline and offset profiles; Stream bed profile; Water surface profile when requested; Two typical channel sections when requested; Description and section under existing bridges if applicable; Extreme high water elevation, date of occurrence, and estimated frequency; Ordinary high water elevation; Extreme low water elevation; A survey for any necessary channel changes or channel cleanouts; Photographs depicting the character of the site; and Miscellaneous field information necessary to complete the Bridge Survey Report form (i.e., pages 1, 2, 3, and 4). Also see EPG 747.2.2.1 Bridge Survey Report.

The profile is taken along the thalweg (lowest elevation within a channel) of the stream. Streambed profile length and locations are provided by Bridge Division . Streambed profiles shall extend from the farthest upstream valley section to the farthest downstream valley section, but not less than 1000 ft. upstream and downstream from the proposed crossing. This distance may be reduced to 500 ft. for some drainage ditches with approval of Bridge Division. When stream bed profiles are required on confluent streams, the limits of the streambed profile for the tributary stream extends from the confluence of the streams to at least the furthest upstream valley section . Tributary Streams, a streambed profile for a tributary stream is required when a valley section(s) is taken on the tributary, see EPG 238.3.36.3.8 Valley Sections, for details on valley section locations at junctions. Streambed Profiles (EPG 238.3.36.3.6)

Streambed Profiles (cont.) Slope Change , if there is a significant change in the slope of the streambed profile within 1000 ft. of the crossing, the profile limits are to extend at least 500 ft. from the slope change. Elevations, for the first 1000 ft. (upstream and downstream) from the crossing, elevations are taken at 25 ft. intervals. The portions of profiles that extend past these limits should capture elevations at horizontal break points, with additional elevations taken along the profile at up to 200 ft. intervals. Drainage ditches with relatively flat uniform streambed slopes the intervals within 1000 ft. of the bridge may be increased to 50 ft. with approval of Bridge Division. Stationing , streambed profile extends from station 0+00 downstream to upstream, with a tie station provided at the survey centerline.

Water Surface Profile (EPG 238.3.36.3.7) When a water surface profile is required, Bridge Division will provide these locations in the Bridge Survey Location Request. Water surface profiles are typically required for drainage ditches to help determine the slope of the stream flow . Water surface elevations should be taken at least two locations on each side of the crossing at 100 ft. intervals from the roadway centerline, but may be omitted if flow in not present.

Valley Sections (EPG 238.3.36.3.8) Location for Sections A minimum of three valley sections are required, one upstream and two downstream of the proposed structure. Bridge Division will provide locations for valley sections via the Bridge Survey Locations Request process shown in EPG 747.1 Bridge Surveys . A Google Earth image depicting the location of valley sections will be supplied to the districts.Survey Location For each surveyed valley section obtain the distance along the channel meander from the roadway centerline. The valley sections are tied to the survey centerline.

Valley Sections (cont.) Length Valley sections extend to at least 5 ft. above the extreme high water elevation , and outside the limits of the 100-yr floodplain. Stationing The stationing along the valley section is established from left to right looking downstream. Ground Cover The type of ground cover and streambed material (i.e., mud, gravel, etc.) should be indicated to assist office personnel in the establishment of Manning's "n" value. MSDIS DataLiDAR data may be used from MSDIS to supplement field survey. MSDIS LiDAR data and absolute values should not deviate more than 1 ft. A supplemental 25 ft. wide channel survey should be done to obtain the channel floor at the valley crossing.

Typical Channel Sections(EPG 238.3.36.3.9) Location Typical channel sections are obtained within 300 ft. of the survey centerline both upstream and downstream when required (Bridge Division requested). Stationing (completed by designer ) The stationing for the typical channel sections is established from left to right looking downstream. Length The typical channel sections extend to the top of the high bank of the stream or, in the case where the stream bank is also the side of the valley; the sections extend to 5 ft. above extreme high water.

Existing Bridges (EPG 238.3.36.3.10) In addition to other required sections, a section showing the entire waterway below extreme high water for existing structures crossing the stream being surveyed is required if they are within the limits of the obtained stream bed profile. A complete detail section is taken under the existing structure with a general description of the structure along with the elevation of extreme high water at the existing structure.

Extreme High Water Elevation (EHW) (EPG 238.3.36.3.11) Extreme high water elevation is obtained for the centerline profile, either by observation of visible high water marks or by conferring with maintenance personnel, local residents, or district recorded high water events. If sufficient information is available to make an accurate determination, extreme high water elevations are obtained for each of the valley sections . The location and elevation of the high water elevations are included in the survey notes and tied to the survey centerline or base lines.

Extreme High Water Elevation (EHW) (cont.) Information obtained from local residents, should be confirmed by field observations or other parole evidence. If any doubt exists as to high water marks reported to the survey party, give location and elevation of all such marks and in every case give dates of occurrence. Survey personnel are encouraged to mark and record, for future reference, high water elevations for at least all major streams during or immediately after floods.

Ordinary High Water Elevation (OHW) (EPG 238.3.36.3.12) The ordinary water elevation is defined by the Corps of Engineers as: “a line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the presence of litter and debris, or other appropriate means that consider the characteristics of the surrounding areas”.

Low Water Elevation (LW)(EPG 238.3.36.3.13) A low water elevation at the centerline profile is necessary for streams that are generally never dry. The low water elevation is defined as “the lowest water elevation during a year of normal rainfall”.

Channel Surveys (EPG 238.3.36.3.14) Aerial and Mobile LiDAR Surveys , terrain model information will be provided. However, the channel floor and any obscured areas (i.e. underneath structure) within the 300 ft. upstream and downstream, will be collected using conventional surveying methods. Conventional Surveys , existing channel is surveyed for 300 ft. upstream and downstream.

Photographs (EPG 238.3.36.3.15) Photographs documenting the site characteristics are necessary. They are taken in an overlapping manner to provide a 360° panoramic view at or near the proposed stream crossing. Photographs are also taken to show the channel, banks, and streambed both upstream and downstream of the proposed structure, as well as the waterway through the existing structure . If the existing roadway is overtopped at extreme high water, photographs are provided showing the roadway on both sides of the existing structure.

Photographs (cont.) Additional photographs are required if land use or stream characteristics are significantly different at upstream or downstream valley sections. Additional photographs are also used to provide information on other site-specific conditions, including any nearby improvements that may be affected by flooding or changes in stream velocity.

Bridge Survey Report Form(EPG 238.3.36.3.16) Pages 1, 2, 3 and 4 of the Bridge Survey Report Form are partially completed in the field to supplement the bridge survey. When completing the “Existing MoDOT Bridge” section of the Bridge Survey Report, use stationing referenced from the new survey centerline and elevations based on the current vertical datum reference for the project.

Multiple Defined Channels A streambed profile is provided for all structures, including overflow structures that have a defined channel, even if that structure is not being replaced.

Overflow Structures A streambed profile is not required for overflow structures that do not have a defined channel. When only the overflow structure is being replaced, the bridge survey is still developed based on all structures that are in the floodplain. Streambed profiles are provided for all other structures in the floodplain that have a defined channel