00 31 21 Survey Information.pdf

Lower Rio Grande Flood Control Project – Interior Floodways Rehabilitation of North Floodway (North and South Levees) and Arroyo Colorado Floodway (North Levee) Hidalgo and Cameron Counties, Texas

SURVEY INFORMATION

USIBWC Contract No.: IBM09B0004 Page 00.31.21 - 1

AVAILABLE INFORMATION 00.31.21

For these Contract Drawings, surveying and data collection was performed as follows:

(1) Light Detection and Ranging (LiDAR) was obtained from the Government and used for preliminary information.

(2) Control was performed in April / May 2009 by RODS Surveying, Inc. who developed and provided the following (at .01-foot accuracy):

(a) Control. The surveyor established points at cross-roads to establish horizontal and vertical control; control sheets were developed for each control point set, signed and sealed by a Texas Registered Professional Land Surveyor (RPLS). The control sheet includes a drawing of the control point with a 3-point tie to existing physical features, description of the control point, X,Y & Z coordinates and the coordinate system. The Contract Drawings include the control information data for all the control points set for the project, signed and sealed by the

RPLS.

(b) Benchmarks. The surveyor established bench marks along project limits; vertical benchmarks were set at 1000-foot intervals at the right of way (ROW) line of the levee reach. A tabulation of the benchmarks is shown within the Contract Drawings.

(3) Ultimately, an aerial survey (at 0.1-foot accuracy) was performed in April / May 2009 by RODS

Surveying, Inc. and RODS Aerial Mapping, LLC who developed and provided the following, which was used as the basis of design:

(a) Field Control for Photogrammetry. The surveyor set panels for aerial photogrammetry along the levee reach for a low-level flight (1500 feet). Panels were set along the flight path at 800-foot intervals and wing panels were set at cross-roads or 2400-foot intervals. The surveyor performed a global positioning (GPS) survey to establish x-y-z coordinates of the panel points.

(b) Aerial Photogrammetry. The aerial photogrammetry was developed as follows:

1. Black and white photography at a 1-inch = 250-foot photo scale (1500 feet above ground level (AGL))

2. Data Processing. The aerial photography was scanned at 12 microns to produce 0.25-foot pixel resolution; aerial triangulation process was performed to orient individual stereo pairs.

3. Planimetric and Topographic Data Compilation. Planimetric and topographic data was compiled (suitable for 1-inch = 50-foot map scale showing 1-foot contours.

4. Digital Orthophotos. A digital elevation model (DEM) was created for the project area to support the orthophoto rectification; rectified mosaic digital images to hold 0.25-foot ground pixel resolutions suitable for a 1-inch = 50-foot map scale.

Lower Rio Grande Flood Control Project – Interior Floodways Rehabilitation of North Floodway (North and South Levees) and Arroyo Colorado Floodway (North Levee) Hidalgo and Cameron Counties, Texas

USIBWC Contract No.: IBM09B0004 Page 00.31.21 - 2

(4) Supplemental ground surveys were performed by RODS Surveying, Inc., Dos Land Surveying, LLC, and Valley Data Collection Specialists as follows:

(a) Voids. A topographic survey was performed by the surveyors to fill-in the voids of the aerial planimetrics; additionally, the surveyor performed topographic survey on existing structures, including bridges, inlets, culverts and irrigation structures.

(b) ROW Verification. The surveyors recovered and staked ROW points from available ROW maps supplied by the Government. This ROW information is shown on the plan / profile sheets of the Contract Drawings.

(c) Geotechnical Borings Survey. The surveyors obtained x-y-z coordinates for the geotechnical borings along the levee reach spaced at approximately 500-foot spacings.

(d) Utility Survey. The surveyors coordinated with utility notification companies to get utilities marked in the field; the surveyor performed field location of underground utilities as marked by utility companies along the levee reach and intersecting streets. These locations are shown on the plan / profile sheets of the Contract Drawings. NOTE: IT IS THE CONTRACTOR’S

RESPONSIBILITY TO VERIFY LOCATIONS OF ALL EXISTING UTILITIES (SHOWN

AND NOT SHOWN ON THE CONTRACT DRAWINGS) PRIOR TO CONSTRUCTION.