Drainage
Drainage in highway side ditches shall not be altered or impeded. When drainage structures are required, the size and other design features shall be approved by TxDOT.
Access driveways shall be constructed to match the grade of the highway pavement edge or the shoulder edge if a shoulder is present. The driveway shall be designed and constructed in such a manner as to not impede the flow of water away from the highway pavement.
If the driveway is approved to be constructed at grade through the roadside ditch or natural grade of the roadside, the driveway shall be paved with a stabilized all weather surface material acceptable to TxDOT to conform to the cross section shape of the ditch or other natural grade of the roadside to form a stable driveway. An exception to using stabilized new surface may be approved by TxDOT if the roadside or ditch is naturally stabilized with rock which may be driven on without eroding or rutting in all types of weather.
Safety end treatments will be used for all driveways with drainage structures constructed within the highway right of way. The side slopes of the driveways must not be greater then the slope of the required safety end treatment and shall match the slope of the safety end treatment at the junction of the two. Approved safety end treatments may be found at standard CAD drawing under Bridge Standards for Safety End Treatments. The most frequently used standard is 'Parallel Drainage for 12"-72" Diameter.' These can be found under
, Safety End Treatments. The design requirements of the safety end treatments are as follows:
- There shall be no culvert headwalls or similar vertical ends.
- Ends shall be sloped at 6:1 (6 horizontal to 1 vertical) or flatter, with concrete riprap to prevent erosion and to protect the pipe end.
- The access driveway embankment slope shall be 6:1 maximum, with 8:1 preferred beginning at the edge of the driveway pavement.
- For pipes greater than 30 inches in diameter or multiple pipes with individual diameters greater than 24 inches, grates shall be provided with maximum slope of 6:1 or a preferred slope of 8:1. Cross-pipes are not required on small (single pipes having a diameter of 30 inches or less) structures regardless of end location with respect to the horizontal clearance requirements; however, the ends of small structures shall be sloped and provided with concrete riprap as described above.
A ditch within the highway right of way may be filled in with dirt or other approved material, provided that prior TxDOT approval is obtained and the following conditions are met:
- The property along the right-of-way frontage has two or more permitted driveways that are in compliance with the "Number, Location and Spacing of Access Connections" requirements described in Section 3 of this chapter.
- Surface drainage shall be provided so that all surface water on the filled-in area shall be carried away from the highway roadbed in a suitable manner.
- The design of a drainage structure underneath the filled-in area shall be adequate to carry the flow of water in the highway ditches.
- The filled-in area shall be sufficiently delineated and, where required by TxDOT, delineation or other satisfactory methods shall be used to prevent the use of the area for parking or travel. The area shall be kept free of obstructions.
- The filled-in area shall extend from the right-of-way line to the edge of pavement, edge of shoulder or back of curb as the case may be. Other requirements may be imposed by TxDOT for filled-in areas in order to conform with planned future improvements to the existing highway section.
- The filled-in area and safety end treatment on the drainage structure may not extend beyond the boundary line of the permittee's property without written consent of the adjoining property owner whose property will contain the extension.