(a) A driveway shall be constructed so that it does not adversely affect the highway drainage or drainage of the adjacent property. The drainage and the stability of the highway subgrade should not be impaired by driveway construction or roadside development. The functional drainage design of a construction project shall not be compromised by field adjustments to compensate for driveway location alteration. In no case shall the construction of a driveway cause water to flow across the highway pavement or to pond on the shoulders or in the ditch.

(b) Drainage collected by ditches, gutters or pipes on private property shall not be discharged into the highway drainage system unless expressly approved by the department. The permittee may be required to submit to the department a drainage study justifying the drainage system proposed and pipe sizes used.

(c) Where construction of a driveway necessitates crossing a highway ditch, a culvert pipe shall be installed in the ditch by the permittee and the low point of the driveway profile shall be at or close to the ditch centerline. On paved driveways, a corrugated metal pipe (C.M.P.) with a slotted top opening (or a grate) may be required to prevent water from running out of the driveway and onto the pavement. A C.M.P. with a top opening is impractical in dirt or gravel driveways or where debris may clog the opening or the pipe. Under no circumstances shall existing ditches or gutters be filled without adequate provision for alternate drainage by the permittee.

(d) Culvert pipe shall be of a size adequate to carry the anticipated flow in the ditch as determined by the department and shall not be smaller than 12 inches inside diameter. The structural material and gauge of the driveway pipe shall be adequate to withstand the load from anticipated vehicular traffic across the driveway. Culvert length shall be determined as the sum of the width of the driveway at the ditch centerline and the length needed to accommodate a sideslope of one vertical to three horizontal from the driveway to the ditch. Tapered end sections, instead of headwalls, shall be installed on the culvert to minimize its potential as a roadside hazard. End section requirements should reflect current design policy.