D.C. Mun. Regs. tit. 24, r. 24-3101
When the overhead or side clearance between a track and any building, structure, or facility is less than the minimum prescribed in this chapter, but was lawfully created prior to September 1, 1958, the minimum clearance prescribed in this chapter shall be provided whenever the building, structure, or facility is relocated or reconstructed, except as provided in this section.
The Minimum Wage and Industrial Safety Board may consider specific requests for the future continuance of clearances existing prior to these regulations at a reconstructed building, structure, or facility, upon application made as required by the provisions of this section.
If restricted clearances are necessary, nothing in this chapter shall be construed as preventing the movement of material over tracks when the material is necessary in the construction or maintenance of the tracks, nor in the movement of special work equipment used in the construction, maintenance, or operation of the railroad; Provided, that the movements shall be carried on under the conditions as are necessary to provide for the safety of all concerned.
The provisions of this chapter shall not be applicable during periods of actual emergency due to wrecks, derailments, washouts, and like conditions; Provided, that reasonable safety precautions are observed.
If, in any particular case, variation from any of the requirements of this chapter is deemed necessary by an employer, the Board shall consider the application of that employer for a variation when accompanied by a full statement of the conditions existing and the reason why the variation is requested.
Any variation granted under this section shall be limited to the particular case covered by the application.
D.C. Mun. Regs. tit. 24, r. 24-3101