(a) Whenever the elevation of the pool created by the Federal dam at Troy, N.Y., shall fall to a point level with the crest of the main spillway, the elevation of which is + 14.33 feet mean sea level, the operation of the power plant shall cease and further operation thereof shall be suspended until such time as the water level rises to or above + 14.43 feet mean sea level.

(b) Flashboards may be maintained on the section of the spillway of the dam having an elevation of + 14.33 feet mean sea level in order to increase the elevation of this section to an elevation equal to that of the auxiliary spillway, or + 16.33 feet mean sea level: Provided, That the flashboards are so erected as to drop automatically when the pool level rises to an elevation of + 18.5 feet mean sea level, and conform in other respects to the plans attached thereto.

(c) The tide staff to be used in determining the elevation of the pool shall be the ceramic tide staff now located on the westerly face of the east lock wall north of the northerly gates, the zero of which is set 2 feet below mean sea level.

(d) The regulations of the pool level and the maintenance of flashboards shall be subject to the supervision and approval of the District Engineer, New York City.