(a) The sections of the Harlem and East Rivers that are regulated by this Part are defined as follows:

1. (1) that part of the East River northerly from an imaginary line extending easterly from pier 4 at the foot of Broad Street, east of Battery Park, New York County, to pier 4 at the foot of Montague Street, Kings County, to the Triborough Bridge where it crosses from:

   1. (i) Astoria (Queens County) over Hell Gate to Wards Island;
   2. (ii) Wards Island over Little Hell Gate to Randalls Island; and
   3. (iii) Randalls Island over Harlem River to Manhattan, New York County; and

2. (2) that part of the Harlem River from the Triborough Bridge where it crosses from:

   1. (i) Randalls Island over Harlem River to Manhattan, New York County; and
   2. (ii) Randalls Island over the Bronx Kill to The Bronx, Bronx County, northerly and westerly to the Hudson River at the Amtrak railroad bridge over the Spuyten Duyvil part of the Harlem River west of the Henry Hudson Parkway toll bridge.