Sidewall extension for drain channel system and method for extending the continuous slope of a drainage channel system

A method for extending the continuous slope of a run of a drainage channel system of the type wherein a plurality of progressively deeper channel segments are interlocked end-to-end below grade with a fluid entrance substantially even with grade, each channel segment comprising a pair of opposing, spaced-apart side walls, a bottom wall connecting said side walls adjacent one end thereof, and a top opening opposite said bottom wall, said side walls and said bottom wall defining a fluid carrying space and said top opening defining a fluid entrance adapted to receive a grate, said method comprising the steps of:

• a. installing progressively taller channel segments in a correspondingly progressively deeper trench, beginning at one end of a run with a channel segment having predetermined, relatively short side walls and continuing along the run with the installation of a first predetermined number of channel segments having progressively taller side walls to a point before the end of the run;
• b. interlocking a channel segment having relatively shorter walls with the tallest channel segment already installed thereby defining a predetermined vertically offset distance between the fluid entrance of the channel segment having the tallest side walls and adjacent channel segment having relatively short side walls;
• c. installing a second predetermined number of channel segments having progressively taller side walls for a predetermined distance along the run;
• d. affixing a side wall extension on top of each of the opposing side walls of the second predetermined number of channel segments with said side wall extensions each being of a height sufficient to collectively define a fluid entrance at the same level along the continuation of said run for a predetermined distance to the end of said run.