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Ii I I 1 : - ~:.j I: I 1 I I 1 I I , . ,'" I 1 I 1 I 1 1 ;.~ ';f 3560 o __ is apP~Gx~mately 42 miles in length with the design capacity increasing from 45 cfs to a maximum of 160 cfs. Bottom widths range from 8 to 22 feet, and water depths from 3.6 feet _to 5.6 feet. The flat terrain of the Closed Basin and the invert of the Rio Grande dictated the use of-a very flat channel gradient that produces a flow velocity of about 1 fps. Preconstruct ion material investigations determined that the channel required lining to reduce seepage to acceptable limits. Some clayey material was located, but the clay was dispersive and thus unsuitable for use in constructing an impervious lining. Subsequent analyses of alternative lining8 showed that a 20 mil thick PVC lining would be the most economical. Thus, PVC memerane covered with varying depths of excavated earth material and pit run sand and gravel has been specified for all of the channel construction contracts. To date, the Closed Basin conveyance channel is the most extensive use of PVC canal lining in the United States. Construction of the conveyance channel included 2 precast concrete siphons, 13 combined check structures and road crossings, 4 constant head (CHO) orifice turnouts, 1 Parshall flume, 1 pumping plant turnout, 1 feeder canal turnout, and 1 pipeline turnout. The normal water surface of the channel is maintained by the combined check structure road crossings and check inlets on the siphons. All of these structures are equipped with either stop logs or remot61y operated slide gates. I Several special aspects of the channel' construction should be noted. The installation of perforated, corrugated, PVC drain tile was specified in certain areas of high ground water to simplify the dewatering of the channel for future maintenance. Manholes have been installed on these drains and water is now pumped from them into the conveyance channel. This is an additional amount of salvaged water which is used by the project. Drip 'irrigated shelter belts are being planted in areas highly susceptible to wind erosion. Further erosion control is being provided by the seeding of areas disturbed by construction with a blen8 of native or adapted grasses and shrubs. These seeding contracts include the requirement to irrigate the seedbed for the first growing season. Further environmental enhcincement was-Obtained bY-mOdifying-- borrow areas in the Alamosa Wildlife Refuge and the Blanca Wildlife Habitat Area. In these locations, the vegetation was stripped and piled toward the center to provide waterfowl nesting islands, and the borrow material was excavated in','a manner---'--, Lv 1JLUy.i.J~ CUI .i.I.L~y"ulcu ,shucelille Lhi:2l.. woulO blend W~Ln tone surrounolngs. to'ayment for the borrow from these odd-shaped areas was made from computer generated quantities and balanced mass diagrams which eliminated the need_for surveys and tedious computations. Programmable Master Supervisory Control System During the early stages of project development the complexities and difficulty of operating the Closed Basin water conveyance system manually became apparent. The maintenance of delivered water quality within desired limits, regulating water' deliveries, detecting equipment problems, obtaining and storing historical data, and operating the water delivery system in a cost efficient manner were tasks that required an integrated approach feom a centralized location. In 1985 a solicitation "ilS ~ssued for Installiltlon .of a ?rogrammable Master Supervisory Control (PMSC) "ystem tc> ,'SSlst In tl1" c('ntraliz<?,j ooeration of the project.