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I !tf .t.,. N ~ '-'1 o SUMMARY < Continued) be added to contrql the surface elevation of the canal water. drainage facilities, consisting of a detention dike and ditch would be constructed to protect the membrane-lined canal. Cross- system, In addition to/the moss and debris removal structure installed under Stage One, two new ~tructures would be installed to remove moss, debris, and other material lfrom the irrigation water and to prevent the buried pipe laterals and m~asuring devices from clogging. Lateral improv!!ments generally would consist of replacing unlined lateral reaches in i the Stage Two area with buried pipe laterals that approximately folloll existing alignment and grade. Laterals alreadY lined would not be ~mproved unless needed. Approximately 700 individual laterals are includ.d, with a total length of approximately 490 miles, of which 308 miles <pr 63 percent) are presently unlined and would there- fore be placed in pllpe. Pipe laterals would be installed in all cases except those in whiqh hydraulics prevent their use; in such 'cases, they .would probably be cqncrete lined.. The pipe sections would range from 6 to 48 inches in di!imeter. Existing structures, such as drops, road crossings, flumes, turnouts, and canal headgates, .would be removed or replaced if necessary. Wildlife. measulies, including lIcquisition of 2,090 acres of land along the Colorado ~ver, would be included to compensate for wildlife habitat losses that; could be expected to result from the canal and lateral improvements.forthe entire Grand Valley Unit. The recommended i plan would reduce the salt loading from the unit area by an estimated '143,500 tons annually; Alternative A Alternative A p~ovides for membrane lining the same three reaches of the Government Hi~hline Canal as the recommended plan; however the existing open earth :laterals that would be placed in pipe under the recommended plan woul~ be concrete lined under alternative A. As with the recommended plan,' existing structures along the canal would need to be evaluated as to th~ir structural and hydraulic soundness and replaced if necessary. Turnoi't structures would be replaced, and several new wasteway and centerli~e check structures would be added to control the surface elevation of the canal water. Cross-drainage f4cilities would be. the' same as for the recommended plan; however, in this plan, the laterals would be open and concrete lined, 'so no moss an,d debris removal structures would be necessary. Conversely, the use qf open late.rals would require additional safety precautions, so safety fences would be installed along laterals adjacent to schools and recre~tion areas that may be frequently visited by children. Wildlife me~sures for alternative A would be the same as for the recommended plan. . S-3 1. ~ /