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<br />XVI <br /> <br />LETTER OF TRANSMITTAL , \ J' <br /> <br />4. In general, the agencies recommended the following items of <br />work: <br />(a) Rehabilitation and extension of the drainage system of the <br />Middlc Rio Grande project, <br />(b) Rehahilitation of the irrigntion system of the Middle Rio <br />Grande project, <br />(c) The drcd~ing of 20 miles of river channel abovc the head of <br />Elephant ButteOReservoir, <br />(<I) Strengthening and extending levees in the Espanola Valley and <br />in the Middle Rio Grunde Valley to provide a flood way of 20,000 <br />cuhic feet per second through the Espanola Valley, and a floodway <br />varying in ""pacity from 30,000 cubic feet per sccond to 42,000 cubic <br />feet per second through thc middle Rio Grande Vallcy, <br />(e) The construction of a reservoir on tbe Jemez River with the <br />capacity of 120,000 acre-feet, <br />(1) The construction of tlw Ch:unita Reservoir near the mouth of <br />the Rio Chnma with the capacity of 945,000 acre-feet, <br />(g) Thc construction of the Chiflo Reservoir near the Colorado- <br />New l\Iexico State linc with the cnpacity of 816,000 acre-feet, <br />(h) The degradation of thc river channel by thc release of impounded <br />flood wat.ers. <br />5, The constructiou of Chiflo Resermir is not justified because of <br />the annual cost of the reservoir, to wit., $1,262,248, as estimat.ed by the <br />agencies, is about three times the total estimated benefit elailued for <br />prevent.ion of flood dnmnges from inundat.ion and scour above Ele- <br />phant Butte Rescrvoir, to wit, $384,560, No credit for prevcntion of <br />inundation and scour bclow Elephant Butte Reservoir can be claimed <br />for the proposed project, because this inundat.ion and scour will he <br />prevented by the San Luis Valley project. Only a small amount of <br />henefit can be claimed for the opemtion of the Chiflo Reservoir for <br />Bediment control as only 1 percent of the sediment appearing in the. <br />river comes from above the ChitIo sile, and thig sediment will be <br />reduced after the construction of the San Luis VI111ey project, It is, <br />thcrefore, apparent. t.hat the Chiffo Reservoir is not economical. <br />6. The Corps of Engineers fixed the nUlximUlll permissible flow <br />throllgh t,he middle valley from spring ftoods at 5,000 cubic feet per <br />second, The design flood used to fix the flood-cont,rol capacities is <br />one which has not occurrcd during the 58 ,years, since stream gaging <br />records have been obtained 011 the river. Neverthele.ss, summer <br />floods, which result from rninfall on the tributaries of the Rio Grande <br />and which are not proposed to be controlled by resen'oirs, will cause <br />floods of a magnitude of 40,000 cubic feet per second or more, It <br />would appear that the flood ways which pass such floods could, at <br />infrequent interva.ls, accollnllodate spring floods in excess of 5,000 <br />cubic feet per seeond, FlIrt,he~, it wOllld appear that flows greater <br />than 5,000 cubic feet per second will be necessary to degrade the chan- <br />nel in accordance wi th the plans of the agencies. <br />7, The operation of the reservoirs of the San Luis Valley project <br />with combined capacit,y in exeess of 1.000,000 acre-feet will substan- <br />tially benefit, the water supply for the Espanola Vnlley area and the <br />}'Iiddle Rio Graude area above Elephant Butte Reservoir; v.ill mate- <br />rially benefit t.hose areas by the redllction of the flood flows, and "ill <br />esscntially eliminate all ftood damage below Elephant, Butte Reser- <br />voir. The reservoir capacities recommended .by the two agencies in <br />