The purpose of this paper is to relate the economic history of the Great Feeder Canal and preform an analysis on its flow of water. Historical chapters are portrayed chronologically and reveal in sight into the rustic irrigation problems that faced those individuals who developed the Great Feeder Canal. The latter part of the paper entails an economic analysis indicating that the Great Feeder Canal is unique in that it uses nearly twice as much irrigation water per acre as other canals in Southeastern Idaho, yet it tends to maximize net social benefits.

The Blacksmith Formation of Middle Cambrian (Albertan) age was studied in southeastern Idaho and northernmost Utah. Lithology and sedimentary structures were compared with modern environments and ancient rocks to determine environments of deposition, paleo-geography, diagenetic alterations and patterns of dolomitization. The Blacksmith Formation can be divided into five basic rock types. Rock type A has cryptalgalaminae, nrudcracks, and lacks bioturbation. Rock type A is inferred to have been deposited in the upper intertidal to supratidal environment. Rock type Bis extremely dolomitized and brecciated. It is inferred that rock type B was deposited in the upper intertidal to supratidal environment. Rock type C may have cryptalgal mats, stromatolites consisting of laterally linked hemispheroids, birdseye structures, vertical burrows and pseudomorphs after evaporite minerals. Rock type C is inferred to have been deposited in the lower intertidal environment. Rock type D is fine grained, often dark gray in color, has trails and often contains fossil fragments. Rock type Dis inferred to have been deposited in subtidal-lagoon or open-platform environments. Rock type Eis ooid-rich, and is often cross-stratified. Rock type Eis inferred to have been deposited in an agitated-shoal or quiet-water shoal environment. All rocks of the Blacksmith Formation were deposited in supratidal to shallow subtidal environments. During Albertan time the study area was located in the tropics, and the adjacent area had little relief. Clay mineralogy of the insoluble residues suggests a relatively humid paleoclimate. Tidal amplitude was probably low, as suggested by ·small algal domes, LLH strornatolites, and cryptalgal mats. Water depth varied throughout the area. Less restricted fauna to the north suggest that water depth increased to the north. It is inferred that a transgression from the west, regression to the west, a second transgression, and possibly a second regression controlled the distribution of facies. Early diagenesis included minor compaction of intertidal or very shallow subtidal deposits, whereas deeper subtidal deposits may have undergone more compaction. Cementation occurred early in the inter-tidal or shallow subtidal environment. Dolomitization of the Blacksmith by a hypersaline brine is suggested by pseudomorphs after evaporites, authigenic quartz, desiccation features and cloudy dolomite rhombs. Chemical analyses for sodium also indicate a hypersaline fluid. The association of some of the dolomite with the oolite-shoal environment suggests that the dolomite distribution may be in part facies-controlled. The hypersaline brine likely developed on tidal flats south of the area, and percolated through the sediments via refluxion and through the permeable sediments via hydrostatic head. The amount of dolomite decreases to the north, farther from the source of the brine. As the dolomitizing brine moved downward, the Mg/Ca ratio was lowered so that a ferroan dolomite formed in the subsurface, under reducing conditions. Late diagenetic events include aggrading neoroorphism by low-Mg calcite which may obliterate grains and cement or preserve grains and episodes of cementation. Late dolomitization, producing coarse dolomite rhombs exhibiting undulose extinction and curved crystal faces may have been epigenetic in origin.

The Harrington Peak Quadrangle is located within the Caribou National Forest of southeast Idaho. Within this quadrangle are outcrops of olivine trachyte of Pliocene(?) age overlying sedimentary rocks of Mississippian to Tertiary age. The region contains thrust faults and later normal faults (generally trending north-south} formed during Basin and Range extension. The Largest outcrop of olivine trachyte (approximately1 1/2 X 3 km) probably formed as the result of a fissure eruption. Two other outcrop areas show evidence of being sites of local extrusion. Whole-rock chemical analyses revealed the olivine trachyte to have moderate amounts of SiO2 and Al2O3, high MgO and CaO, and K2O in excess over Na2O (approximately 2:1). Mineralogical characteristics include microphenocrysts of Mg-rich olivine and diopsidic augite in a groundmass of Ba-rich sanidine, diopsidic augite, Fe-Ti oxides, and less commonly phlogopite and/or plagioclase. The olivine trachyte closely resembles the ciminites from the Viterbo region of Italy and has some petrological and mineralogical similarities to many other continental potassic volcanic rocks. The olivine trachyte may have formed by partial melting of a heterogenous mica peridotite mantle source enriched in incompatible elements during a previous tectonic event.

Geologic mapping, basin analysis, and tephrochronologic analysis in the Clifton quadrangle of southeast Idaho indicates that the modern Basin-and-Range topography is only a few million years old and that the bulk of Cenozoic extension was accommodated by slip on an older low-angle normal-fault system, the Bannock detachment system. The detachment system was active between ~12 and < 4 Ma and accommodated ~50 % extension. Cross-cutting relationships show that the master detachment fault, the Clifton fault, is the youngest low-angle normal fault of the system, was active at a low angle, and has not been rotated to a low-dip angle through time. Map patterns and relationships indicate that the hanging wall to the detachment system began as a cohesive block that later broke up along listric and planar normal faults that either sole into or are cut by the master detachment fault. The Miocene-Pliocene Salt Lake Formation, a syntectonic, basin-fill deposit of the Bannock detachment system, was deposited during three sub-episodes of extension on the detachment system. Depositional systems within the Salt Lake Formation evolved from saline/alkaline lakes to fresh water lakes and streams to braided streams in response to the changing structural configuration of rift basins in the hanging wall of the detachment system. After breakup of the hanging wall began, the master detachment fault excised part of the hanging wall and cut hanging-wall deposits and structures. The structural geometry of the Bannock detachment system strongly resembles that of detachments documented in metamorphic core complexes. Therefore, we interpret the Bannock detachment system as a proto-metamorphic core complex, akin to the Sevier Desert detachment fault. The Bannock detachment system also collapsed the Cache-Pocatello culmination of the dormant Sevier fold-and-thrust belt, much like the Sevier Desert detachment collapsed the Sevier culmination. Structures of the Bannock detachment system are overprinted by a second episode of extension accommodated by E- and NE-trending normal faults that may be related to subsidence along the Yellowstone hotspot track and a third episode of extension accommodated by high-angle, Basin-and-Range normal faults. This last episode of extension began no earlier than 4-5 Ma and continues today.

The engineering properties of waste spoil from phosphate mines in Southeastern Idaho were determined through field and laboratory testing. The testing included compaction tests, grain size analysis, powder x-ray defraction tests, permeability tests, compression tests, triaxial and direct shear strength tests, and nutrient analyses. Based on these tests, the slope stability and settlement characteristics of phosphate spoil dumps were investigated. The study showed that the foundation is an important component of the stability of a spoil dump. Hypothetical examples were used to illustrate possible modes of foundation failures. Such failures might occur when weak foundation soils exist or when there is a lack of embankment-foundation preparation prior to the disposal of waste material. When considering failures through only the middle waste shale embankment material, the study showed that dumps constructed by end-dumping the spoil material over angle of repose embankments or by scraper filling the material in horizontal lifts will be adequately safe against slope failure if: o Embankment slopes are graded to 21/2 horizontal to 1 vertical or flatter. o Proper precautions are taken to prevent the build-up of a phreatic surface near the top of the embankment. The study also showed that post construction settlement in spoil dumps can be attributed to: o A slow continuing settlement which is linear with the log of time. o Saturation collapse settlement which occurs with increases in the moisture contents. Post construction settlement in spoil dumps is caused principally by increases in the moisture content in layers of middle waste shales and soft cherts. A rationale method for predicting magnitudes of post construction settlement in spoil dumps was also developed as part of this study.