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. . . CHAPTER I Co.) f\) CO c:.n INTRODUCTION ...J (,";; Purpose of Plan of Study This plan of study has been prepared to outline the upcoming feasibility investigation for the Glenwuod-Dotsero Springs Unit of the Colorado River Water Quality Improvement Program concerning plans for data collection, exchange of information, plan formulation and evaluation, scheduling of work, and input from various offices of the Water and Power Resources Service and other agen- cies. It also provides a plan for public involvement. The need for the study and the work required to satisfy its requirements is outlined. The organiza- tion of the study team and the methods to be employed are discussed, and the legal requirements and constraints governing the effort are identified. In short~ the plan of study wi11.document the essential elements of the investiga- tion. Purpose of the Investigation The investigation is being conducted to identify and delineate the saline ground water system or systems in the Glenwood-Dotsero Springs area that are annually contributing about 500,000 tons of dissolved solids to the Colorado River and to study and evaluate possible plans to' reduce or eliminate that contribution. One of the major problems facing the people in the Colorado River drainage is that of maintaining adopted salinity standards while the Basin States continue to develop their compact-apportioned waters. About half of the 500,000 tons of dissolved solids entering the river each year through the study area comes from 10 identified hot mineral springs. Ten of these springs are clustered near Glenwood Springs and eight are grouped about 2.5 miles downstream from Dotsero. The remainder of the salt apparently enters unseen through springs in the stream gravels with small amounts entering with surface runoff from the surrounding area. The Colorado River at its headwaters in the mountains of north-central Colorado has a salinity of only about 50 milligrams per liter (mg/L). The salinity progressively increases downstream as a result of water diversions and salt contributions from a variety of sources and in 1977 averaged about 820 mg/L at Imperial Dam, the last major diversion point in the United States. Unless control measures are undertaken, the concentration will continue to in- crease, reacqing levels estimated by the Water and Power Resources Service of 1,150 to 1,210 mg/L at Imperial Dam by the year 2000. Water of 1,000 mg/L or less is generally considered to be satisfactory for irrigating most crops, although concentrations of 500 mg/L can have detrimental effects on sa1t- sensitive crops. The Environmental Protection Agency (EPA) secondary standards recommend that public drinking water supplies should contain less than 500 mg/L. 2