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Show deposits, or placers, and hydraulic mining methods were extensively used. The streams of the Central Valley supplied water required in the placer opera- tion, and also carried away the waste gravels after the gold -was removed. Huge quantities of debris were thus moved downstream, and were deposited in the channels and irrigation canals. Valley in- terests obtained injunctions in 1884 which pre- vented deposition of debris in stream channels because of damage to navigation and farming. In 1893 Congress created the California Debris Commission, an organization under supervision of the Chief of Engineers, to permit resumption of hydraulic mining under regulated conditions. The functions of the Commission include administra- tion, planning, inspection, and the issuance of per- mits, as well as construction of debris control projects. Six such projects have been authorized to date and four of these, the Daguerre Dam, Yuba River restraining barrier, Englebright Dam (Yuba River), and North Fork Dam (North Fork, Amer- ican River) have been constructed. The two re- maining authorized projects call for the construction of debris dams on the Middle Fork of the American River and on the Bear River. Because of changed conditions^ these latter two projects will be re- analyzed. The four constructed projects are satis- factorily preventing hydraulic mining debris from passing into downstream channels where it would be detrimental to navigation, flood control, and other stream uses. A problem has arisen as to repayment by mining interests for the services provided by the projects. Originally the legislation provided for collection of a 3-percent tax on the gross proceeds of each mine using the facilities. However, subsequent legisla- tion substituted an annual tax per cubic yard of material mined, such tax to be determined on the basis of the capital cost (without interest) of each dam or other restraining works and the total storage capacity pr-ovided Hydraulic mining activities in California have materially declined in recent years because of un- favorable economic conditions and because of in- adequate water supply. As a result, the amount of debris stored behind the Englebright and North Fork Dams, completed about 1940, is small, and mining interests have repaid very little of the cost of these structures. The projects have limited use for other pxirposes because of their small capacity and their location. The head created by Engle- bright Darn is used for power generation by the Pacific Gas & Electric Co. under license from the 126 Federal Power Commission. The State paid one- half of the costs of the Daguerre Dam Project. If other structures are necessary, debris storage can be made a function of some multiple-purpose projects. In numerous agricultural areas gold has been found in quantity sufficient to warrant dredge mining. In this operation old river wash material is dredged from as deep as 50 feet. In the process boulders and other rock materials are left on the surface, the soil completely disappearing. Great windrows of useless boulders and rock mark the destruction of the basic soil resource. In some cases these rock piles have been partially leveled and planted to fruit trees, but with indifferent success. It is estimated that 57,870 acres of land, of which 36,560 formerly had agricultural value, have been dredged in the basin. Considering the present plans for extending irrigation the once cultivable land lost may be as much as 38,000 acres.13 Conclusions Damage to downstream channels from hydraulic mining activities in the Central Valley no longer is important. A large part of this formerly serious problem has been reduced by State and Federal regulation and by the construction of debris control projects. However, a problem of recapturing the Federal investment for completed projects exists because of a decline in hydraulic mining operations in recent years. The contract terms practically preclude any solution. Future projects should be based on more realistic repayment arrangements, with min- ing interests at least sharing the risk of an idle investment. The possibility of combining projects for debris control with projects for other purposes should be fully considered. The continued operation of gold-mining dredges is destroying some valuable agricultural land. Although the mining companies pay for such land it is questionable that in a region of such potential high agricultural development and productivity, the permanent withdrawal of such land from crop- land agriculture uses is desirable land policy. In any event, the companies should be required to return the lands to a productive or beneficial use, including such uses as forest or pasture, where original conditions did not favor cropping. Con- sideration should be given to the requirement of 13 Estimate of the U. S. Department of Agriculture. |
