be compared with historic measurements to show whether significant changes have taken place. Since such comparisonsre- 20 quire statistical analysis, continued 15 monitoring by the present E seismograph networkis essential to enlarge the existing data base. _ oO gy £10 . @® a a Conclusions On the basis of assessments con- | 5 et ll Ane 0 ia ty Mit ar ty } Salto n To ri AY) geothermal facilities can be operated in an environmentally acceptable manner. However, contro! 640 sulfide abatement) will probably be required. Continuous monitoring UI Sea << TT5200 ME 3630 Uryy 3650 . Ordinate 3670 *~ km [Fig al — 3690 680 ducted so far, we believe that 6 660 Subsidence for a 5-year period (1972-77) on a line of bench ° marks that runs from north to south in the central part of the Imperial Valley. We recommend that measurements of surface elevations be continued after geothermal operations begin to determine whether the extraction of geothermalfluids results in subsidence significantly greater than that occurring naturally. technologies (such as hydrogen will play an important role in deciding what preventive actions and environmental controls-are necessary.” We also hope to use the data so obtained to verify our predictive assessments. Key words: geothermal energy—environmental studies; hydrogen sulfide; Imperial Valley; Salton Sea area. Notes and references 1. A progress report on the IVEPis included in the May 1976 Energy and Technology Review (UCRL-52000-76-5), pp. 21-25. 2. D. W. Layton, L.R. Anspaugh, N. B. Crow, D.L. Ermack, C. H. Hall, J. R. Kercher, P. Leitner, W.F. Morris, and Y.E. Ricker, An Assessment of Geothermal Development in the Imperial Valley of California, Vol J. Environment, Health, and Socioeconamics. USDOE, Washington D.C. (in press). 22 a IOG8E Lb a