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` ~~~ This figure would be for an average year. It is possible that during a year of extremely poor snowpack that surface water originating within the basin is essentially zero. The past winter of 1980-1981 is an example of this. The maximum amount of trans-basin water diverted into the Bolton Draw watershed by the Speer Ditch can also be estimated by the following expression: (65 days)(60 sec)(60 min)(24 hrs)~11.5 ft3) min hr day Sec 43,560 acre 1,483 acre-ft Hence, depending on whether average snow conditions prevail, the ratio of the amount of available water contributed by the basin vs. the amount contributed by the Speer Ditch under maximum possible usage for the normal irrigation per- iod (+ 65 days) is about 758:258. However, during an abnormally dry winter (such as 1980-1981) it is entirely possible that the ratio is nearly 0$:1008. In either event, it has been previously documented in the permit application on Page 92 that "...only 2.78 of the potential surface water flow to the Bolton Draw drainage will be reduced by sediment: pond detention from the Canadian Strip Mine." It was previously stated on Page 112 that "Studies concern- ing the potential areas of subirrigation were limited to the North Fork of Bolton Draw. Certain downstream regions of Main Bolton Draw are undoubtedly subirrigated to a certai extent, especially immediately downstream of the Bolton Dr ac. stock reservoir." The importance of subirrigation in Main Bolton Draw is limited to providing an available water supply both within and adjacent to the active stream channe] which helps promote native vegetation within the draw. Subirrigation within Main Bolton Draw is not important from an agricultural usage standpoint. This fact has been pre- viously documented on Page 111 which states that "According to Mr. John Nuding, manager of the nearby Noffsinger Ranch, the soil in Bolton Draw is not suited for crops as hay because of its poor characteristics (mainly high clay con- tent)." This statement has been reconfirmed by the unpublished document "Soil Survey of Jackson County, Colorado" referred to on Page 10 of this Addendum. Further information concerning soil characteristics and vegetation types in this vicinity (Spicerton series) may be found in the discussion on Page 10 of this Addendum. Wyoming Fuel Company has previously documented the minimal impact that the proposed mining operations will have on the downstream reaches of Main Bolton Draw. Tltis information m~ be found in the prediction of probable hydrologic conseq- uences, Section 2.05.6(3)(b)(iv) pages 92-99. In this discussion and summary, it is evident that the surface water contribution to Bolton Draw is of considerably greater importance than the groundwater contribution. Also, -12-