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The auxiliary ditch has been designed to convey flows generated by the Probable Maximum Thunder Storm. These flows were calculated by Charles F. Leaf in March, 1978. As indicated in this report a high point exists in the diversion channel with the flow being directed in both directions around the surface facilities. The auxiliary diversion ditch recommended herein would follow this general pattern. Access across this ditch would be provided at the high point and just east of the fan. The auxiliary diversion ditch, as it is located on the fan level proper, will collect disturbed flows generated on the bench as well as upstream flows introduced by a faffure of the primary diversion ditch. A small culvert will be provided to reintroduce disturbed flows to the original drainage system on the east end of the fan level. Flows in excess of these flows will be directed into the original diversion ditch. The diversion structure will consist of a 21 inch CMP culvert and a concrete weir. The culvert will pass all minor flows without bypassing the sediment control system. The concrete weir will be overtopped only when flows in the auxiliary diversion ditch exceed the minor system design flow of 13 efs. Very little disturbed flow will enter the auxiliary ditch which flows west, consequently no separation method will be provided. PORTAL BENCH: Some problems with drainage clearly exist on the portal level; however, according to Geo-Hydro Consulting, they appear to have only a limited affect on the stability of this fill. • The ditch on the upstream side of the access road above the portal bench diverts flow around the bench. This ditch is constructed at the same grade as the access road. The swale to the west of the bathhouse is virtually non-existent. The area in the vicinity of the ditch was saturated at the time of the site visit, on October 28, 1981. This ditch should be re-established to prevent saturation of this area. The ditch should be regraded to drain to the south to Node 4, as shown on the surface facilities drawing. This will alter the original drainage pattern by redirecting flow generated west of the bathhouse from Pond 1 to Ponds 3 & 4. We feel the flow should be discharged from the fill as quickly as possible to prevent any possible saturation problems. The other swales on the portal bench are not well defined; however, the ditches and the bench in their vicinity are paved and therefore should prevent saturation of the f~11. SUBSTATION FILL AND TRANSFER TOWER iil FILL: After having reviewed this with Geo-Hydro Consulting, we feel there are no drainage related stability problems associated with these fill areas.