More investigation & photos: Prior to the new Armoring of the Emergency Spillway, there existed a collection zone of water close to the Large Concrete Ogee Weir. This "drain zone" was in the prior basin where the old access road crossed. A 2ft dia Corrugated Steel pipe provided drainage under this road crossing.
A "best fit" assumption is that this pipe remains as a collection point, but new segments have been added to extend the pipe outlet to its current downslope location. The extension was constructed before the large armoring rock & aggregate was emplaced around the new pipe. Afterward, the thick layering of gunite concrete was poured, thus completing the sealing of this pipe underneath the new armoring. The origin of the waterflow to this new pipe outlet likely remains in this "drain zone" near the original inlet. As new images reveal, there is no visible waterflow on the surface of the armoring up and to the footing of the Large Ogee Weir. Thus, the flow of water would be from under the armoring & most likely close to the Large Ogee Weir. The downhill slope of the footing of the Large Ogee Weir - from tapering in height - could tend to route any ground water seepage from the weathered rock towards this "drain basin". However, the underdrains in the Weir should route this flow straight downslope from the box drain outlets (as demonstrated by the abutment seepage).
April 15 photo showing Emergency Spillway Armoring - New pipe outlet waterflow noted by arrow. Inlet to this pipe inferred to be the original inlet in the basin immediately behind the Large height section of the Ogee Weir (approx 100-150ft near directly upslope).
April 15 reverse view photo showing Emergency Spillway Armoring - New pipe outlet waterflow noted by arrow. Inlet to this pipe inferred to be the original inlet in the basin immediately behind the Large height section of the Ogee Weir (approx 100-150ft near directly upslope).
Original 2ft dia Corrugated Steel pipe. Served as drain under service road. The new pipe outlet is inferred to be an extension from this original pipe - all of the pipe, including the original were encapsulated within the rock & concrete armoring. The rock & aggregate lower layer would provide an "under drain" access to this inlet drain zone.
