Overview

Keene Creek Dam is a 78-foot-high, 558-foot-long zoned earthfill embankment dam located 16 miles east of Ashland, Oregon, on Keene Creek. Behind the dam is the Keene Creek Reservoir with a total capacity of 390 acre-feet (active 260 acre-feet), which has sufficient water for the weekly cycle of powerplant operation for peaking power production of Green Springs Powerplant. The purpose of Keene Creek Dam is to reregulate releases from Howard Prairie and Hyatt Reservoirs to provide forebay pondage for Green Springs Powerplant.

Geology

The Keene Creek Dam and Reservoir are located in the Western Cascade geotectonic province of the Cascade Range on the West Side of that volcanic mountain belt. The project is in the easternmost part of the Western Cascades, which is characterized lithologically by slightly deformed and partly altered andesitic and bastalic lava flows and pyroclastic rocks of mid Tertiary age and physiographically by a deeply-eroded mature. Topography with deep canyons and fairly strong development of cuesta-type ridges expressive of the easterly dip of 10 to 20 degrees of the volcanic strata. This volcanic sequence has a thickness of 3,000 to 5,000 feet. Structurally it is complicated by intrusives and faulting and folding as well as the eastward tilting. Within one mile west of the project High Cascade geotectonic province forms the highest part of the Cascade Range. It is characterized by late Tertiary to Holocene volcanism, which is represented locally by the lower slopes of the Chinquapin Mountain. This volcano of probable Pleistocene age has a peak elevation of 6106 feet, is 2.5 miles northwest of the dam and lies several miles west of the main chain of volcanoes. Crater Lake which erupted about 6,000 years ago is 60 miles to the north. The closest Holocene volcanism is believed to have been at Mount Macloughlin, about 22 miles to the north. Pleistocene glaciation in the Cascade Range did not extend south of Mount Macloughlin, but the effects of wetter climate appears to be expressed in the deep weathering alteration of the volcanic bedrock, steep-sided valleys and landslides in the Western Cascades.

General

Dimensions

Hydraulics & Hydrology