In collaboration with The Conservation Fund, Eklutna, Inc. completed deconstruction of the 60-foot high lower Eklutna River Dam in 2018. The deconstruction project was permitted, in part by the United States Army Corps of Engineers (USACE) which required Eklutna Inc. to collect a suite of pre- and post-project geomorphic and water quality data. These data were necessary to evaluate secondary effects of dam removal and sediment mobilization on the physical characteristics of the lower river for three years following dam removal. During Autumn of 2017, baseline data were collected describing channel geometry, substrate composition, and water quality at three monitoring locations downstream from the dam site. Year 1 (2018) of this monitoring project was completed by Eklutna Inc. in collaboration with the National Oceanographic and Atmospheric Administration (NOAA), the Native Village of Eklutna, and the Alaska Department of Fish and Game (ADF&G)–Habitat. In 2019, Eklutna Inc. contracted with the ADF&G–Habitat to complete the final two years of USACE required monitoring.

ADF&G Document Citation:

Kirsch, J. M. and R. Benkert. 2019. Eklutna River aquatic habitat monitoring, 2019. Alaska Department of Fish and Game, Technical Report No. 19-13, Palmer, AK.

We conducted two sampling events during 2019, visiting four previously established monitoring locations. Two of these monitoring locations were downstream from the deconstructed dam site but upstream from the Thunder Bird Creek confluence; one site was downstream from Thunder Bird Creek; and one site was above the sediment plug upstream from the dam site. At each of the three lower sites, a suite of variables including channel geometry, substrate composition, and water quality were recorded. Continuous water temperature monitoring sites were established at two of these three locations. At the one site upstream from the dam site, only water quality variables were recorded in addition to the establishment of a third continuous temperature monitoring location.

At the two monitoring sites upstream from the Thunder Bird Creek confluence, channel geometry measurements indicated aggradation occurred following dam deconstruction. Dominant substrates generally transitioned from silt/sand and cobble prior to dam deconstruction to mostly medium gravel dominance with the D50 particle size generally increasing, and D84 particle size generally decreasing. Water quality at these two sites were generally within expected ranges; however, pH was consistently high, ranging from 8.44 to 8.70.

All recorded variables from the monitoring site downstream from the Thunder Bird Creek confluence generally remained unchanged.
At the water quality sampling location upstream from the sediment plug, all variables were found to be within expected range. Interestingly, pH was again high; however, it tracked closely to measurements taken at each of the other monitoring sites.

During Autumn of 2017, baseline data were collected describing channel geometry, substrate composition, and water quality at three monitoring locations downstream from the dam site. Year 1 (2018) of this monitoring project was completed by Eklutna Inc. in collaboration with the National Oceanographic and Atmospheric Administration (NOAA), the Native Village of Eklutna, and the Alaska Department of Fish and Game (ADF&G)–Habitat. In 2019, Eklutna Inc. contracted with the ADF&G–Habitat to complete the final two years of USACE required monitoring.

We conducted two sampling events during 2019, visiting four previously established monitoring locations. Two of these monitoring locations were downstream from the deconstructed dam site but upstream from the Thunder Bird Creek confluence; one site was downstream from Thunder Bird Creek; and one site was above the sediment plug upstream from the dam site. At each of the three lower sites, a suite of variables including channel geometry, substrate composition, and water quality were recorded. Continuous water temperature monitoring sites were established at two of these three locations. At the one site upstream from the dam site, only water quality variables were recorded in addition to the establishment of a third continuous temperature monitoring location.

At the two monitoring sites upstream from the Thunder Bird Creek confluence, channel geometry measurements indicated aggradation occurred following dam deconstruction. Dominant substrates generally transitioned from silt/sand and cobble prior to dam deconstruction to mostly medium gravel dominance with the D50 particle size generally increasing, and D84 particle size generally decreasing. Water quality at these two sites were generally within expected ranges; however, pH was consistently high, ranging from 8.44 to 8.70.