Alternatives Analysis: Mallorie’s Dairy

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Jul 16, 2014/ 0 Comments / in Permitting Updates, Project Details / by
Alternatives Analysis: Mallorie’s Dairy
Mallorie's Dairy

Mallorie’s Dairy is located near the intersection of Hazelgreen Road and Brush Creek Road. It is bound to the south and west by Silver Creek and the Pudding River. 

Overview

The Mallorie Dairy site is located near Silverton at the intersection
of Hazelgreen Road and Brush Creek Road. The site is flanked by
Silver Creek to the South and the Pudding River to the West.
The reservoir could be constructed by excavating nearly 20 million
cubic yards of material to create a reservoir that is 4,000 feet by
2,000 feet and 80 feet deep. Berms or embankments would be
created on the west, north and south sides of the property. This
reservoir could store 12,000 acre feet of water.
Water could be diverted from the Pudding River or Silver Creek
through screened direct river diversion and/or pumping.


Excavation and Reservoir Construction

In order to store 12,000 acre feet of water, approximately 20 million cubic yards of material would need to be excavated from the Mallorie’s Dairy site. Approximately 70,000 cubic yards of that material could be used to create a 10-ft berm along the west, north and south sides of the property. Thus, about 19 million cubic yards of material would need to be disposed of offsite. This excavation would result in a reservoir that is 4,000-ft x 2,000-ft and approximately 80-ft deep. Due to conditions on the property, the reservoir would likely need to be lined with 10 million square feet of material.

Ecological Impacts pros - cons image

The site sits within a Priority 3 crucial habitat area as  defined by the Oregon Department of Fish and Wildlife. (Drift Creek site is a
Priority 4 for aquatic species and 5 for terrestrial species. Priority 1 is considered the most crucial habitat.) Steelhead trout, listed as an endangered species, are present at the site. Wetlands were observed along the banks of the Pudding River and Silver Creek.

Construction and operation of the reservoir would cause temporary and permanent impacts to riparian habitat and aquatic species, including endangered Steelhead. A fish ladder would likely be necessary for Steelhead to continue migrating in the area.

Groundwater Limitations

Based on local well logs, static groundwater appears to be found at about 20-50ft below the surface. The deep excavation required by this type of reservoir would disturb the aquifers. Oregon law states that a waste of groundwater cannot occur due to excavation activities. Furthermore, regulations would likely require the reservoir to be lined to isolate stored water from the groundwater. This would require 10 million square feet of material, costing approximately $42 million.

Permitting

Permitting of an excavation project nearing 20 million cubic yards of material will be a substantial effort. The presence of endangered
Steelhead will require additional measures to ensure their safety. In addition to environmental impacts, a county grading permit and associated haul and placement permits will be required. There will likely be a risk of pavement and road damage in the area of the site due to removal of the material. Additional permits will be needed due to the groundwater impact.

Cost

The District discussed the cost of excavation with a local contractor. The cost of removing the material is $4/cubic yard. Disposal of the material is $5-7/cubic-yard. Construction of the berm is $4/yard. With a net of 19,290,000 cubic yards of material needing to be removed, with a 70,000 cubic yard berm, and 10 million square feet of liner, construction of the reservoir would be over $235 million. With engineering, administrative, and regulatory costs, the project could reach $240 million. In contrast, the current cost estimate of the Drift Creek site is $40-50 million for construction, administrative, engineering and all other costs.

This post is part of a series regarding the alternatives analysis being performed by East Valley Water District. For more information regarding other alternatives, please click here.

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