033016-GeoDesign_Report_Well.pdf

Memorandum

15575 SW Sequoia Pkwy, Suite 100 l Portland, OR 97224 l 503.968.8787

To: Barbara Clement From: Erik A. Hedberg, P.E. (Oregon) and

Jeffery D. Tucker, P.E., G.E.

(Oregon)

Company: FFA Architecture and Interiors, Inc. Date: March 30, 2016

Address: 520 SW Yamhill Street, Suite 900

Portland, OR 97204 cc: n/a

GDI Project: NatPark-2-03

RE: Water Supply Well Recommendations

MIIN Visitor Contact Station (PMIS 159776)

Minidoka Internment Camp

Hunt, Idaho

INTRODUCTION

This memorandum provides a summary of our recommendations associated with an existing water supply well (warehouse well) located at the National Park Service (NPS) MIIN Visitor Contact Station – Minidoka Internment Camp facility in Hunt, Idaho. Specifically, this memorandum summarizes our understanding of the subject well and presents our recommendations for securing a potable water supply for the planned site upgrades.

SUMMARY OF EXISITNG WELL

Based on our review of information provided by FFA Architecture and Interiors, Inc. (FFA) and other members of the project team, we understand the following:

The subject well was drilled in 1947 as the “warehouse well,” which provided domestic water to the site facilities. An original water well log detailing original construction specifics is not available for the well.

Based on the age of the well, it has been assumed that the surface seal of the well likely extends to approximately 18 feet below ground surface (BGS), which reflects the previously established minimum seal depth. This seal depth is substantially less than the current minimum requirement of 38 feet BGS (general water wells) and 58 feet BGS (public supply wells).

The well has been inactive for some period of time (several years), and the submersible pump formerly in operation was removed from the well casing in March 2015. It was noted during the March 2015 pump removal that the pump column (riser pipe) was substantially corroded.

The static water level in the subject well is approximately 225 feet BGS.

The total depth of the well is approximated at 440 feet BGS. The wellhead is situated within an excavated vault (pit) with approximate dimensions of 4 feet wide by 5 feet long by 4 feet deep.

A camera survey completed in February 2016 indicated that the surface casing consists of 6-inch-diameter carbon steel, which telescopes/transitions to a 4-inch-diameter casing within a few feet from the top of casing. This initial camera survey also revealed free-floating material/debris at approximately 250 feet BGS and an obstruction (likely an old submersible pump intake screen) at approximately 252 feet BGS. The presence of this obstruction denied further access for completion of the camera survey.

SUMMARY OF OPTIONS FOR WATER SUPPLY WELL

In review of the available information, the project team has contemplated two options involving the site water supply well, as follows:

1. Continue use of the existing warehouse well for potable supply to the site. Evaluations associated with this option would include a review of construction standards/requirements and permitting, well redevelopment, flow testing, and water quality sampling.

2. Abandon the existing well in accordance with state regulations. Identify a new location to drill, construct, and test a new supply well for the site.

GeoDesign prepared a series of scope and cost summaries reflecting a step-wise approach to the evaluation of the existing well. In review of these summaries, the project team agreed that some preliminary research that revealed the most appropriate path forward was necessary.

PRELIMINARY RESEARCH AND CORRESPONDENCES

Identification of the most appropriate option regarding the existing well includes consideration of two factors. First, a determination of regulatory requirements for construction (i.e., minimum seal depth required) as prescribed by the Idaho Department of Water Resources (IDWR) was required.

Second, a determination of the physical feasibility of redeveloping, reconditioning, and/or augmenting the existing seal depth was required.

GeoDesign contacted Chad Hersley of IDWR on March 30, 2016 to discuss our understanding of the existing well construction and the minimum seal depths required for a water supply well of this nature. Mr. Hersley indicated that based on the age, location, and proposed use of the well, IDWR would not recommend a surface seal of less than 38 feet. The primary basis of this decision, according to IDWR, is the relative lack of low-permeability lithology (i.e., clay) situated above the fractured basalt water-bearing units beneath he site, which would otherwise act as a natural barrier to prevent preferential migration of potential contaminants. Mr. Hersley also indicated that the Idaho Department of Environmental Quality would require a minimum seal depth of 58 feet for a public supply well of this type. Therefore, continued use of the existing well for the purpose of a potable public supply would require an alteration process involving over-reaming the existing casing to establish the required minimum applicable seal depth of 58 feet BGS.

GeoDesign contacted two licensed well drilling contractors with demonstrated ability and history of water well drilling in the site area (Walker Water Systems and D&C Drilling). We provided a summary of existing well conditions and project objectives to these contractors and requested feedback regarding the ability to repair, redevelop, and re-use the existing warehouse well. The following summarizes the comments we received from the two water well drillers:

The presence of the vault/pit structure poses safety/caving issues with regard to the positioning of large drilling equipment over the below-ground vault and well casing. This arises from the weight of the drilling rig and associated tooling needed to perform work on a well of this depth (over 400 feet BGS). In addition, the presence of unbraced tooling between the upper ground surface and well casing (approximately 4 to 5 feet) posed a secondary safety concern.

The specialized tooling required to over-ream the casing (in order to install an augmented seal depth around the existing casing) would be difficult to achieve given the nature of the basalt rock material in close proximity to ground surface at the well location. According to the drillers, these difficulties would result in a repair/reconditioning costs that approaches or matches the cost of drilling a new well.

The standard tooling size (4.875 inches in diameter) used by the drillers and required to redevelop the well (swabbing, jetting, airlifting, impulsing, etc.) would not fit within the 4-inch-diameter well casing that was revealed in the initial camera survey. Therefore, the only feasible redevelopment activity would include some limited, open-ended airlifting and/or deployment of a submersible pump to remove accumulated sediment from the well bore. Depending on the condition of the well (which is not fully understood based on the limited, initial camera survey), this pumping technique alone may not achieve the goal of redeveloping the well sufficiently for long-term use.

In summary, the comments received by the water well drilling contractors suggests that there are potentially serious physical limitations to performing alteration and/or redevelopment work on the exiting well. Consequently, the statement repeated by both contractors was that this type of work would likely result in costs that mimic the drilling and construction of a new water well.

CONCLUSIONS

Based on results of our review of the available information and our correspondences with IDWR personnel and well drilling contractors, it is evident that there are significant regulatory and physical challenges associated with re-use of the existing water supply well. Navigating these challenges to restore and redevelop the existing well would likely result in project costs that reflect new well construction. For these reasons, we recommend that the NPS move forward with abandonment of the existing water supply well and procure a licensed drilling contractor to drill, install, and develop a new water well that meets current water well construction standards and provides the quantity of water specified by the project.

At the direction of FFA, GeoDesign can prepare performance specifications and bidding documents for the new well installation, testing, and commissioning.

EAH:JDT:kt

One copy submitted (via email only)

Document ID: NatPark-2-03-033016-geom.docx

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