Engineer_Investigation_Report_Final_0002.pdf

HIDDEN LAKE CAMPGROUND & SKILAK LOOP

Dump Stations

Kenai National Wildlife Refuge

SITE INVESTIGATION REPORT

Prepared by:

PND Engineers, Inc.

1506 West 36th Avenue Anchorage, AK 99503

Prepared for:

U.S. Fish & Wildlife Service 1011 E. Tudor Road Anchorage, AK 99503

November 2022

HIDDEN LAKE CAMPGROUND & SKILAK LOOP November 2022

Site Investigation Report

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Table of Contents

Table of Contents

List of Appendices

1 Introduction

1.1 Background Information

2 Existing Conditions

2.1 Hidden Lake Campground Dump Station

2.2 Skilak Loop Dump Station

3 Potential Solutions, Alternatives and Recommendations

3.1 Hidden Lake Campground Dump Station

3.1.1 Dump Station Maintenance Recommendations

3.1.2 Alternative 1 – Replace Septic Tank

3.1.3 Alternative 2 – New Well House Solar Power Well Pump System

3.2 Skilak Loop Dump Station

3.2.1 Dump Station Maintenance Recommendations

3.2.2 Alternative 1 ‐ Decommission Lagoon and Reconstruct Cells

3.2.3 Alternative 2 ‐ Decommission Lagoon and Construct Septic System

3.2.4 Alternative 3 – Replace Well House Solar Power Well Pump System

4 Expected Permitting

5 Construction Cost Estimation

5.1 Hidden Lake Campground Dump Station ROM Cost Estimates

5.2 Skilak Loop Dump Station ROM Cost Estimates

List of Appendices

Appendix A: PND Project Field Visit Report ‐ October 6, 2022

Appendix B: Design Concept Drawings

Skilak Loop Dump Station Alternative 1 – Decommission Lagoon and Reconstruct Cells

Skilak Loop Dump Station Alternative 2 – Decommission Lagoon and Construct Septic System

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1 Introduction

The project as specified by Statement of Work Line Item 08 consists of two separate dump station facility locations: the Hidden Lake Campground RV Dump Station, and the Skilak Loop RV Dump Station. Both dump stations need various infrastructure improvements and maintenance in order to modernize the facilities and reduce reoccurring operation and maintenance (O&M) efforts of U.S. Fish & Wildlife

(USFWS) staff. The intent of this report is to provide the USFWS with narrative descriptions, potential solutions and repairs, schematic alternatives for facility improvements, a schedule of probable required project permits needed to perform the proposed work, and construction cost estimates.

1.1 Background Information

PND Engineers, Inc. (PND) performed a site visiting on October 6th, 2022 to evaluate the existing Hidden

Lake Campground and Skilak Loop dump station facilities and discuss the scope of the proposed work.

The site visit and subsequent discussions with USFWS personnel identified several issues that the proposed project intends to address. The Field Visit Report summarizing the findings of the site visit to both project locations is included in Appendix A and details pertaining to each task are discussed below.

2 Existing Conditions

Both project locations are located within the Kenai National Wildlife Refuge along Skilak Lake Loop Road.

See Figure 1 for locations of dump station facility locations.

Figure 1: Hidden Lake and Skilak Loop Dump Station Vicinity Overview

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2.1 Hidden Lake Campground Dump Station

The Hidden Lake Campground RV Dump Station was constructed in 1989 and is located off Skilak Lake

Road approximately 3.6 miles south of the eastern Sterling Highway intersection. The dump station consists of a paved pull‐thru loop with a hatch style dump station, water tower, septic tank, leach field, and a well house which houses the fresh water system. The dump station systems are in generally good condition. The campground has 44 camp sites, with 54 total camp site trailer stalls. The campground boat launch area has an additional 41 trailer stalls used for boat trailer parking and overflow camping.

Figure 2: Hidden Lake Campground Dump Station Pull‐thru Loop Entrance

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2.2 Skilak Loop Dump Station

The Skilak Loop RV dump station was constructed in 1994 and is located off Skilak Lake Road approximately 7.3 miles south of the western Sterling Highway intersection. The dump station consists of a paved pull‐thru loop with vehicle parking stalls, four (4) hatch style dump stations, four (4) water towers, a two‐cell wastewater treatment lagoon, and a well house which houses the non‐potable water system. The dump station serves the Upper and Lower Skilak Lake Campgrounds, which have a combined

40 camp sites with 43 total camp site trailer stalls. Both campgrounds have boat launch facilities with a combined 30 trailers stalls used for boat trailer parking and overflow camping.

The wastewater treatment lagoon system appears to be functional; however, the current depth of effluent within the primary impermeable cell used for stabilization of solids is well below design operating levels necessary for transfer of decanted effluent to the secondary cell for percolation.

The dump station non‐potable water system is currently inoperative. The well pump and pressure tank system contained within the well house building is equipped with a solar power system. Difficulties with retrofitting the existing power system with updated components have rendered the system inoperative until upgrades are complete. The water system was not functional for the 2022 use‐season.

Figure 3: Skilak Loop Dump Station Pull‐thru Loop

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3 Potential Solutions, Alternatives and Recommendations

3.1 Hidden Lake Campground Dump Station

3.1.1 Dump Station Maintenance Recommendations

The existing dump station, septic tank, and leach field systems were originally constructed in 1989 according to historical as‐built record documents. Given the age of the facility, PND recommends the leach field and septic tank connection be surge tested to determine if the leach field is capable of absorbing a surge load (approximately 700 gallons) within a 4‐hour period per current ADEC recommendations. Leach field surge testing should be conducted during the summer operating season when the wastewater system is subject to typical seasonal effluent loading. Additional water should be added to the leach field after completion of surge testing to verify the system can treat and dispose of the estimated maximum daily flow (approximately 1,750 gallons) required by ADEC. Water for surge testing may introduced through the existing field monitoring tube(s) or directly through the septic tank, if necessary.

Additional water should also be added to the septic tank cleanout to verify the connection between the septic tank and leach field is functional.

Figure 4: Hidden Lake Dump Station Leach Field

Leach Field Monitoring Tube

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3.1.2 Alternative 1 – Replace Septic Tank

Dependent on the results of the leach field testing and visual evaluation of the exposed existing septic tank, replacement of the septic tank and/or leach field may be warranted.

Given the existing septic tank has been in service for more than 30 years, the tank may be approaching the end of its service life. Steel septic tanks generally have an average expected life span of 25 years.

Failure generally occurs due to corrosion causing leaking or when internal baffles used to keep solids out of the leach field have corroded.

Should the existing condition of septic tank warrant replacement, PND recommends the steel tank be removed and replaced in‐kind with a new steel tank of equal size. USFWS reports the existing system functions well, with no reported issues relating to septic tank or leach field size for current usage.

Replacement of the septic tank will be subject to ADEC Engineered Wastewater System Plan Review and approval. A design waiver or professional engineer justified sizing criteria for wastewater flows may be required, as the existing tank appears to be undersized based on current design wastewater flow criteria for campgrounds. Based on the 95 trailer stalls in the campground area, and design wastewater flow of

50 gallons per day per site, replacement of existing tank with a new 6,000‐gallon septic tank may be required by ADEC. Actual required size of tank is subject to ADEC plan review and approval conditions.

ROM cost estimate information for Hidden Lake Campground Dump Station Alternative 2 is provided in

Section 5.1.

Figure 5: Hidden Lake Dump Station Septic Tank; General Area and Damaged Riser Pipe

Existing Septic Tank, General Area

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3.1.3 Alternative 2 – New Well House Solar Power Well Pump System

The existing Hidden Lake Campground well house water system is not equipped with a permanent power supply system. USFWS staff are required to mobilize an electric generator unit multiple times per season to power the well pump in order to refill the 3,000‐gallon holding tank which supplies non‐potable water to the dump station. USFWS staff generally must remain on‐site for the duration of filling operations, which is a costly use of personnel hours and financial resources. The total amount of times the holding tank must be refilled during the operational season is irregular and variable dependent on public usage from year to year.

The existing well house and pump can be retrofitted with a modern solar power system, appropriately rated for the existing well pump demand, to mitigate or likely eliminate the need for USFWS staff to power the well pump with a generator unit. A 400‐watt solar well pump system is anticipated to be sufficient given the assumed daily recharge flow demand and large existing holding tank. Additionally, the holding tank can be equipped with a float switch to keep the tank filled during the operational season. A high water and low water light indicator could also be installed on the well house building exterior, mitigating the need for USFWS staff to visually check the interior of the well house and holding tank level.

ROM cost estimate information for Hidden Lake Campground Dump Station Alternative 2 is provided in

Section 5.1.

Figure 6: Hidden Lake Dump Station Well House Non‐potable Water Holding Tank

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3.2 Skilak Loop Dump Station

3.2.1 Dump Station Maintenance Recommendations

The original wastewater lagoon capacity appears to be significantly oversized for actual usage of the facility. For the wastewater lagoon to function properly, there must be enough septage effluent and precipitation input into the system to maintain the liquid operating level, which allows decanted effluent to pass from the stabilization cell to the percolation cell. The current effluent liquid level is well below the operating level and no transfer of effluent to the percolation cell is occurring.

To adequately size potential dump station wastewater system improvements, either a newly constructed stabilization cell or a new septic tank and leach field, PND recommends USFWS conduct a field study to determine actual usage and septage input flows for the facility. For campground dump stations, current ADEC and EPA guidance for wastewater flows vary from 50 gallons per day per camp site (campgrounds with no water or septic hook ups) to 125 gallons per day pr camp spot (campgrounds with hook ups).

The dump station foot‐operated hatches are currently seized, and do not allow for their intended hands‐ free foot‐operations. PND recommends these hatch covers be well lubricated to resolve seizing, or replaced with new hatch covers if necessary.

Figure 7: Skilak Loop Existing Stabilization Cell

Failed Discharge Assembly

Liquid Below Operating Level

Vegetation Growing Thru Cell Liner

ChristopherEdwards Line

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3.2.2 Alternative 1 - Decommission Lagoon and Reconstruct Cells

The existing dump station, wastewater lagoon, and water systems were originally constructed in 1994 according to historical as‐built records and permit documents. According to original permit documents, the existing wastewater lagoon was sized for a five‐year sewage solids capacity, at which point the original stabilization cell would be decommissioned and a new primary cell constructed adjacent to the percolation cell. Subsequent primary cells were not constructed, and the dump station facility still utilizes the same primary cell nearly 30 years after original construction.

As the lined primary cell is well beyond it’s expected service life, and the lagoon has not been maintained for some time, the primary cell should be closed and decommissioned. Decommissioning of lagoon involves pumping the existing liquid effluent from the stabilization to the percolation cell, then lining and capping the cell with soil backfill and seeding. Sewage solids can either be left in‐place, or hauled off‐site to a permitted disposal facility. For lagoon cell closure, an ADEC Solid Waste permit and

Engineered Wastewater System Plan Review and ADEC One‐Time Sewage Solids Landfill Authorization

Permit (if disposing of solids in‐place) is required.

If USFWS prefers to cap sewage solids in‐place, PND recommends USFWS verify Kenai National Wildlife

Refuge lands are not regulated by 36 CFR Part 6, which prohibits final disposal of domestic sewage solids within National Park System lands. If allowed, final disposal of sewage solids in‐place is recommended as the lower cost final disposal method.

If a new lagoon cell is preferred, a new stabilization cell would be constructed adjacent to the existing percolation cell, and new dump station and cell transfer piping would be installed to connect existing features to the new cell. Per current ADEC Lagoon Construction Guidelines, the new stabilization pond would be sized for a 20‐year service life. The footprint of the new stabilization cell would be approximately 7,500 square feet, with a total cell depth of seven (7) feet. The existing percolation cell sand and loam would also be reconditioned or replaced with two (2) feet of new sand filter material, dependent on the results of a percolation test.

A Design Concept Drawing of proposed site layout decommissioning the existing stabilization cell and reconstructing the lagoon cells is provided in Appendix B.

ROM cost estimate information for Skilak Loop Dump Station Alternative 1 is provided in Section 5.2.

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Figure 8: General Area of New Stabilization Cell; Looking South from Lagoon Access Driveway

3.2.3 Alternative 2 - Decommission Lagoon and Construct Septic System

Like Alternative 1, this alternative also proposes to decommission the existing stabilization cell by capping sewage solids in‐place. However, rather than reconstructing lagoon cells, a new septic tank and leach field would be constructed to replace the wastewater lagoon system entirely.

As the current wastewater lagoon system has proven difficult to regularly maintain the operating level of effluent as well as perform routine pond skimming of debris, replacement with a septic tank and leach field offers a system which will be easier to monitor and maintain. USFWS currently performs maintenance pumping of the Hidden Lake Campground septic tank, thus replacing the lagoon with a septic tank system is in‐line with current operational procedures and maintenance schedules.

Based on the number of camp sites trailer stalls and overflow trailer stalls at Upper and Lower Skilak

Lake campgrounds, a new 5,000‐gallon septic tank is recommended using a design flow criteria of 50 gallons per day per site. The actual size of the tank may be subject to increase, dependent on ADEC

Engineered Wastewater System Plan Review approval conditions.

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The new proposed leach field would be constructed within the existing percolation cell footprint to minimize impacts to previously undisturbed areas and reduce costs associated with clearing and excavation.

A Design Concept Drawing of proposed site layout decommissioning the existing stabilization cell, installing a new septic tank, and repurposing the existing percolation cell for the new leach field is provided in Appendix B.

ROM cost estimate information for Skilak Loop Dump Station Alternative 2 is provided in Section 5.2

Figure 9: General Location of New Septic Tank; Looking Southwest from Dump Station

3.2.4 Alternative 3 – Replace Well House Solar Power Well Pump System

The water system which supplies the dump station is currently inoperable due to difficulties retrofitting the existing solar power system with updated components. The current solar power system was installed during the original construction in 1994. Much of the system components appear to have been retrofitted and replaced over time.

General Proposed Location of New Septic Tank

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Rather than continue with retrofitting the existing system, PND recommends the entire solar power system be replaced with a new “turnkey” system, designed specifically for the well pump and pressure tank demands of the facility. Solar power system technology has evolved significantly since the time of original construction, and a replacement with a complete site‐specific system will ensure all components function together to power the water system. Replacement with a new system will also ensure that components are available should they require replacement in future. Additionally, replacement with a new system would offer a facility specific O&M manual which will significantly improve USFWS staff’s ability to troubleshoot potential future issues. Given the well house is currently equipped with a pressure tank system, a need for an 800‐watt solar well pump system with a 48‐volt battery supplemental power supply is anticipated in order to maintain pressure tank volume during periods where multiple dump station water towers are in use, or during extended periods of cloud cover. Alternatively, a larger or additional supplemental pressure tank could be integrated to increase holding capacity of the well house system in lieu of a supplemental battery system, if preferred.

ROM cost estimate information for Skilak Loop Dump Station Alternative 3 is provided in Section 5.2

Figure 10: Skilak Loop Dump Station Well House; Existing Well Pump and Pressure Tank

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4 Expected Permitting

A preliminary list of potential permits and approvals for the Hidden Lake Campground and Skilak Loop

Dump Station Improvements project is shown in the table below. Currently anticipated improvements include potential replacement of the Hidden Lake Campground Dump Station septic tank, decommissioning the existing Skilak Loop Dump Station wastewater lagoon, installing a new septic tank and leach field system, and providing new solar power well pump systems to the existing water systems at both well house locations.

Agency Code Permit/Authorization

USFWS

NEPA, Refuge Authorizations Consideration and documentation of environmental impacts or proposed improvements. Compliance with applicable Refuge mandates and policies.

Migratory Bird Treaty Act, Bald and

Golden Eagle Protection Act

Consideration of potential impacts to migratory birds and to bald and golden eagles. Project timing considerations for potential disturbance activities, including clearing.

USACE

Clean Water Act Section 404: Permits for Dredges or Fill Material; Regulates the discharge of dredged and fill materials into waters of the

U.S., including wetlands. Improvements to recreational facilities may be covered under Nationwide Permit #42.

May be required if wetlands are present in dump station areas.

ADEC

18 AAC 83

Alaska Pollution Discharge Elimination

System Program (APDES)

APDES Permit Program, Construction General Permit for

Storm Water Discharges for Large and Small Construction

Activities (2021 CGP)

18 AAC 72

Wastewater Disposal

Engineered Wastewater System Plan Review, Approval to

Construct, And Approval to Operate.

18 AAC 60

Solid Waste Management

One‐Time Sewage Solids Landfill Authorization Permit

ADNR/SHPO

National Historic Preservation Act Section 106: Review and assessment of efforts on historic properties. This process includes consultation with

SHPO/THPO, and Alaska Native Tribal Organizations.

Acronym Text

AAC Alaska Administrative Code

ADEC Alaska Department of Environmental Conservation

ADNR Alaska Department of Natural Resources

NEPA National Environmental Preservation Act

SHPO/THPO State Historic Preservation Office/Tribal Historic Preservation Office

USACE United States Army Corps of Engineers

USFWS United States Fish & Wildlife Service