24R0040_Design_Analysis_12Apr2023_SS_1.pdf

Bureau of Land Management Nome Creek Road Repair Nome Creek Road, Alaska

Final Construction Documents

For:

222 University Avenue Fairbanks, Alaska 99709

April 12, 2023

Nome Creek Road Repair Nome Creek Road, Alaska

Final Construction Documents

Table of Contents Design Analysis Narrative Appendices Appendix A – Borrow Sites Geotechnical Findings Report Appendix B – Traffic Control Memo

Cost Estimate (To be provided separately) 95% Design Review Comments

By:

Design Alaska, Inc.

601 College Road Fairbanks, Alaska 99701

April 12, 2023

BUREAU OF LAND MANAGEMENT

NOME CREEK ROAD REPAIR

NOME CREEK ROAD, ALASKA

FINAL CONSTRUCTION DOCUMENTS

CIVIL NARRATIVE

Design Alaska, Inc. Page 1 of 14

INTRODUCTION/HISTORY

BLM in cooperation with Design Alaska is proposing to rehabilitate Nome Creek Road located within the White Mountain Recreation Area of Alaska, accessible via US Creek Road, located at milepost 57 of the Steese Highway.

Nome Creek Road provides access to several hiking and motorized recreational trails, campgrounds, gold panning and camping opportunities. It is a critical access point for the White Mountains Recreation Area.

The road is primarily used by the recreating public during the summer months. During winter, both campgrounds are closed, and maintenance and snow removal is suspended for the season. The road is still utilized for recreation access by snowmachine, ski, and dog sled.

Nome Creek Road was originally constructed by the Alaska Department of Transportation and Public Facilities (AKDOT&PF) in 1995. Since initial construction, continuous use, maintenance, and soil settlement has decreased the overall embankment height and impacted the performance of the designed drainage system. The intent of this project is to improve the overall drainage and driving surface along Nome Creek Road. The project involves 18 miles of gravel road between Mt. Prindle Campground to the east and Ophir Creek Campground to the west beginning at the Nome Creek bridge, roughly centered between the campgrounds. This project is a Preventative Maintenance project and design elements are intended to extend the life of and restore functionality of existing improvements by repairing drainage structures and the driving surface of Nome Creek Road. Specific road surface and drainage conditions are described further in the Project Description section of this report.

Design Alaska conducted several site visits during the summer of 2021. Site visits were performed just after spring breakup, during summer, and immediately before heavy snow accumulation in the fall. During site visits, Design Alaska performed an inventory of 124 existing culverts along the Mt. Prindle alignment to the east of the bridge, and the Ophir Creek alignment to the west of the bridge. The general condition of the road and campgrounds was also noted, and specific problem areas were identified and discussed with the maintenance personnel present at the site. The condition of the gabions and stream channel migration at Nome Creek Bridge was also investigated.

Design Alaska performed a topographic survey of the entire Nome Creek corridor including photogrammetric and aerial mapping flights. The aerial mapping data was correlated with ground survey data to produce a detailed survey of the existing grade along the entire extent of the project.

Shannon and Wilson performed geotechnical borings along the road to assess in place material and subsurface conditions along the road corridor, especially at areas of significant settlement and embankment failure. Exploratory drilling was also performed for the purpose of assessing material availability and suitability at several sites near the project area.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 2 of 14

PROJECT DESCRIPTION

Existing Conditions

Nome Creek Road was constructed as an AKDOT&PF project approximately 30 years ago. Several major repairs have been performed since the initial construction, including significant embankment buildup and culvert upgrades at both Twin Creek crossings and at Moose Creek. Extensive maintenance is performed each spring in preparation for opening to the public. Several areas have experienced recurring washout and embankment failure and have been specifically identified as needing additional analysis and strategic repairs. Several specific areas of interest are discussed below.

Some portions of Nome Creek Road experience buildup of aufeis during winter months. Aufeis is a condition unique to arctic and sub‐arctic climates which can present significant design challenges for roadways. Generally, aufeis will accumulate in stream channels and swales especially at culverts, in road cuts that intercept the subsurface flow paths, and other improvements intended to capture and convey runoff during summer months. In the springtime, the large accumulation of aufeis at some culverts and stream crossings will remain in place, blocking drainage flow long after the surrounding, loose snowpack has melted. As runoff from melting snow follows the natural drainage paths, it is impeded in the areas where the accumulated aufeis has blocked stream channels, ditches, and culverts. The flowing meltwater will frequently overtop the road embankment causing washouts and significant erosion damage. The location and extent of aufeis accumulation is not consistent year to year, as it is highly dependent upon specific seasonal snowfall, summer/fall rainfall accumulation, air/soil temperature, subsurface soil and rock conditions, and subsurface flow conditions. Though this makes predicting and mitigating potential damage very challenging, some consistency can be anticipated, and controls put in place to protect areas of frequent recurrence.

Road Surface and Ditches

Since construction, the road has been maintained by general blading and repair of specific damaged areas.

Frequent blading, hydraulic segregation, and fugitive dust caused by vehicle traffic has significantly deteriorated the surface course of the existing road in many areas. Much of the fines from the original road surface have accumulated in the ditches, along with other soils from suspended sediment and blading repairs. In addition to the decreased capacity of the existing ditches caused by accumulated sediment, many of the culvert inlets have also become partially obstructed by sediment, further decreasing the effectiveness of the designed drainage system along the road corridor. The originally constructed crown of the road has also been largely eliminated. Re‐establishing and maintaining the crown has become increasingly challenging for maintenance crews as the surface course has become very thin or completely absent over years of use and maintenance. In some areas, large cobbles are visible in the traveled way where the tailings used for subbase have become exposed. These large, exposed cobbles are an impediment to travel and user safety. The decreased drainage potential of the road has resulted in frequent saturation of portions of the embankment, causing failure and blowout of many areas.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 3 of 14

Existing Culverts

During initial site investigation, an inventory of the existing culverts was performed. Approximately 30 of the 124 culverts inventoried are in need of repair or replacement. Many of the culverts have been obstructed by accumulated sediment in the ditches and by settlement of the road embankment.

The Nome Creek valley is underlain by permafrost at varying depths along its entire length. In many areas the altered thermal regime of the soils and the poorly performing drainage structures has accelerated permafrost degradation along the road corridor. As permafrost thaws under the road embankment, the soils consolidate, and differential settlement occurs relative to the adjacent undisturbed soils. This differential settlement causes a belly shape in the culverts, which can greatly reduce their effectiveness at conveying water under the embankment. In some cases, the belly can be severe enough to cause separation of the culvert, allowing runoff water to be injected directly into the roadbed.

Informational Signs

Many of the existing signs along Nome Creek Road are in need of replacement. Existing signs include traffic signs, information signs, parking signs, campground signs and mileage markers. An inventory of the existing signs is included in the drawings for this project.

Dickie’s Hole

Dickie’s Hole is a developing problem site that has experienced significant sedimentation buildup, washout, and settlement in recent years. The upstream permafrost appears to be rapidly degrading, as evidenced by the terrain upstream of Dickie’s Hole, and eroding and forming a more pronounced drainage channel. Past destruction of surface vegetation by wildfire has contributed to the increased surface erosion and permafrost thaw. With less vegetation present to retain moisture and delay runoff, more runoffs occurs.

The degrading permafrost is also changing the erosion regime and significant sedimentation has accumulated where the drainage encounters Nome Creek Road. During high seasonal or stormwater flow, the existing culverts are inadequate to convey the runoff. The increased sedimentation upstream of the road further reduces ditch volume and clogs the existing culverts. At the time of the most recent site visit, deposited sediment had accumulated against the road embankment to a depth of at least 8 feet.

Culvert damage is also occurring due to aufeis accumulation. Aufeis, built up at the culvert inlet over the winter, freezes around the culvert inlet. As water levels rise within the flowline of the ditch, buoyancy forces acting on the aufeis clinging to the drainage structure impart uplift forces, causing buckling and failure of the culvert inlet. This damage will, at best, reduce the effectiveness of the culvert, but often damages the culvert within the embankment, allowing flow to escape within the embankment and cause massive erosion. Saturation of the embankment can further lead to loss of soil strength and blowout of the roadway. The failed ditches and culverts have led to overtopping of the road embankment, washout, and further erosion.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 4 of 14

Moose Creek

The Moose Creek crossing was the subject of a major repair project in 2006 to correct damages similar to what is presently being observed at Dickie’s Hole. In the recent past, the corrections and improvements to the Moose Creek crossing have begun to degrade, settle, and show signs of damage.

Mt. Prindle Campground

Mt. Prindle Campground has experienced seasonal flooding in recent years which has degraded the existing roads and camp sites. The embankment height of the campground roads and campsites are relatively low, making them susceptible to flooding. Vegetation around the campground is a mix of low willow, alder, and some small black spruce. The low vegetation provides great access to the surrounding viewshed but provides limited erosion protection.

Nome Creek has experienced significant aufeis buildup near the campground in recent winters. This aufeis occasionally forms a complete blockage of the stream channel. With the primary channel blocked, accumulated spring runoff is diverted around the stream channel. In the area of Mt. Prindle Campground, runoff flows through the campground, causing widespread erosion and washout of campground drives and campsites.

Vehicle circulation at the Mt. Prindle Campground is generally in the form of an elongated loop drive with campsites arranged around the outside of the loop. Well and outhouse structures are located on the inside of the loop to provide the shortest access to the most campsites. Maintenance and repair have generally been focused on the access drive loop, and the inner foot trail connecting the drive loops to the well is in need of reconstruction. The existing well located near the center of the campground is a hand operated pitcher pump on a 4‐inch concrete slab. During a recent flooding event, which washed out the foot trail leading to the well, the concrete slab was severely undercut and eroded, causing uneven settlement and instability of the slab.

Ophir Creek Campground

Ophir Creek Campground also experiences significant spring flooding and washout for similar reasons to Mt. Prindle Campground. However, the flooding at the Ophir Creek Campground is likely caused by ice/debris damming of the stream channel during breakup rather than primarily by aufeis buildup. Where Mt. Prindle Campground experiences widespread, general overtopping and washout, Ophir Creek Campground experiences channelized and concentrated washout at specific locations. This is partially because the road and campsite embankment height are greater at Ophir Creek than at Mt. Prindle. Ophir Creek Campground is also surrounded by larger, mature trees including spruce, birch, and aspen. The trees and root mass protect the surrounding area from erosion by trapping ice and slowing runoff velocity.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 5 of 14

Ophir Creek Campground has several historic minor channels running through the campground. These channels are generally dry throughout the summer months, but during spring melt, they are major conduits for diverted and flooded stream flow. This concentrated channelization reduces widespread erosion but causes severe damage where the channels encounter campground drives and campsites.

Existing culverts at these locations adequately handle peak flows during spring runoff and major repairs are typically required each spring before the campground can be reopened.

In general, the road and campsite surface at Ophir Creek Campground is in good condition. Major reshaping throughout the campground is not anticipated. Flood control and road embankment repair will be limited to areas of recurring washout damage.

Nome Creek Administrative Access Road

This project will not evaluate the safety or code compliance of the runway for aircraft use. Consideration of any aircraft or runway code is outside the scope of work performed herein. Repairs will be limited to addressing drainage and grading failures.

BLM operates a small, gravel access road to the Nome Creek Administrative site and maintenance yard along the Ophir Line. This access road is occasionally used as a small aircraft landing area. The road has experienced settling and water often overtops the road from a drainage settling pond which makes use by highway vehicles and/or aircraft unsafe

Nome Creek Bridge and Gabion Revetment

Nome Creek Bridge is a vehicle bridge crossing Nome Creek and was installed as part of the original road construction. The bridge is 24 feet wide with metal guard rails and spans 30 feet between abutments. The bridge deck is a voided, reinforced concrete slab with a 3 percent cross slope. The bridge abutments are a pile supported timber wall with a concrete cap supporting the bridge decking. The initial construction of the Nome Creek Bridge included installation of a network of interlocking, 3‐foot by 3‐foot, galvanized chain‐link gabion baskets to control erosion upstream and downstream of the bridge.

As part of the bridge construction, the stream channel was altered to concentrate flows at a location suitable for bridge construction. Since construction, the stream has been slowly eroding and migrating, forming a new path. The channel migration has caused undercutting of the upstream and downstream erosion protection gabions.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 6 of 14

Demolition

Demolition for this project is limited to removal of several of the failed culverts along the alignment.

Demolition will be limited to the extent needed for replacement work.

Renovated Or New Work

Repairs to the existing road will include reconditioning and resurfacing of the entire length of road. The road prism will be re‐shaped and graded where needed to improve surface runoff. The ditches will be cleaned and reconditioned as needed to improve roadside drainage. In areas where embankment settlement has reduced the ditch depth or other areas where ditch depth is inadequate, ditches will be enhanced by adding additional height to the embankment. Past repairs and improvements have demonstrated that in areas where the vegetated mat is disturbed by excavation, the regrowth and revegetation can take as long as 10 years. During that time improvements and disturbed soils are subject to substantial erosion. In order to avoid erosion damage, the existing vegetative mat will be maintained as much as possible.

Road Surface

The existing ditches will be cleaned of accumulated sediment and vegetation as much as possible without disturbing the native vegetation nearby. Some portions of the embankment will require reshaping and revisions to the vertical grading. This effort will be performed where needed to add ditch depth, improve flow, and generally move runoff away from the embankment more quickly.

Once changes to the road structure, ditch lines and culverts have been completed, the driving surface of the road will be improved by adding a maximum of 4 inches of additional crushed aggregate surface course to the entire length.

Culverts

The inventory of the existing culvert conditions and signs of past performance were evaluated. Many of the culverts are in need of minor inlet repairs, erosion protection at the outlets and clearing of grown‐up vegetation within the ditches. A few of the culverts have failed or been damaged beyond simple repair and will require replacement. The culverts were ranked by priority for replacement. High priority culverts are shown in the attached appendix. Some culverts will require lengthening where road embankment buildup and alterations will widen the road assembly beyond the extent of the existing culverts. Culverts repaired or replaced by this project will include steel cable installation for spring thawing and carsonite marker posts with placards for culvert identification. New culverts will be galvanized, corrugated, welded seam metal pipe.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 7 of 14

Informational Signs

This project will replace all roadside signs and signposts including, but not limited to, parking signs, creek signs, campground signs, and road milage marker signs within the project area. All existing signs shall be salvaged for future reuse. The contractor will deconstruct and store all existing signs in a designated salvage location identified on site for owner collection. New and replaced roadside signs will comply with AKDOT&PF standard drawing S05.02 for rural roads. Campground and Information Signs will meet BLM sign standards and be similar to other BLM Campgrounds in Interior Alaska.

Dickie’s Hole

The primary cause of the sediment accumulation and damage at Dickie’s Hole is believed to be deterioration of the permafrost and expansion of the drainage channel upstream of the road. Addressing this cause is not within the scope of this project, but this project will instead focus on mitigating the effects. Specifically, this project will address the following items: sediment accumulation; standing, confined water against the road embankment; runoff overtopping of the road embankment; and recurring damage to the drainage structures. Quantifying the design flood intensity and recurrence interval is a unique exercise for this situation, as the worst case flooding event is not caused by precipitation, but by snowpack melt. Also, catchment area, time of concentration, and drainage paths vary year to year as aufeis blockages are not consistent. The volume of water contained in a measured snowpack is highly variable, and dependent upon wind conditions, snowfall, relative humidity, and air temperatures throughout the winter months.

Standing water against the embankment and sediment accumulation at the inlet end of drainage structures are believed to be caused by the same overall problem. Specifically, inadequate capacity of the culverts prevents free passage of runoff under the road embankment. While the culverts may be adequately sized to convey the design storm event in summer months, the culverts are partially or completely obstructed by accumulated ice during spring melt. For these reasons, initial repairs will include installation of a larger culvert along with two overflow barrels.

A 58 inch wide by 36 inch tall arch pipe culvert installed at the flow line of the drainage will provide more space for ice accumulation and bypass flow. The arch culvert will be constructed with a cross slope of at least 4 percent to ensure that flow velocity does not fall low enough to allow suspended sediment to precipitate and accumulate at the inlet or within the culvert. Two 36‐inch overflow culverts will be installed in combination with the arch culvert. When the stream channel, including the arch culvert, becomes completely obstructed by accumulated aufeis, runoff flow will be conveyed through the embankment by the overflow culverts. This will eliminate the opportunity for overtopping, reducing annual maintenance and reconstruction in this location.

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Design Alaska, Inc. Page 8 of 14

Repairs at Dickie’s Hole will also include removal of accumulated sediment against the road embankment, restoration of the natural flow channel for at least 50 feet upstream of Nome Creek Road, and measures to protect the drainage structures from damage. Restoring the natural stream channel will help to prevent ponding and sediment buildup against the road embankment. Measures to protect the new culverts will include riprap aprons at the outlet ends, and pipe ends mitered to conform to the road embankment slopes.

During site visits, erosion of the stream channel was noted both upstream and downstream of the culvert location, with a plunge scour pool at the outlet. To control outlet scour velocity, a riprap apron approximately 15 feet long will be constructed at the outlet.

In addition to riprap aprons in the channel, armoring of the embankment slopes at the inlet and outlet was also considered. However, site visits did not indicate embankment erosion at these locations, and riprap on the embankment is not considered necessary.

Finally, in order to prevent damage to projecting culvert ends, both pipe arch culvert and overflow barrels will be mitered to conform to the road embankment slope. The 58‐inch by 36‐inch arch pipe will be fitted with an end section at the inlet in order to increase hydraulic efficiency and reduce any possible erosion.

Moose Creek

A culvert inspection report from summer 2022 noted the 15‐foot diameter steel plate pipe culvert at Moose Creek Crossing as being in fair condition overall. This project will address the issues described in the report. Specifically, scour damage at the inlet and outlet of the 15‐foot diameter major culvert will be repaired and regraded.

Significant scour and undermining of the concrete headwall (paved slope) was noted, including a scour hole on the right side of the inlet measuring 13 feet by 6 feet by 8 inches. Undermining of the concrete apron at the inlet and outlet will be repaired by grouting. A layer of angular riprap will be installed to a depth of 3 feet on the inlet and outlet sides of the culvert to mitigate further erosion and undermining. This will include riprap armoring of the embankment slope on both sides of the inlet.

BLM road maintenance has indicated that the existing steam thaw pipes attached to culverts on Nome Creek Road are not used; thaw wires are used instead. Therefore, the existing thaw pipe and thaw wire will be removed and replaced with a single thaw wire suspended from the top of the culvert barrel and supported at intervals of 4 feet.

Some overflow culverts were also identified by the report as needing erosion correction. The overflow culverts are numbered in the direction of alignment stationing from 1 to 5 consecutively.

NOME CREEK ROAD, ALASKA

Design Alaska, Inc. Page 9 of 14

Overflow Barrel 2: Repair scour and undermining at inlet (5‐foot‐8‐inch scour) and outlet (4‐foot‐9‐inch undermining) end and replace scoured material. Repair with grout at inlet. Install riprap at outlet end to prevent future damage by erosion and scour. Install thaw wire and suspend from the crown of the barrel at 4‐foot intervals.

Overflow Barrel 3: Repair scour and undermining at inlet (6‐foot scour) and outlet (11‐foot undermining) end and replace scoured material. Repair with grout at inlet. Install riprap at inlet and outlet ends to prevent future damage by erosion and scour. Install thaw wire and suspend from the crown of the barrel at 4‐foot intervals.

Mt. Prindle Campground

The road and campsites at Mt. Prindle Campground will be reshaped to add additional height relative to adjacent grade. The road and campsites will be resurfaced similar to Nome Creek Road. All campground road, directional, and information signs will be replaced as described in the sign replacement portion of this design narrative.

A foot trail will be constructed connecting both sides of the loop drive to the center well. The well head hand pump, and concrete slab will be removed and replaced.

Ophir Creek Campground

Repairs at Ophir Creek Campground will be limited to locations damaged by recurring flooding and general resurfacing of the roadway. Two locations within the Ophir Creek Campground will require major reconstruction and reshaping of the road prism. Alterations to grade leading to and from the affected areas will also require reshaping. At the locations depicted in the design drawings, the embankment upstream and downstream of the overtopping location should be armored with riprap while the surface at the sag should be armored with larger boulders. The best case scenario at this location is to strengthen the overtopping surface requiring replacement of only the surface course after erosion events. See drawings for illustration.

Nome Creek Administrative Access Road

Repair work at Nome Creek Administrative Access Road will be limited to regrading settled areas. To mitigate the drainage and associated settlement issues, water from the settling pond should be directed to flow to Nome Creek. To accomplish this work the settling section of the access road is designed to be filled and resurfaced over a 36‐inch culvert allowing water to flow under the road with an increased road embankment along the adjacent pond. A 4‐foot wide drainage channel will deliver water though the culvert and under the access road to Nome Creek, mitigating future erosion and settlement issues. The road will be center crowned along its entire length with a 3 percent cross slope. Shoulders will slope at 6H:1V to grade.

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Design Alaska, Inc. Page 10 of 14

Nome Creek Bridge and Gabion Revetment

Repair work at Nome Creek Bridge will be limited to placement of boulder revetment rock at the toe of the gabions. The rock will help to stabilize the undercutting of the gabions but will not alleviate the underlying issue of the constriction through the bridge or the meander of the stream. See drawings for illustration.

DESIGN CRITERIA – GOVERNING CODES AND REGULATIONS SSHC 1140.3

Authority Having Jurisdiction BUREAU OF LAND MANAGEMENT

USACE, CWA 404 Permit Regulations

ADEC, CWA 401 Water Quality Certification

BLM Manual 9100 – Engineering BLM Manual 9113 – Roads BLM Manual 9130 – Signs

State of Alaska – AS 16.05.841 – Fishway Required, 2020

AKDOT&PF, Standard Specifications for Highway Construction, 2020

Manual on Uniform Traffic Control Devices, 2009

Alaska Highway Preconstruction Manual, 2020

American Association of State Highway and Transportation (AASHTO) A Policy on Geometric Design of Highways and Streets, 2020

AASHTO Guidelines for Geometric Design of Low‐Volume Roads, 2019

Occupational Safety and Health Administration

DESIGN EXCEPTIONS

This project is a Preventative Maintenance project, and as‐such the following design elements were not considered:

Discussion and Comparison of Design Alternatives 3R Analysis Traffic Analysis

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HORIZONTAL/VERTICAL ALIGNMENT

Since the road was constructed in 1995, there has been significant embankment settlement and overall degradation of most of Nome Creek Road. The aim of this project is to generally re‐establish the original as‐built horizontal and vertical geometry. Minor deviations will be required in both the horizontal and vertical directions to efficiently utilize fill along the road corridor.

TYPICAL SECTIONS

Typical sections are included in the plan set.

PAVEMENT DESIGN

There is no pavement for this project.

PRELIMINARY BRIDGE LAYOUT

There is no bridge construction or improvements for this project.

RIGHT‐OF‐WAY REQUIREMENTS

Nome Creek Road and the surrounding area are owned by BLM so, there are no right of way requirements for this project.

MAINTENANCE CONSIDERATIONS

This project does not change the overall road area of Nome Creek Road. An increase to the overall road elevation, culvert replacement, improvements to embankment height, and ditch clearing aims to reduce overtopping events and thereby reduce yearly maintenance efforts needed to open Nome Creek Road for summer activities.

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MATERIAL SOURCES

Additional work by Shannon and Wilson involved an assessment of possible material source sites. Material Site 5 was chosen to be suitable for this project. Material Site 5, or Moose Creek Pit, is approximately 38 acres with scattered sparce spruce trees and tundra on the north site. Subsurface conditions at the Moose Creek Pit consist of approximately 2 feet of frozen silt over 6 feet of silty gravel and cobble. Geotechnical investigations indicate that approximately 274,000 CY of gravel and cobble are available at the site.

The mining plan for this site requires a 100‐foot vegetation buffer along the ordinary highwater mark of Nome Creek. No disturbance may occur in this area except for temporary access routes to the material site. There are four borrow areas that are anticipated to have the highest yields of material. Two borrow areas on the north side of Nome Creek and two to the south. To reach the material sites to the south, Nome Creek must be crossed by a temporary bridge system to minimize disturbance to the creek bank.

The mining plan is arranged to minimize disturbance and undue environmental degradation. Pit reclamation requirements ensure that the site will be revegetated with native foliar and sediment controls are in place throughout the life of the operation.

UTILITY RELOCATIONS AND COORDINATION

There are no utilities that have been identified for this project.

SAFETY IMPROVEMENTS

This project is meant only to address maintenance concerns for the road. Therefore, the only safety improvements will be reflected in a smoother road that will provide safer vehicle passage. No work for this project aims to accommodate pedestrian or bicycle traffic.

INTELLIGENT TRANSPORTATION SYSTEM FEATURES

There are no intelligent transportation system features identified for this project.

DRAINAGE

Existing drainage conditions and proposed improvements for each of the points of interest for this project are described in the Existing Conditions portion of this narrative.

SOIL CONDITIONS

Existing soil conditions are described in the Geotechnical Report attached to this document.

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EROSION AND SEDIMENT CONTROL

This project will disturb roughly 100 acres. This includes areas adjacent to and on Nome Creek Road and the Moose Creek Pit. A contractor developed Storm Water Pollution Prevention Plan will be required and approved by BLM and ADEC prior to commencement of ground disturbing activities. The project extents will be comparable to the 1995 as‐builts with exceptions for where culverts will be removed and replaced.

The project area is vegetated by a range of small brushes, willow, spruce, and alder. Fish habitats are apparent in the small tributaries and streams passing through the campgrounds and parts of Nome Creek Road. Replacement of culverts may temporarily affect some drainage through construction. Dewatering, temporary stream diversions and associated erosion and sediment control measures are expected.

Temporary erosion control Best Management Practices may include, but are not limited to: temporary seeding, erosion control mats, silt fence or fiber rolls, watering and/or chemical stabilization for dust control, velocity controls, and perimeter protection. The preferred perimeter protection method in the project area will be a vegetated buffer, with positive protection devices as needed. Ditch regrading will require inlet protection near adjacent culverts. All disturbed ground will be seeded for permanent stabilization.

ENVIRONMENTAL COMMITMENTS

Environmental permitting is being conducted by BLM.

WORK ZONE TRAFFIC CONTROL

Work on Nome Creek Road will occur Monday through Friday. As such, the road will be closed during this time. The road will be reopened to the public for Saturday and Sunday. Areas that require culvert replacement will utilize a halfwidth construction methodology and roadway detours to ensure the road is passable for construction activities during the week and visiting guests during the weekend.

VALUE ENGINEERING

A value engineering analysis will not be performed for this project.

COST ESTIMATE

A cost estimate is being provided by Estimations Inc. This will follow each design submittal by two weeks.

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APPENDICES

Appendix A – Borrow Sites Geotechnical Findings Report Appendix B – Traffic Control Memo

Appendix A Borrow Sites Geotechnical Findings Report

SUBMITTED TO:

Design Alaska Inc.

601 College Road Fairbanks, AK 99701

BY:

Shannon & Wilson 2355 Hill Road Fairbanks, AK 99709

907-479-0600 www.shannonwilson.com

GEOTECHNICAL FINDINGS REPORT

White Mountains Recreation Area Borrow Sites Exploration - Site 5

NOME CREEK ROAD, ALASKA

March 20, 2023 Shannon & Wilson No: 107285-004

White Mountains Recreation Area Borrow Sites Exploration - Site 5 Geotechnical Findings Report

107285-004 March 20, 2023

PAGE INTENTIONALLY LEFT BLANK FOR DOUBLE-SIDED PRINTING

107285-004 March 20, 2023 ii

Submitted To: Design Alaska Inc.

601 College Road Fairbanks, AK 99701 Attn: Jeff Putnam, PE

Subject: GEOTECHNICAL FINDINGS REPORT, WHITE MOUNTAINS RECREATION

AREA BORROW SITES EXPLORATION - SITE 5, NOME CREEK ROAD,

ALASKA

Shannon & Wilson prepared this report and participated in this project as a subconsultant to Design Alaska, Inc. Our scope of services was specified in Agreement Amendment dated August 20, 2022. This report presents our findings and was prepared by the undersigned.

Sincerely, SHANNON & WILSON

Wendy Presler, P.E.

Senior Associate / Geotechnical Engineer

Wendy Presler 2023.03.20 10:42:44 -08'00'

107285-004 March 20, 2023 iii

CO

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CONTENTS

1 Introduction

2 Field and Laboratory Studies

2.1 Field Exploration and Methods

2.1.1 Geotechnical Test Pits

2.2 Laboratory Testing

3 Site Conditions

4 Closure

5 References

Exhibits Exhibit 2-1: Aggregate Quality Test Results

Figures Figure 1: Material Site 5 Test Pit Locations

Appendices Appendix A: Soil Classification Appendix B: Laboratory Test Results Important Information

107285-004 March 20, 2023 iv

AC

RO

NY

MS

ACRONYMS

ADOT Alaska Department of Transportation & Public Facilities ASTM ASTM International ATM Alaska test method bgs below ground surface MS material site

107285-004 March 20, 2023

1 INTRODUCTION

This report was prepared for the Nome Creek Road project in the White Mountains Recreation Area. This report presents our findings from the material site (MS) explorations, laboratory test results, and discussion of the identified material source.

The project includes development of a borrow source to provide suitable aggregate for construction and for future maintenance.

After our completed findings report, and March 8, 2023, meeting, we understand you have chosen MS 5 as the preferred borrow site. This report presents the findings from MS 5.

2 FIELD AND LABORATORY STUDIES

The field explorations for Site 5 consisted of 6 test pits. Site 5 and the approximate test pit locations are presented in Figure 1.

At each test pit we collected representative samples of gravel and cobble material and combined materials from all six test pits to create a combined sample. The combined sample was transported back to our laboratory for aggregate quality testing. We split the bulk sample into two subsamples and conducted LA Abrasion, Degradation, and Sulfate Soundness testing on the subsamples, designated 5-1 and 5-2.

2.1 Field Exploration and Methods

The test pits were advanced by our subcontractor using a Doosan DX 225 LC excavator.

2.1.1 Geotechnical Test Pits

We advanced test pits at MS 5 on August 2, 2022. The test pits advanced within the identified source areas were advanced to depths ranging from 8 feet below the ground surface (bgs) to 11 feet bgs.

Nathan Adamczak, an experienced geotechnical staff member with our firm, observed the test pitting operations, created a test pit log for each test pit, and collected the material samples for aggregate quality testing in our laboratory. Material samples were recorded and transported to our Fairbanks, Alaska laboratory. The test pits were backfilled with the excavated material after completion of each pit.

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Shannon & Wilson uses a soil identification system modified from the Unified Soil Classification System. Soil descriptions are based on visual-manual procedures consistent with ASTM International (ASTM) D2488 Standard Practice for Description and Identification of Soils (Visual-Manual Procedure) and laboratory testing procedures consistent with ASTM D2487 Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System).

Soil and excavation observations are included in the test pit logs presented in Appendix A.

Our observations are specific to the locations, depths, and dates noted on the logs, and may not be applicable to all areas of the site.

2.2 Laboratory Testing

The aggregate quality testing consisted of the following test methods: LA abrasion consistent with ASTM C131 Standard Test Method for Resistance to Degradation of Small-size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine, sulfate soundness consistent with ASTM C88 Standard Test Method for Soundness of Aggregates by use of Sodium Sulfate or Magnesium Sulfate, and degradation testing consistent with Alaska test method (ATM) 313 Degradation Value of Aggregates. The LA Abrasion test is used to characterize the aggregate toughness and abrasion resistance, the Degradation test characterizes the aggregate durability and relative resistance to produce clay like fines during a prescribed abrasion process in water, and the Sulfate Soundness test characterizes the aggregate resistance to breakdown from weathering during wetting/drying and freezing/thawing.

Test results are presented in Appendix B and summarized in the following table. The table also includes Alaska Department of Transportation and Public Facilities (ADOT) specification limits for Base Course and Surface Course aggregates for comparison purposes.

Exhibit 2-1: Aggregate Quality Test Results

Sample ID (Site-Sample)

LA Abrasion Percent Loss Degradation Value

Sulfate Soundness Percent Loss

5-1 40 81 1

5-2 39 79 0

ADOT Base Course Specifications

50, max. 45, min. 9, max.

ADOT Surface Course Specifications

45, max. 45, min. 9, max.

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3 SITE CONDITIONS

The area originally identified as MS 5 was approximately 38 acres. Based on access, vegetation, and topography information collecting during our site explorations, and using subsurface data collected, the area was reduced to a total area just under 28 acres. Surface conditions consisted of tundra with sparse black spruce and low-lying areas of saturated tundra and grasses on the north side of the site. The surface conditions at the west end of the site included tundra with dense tall black spruce and white spruce. The east side of the site also consisted of tundra with tall black spruce, white spruce, and alder.

Subsurface conditions at MS 5 consisted of frozen silt and silty gravel to the depth explored in areas with tundra and sparse black spruce. In an area of tall white spruce on the west side of the site we observed approximately two feet of silty material underlain by approximately five feet to six feet of gravel with cobbles. In an area of tall white spruce, black spruce, and alder on the east side of the site we observed approximately two feet to three feet of silty material underlain by approximately six feet to eight feet of gravel and cobble.

4 CLOSURE

Our interpretations, analyses, conclusions, and recommendations are based on:

The limitations of our approved scope, schedule, and budget.

Our understanding of the project and information collected during our explorations, as well as information provided by the Owner and our client.

Our previous experience near the project site, and on similar projects in the area.

This report was prepared for the exclusive use of Design Alaska, Inc. for specific application to the design and construction of the White Mountains Recreation Area Access Improvements project. This report is not intended to be used or relied upon for any other purpose. Please review "Important Information about your Geotechnical Report", which can be found at the end of this report.

5 REFERENCES

ASTM International, 2017, Standard practice for description and identification of soils

(visual/manual procedure), D2488-17e1: West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.08, soil and rock (I): D420 - D5876, 13 p., available: www.astm.org.

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ASTM International, 2018, Standard test method for soundness of aggregates by use of sodium sulfate or magnesium sulfate, C88-18: West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.02, concrete and aggregates, 6 p., available: www.astm.org.

ASTM International, 2020, Standard practice for classification of soils for engineering purposes (unified soil classification system), D2487-17e1: West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.08, soil and rock (I): D420 - D5876, 10 p., available: www.astm.org.

ASTM International, 2020, Standard test method for resistance to degradation of small-size coarse aggregate by abrasion and impact in the Los Angeles machine, C131-20:

West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.02, concrete and aggregates, 5 p., available: www.astm.org.

ASTM International, 2021, Standard test methods for laboratory determination of density (unit weight) of soil specimens, D7263-21: West Conshohocken, Pa., ASTM International, Annual book of standards, v. 04.09, soil and rock (I): D5877-latest, 7 p., available: www.astm.org.

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Maxar Technologies Inc., Alaska Geospatial Office, USGS

0 600 1,200

Feet

Borrow Sites Exploration White Mountains Recreation Area

Nome Creek Road, Alaska

MATERIAL SITE 5

TEST PIT LOCATIONS

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Possible Material Site

Map adapted from aerial and satellite imagery provided through the Alaska Department of Natural Resources.

http://gis.dnr.alaska.gov/terrapixel/cubeserv/OIM_BDL?

Nome Creek Road

10.7 Acres 2.9 Acres

14.3 Acres

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Appendix A: Soil Classification

Appendix A

Soil Classification

CONTENTS

Table A1 Frozen Soil Classification

Figure A1 Soil Description and Log Key

Figures A2 through A6 Logs of Test Pits

Table A1 - Summary of Frozen Soil Classification System Designation

No excess ice Nbn

Excess ice Nbe

Vx

Vc

Vs

Vr

Vu

ICE + soil type

ICE

NOTE:

Based on Linell, K.A. and C.W. Kaplar, 1966, Description and Classification of Frozen Soils, U.S. Army Cold Regions Research Engineering Laboratory, Technical Report 150, Hanover, N.H

Nf

Well bonded – Soil particles strongly held together by ice

Ice greater than 1 inch thick Ice with soil inclusions

Ice without soil inclusions

Uniformly distributed ice

Description

Segregated ice is visible by eye (less than 1 inch thick)

Individual ice crystals or inclusions

Ice coatings on soil particles

Stratified or distinctly oriented ice formations

Randomly or irregularly oriented ice formations

Segregated ice is not visible by eye

Friable, poorly bonded Material is easily broken up

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Appendix B: Laboratory Test Results

Appendix B

Laboratory Test Results

CONTENTS

LA Abrasion Test Results

Degradation Test Results

Sulfate Soundness Test Results

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Important Information About Your Geotechnical Report

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CONSULTING SERVICES ARE PERFORMED FOR SPECIFIC PURPOSES AND FOR

SPECIFIC CLIENTS.

Consultants prepare reports to meet the specific needs of specific individuals. A report prepared for a civil engineer may not be adequate for a construction contractor or even another civil engineer.

Unless indicated otherwise, your consultant prepared your report expressly for you and expressly for the purposes you indicated. No one other than you should apply this report for its intended purpose without first conferring with the consultant. No party should apply this report for any purpose other than that originally contemplated without first conferring with the consultant.

THE CONSULTANT’S REPORT IS BASED ON PROJECT-SPECIFIC FACTORS.

A geotechnical/environmental report is based on a subsurface exploration plan designed to consider a unique set of project-specific factors. Depending on the project, these may include the general nature of the structure and property involved; its size and configuration; its historical use and practice; the location of the structure on the site and its orientation; other improvements such as access roads, parking lots, and underground utilities; and the additional risk created by scope-of-service limitations imposed by the client. To help avoid costly problems, ask the consultant to evaluate how any factors that change subsequent to the date of the report may affect the recommendations. Unless your consultant indicates otherwise, your report should not be used

(1) when the nature of the proposed project is changed (for example, if an office building will be erected instead of a parking garage, or if a refrigerated warehouse will be built instead of an unrefrigerated one, or chemicals are discovered on or near the site); (2) when the size, elevation, or configuration of the proposed project is altered; (3) when the location or orientation of the proposed project is modified; (4) when there is a change of ownership; or (5) for application to an adjacent site.

Consultants cannot accept responsibility for problems that may occur if they are not consulted after factors that were considered in the development of the report have changed.

SUBSURFACE CONDITIONS CAN CHANGE.

Subsurface conditions may be affected as a result of natural processes or human activity. Because a geotechnical/environmental report is based on conditions that existed at the time of subsurface exploration, construction decisions should not be based on a report whose adequacy may have been affected by time. Ask the consultant to advise if additional tests are desirable before construction starts; for example, groundwater conditions commonly vary seasonally.

Construction operations at or adjacent to the site and natural events such as floods, earthquakes, or groundwater fluctuations may also affect subsurface conditions and, thus, the continuing adequacy of a geotechnical/environmental report. The consultant should be kept apprised of any such events and should be consulted to determine if additional tests are necessary.

MOST RECOMMENDATIONS ARE PROFESSIONAL JUDGMENTS.

Site exploration and testing identifies actual surface and subsurface conditions only at those points where samples are taken. The data were extrapolated by your consultant, who then applied judgment to render an opinion about overall subsurface conditions. The actual interface between materials may be far more gradual or abrupt than your report indicates. Actual conditions in areas not sampled may differ from those predicted in your report. While nothing can be done to prevent such situations, you and your consultant can work together to help reduce their impacts. Retaining

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A REPORT’S CONCLUSIONS ARE PRELIMINARY.

The conclusions contained in your consultant’s report are preliminary, because they must be based on the assumption that conditions revealed through selective exploratory sampling are indicative of actual conditions throughout a site. Actual subsurface conditions can be discerned only during earthwork; therefore, you should retain your consultant to observe actual conditions and to provide conclusions. Only the consultant who prepared the report is fully familiar with the background information needed to determine whether or not the report’s recommendations based on those conclusions are valid and whether or not the contractor is abiding by applicable recommendations.

The consultant who developed your report cannot assume responsibility or liability for the adequacy of the report’s recommendations if another party is retained to observe construction.

THE CONSULTANT’S REPORT IS SUBJECT TO MISINTERPRETATION.

Costly problems can occur when other design professionals develop their plans based on misinterpretation of a geotechnical/environmental report. To help avoid these problems, the consultant should be retained to work with other project design professionals to explain relevant geotechnical, geological, hydrogeological, and environmental findings, and to review the adequacy of their plans and…