20201951 Ver 1_Proposal Cascade Lake Road_20201216

Phone: [phone] | Fax: [phone] | www.geostabilization.com
GeoStabilization International®
Dru Miller, PE
Project Development Engineer
[e-mail] | 601.527.4927
November 13, 2020

Mr. Ben Williams, PE
NCDOT Division 14
151 Locust Street
Columbus, NC 28722

Subject: Proposal for Roadway Stabilization at Cascade Lake Road
Transylvania County, North Carolina

Mr. Williams,

This letter presents our proposal to provide roadway stabilization and wall construction
at the failed fill roadway and shoulder slope along Cascade Lake Road in Transylvania
County. Recent instability resulted in the loss partial roadway outboard lane and
associated shoulder within an approximate 90-foot long section of the road. The site
latitude and longitude are N35.2230, W82.6367.

Project Site – Cascade Lake Road, Transylvania County

To allow stabilization of the roadway platform and provide for a shoulder and future
guardrail placement, we propose to construct a Geosynthetically Confined Soil® Wall
(GCS® Wall) wall along the outboard section of the project site.

Proposed Repair
Your forces would first prepare the site by excavating along the failed roadway section at
an approximate 0.25:1, horizontal to vertical, slope to create a bench along the proposed

Cascade Lake Road
Transylvania County, NC
2

wall alignment. The bench excavation will be approximately 10 to 15 feet vertically below
the road surface. The top of the excavation would begin along the failed edge of existing
roadway where applicable; outside of the immediate failed area, excavation would begin
as far back behind the existing guardrail alignment to leave intact shoulder in-place.

The excavation may need to be performed in lifts of 4 to 5 feet to prevent further
instabilities or to provide a working bench during each lift construction. This site
preparation will be observed by a representative of GSI to ensure a proper slope for the
working face of the stabilization system. The base of the excavation will need to be
sloped slightly for natural drainage and the excavated materials will need to be hauled
off site.

We will then install soil nails in the excavated backslope. The backslope will receive a
reinforced shotcrete facing to serve as shoring and provide temporary support of the
roadway. Our forces will then install an array of up to 20-ft deep micropiles to provide
axial support for a GCS® Wall and lateral support to resist sliding. The micropile (and
resulting wall) alignment will be approximately 6 feet off the desired edge of roadway.
We will construct a reinforced shotcrete micropile cap along the length of the project and
wet-set an initial course of block for the GCS wall. A 66-foot long GCS® Wall will then be
built by our forces using 8-inch layers of granular fill (#57 stone provided and placed by
NCDOT) compacted between layers of geotextile fabric. This wall will utilize split-faced
concrete block on its face and will be 10 to 15-feet high.

Additional details will be provided on P.E. stamped drawings once a Purchase Order is
issued. Barring any unforeseen delays, our work on this project should take
approximately three weeks to complete.

Project Cost
The following table summarizes the anticipated quantities and costs for the stabilization
under our existing on-call contract with Division 14:

LF QTY Unit Line Item Unit Price Price
90 1 EA 1 Mobilization $5,077.50 $5,077.50
90 1 EA 2 Plan Submittal $3,046.50 $3,046.50
90 77 EA 31 Self-Drilling Soil Nails up to 20' $812.40 $62,554.80
90 1105 SF 40 6" Reinforced Shotcrete $23.36 $25,812.80
90 66 EA 24 Self-Drilling Micropiles up to 20 feet $1,066.28 $70,374.48
90 198 SF 39 12" Shotcrete as MP Cap $36.56 $7,238.88
90 800 SF 42 Geosynthetically Confined Soil Wall $21.83 $17,464.00
90 1 EA -- Soil Nail Verification Test $2,499.50 $2,499.50
90 1 EA -- Testing Mobilization $2,197.00 $2,197.00
TOTAL $196,265.46

Traffic Control
Due to the limited roadway width and existing site conditions, it is understood that a full
roadway closure with detours will remain in place during the duration of the project. The
outboard lane or pull-off areas will be occupied by our materials and drilling equipment.

Cascade Lake Road
Transylvania County, NC
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Items Furnished by NCDOT
Our NCDOT contract calls for us to do our specialty work and NCDOT forces to perform
other items such as traffic control, surface water drainage improvements, excavation and
hauling, guardrail installation, paving, striping, erosion control, etc. Utility locations,
relocations, and repairs are not included in our pricing. This proposal includes NCDOT
providing yard space to receive and unload materials shipped by GSI.

Our work also carries a five-year warranty commencing after GSI project completion.
This warranty is void absent GSI receiving mutually agreed project payment. If at any
point within the warranty period the repaired section becomes unstable, GSI will, in a
timely manner, remedy the situation with a design/construction solution at no cost to the
owner. This warranty does not cover work completed by others or shallow surface
erosion problems that may develop in the future. Exceptions to the warranty include
catastrophic seismic, weather, or other events outside reasonable accounting in design
(including earthquakes and weather events exceeding expectation for the region) or
further construction by third parties that destabilizes the repair (including utility trenches
dug into or through any soil nails, deep excavations in the area, etc.). Extreme storm
water volumes may cause erosion which could undermine the repaired areas which may
void this warranty. After such an event these areas should be checked for erosion.

THIS COMMUNICATION CONTAINS GEOSTABILIZATION CONFIDENTIAL/PROPRIETARY
BUSINESS INFORMATION NOT SUBJECT TO FREEDOM OF INFORMATION ACT (FOIA).

Please feel free to let me know if you have any questions or comments on this proposal.

GeoStabilization International

By: Dru Miller, PE
Project Development Engineer