Design_Tech_Memo_409(2).pdf

Lees Ferry Ranch House Access Road

AZ FTNP GLCA 409(2)

NPS PMIS # 251927

Project Technical Memorandum by Federal Highway Administration

Central Federal Lands Highway Division

8/30/2018

I. Introduction

The scope of this project is to repair/replace an existing gabion wall at the Lonely Dell Orchard area that was undermined during a high flow event on the Paria River. The event was not out of expectations for an annual flow event.

There is additional project information available for this area of the river based on previous projects including GLCA 99(1), GLCA 1(1)3(1)mod for emergency repair, GLCA 5(2) and other GLCA projects.

River modeling and upstream and downstream design is anticipated for a future project.

If the upstream structures are not realigned the flanking is likely to continue. Immediate corrective action including modeling and design is recommend for the Paria River from upsteam of the maintenance and water treatment plant to downstream of the existing Lees Ferry Road Bridge.

II. Project Cross Functional Team

Name Phone Email

Project Manager James Kerrigan 720-963-3362 James.kerrigan @dot.gov

Design Darin Lockhart 720-963-3212 Darin.lockhart@dot.gov

Environment Michael Kulbacki

NPS - DSC

303-969-2829 Michael_Kulbacki@nps.gov

Permits Greg Bergquist 720-963-3571 Greg.bergquist@dot.gov

Geotechnical Dustin Robbins 720-963-3586 Dustin.robbins@dot.gov

Construction

III. Existing Conditions Paria River channel is increasingly the eroding bank on north side of the river. Upstream gabion spurs that were placed to protect the maintenance area are directing the river flow across the channel and eroding the bank and flanking the gabion wall. The gabion wall is collapsing. This is possible due to water pressure from saturated soils behind the wall and a quick draw down of the river at the face of the wall.

Based on the existing conditions it appears the north side of the channel will continue to erode and flank the proposed structure and Lonely Dell Orchard unless additional methods are used to redirect the channel. A hydraulic analysis that considers both the upstream and downstream impacts of the channel is necessary. Alterations in the channel can have impacts downstream that may cause additional erosion and flanking of the existing downstream armoring and bridge protection.

On August 26, 2018 a storm event occurred and has further eroded the bank.

Existing 20ft wide earth/gravel road accessing a parking area for the Lonely Dell Orchard and Ranch House.

IV. Traffic Data

No traffic volumes are available. Based on information from Park staff there is less than 400 vehicles per day.

V. Crash Data

No known accidents were reported by the Park staff and there are no visual evidence of accidents. No documented crash data is available.

VI. Survey

No existing ground survey was performed for this project. The contractor will be responsible for survey as part of the contractor designed MSE wall

Existing ground contours from a 2016 survey were modified based on site visit measurements. On August 26, 2018 a storm event occurred and has further eroded the bank.

VII. Environmental

The NPS-DSC is providing the environmental documents for this project.

VIII. Design Speed

Road classification is Class III, Special Purpose with low volume, < 400 VPD, Flat. NPS 1984 Park Roads Standards 15 mph minimum design speed.

No speed limit signs are posted.

IX. Typical Section

The roadway structural section is 4” depth aggregate surface course. The road is earth/gravel with an approximate width of 20 ft. The road will be replaced to match existing with 3% to 4% crown typical for gravel roads.

Replacing the existing road where it is impacted by wall excavation.

X. Roadway Design and Safety

FLH Supplemental Design Standards

FLH

Standard

Used on This Project

Clear Zone 7 feet 7 feet Barrier Crashworthiness NA NA

XI. Geotechnical

See Geotechnical Memo for wall design analysis.

XII. Pavements and Materials

4” aggregate base surface course. No pavement design on this project.

XIII. Hydraulics

A future study is highly recommended for upstream and downstream design.

The scope of work for this project did not include hydraulic analysis. No hydraulics or drainage design was performed for this project.

XIV. Erosion and Sediment Control

Rolled erosion control product, temporary seeding and stabilized construction exit included for this project.

XV. Traffic Control

Existing road can be closed to public during construction. A minimum 10 ft wide access will be maintained during construction for access by Park staff and emergency vehicles.

A site traffic control plan is included in the plans for general layout of Type III barricades.

XVI. Signing and Striping

Roadside 4 delineators are being removed and reset, no other signs are being added or replaced on this project.

XVII. Revegetation

Temporary seeding is included in the design quantities, the park will need to submit a mix design.

XVIII. Right-of-Way

Project is within the Park.

XIX. Utilities

No known existing utilities are located within the project limits. A proposed 4 inch waterline conduit is included but will not be connected to service with this project.

XX. Specifications

SCRs included for FP14

XXI. Construction Schedule

Construction scheduled developed for this project.

It is estimated there are 63 days for Survey and design of the MSE wall and 62 days for construction for a total duration of 127 working days.

Notice to proceed is estimated for November 5, 2018 and substantial completion on April 30, 2019.

XXII. Construction Cost Estimate

Engineers estimate is based on a fixed cost for 2018 construction. Wall prices were adjusted to fit this budget. The UPA represented a higher cost.

The EE for this project is $944,430 and the program amount in fundsmap is $390,000 as of 8/29/2018.

Appendices:

A. Geotechnical Memorandum