CA FLAP LA CR2N40(1) Santa Anita Canyon Road

PROJECT NUMBER:  CA FLAP LA CR2N40(1)

PROJECT NAME:   Santa Anita Canyon Road

PROJECT DESCRIPTION:  Santa Anita Canyon Road (SACR), also known as Chantry Flat Road, is a scenic mountain road and the only access route to a network of recreational opportunities including over 30 miles of hiking trails, picnic areas, and campgrounds as well as Santa Anita Dam and firefighting operations in the Angeles National Forest (ANF).  SACR also provides access to the historic Adams' Pack Station, a launch point for transporting supplies to permanent cabins in the forest area inaccessible by motor vehicle.

The project is located approximately 4 miles north of Arcadia, California.  The cities of Sierra Madre and Monrovia also own portions of the area the project traverses.  However, Los Angeles County Public Works Department maintains the roadway.

The route is approximately 3.2 miles in length.  The project includes spot improvements at three locations along the route and a pavement rehabilitation segment of approximately 0.6 miles. All spot improvements and pavement rehabilitation are included in a single schedule (Schedule A).

SCOPE OF THE WORK:  General work to be performed is shown in the table below.

Project Sites

Location

Station to Station

Work Performed

Site 1

177+60 to 180+00

Rockfall Mitigation

Site 2

67+00 to 68+40

Drainage Improvements

Site 3

28+00 to 29+40

Retaining Wall Reconstruction

Site 4

21+20 to 24+70

Subgrade Repair

Site 5

59+00 to 91+60

Pavement Rehabilitation

Note:  The wall at Site 3 failed during the project development process.  Los Angeles County has replaced the wall under a separate construction contract. 

Site 1, Rockfall Mitigation, requires that an existing 1:1 rock slope, directly adjacent to the roadway and roadside parking be mitigated for potential rockfall.  Increasing the roadway width in this area to provide additional catchment or separation width is not feasible given environmental constraints and project scope.

Geotechnical investigation and subsequent analysis were based on observations of the strike and dip of the rock jointing from the roadway elevation.  The general site is approximately 140 feet across the rock outcrop brow and 140 feet horizontally in plan view.  The length along the slope to be mitigated is approximately 200 feet given the approximate 1:1 slope. The current design anticipates that a draped system will be employed and assumes that rocks of 12 to 18 inches would be contained within the draped system. 

Work at Site 2 site includes improving a previous slope failure location where the current mitigation improvement is to restore the historical drainage crossing at this site and build an upstream debris containment basin. As a part of the drainage improvements, a pipe rundown and energy dissipater will be constructed on the downstream/embankment side of the roadway.

Due to a 2019 rainfall event during design and subsequent erosion on the roadway embankment, a new secant wall was proposed to address new slope failure and will be adjacent to an existing gabion wall.  The proposed secant wall will consist of 48-inch shafts, concrete barrier with moment slab base, ground anchors, and reinforced shotcrete wall facing.

Site 4 is a subgrade stabilization repair and barrier replacement. The Site is approximately 500 feet in length. Standard sub-excavation efforts are planned, which are simply over-excavation of the failing soils and backfilling with engineered materials. Cast-in-place concrete barrier exists downhill of the Site on the east side of the roadway.

Site 5 consists of pavement rehabilitation, including Full Depth Reclamation and asphalt overlay.