Department of Transportation

I-80 Rockfall Mitigation Photo


The Concept Development phase is complete. As part of this phase, data was collected and analyses were conducted in order to develop a feasible solution that would be cost-effective while meeting all New Jersey Department of Transportation (NJDOT) and Federal Highway Administration (FHWA) standards. The critical end products of the process were: a well-defined Purpose and Need Statement; a concept (alternative) that met the approval of NJDOT’s Subject Matter Experts (SMEs), FHWA, the local municipality, and the public; and a determination of the type of environmental document that would be required under the National Environmental Policy Act (NEPA).

Purpose and Need Statement

This Interstate 80 (I-80) segment, between mileposts 1.04 and 1.45, has been continually characterized as having the highest rockfall hazard rating scores (i.e., highest risk) in NJDOT’s Rockfall Hazard Management System (RHMS), which is based on the FHWA’s Rockfall Hazard Rating System. The purpose of the proposed rockfall mitigation Project on I-80 westbound is to improve the safety and mobility of the traveling public by reducing the frequency and severity of rockfall events impacting the roadway.

Although other roadway and traffic deficiencies were inventoried and noted during the Concept Development stage, the scope of the Project is not intended to address any geometric or traffic features of the I-80 corridor in this area.

Preliminary Concepts

Field investigations were conducted by geotechnical and environmental staff as well as coordination with the National Park Service (NPS) and other stakeholders. Multiple concepts were developed for each of the four areas (A through D) that were then scored using eight categories: risk reduction, right-of-way needs, future maintenance requirements, construction impacts, construction difficulty, construction duration, cost, and aesthetic impact. The alternative that best meets the requirements of the Project was selected and incorporated into the overall Preliminary Preferred Alternative (PPA). Individual PPAs were selected for the various areas (A through D) to meet the specific conditions. The Project need was confirmed, and the Project was recommended to advance to Preliminary Engineering in 2011. The following rockfall mitigation measures were proposed based on very preliminary rockfall hazard analyses and the projection that possible right-of-way impacts would be incurred:

  • Area A: the installation of a concrete barrier curb with 42 to 72 inch height and sacrificial timber lagging attached to the back for energy dissipation.
  • Area B: the installation of a concrete barrier curb with 42 to 72 inch height and sacrificial timber lagging attached to the back for energy dissipation.
  • Area C: a hybrid system, as it provides the best rockfall risk reduction.
  • Area D: combination of rock control fence and excavating with reinforcement to the existing talus slope to create an enlarged catchment area.
NEPA Classification

The CD Phase concluded that a Categorical Exclusion with appropriate technical studies including Ecology and Cultural Resources would be prepared to satisfy NEPA requirements. However, after conferring with FHWA, the National Park Service, and the NJDEP during the project's Preliminary Engineering Phase, it was decided that an Environmental Assessment (EA) would be prepared to satisfy NEPA requirements due to the project's unique location and to allow for additional public involvement.

Concept Development Report

Please follow the link below for the Concept Development Report, dated September 2011, prepared for NJDOT by HNTB Corporation.


Last updated date: March 28, 2023 9:06 AM