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Rt 42 Over Blackwood Railroad Trail Arched Tunnel Install

Rt 42 Over Blackwood Railroad Trail Arched Tunnel Install
Reading Time: 7 minutes

NJDOT contractors recently started installing the arched tunnel elements for the large tunnel which will go under Route 42 at the Blackwood Railroad Trail, as part of the bridge replacement project.

Yes I first reported on this project 2 months ago, but honestly that article was a little lighter on details.

In this update article not only do I share recent images to visually show how large the pedestrian tunnel will be, I also have new information on the full project and design reasonings.

Honestly the tunnel is larger than most would expect from a pedestrian tunnel, and several factors were in play to have the design for the tunnel made larger.

Arched tunnel roof elements are being installed at Gloucester Township Blackwood Railroad trail, ahead of the Route 42 bridge removal and rebuild

Also, while the bridge removal and pedestrian tunnel are the two most significant aspects of the project, NJDOT will be widening the Route 42 roadway in this area to provide wider shoulders and auxiliary lanes used at the nearby exits. To accommodate the added width they are also adding retaining walls in two locations.

The full $21.3 million dollar project is expected to be complete by July 2024.

It’s actually a very complex effort in having to keep traffic flowing as they teardown each bridge element, backfill the valley with earth, and only then recreate the roadway surface! At times temporary roads will be developed in the center of Route 42 to accommodate shifting traffic.

Keep scrolling and reading for more information and images on this project.

Route 42 Bridges Over Blackwood Railroad Trail

What we see today as a pedestrian trail was previously a railroad train track. Many years ago the trains stopped using this segment of track through Gloucester Township. The tracks were later removed and a paved pedestrian trail was installed.

Today the township calls the trail “Gloucester Township Health & Fitness Trail” but NJDOT identifies it as the Blackwood Railroad Trail in it’s documentation. (Bike Share Program)

42Freeway first introduced this Route 42 project to readers on September 6th, 2022.

This effort is to remove and replace the Rt 42 bridges which go over the Blackwood Railroad trail in Gloucester Township.

Drone image shows the tunnel being developed under Route 42 in Blackwood NJ. The overpass bridges will be removed and in their place will be a more traditional earth-based roadbed. A portion of the wider auxiliary lanes and retaining walls can be seen

Transportation departments around the country are working to replace older bridges and infrastructure which are at risk of deteriorating to unsafe levels.

The interesting twist on this Route 42 project is that since the train no long runs in that area, NJDOT determined full bridges were no longer needed for the rebuild.

The replacement for the bridges will really just be a standard roadway. To accommodate the pedestrian trail they are developing a tunnel underneath Route 42.

The remainder of the current space in the valley will be filled in with earth, and the Route 42 roadway in this section will become a more traditionally paved roadway.

The reason for not rebuilding as bridges is they are much more complex (and expensive) infrastructure to build and maintain. If there are no trains or roadways underneath Route 42 in this section, the added costs of rebuilding as bridges just wouldn’t make sense.

New Tunnel: Wider and Taller for Several Reasons

Many residents expressed concern when they heard “pedestrian tunnel”. They immediately think of a narrow and intimidating passageway.

This new Blackwood Trail Tunnel is surprisingly big at 22 feet wide and 17 feet high. I think that’s larger than most would’ve expected for a pedestrian only tunnel.

One obvious aspect for a tunnel that large would simply be to provide a safer passageway for pedestrians and bicyclists traveling on the trail, reducing that feeling of being closed in.

At 22 feet wide, the new tunnel for the Blackwood Railroad pedestrian trail should be wide enough for comfortable travel, and occasional utility maintenance vehicles.

Another aspect in the design is Utility Entities have used the railroad track right-of-way to run their supply lines, as it offered easy access across communities.

Consider that most railroad tracks in our area were developed 80 to 100 years ago (or more) before larger communities were developed. Decades later this open passages between towns became an effective way of installing utility lines through developed communities.

With the new design NJDOT also needed to account for the ability of the utilities to safely maintain their infrastructure going forward in a cost-effective manner.

Taking It Wider : Underground Concerns

At 22 feet wide there will be plenty of room for residents to pass each other in opposite directions. People will feel much more comfortable moving through the tunnel with it’s larger sized construction.

But another reason for the wider tunnel is that underground alongside the trail are sanitary sewer mains.

Both the CCMUA (Camden County) and GTMUA (Gloucester Township) entities have larger sewer mains running in this area, parallel with the pedestrian path.

So by going wider with the tunnel, engineers also avoided additional impacts and costs regarding the sewer lines.

A portion of the Blackwood Railroad Trail in the area of Route 42 has underground sewer mains running alongside.

A thinner tunnel could’ve positioned the weight of the concrete tunnel on top of the sewer mains. Or if the area over the underwound sewer mains were covered with earth to the road surface high above, it would make future repairs on the sewer lines virtually impossible.

Wider basically keeps those underground sewer lines accessible from the original ground level as they are today, with no additional load… and easier access if the need to be repaired.

So yes it’s absolutely more beneficial for pedestrians to have a wider tunnel, but it was also likely cheaper to simply make the tunnel wider for several reasons.

A rare “Win-Win” solution.

Making it Taller: Overhead Concerns

Another aspect which played into the larger design of the tunnel is a request/requirement of electrical utility PSE&G.

PSE&G maintains the electrical infrastructure for a large part of South Jersey, which at times requires very high powered electrical cables to run high above the communities. Sort of like an “electrical highway”

Such is the case with the Blackwood Railroad Trail, as high overhead are high-powered electrical transmission lines.

Those power lines over the trail are crucial to maintaining electricity throughout all of South Jersey.

In fact, PSE&G has been building a very large switching sub-station on the Black Horse Pike that these same high-powered lines over the railroad trail will connect too! (42Freeway Jan 2022)

Drone image shows the overhead high-power lines running with the Blackwood Railroad Trail at Route 42. The wider roadway and retaining walls in the image are to support cars entering from Black Horse Pike

So to get to the point… PSE&G requested that the tunnel be high enough to support their trucks being able to pass through the tunnel, only in case they need to maintain the power lines overhead.

While emergency situations are rare, you could imagine if they needed to perform emergency service on the very important powerlines, having them blocked by a very small pedestrian tunnel could be problematic.

So the 17 foot tall height of the tunnels were at the request of PSE&G.

Similarly though this also makes it easier for local emergency services to move through the area in the rare occasions they are needed.

Route 42 Wider: Shoulder and Auxiliary Lanes

With Route 42 in this section being redeveloped, designers also decided to make the roadway safer to travel on, specific to the Black Horse Pike exits.

Currently there is a very popular exit for the Black Horse Pike less than 1000 feet away to the South of the bridge project.

With the original design of Route 42 in the 40s, engineers provided very short auxiliary lanes for cars exiting Route 42 (north to Black Horse Pike) as well as cars entering Route 42 North.

A wider northbound Route 42 section is being developed to provide a longer acceleration lane for traffic entering from the Black Horse Pike. A long retaining wall is being installed accommodate the wider area.

As an example, when exiting from Rt 42 South to the Black Horse Pike it feels like you just don’t have enough distance to safely slow down from highway speeds to the much lower speed needed to navigate the tightly curved exit.

With this new project, this area of Route 42 will be widened to accommodate longer exit/entrance auxiliary lanes so that traffic moving on and off of Route 42 have more roadway to adjust their speed.

With Route 42 being a raised road in this area, the project calls for two retaining walls to be developed to support the wider roadway.

A wider road surface would mean the slope to the raised roadway would also protrude out wider… but today there are homes and businesses in those areas adjacent to the highway, hence the need for the retaining walls.

The new retaining wall segment as seen from Anchor Pools parking lot on the Black Horse Pike

One longer retaining wall can be seen already mostly developed in the area of Anchor Pools on the Black Horse Pike.

The other will be behind several homes on Woodland Ave (on the other side of 42).