Wednesday, December 30, 2020

Gas Pipeline Job Kicks Off Mass Ave Road Rebuilding

Big machines. Trucks. Orange Cones. Yellow-vested workers.

What are the crews doing in the Massachusetts Avenue roadway? Why are they funneling traffic to fewer lanes? Why must we walkers and runners dodge their stuff? It's been going on for months!

Stepping around the cones and you'll step into the world of District underground infrastructure.

These big cutting machines scratch the surface of the bother we'll have for years along Mass Ave from 20th Street to Waterside Drive. Their work is the opener of a big DDOT road-and-sidewalk replacement known as MARP, for Massachusetts Avenue NW Rehabilitation Project, due to start in 2021.

Restore Mass Ave has been concerned about the MARP. That project will replace roadbed, sidewalks and street lights between 20th Street and Waterside Drive - the most historic mile of Embassy Row where we have been growing mature trees. Since the first MARP plans were released in 2017, RMA worked to make them tree-friendly.

In advance of the MARP, Washington Gas moved up its plan to replace the old underground gas system on this route. The gas pipeline web that carries gas to each address is one of the entanglements that underlie District streets.  The gas work here is part of PROJECTPipes, a $300 million replacement of the gas system, to stop leakage of CO2 and methane and water leaks which can disrupt service. (Below are links for PROJECTPipes' cool map and for the Washington Gas Climate Business Plan.)

The yellow pipes you see are waiting to be set into the roadbed. Pull out the old! In with the new! But watch out! They must be hitched up seamlessly!  Then dump trucks refill the trenches with piles of dirt. The road surface gets topped with steel plates or asphalt. It becomes driveable but hardly smooth.

Will the gas line replacement hurt the trees? RMA gets care for 200 "street trees" that form rows along the curbs. Most are lindens. Some are of impressive age and size. Their roots link to each other underground. Aboveground their leaf canopies join with the next in the row to make shade.

Trenching the roadway  Most of the yellow pipe is set in long trenches aligned with the street. The diggers have almost no chance of finding roots there. Utility lines have been buried in District main arteries since the late 19th century  - when the first street trees were planted.  Street trees that have survived know better than to search past bundles of buried wires and pipes.

At street intersections the new gas lines must be hitched together seamlessly. The contractor, Miller Pipeline, returns over and over to reopen those nodes. Fortunately, there are no tree roots there!

Service lines into yards  From the main lines under the road gas, is distributed in spurs, or "service lines." (See graphic below.) These pipes tunnel under sidewalks into the front yards (which are DC land) to a local line or even straight to the building.  Many service lines here are old.
Replacing service lines poses the biggest risk to trees.

 To grow big above ground, a tree's roots must find good soil. The roots of a street tree grow sideways, into the soil of the tree next tree, if there is one.  Research shows that root systems of neighboring trees feed one another, helping them both grow. The roots of curbside trees along Mass Ave often grow back under the sidewalk into the generous 'yards.'  And down-pointing roots add stability and growth.

These roots are the odd three -way scaffold that upholds the big street trees we all enjoy.

Alas the Washington Gas Construction Process page does not mention trees or tree protections. Fortunately, the Miller Pipeline contractors are bound by DDOT rules for work in public space - including tree protections. Miller Foreman Vincent A. showed me the copy of these rules he keeps on his truck.

Among the rules: No root greater than 2" diameter may be cut, until an Urban Forestry Division arborist has inspected. If a root greater than 2" diameter is left exposed by digging it must be covered with a wet cloth until filled over.     

You can be an RMA Observer! Download the six points to look for here.

What do we get for it? 

We get the upgrade of a major utility locally and to the city. PROJECTPipes is not cheap. The regiowide work through 2024 costs $305 million - paid in part by a $4 surcharge on DC residents' monthly gas bills. 

Climate impact: Old gas pipes leak methane - a terrible greenhouse gas. Gas leakage also harms soil. At an online community meeting July 29, Washington Gas said it had been one of 10 national leaders in climate -friendly actions for the three years. The first phase (2014-2019) removed 5,674 metric tons of carbon dioxide equivalent by upgrading parts of the  system.

We tree-huggers like that Washington Gas is part of efforts to halve DC's greenhouse gas emissions by 2032, and the more ambitious DC goal of carbon neutrality by 2050.

But note: The rows of street trees  - old sturdy ones and those just now maturing - already provide huge environmental services. Our present tree rows combat the District's urban heat island.  They offer walkable, shady public space for decades to come. And they're a "sunk" investment, so basically no cost. -

Trees v. gas upgrade tradeoff:  RMA and friends will work towards zero-tradeoff between street trees (and all other trees) and  gas line upgrade.

We know that pipeline workers love the District's trees as much as we do. 

Links to go here.


No comments:

Post a Comment