Home News The race begins to dig a 2-mile sewage tunnel under the Potomac...
The race begins to dig a 2-mile sewage tunnel under the Potomac River

The race begins to dig a 2-mile sewage tunnel under the Potomac River


A vital race in opposition to the clock to dig a tunnel underneath the Potomac River will depend on a powerhouse participant: a 15-foot-wide, 380-ton machine named “Hazel.”

This spherical, metallic gadget, a custom-made tunnel boring machine that’s embellished with colourful handprints, was lowered right into a 138-foot shaft weeks in the past and is now getting ready to dig a two-mile sewer tunnel in Alexandria.

This mission — the biggest infrastructure challenge undertaken on this Northern Virginia neighborhood — is supposed to handle the town’s most evident air pollution drawback: the thousands and thousands of gallons of uncooked sewage that it places into the Potomac yearly.

“That is actually pushed by the objective of enhancing the well being of our metropolis’s waterways,” mentioned Justin Carl, a program supervisor at Alexandria Renew Enterprises, or AlexRenew, the native wastewater authority. “We’re constructing this mega-project in a really historic space, and we’re doing it on an unprecedented timeline.”

The overwhelming majority of houses and companies in Alexandria have separate pipes for storm water and sewage, however the metropolis’s historic Previous City depends on a mixed sewer system with only one pipe for each.

That signifies that when heavy rains strike the town — which they do about 70 instances per yr — these mixed pipes overflow into outfalls across the metropolis, bringing alongside as a lot as 140 million gallons of untreated human waste into the Potomac and two of its tributaries, Hooffs Run and Looking Creek.

It’s a difficulty confronted by greater than 700 different U.S. cities, which even have dense neighborhoods that urbanized earlier than the flip of the century and rely upon these mixed sewer overflows (CSOs).

Environmental lawsuits and state laws have compelled many of those communities to undertake remediation efforts much like Alexandria’s: D.C. has largely completed on a 13-mile community of sewage tunnels underneath the Anacostia River, and cities like Seattle, Columbus, and Pawtucket, R.I. have launched into their very own initiatives.

Like many different tunnel boring machines, Hazel is named after a lady — on this case, the “mother” of the trendy environmental justice motion, Chicago activist Hazel Johnson — in accordance with Sixteenth-century mining lore of tunnel-diggers trying to Saint Barbara for defense.

However in contrast to different machines, Hazel faces an particularly tight timeline: The machine has 14 months to attach two of the town’s outfalls again to its wastewater therapy plant, so the sewage may be captured, handled after which pumped again into the river.

Lawsuit alleges Alexandria has been polluting Potomac with coal tar

The complete remediation challenge have to be accomplished by 2025, due to a deadline imposed by state lawmakersfew of whom knew in regards to the difficulty till environmental teams started sounding the alarm.

Virginia State Sen. Scott A. Surovell (D-Fairfax), who represents an space simply downstream from Alexandria, mentioned he was “fully shocked that we have been dumping uncooked human waste into the Potomac River regularly.”

Whereas Richmond and Lynchburg additionally depend on CSOs, he identified that Alexandria has a repute as a neighborhood of environmentalists — it was the primary in Virginia to undertake an “eco-city constitution” — and enjoys one of many wealthiest populations within the Commonwealth, which means it has the cash essential to remediate the problem.

“That is one thing most individuals thought ought to have been taken care of 30 years in the past,” Surovell mentioned. “If the town of Alexandria couldn’t discover the sources to plug the uncooked sewage discharge into the Potomac, I’m not clear how we may anticipate anyone to do it.”

Carl, this system supervisor engaged on the RiverRenew Tunnel Project, mentioned Hazel is attempting to resolve what he known as a “150-year-old drawback.”

Across the time of the Civil Struggle, engineers in Alexandria constructed a CSO to direct human waste away from the houses and companies of Previous City and into the close by river. The system was thought-about an enormous enchancment from outside latrines, which discharged sewage into the bottom, polluting the town’s ingesting water and getting residents sick.

“Once they have been initially constructed, they have been modern. It was thought-about an enormous leap for human well being,” Carl mentioned of CSOs. “Clearly, we’ve realized rather a lot since then with the impression that has on our waterways, and the fish and wildlife in our waterways.”

Though fashionable wastewater therapy — beginning within the Nineteen Fifties — has helped clear up a polluted river that newspapers as soon as declared was “too thick to drink” however “too skinny to plow,” heavy rainfall continued to overload the CSO system. That has at instances led to harmful ranges of E. coli and nitrogen and phosphorous air pollution.

Caitlin Feehan, AlexRenew’s director of communications and exterior applications, identified that Hazel will solely handle considered one of three flooding-related points in Alexandria.

Exterior the CSO space in Previous City, some storm water pipes — significantly in low-lying neighborhoods like Del Ray and Rosemont — can not deal with the rain from extra frequent storms and fill the streets with water. And nearer to the Potomac, rising sea ranges imply that king tides will typically flood the riverbank in Previous City.

Alexandria already wanted to repair its storm pipes. However local weather change is making it worse.

The $615 million challenge is being funded via grants from the American Rescue Plan Act and low-interest loans from a Virginia clear water fund and the Environmental Safety Company, which can finally have to be paid again by native taxpayers.

Month-to-month wastewater charges for purchasers in Alexandria have already risen by about $12 for a median resident because the RiverRenew challenge began and are anticipated to extend to roughly $75 when it’s full in three years.

RiverRenew engineers and building crews final month lowered Hazel — break up into two huge, spherical metallic shields — down considered one of two shafts they’d dug at a web site close to the town’s wastewater therapy plant.

Hazel is anticipated to truly start work on the tunnel in October, when it’s going to dig via Potomac clay soil and ship it again as much as the plant whereas concurrently constructing a concrete-lined 12-foot-wide sewer tunnel.

The machine’s vacation spot is at an outfall on the finish of North Pendleton Road in Previous City, close to Oronoco Bay Park. Though the machine may have dug a tunnel underneath Previous City, the realm’s historic standing and the potential for some disruption — in addition to its tougher soil situations — made it a simple option to route it underneath the Potomac as a substitute, Carl mentioned.

“It’s each engineering and community-driven,” he added. “We didn’t sit right here in an workplace and give you a tunnel route completely primarily based on technical choices.”


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