Big Dig bailing out tunnels
Flow topped million gallons per month
More than 1 million gallons of water a month flowed into the Big Dig tunnels through April of this year, a year and a half after managers of the multibillion-dollar project pledged to minimize leaks.
The Massachusetts Water Resources Authority, which recently concluded a yearlong investigation of the tunnels, is revising the permit that allows the Massachusetts Turnpike Authority to pump water from the tunnels to the Deer Island waste water treatment plan.
The MWRA recommended that the Big Dig seek permission to discharge the water, which is not polluted, into the Fort Point Channel. That would require the approval of state and federal environmental agencies.
``We would always expect some leakage -- seepage is the word -- but obviously the volumes in the tunnel are greater than that," said Michael Hornbrook, MWRA chief operating officer.
Big Dig officials refused repeated requests by the Globe to detail the water flowing into the tunnels. But, using figures available on the Mass. Pike website, the Globe calculated that an average of 1.1 million gallons a month was pumped during the first four months of this year from the Interstate 93 tunnel alone, a period of unusually dry weather.
The Globe analysis found the 2006 level is about 38 percent less than 2004 and about 34 percent less than last year, but still higher than expected. The water pumped from the Interstate 93 tunnels for the first four months of 2004, 2005, and 2006 totaled 7.2 million gallons, 6.75 million, and 4.4 million respectively, or about 1.1 million a month for 2006, according to the Globe analysis.
The MWRA's permits for the pumping specified an expected volume of 36,000 gallons a month from all Big Dig tunnels.
Managers at the Massachusetts Turnpike Authority, which operates the tunnels, insisted that the tunnels are becoming drier, and said they are beating industry standards for a dry tunnel. ``Actual infiltration over the past year is down significantly," Mass. Pike spokeswoman Mariellen Burns wrote in an e-mail to the Globe.
On its website, the Turnpike Authority has posted a chart showing the current levels of water infiltration as lower than the industry norm.
The MWRA last month notified the Turnpike Authority it was revising its permit to pump the water, ordering it to develop a plan to dump water elsewhere and step up reporting obligations. The Turnpike Authority is reviewing the MWRA order and has appealed it to the agency.
``We are telling them they have to come into compliance" to continue pumping into the Deer Island facility, Hornbrook said.
The high volume of water is a concern because it indicates the Big Dig's steps to address the leaks may be only partially successful after more than a year. Also, because water weakens concrete and deteriorates steel, the state may be stuck with higher maintenance costs in the future, as more crews are needed for frequent inspections and repairs.
Part of the issue stems from the various sources of water flowing into the tunnels. It includes water trucked into the tunnels to wash walls, rainwater that gets past storm drains at the tunnel portals, rain and snow from vehicles in the tunnels, and water that infiltrates the tunnel walls, leaks.
The MWRA ordered the Turnpike Authority to spell out how much water comes from the various sources. But the Turnpike Authority said it may be impossible to document the totals from each.
The MWRA, in its letter to the authority, said it could not longer tolerate the authority's present practice of pumping all types of water into the authority's system. The initial permit was granted primarily for water used to wash walls in the tunnels and negligible seepage.
``This . . . changes the status of your permit from a Non-Significant Industrial User to a Significant Industrial User due to the [Turnpike's] potential to violate pretreatment standards and requirement," the MWRA wrote in its May 11 letter. ``The revised permit supersedes all previous permits."
In its May 25 appeal letter, the Turnpike Authority said it wanted to meet with the MWRA to resolve concerns, but said ``it is not possible to totally eliminate infiltration into the [Turnpike] tunnels."
A bypass to dump water into the Fort Point Channel would require the Turnpike Authority to obtain a permit from the state Department of Environmental Protection and the federal Environmental Protection Agency.
Turnpike Authority officials refused to discuss how much of the water infiltration is due to leaks, why the flow has dropped, and if the authority expects it to fall further. The Globe sought details in written requests to the authority since mid-May.
In a chart on its website, the Turnpike Authority indicates that water infiltration amounts to less than 1 gallon per minute per 1,000 linear feet of tunnel, which the Turnpike Authority calls the industry norm. While the mainline tunnel is approximately 8,200 feet between its northern and southern portals, the Turnpike Authority uses a much greater length -- 36,148 feet, including ramps and other portions of the tunnels -- when computing its gallons per minute figure to compare with the industry norm.
To estimate water flowing into the tunnel, the Globe used a breakdown the Turnpike Authority posted on its website on May 25 that showed pumping volumes for the Interstate 93 tunnels by the six underground stations used by the Big Dig. The volumes are in roughly two-week increments.
Adding the volumes for all the pump stations totals 5.8 million gallons for the first four months of 2006. Two of the stations were added in November 2005, but the Globe excluded them to make better comparisons with earlier periods, leaving a total of 4.4 million gallons for the first four months of this year.
In 2004, Big Dig managers said as much as 50 percent of the water then in the tunnel came from sections of the roof temporarily open to rain due to ongoing construction and would be removed with the end of construction. Moreover, they said a further reduction would occur due to an ongoing program of repairing leaks by injecting grout sealant into the problem areas.
Pumping records were regularly posted on the Turnpike website after revelations of leaks caused a political firestorm in November 2004. But the Turnpike Authority went almost six months without posting new pumping records until the Globe filed a request for the data under the state public record disclosure act.
Burns, the Turnpike Authority spokeswoman, said in a written statement, ``It is expected that in the first quarter of each year the pumping volumes will be the highest due to seasonal variations in rain and snowfall and the fact that tunnel washing begins during this season [that being said, other times of the year may vary due to weather events and other no-infiltration events]."
But National Weather Service records show a relatively lower amount of precipitation during that period this year. There were 9.63 inches of precipitation from January 1 through April 30, 2006, compared with normal precipitation of 14.67 inches. 