People walking though modern Washington, with its wide boulevards and sidewalks, seldom think about what goes on beneath them. Given the relative transience of the population, few know that Washington was built on a swamp. When Pierre L’Enfant designed the city, much of the area south of the Mall was fetid swamp and lowlands, often inundated by overflows from the Potomac River and Tiber Creek. The land on which the Lincoln Memorial sits did not even exist when the city was established. Until the late 1800s, the Washington Monument marked the shoreline of the Potomac River. When the U.S. Army Corps of Engineers deepened the river, the dredged silt deposited along its banks expanded the land to its current configuration. Almost immediately, the reclaimed land was proposed as the site for a memorial to Lincoln. At first this nearly mile-wide swath of dredged mud formed an unappealing space; but after landscaping and engineering transformed its appearance by the early 1900s, more and more people recognized the viability of the area. The decision to place the memorial at its current location came in 1913, and construction started the following year.
The Tiber Creek, originally called Goose Creek, flowed through the Law Center’s neighborhood. It flowed southward between North Capitol Street and First Street, NE, crossing back over North Capitol at E Street NW and then southwesterly, reaching B Street (Constitution Avenue) at Second Street, NW. It flowed into a canal on the Mall and then into the Potomac River. For more on Tiber Creek, see http://archive.org/stream/AHistoryOfTiberCreekWashingtonD.c/OwensHMalcolm-univarch-014809_djvu.txt
The area along North Capitol Street called Swampoodle (originally swamp-puddle, then swamp-poodle) was the home of poor Irish immigrants who had escaped the famine. It was also a center of crime and vice. The center of the neighborhood was just east of North Capitol Street, where a large branch of the Tiber Creek ran. The Creek created the low, swampy ground from which the area took its name, a name bestowed upon it by a reporter covering the dedication of St. Aloysius Church in 1859. He noted that the area around the church was dotted with “swamps and puddles.” For more on Swampoodle, see http://whenwashingtonwasirish.blogspot.com/2010/11/swampoodle.html
Although the I-395 Freeway was not directly in the path of the Creek, frequent rains caused water from the many waterways that emptied into the Tiber Creek to overflow onto what are now the Law Center property and the highway. Of course, that was long ago. Today, hundreds of miles of sewers run below the city, carrying storm water and sewage away and eliminating most floods and all of the swamps. What we are witnessing on 2nd Street in front of McDonough Hall is a relocation and replacement of some of those sewer lines. Two sewer lines currently run under 2nd Street, one under the sidewalk in front of McDonough Hall and one in the street farther to the west. The one to the west was built around 1894. It runs south from H Street until it connects with a larger line, installed in 1903, that runs under our Tower Green. The line under our sidewalk, built around 1936, deposits storm water runoff from 2nd Street before it turns into the line that runs under the Green. The westernmost sewer line has to be disconnected and removed to permit construction of a new portal leading to a redesigned off-ramp from the I-395 Highway onto 2nd Street. Thus, the line under our sidewalk has to be enlarged in order carry the combined runoffs from the original two sewer lines to the line that runs under the Green.
The physics of sewer lines is fascinating, at least to me. In order to accommodate the larger amount of water, the current 18-inch- diameter precast sewer is being replaced by a 24-inch line made of a plastic substance not unlike the PVC used for the drain pipes beneath your sinks. You have probably observed the blue-green pipe sitting on the street before it is installed. The capacity of the sewer must be sufficient to prevent flooding in a 15-year storm — a calculation related to an amount of standing water during a rain storm. The description of this calculation is too complex for our purposes. If you are really interested, you can see the calculation method described at http://en.wikipedia.org/wiki/Return_period.
We have been watching excavators dig the sewer path to a depth of 20 feet. Because all deep trenches carry a danger of collapse, steel supports are lowered into the bottom of the trench. Because the trench supports are not 20 feet tall, two other supports are placed on top of the lowest one until the trench walls are supported up to the surface. Because the earth is packed solid, the trench supports have to be pounded by the excavator shovel to secure the base.
That pounding caused the noise we heard early in the process. Because the noise and vibration proved to be too annoying for our community, the contractor, Balfour Beatty, authorized digging the trench wider than its necessary width so that the trench supports could be lowered into place without pounding. This required that the area between the earth and the trench support wall be backfilled to secure the wall once it was in place.
If one were to view a segment of the sewer line at the bottom of the trench, it would appear to be level — but it is not. At its highest point, the sewer under our sidewalk will be about six feet below the surface. At its lowest, it will be 20 feet deep. Sewer lines are gravity-based systems. Water flows from a higher to lower elevation by the force of gravity, not a pump. The line beneath the McDonough sidewalk is at a 2% slope. The smaller the slope, the slower the water runs through the sewer.
As sections of the blue–green sewer pipe are lowered into place, gaskets are placed on the inside of the slightly larger end of one section — a segment called the bell. A lubricant is then placed on the outside end of the section to be attached, and the two sections are joined. Pressure is then applied to seal the connection. This continues until the line is completed. Because the new sewer line is being connected to the still-active western sewer coming from H Street, the work must cease if there is a high chance of rain. When rain is expected, a flexible, temporary flume must be installed to connect the old line and the new line to maintain drainage. The flume is also installed when work is completed for the day.
Rain water runs into the sewer lines from catch basins (also known as storm inlets) that are usually located within a curb. They are a vital part of flood control. The inlets allow water to quickly drain from the streets; but the water does not flow directly into the sewer line. The catch basin is like a vault with storm water lines running out of it about 18 inches above the lowest level of the vault. The water sits at the bottom of the catch basin until enough accumulates to enter the sewer line. This allows debris to settle below the sewer line, preventing it from clogging the line. It also permits water to evaporate so less is sent into the Blue Plains Advanced Wastewater Treatment Plant and the Potomac River.
Despite the catch basin, clogs can still develop at the inlet. Because sewer lines do not run straight or uninterrupted for long stretches under the street, they can also develop at other places along the line. Manholes intercept the sewer lines where they change direction to prevent clogging and to provide a way for workers to enter the sewer lines to inspect and clear them. Additional manholes are also installed on the occasional long straight stretches of sewer to provide access for maintenance. Like catch basins, the bases of the manholes are lower than the sewer lines that connect through them. Water from the sewer line fills the bottom of a manhole until the water rises to the level of the sewer line, after which it flows out. If the sewer merely turned or connected at a 90% angle, the line could become clogged as the debris-filled water changed direction. The manhole permits the debris to settle, letting the water run smoothly.
Notwithstanding the manhole, clogs can still occur. Ladders along the side of the manhole enable a technician to descend into the sewer to clear the line, a job that is clearly underpaid given the odors and the nature of the debris.
All of these structures are being lowered into the ground outside our windows as we go about our days. Once they are installed, the earth is slowly replaced and compacted to solidify the earth and prevent cave-ins. The compacting occurs at 12-inch intervals as the trench walls are slowly removed. Again, this is no easy task. The pressure of the earth is so fierce that the back of the excavator sometimes rises slightly off the ground as its shovel arm strains to remove the embedded supports.
Sewer lines like these run underground all through the city. Hundreds of miles of lines take storm water and sewage away. The water flows along paths more complicated than any slide in a water park, until it finally reaches the Blue Plains water treatment plant sitting on the banks of the Potomac in far southeast Washington. But it wasn’t always like this. When Washington was founded, streams, creeks and swamps covered much of the area. As the population dramatically increased during and after the Civil War, people demanded more in terms of convenience and health safety.
The first sewage canals in the District of Columbia were dug in the mid to late 1850s, but poor planning led to sanitation problems. While the Capitol’s sewers emptied underground and drained harmlessly toward the Mall and the Washington Canal, runoff from the White House stagnated and festered in the low-lying area now known as the Ellipse. The addition of pipes in the area proved of little use, since sewage bound for the canal flowed into Tiber Creek at low tide but backed up at high tide until sediments built up enough to stop the flow entirely. City planners had designed several surface drainage sewers but did not allow them to be used for sanitation. Though householders could pay a special tax to empty their cellars into the Washington Canal, businesses and the few private homes with modern toilets sent their waste directly into streams or empty lots. You can learn more about the Washington Canal, once envisioned as a key artery linking the capital with the West via the Potomac and C&O Canal, at http://civilwarwashingtondc1861-1865.blogspot.com/2012/04/washington-canal-cesspool-in-midst-of.html.
The real transformation of Washington from a swampy southern town into what would become a city of classic urban design and proportion began in 1870. President Grant appointed Alexander Shepherd (namesake of the Shepherd Park neighborhood) to the DC Board of Public Works. A visionary with a larger-than-life personality, Shepherd quickly became the “Boss” of the board and set about a grand plan to modernize the District. In 1871, he presented a three-year plan for comprehensive capital improvement that included the development of a sewer system using portions of the Washington Canal. The plan would alter street levels so that sewage from the city’s most populous areas would be carried downhill into the canal. Although Washington was a “new” city in the world, its sewer and sanitation problems were not all that different from those of London or Paris. Napoleon III and Baron Haussmann redesigned the Paris system between 1855 and 1878, and London did the same between 1858 and 1878. It might surprise you to know that Sir Joseph William Bazalgette, the great-grandfather of Professor Don Wallace’s wife Daphne, was the driving force behind the creation of the London sewer system.
For the next three years, until the nationwide depression of 1873, Shepherd directed a massive public works project to turn the miles of dirt roads into brick, wooden, and paved streets and sidewalks, lined with trees and gas lamps, and to transform the fetid, disease-filled swamps, creeks, and canals into a modern sewer system. From the beginning, citizens were alarmed by the cost of the plan and how quickly it was moving forward; however, Shepherd was adept at assuring his critics. Armed with his assurances and secretly expecting Congress to foot at least half the cost, Shepherd plunged the city into numerous construction projects but also into debt. He insisted that work begin all over the city simultaneously to prevent piecemeal execution, and that the city adopt pay-as-you-go funding. Unfortunately, Shepherd knew nothing about engineering and refused to wait for a proper assessment of technical problems. His “plan” seldom included specific calculations and was not based on any significant professional surveying. Thus, errors were large and frequent. Houses on F Street were left perching on embankments while workers scrambled to change the road level. Newly paved roads often had to be dug up so workers could lay a forgotten sewer line. The engineer in charge of installing the main sewer line merely guessed at the levels at which lines should be placed, so when workers laying a line on 2nd Street reached the point where the line should have connected with the main, they found the line was 10 feet too low.
Despite the pitfalls of Shepherd’s modus operandi, the improvements were visible enough by the spring of 1873 to impress visitors and encourage public and private real estate development. Ultimately however, Shepherd had no money to pay the bill — a sad fact discovered only after the depression took hold. Amid complaints about arbitrary construction decisions, outrageous salaries, and irresponsible bookkeeping, and in response to allegations of corruption among Shepherd’s crew, the House Committee on the District conducted a four-month investigation of the operation. The Boss was ultimately driven out of town by his political enemies in 1876 and moved to Mexico; but he returned to a triumphant parade in his honor in 1887. His statue now stands in front of the John Wilson Building, headquarters of the D.C. government.http://www.dcmemorials.com/index_indiv0000650.htm
Notwithstanding Shepherd’s endeavors, sewer problems remained. Heavy precipitation in 1877 caused water levels to rise as much as 10 feet. When the Tiber Arch broke, the city was nearly inundated with sewage overflow. Necessary repairs could have been made; but the projected $2,500,000 cost made the U.S. Senate unwilling to include the measures in a general rivers and harbors bill. Not until 1882 did federal funding afford a partial fix. The new project included filling the marshes behind the monument grounds and building a tidal basin and a deep channel from Long Bridge to Arsenal Point to control water flow. By 1877, most of the Tiber Creek was enclosed in a sewer; but it was not completely tamed and consigned to the deep earth until 1907 when Union Station was built.
Errors like those that plagued Shepherd’s dreams are not likely to bedevil the work being done outside our windows. This project took over six years to plan. Surveys are accurate despite sometimes inaccurate engineering drawings from earlier sewer installations. The engineers are experts, and the construction team is led by a dynamic group of skilled builders and mangers. I meet with the team weekly to follow their progress and ensure that the Law Center’s interests are protected. Although we have experienced some serious noise and some sometimes surprising and even frightening vibration throughout the building during this phase of the project, I am reasonably confident that this project will prevent the floods that plagued the city in its early days.
Thanks to Haley Etchison, GULC 2016; and Marks Brewbaker, Assistant Project Manager for Balfour Beatty Construction D.C., for their help in collecting material for this note.
DC Water Proposes Modifying Long Term Control Plan for Green Infrastructure, District of Columbia Water and Sewer Authority, www.dcwater.com/green (last visited July 15, 2012).
District of Columbia Water and Sewer Authority, Combined Sewer System Long Term Control Plan (2002).
Department of the Army Baltimore District Corps of Engineers, Metropolitan Washington Area Water Supply Study, Appendix D: Supplies, Demands, and Deficits (1983).
Constance McLaughlin Green, Washington: A History of the Capital, 1800–1950 (1976).
Wallace Mlyniec, Construction Notes, Transforming a Campus in Washington, D.C. (2006)