The federal city – the plan

History enthusiasts, or students just out of an American History course, might remind us that it was President George Washington who selected the site that would become the federal city on the Potomac, Washington, D.C.

Around 1790, seven years after the signing of the Treaty of Paris that ended the Revolutionary War, President Washington employed the services of French artist and engineer Peter L’enfant to design the nations’ capital city. L’enfant started by surveying the 68.3 square miles that would become Washington, D.C. In the process of walking the area he identified locations that would eventually be the sites for the White House, the Capitol, and the primary business district.

L’enfant’s design for Washington suggested avenues radiating from focal points that resulted in geometric patterns featuring ceremonial green-space and grand avenues. As brilliant and creative as L’enfant was, his plan for the federal city had no design or provisions for utility infrastructure.

Water infrastructure – the historical foundation

Construction of the City of Washington, D.C., started in 1790 and by May 1800 was complete enough that President John Adams signed the authorisation to move the Capital from Philadelphia to Washington, D.C. (District). According to archived records, the first installation of water piping in the District did not occur until 1808. The pipe was a simple 2 inch bore through pine logs that conveyed artesian spring water to Pennsylvania Avenue by gravity flow. Water distribution systems in the early 19th Century were constructed of either bored out logs, grey iron pipe imported from England, or pit-cast grey iron pipe produced domestically after around 1834. It wasn’t until 1824 that the United States Army Corp of Engineers’ constructed a grey cast iron water line from an artesian spring to serve the White House. In 1850, the Corps would be challenged with design and construction of facilities that would bring untreated Potomac River water to the District for distribution to the residents, estimated to be nearly 52,000. This water delivery system, the foundation that the present system still relies on, would be called the Washington Aqueduct.

The Washington Aqueduct was a massive civil engineering project started by the Army Corps of Engineers in 1853 with construction of a cut-stone dam at Great Falls, M.D. The site for the dam was approximately twelve miles upriver from the Dalecarlia Reservoir and an additional two miles to the Georgetown Reservoir. Based on future system demands the Corps designed and constructed a 9 foot diameter brick, stone, and mortar conduit using tunnelling and open-cut excavation. The MacArthur Boulevard raw water conduit, as it was named, was a single, inverted “U” shaped tunnel that provided sufficient flow for nearly 75 years until the second conduit was needed in 1925.

Started in 1883 and completed in 1901, the 21,000 foot long Washington City Tunnel conveys water from the Georgetown Reservoir east to the McMillan Water Treatment Plant. The tunnel’s construction is similar to that of the MacArthur conduits, an inverted “U” shape approximately 9 foot tall and 9 foot, 10.5 inches wide. Its volume is approximately 11.4 million gallons a day (MGD). When it was commissioned in 1905, the McMillan Water Treatment Plant produced 75 MGD using slow-sand filtration. (Sand filtration is a treatment method that uses a bed of fine sand that is laid over graded gravel and used to remove impurities from a water supply). Until this simple filtration process was added, water from the Potomac River, which had been routinely described by National Parks Service as murky, was sent untreated to the estimated 300,000 area residents.

Serving the residential, commercial, government, and industrial water customers, the District uses approximately 1,300 miles of pipe that vary in diameter from 4 inches through to 78 inches. Pipes are generally classified as either transmission pipelines (16 inch diameter and larger) or distribution pipelines (12 inch diameter and smaller). Nearly 90 per cent of the system’s water piping is either grey unlined, cement lined or ductile iron with cement lining. Cement mortar lining eliminates red water that results from internal corrosion, as well as internal tuberculation.

Wastewater infrastructure – the history

In 1800, when Washington became the official capital city of the US, the population of the area was estimated to be about 8,200. By 1810 the population had almost doubled to 15,500. The period spanning the American Civil War (1861 through 1865) saw the largest per cent increase in the District’s population, up to 131,000. The first combined sewer pipelines were randomly constructed and were discontinuous. This, along with the dramatic increase in pollution, resulted in the death of thousands of residents due to water borne diseases such as smallpox, typhoid and malaria.

Sporadic construction of combined storm and sanitary sewers continued through to 1890 when the District made the decision to retain the existing combined sewers but to require that any extensions be separate collection systems. The District authorised the construction of large interceptor sewers to collect the sewage flows and discharge the collected flow into the Potomac River at a point that would prevent any flow from entering the raw water delivery system and contaminating the water source.

“The solution to pollution is dilution” is a dictum that summarises a traditional approach to pollution management whereby sufficiently diluted pollution is not harmful. This was the District’s treatment philosophy through the early part of the 20th Century. It wasn’t until 1938 that the wastewater treatment plant at Blue Plains opened to provide primary treatment (solids removal) before discharging less than 100 MGD into the Potomac River. The Blue Plains Wastewater Treatment Plant (Blue Plains) was expanded in 1959 to treat 240 MGD and to improve treatment processes to provide secondary treatment. Starting in 1890, when the Potomac achieved notoriety for the stench of its sewage within yards of the White House, until 1965, when President Lyndon B. Johnson labelled it “a national disgrace”, the river was largely a conduit for sewage from the rapidly expanding metropolis. Further expansions and improvements from 1970 through 1983 to treat 300 MGD and to provide tertiary or advance treatment are credited with improving the Potomac River water quality to pre-1950s levels.

There are approximately 1,800 miles of sanitary and combined sewer ranging in size from 8 inch through 27 foot arch tunnels. Fortunately, approximately two-thirds of the system is separated into sewer and stormwater. Historically, these sewers were made of brick, concrete, or vitrified clay pipe. In recent years the utility has transitioned to using concrete, ductile iron, or PVC.

The challenges of a forgotten infrastructure

The population of the District and surrounding communities continued a pattern of double digit increases through World Wars I and II peaking in 1950 at 802,000. From 1938 to 1996, the District of Columbia Water and Sewer Utility Administration (DC WASA) was part of the D.C. Government. Under an organisational structure like this, it is often difficult for politicians to overlook the revenue and the necessary reinvestment dollars generated by rate-based utilities. Generally, utilities attempt to cover replacement costs on a schedule that is based on condition assessment and how critical specific assets are within their system. In 1996, perhaps in recognition that this may have been a contributing factor to the deterioration of the water and wastewater systems in the District, DC WASA was created as a financially separate, semi-autonomous municipal utility. DC WASA provides treated water, and wastewater service, and wholesale wastewater treatment for certain suburban jurisdictions.

In the ten-year plan for DC WASA prepared in June 2009 by Hatch, Mott, MacDonald, engineers for DC WASA, the following buried water system initiatives were recommended:

• Replace existing 30 inch grey iron pipe in Canal Road with a new 48 inch pipe.
• Conduct internal joint repairs for existing grey iron pipes with leaking lead joints.
• Rehabilitate five of the most critical large diameter steel pipes through design, installation, and recommended frequency of proper CP testing.
• Prioritise the remaining steel pipelines.
• Develop a plan to investigate the condition of all pre-stressed pipe in the system.
• Establish a database associated with the Geographic Information System that captures critical condition assessment information.
• Increase funding to $US30 million for small diameter (12 inches and smaller) rehabilitation, including cleaning and lining with cement mortar.

In early 2003, DC WASA received a document from the United States District Court for the District of Columbia detailing a Court Decree settling suits between defendant DC WASA against the Anacostia Watershed Society and other plaintiffs, and defendants DC WASA and the District of Columbia against the US. In brief, the decree requires nine items be observed as conditions of the lawsuit. The nine items are as follows:

• 1. Proper operation and regular maintenance for the combined sanitary sewer
• 2. Maximisation of storage in the collection system
• 3. Pre-treatment
• 4. Maximisation of flow to the Publicly Owned Treatment Works for treatment
• 5. Combined sewer overflows (CSOs) discharges during dry weather
• 6. Control of solids and floatable material in CSOs
• 7. Pollution prevention programs
• 8. Public notification
• 9. Monitoring.

The necessary work must be completed based on schedules outlined in the Court Decree. However, there are trenchless installation options that can minimise the disruption to authority customers and also minimise additional social costs associated with pipeline construction. DC WASA has used several different trenchless installation methods and recognises the value that these less disruptive construction technologies offer.

DC WASA has had several projects that are specifically related to the Consent Decree that have used trenchless technologies. For example, a slip line rehabilitation of a failing piece of sewer pipe located at 2nd and F Streets, N.E. The pipe was a collapsed section of 114 inch brick sewer tunnel that was approximately 35 feet to the top outside of the brick sewer. The pipe that was used to slipline the existing sewer was a 96 inch, low stiffness, reinforced plastic mortar pipe (RPMP). After assembling the 5–10 foot long pipe sections into a 50 foot, water tight repair section and assuring the location of the pipe in the annular space between the existing brick sewer tunnel and the outside of the RPMP, it was grouted with a Portland cement base grout under controlled head pressure with extreme care taken to not collapse the pipe. This 2007 project is just one of many completed to prevent the potential, catastrophic damage of a failed piece of a forgotten sewer infrastructure.

Conclusion

Although this was a story about the federal city, Washington, D.C., it is appropriate to conclude with a quotation from the former Mayor of the City of Atlanta, the Honorable Shirley Franklin. The self-proclaimed “Sewer Mayor” saw an unpopular problem and confronted it head on, convincing her constituency of the legitimacy of the costly solution. She has said on many occasions that “without wastewater infrastructure and drinking water infrastructure the economy will stop.”

Acknowledgement

The author would like to give special thanks to Emmanuel Briggs and all his Associates at DC WASA for providing the information and sources for the information that made this paper possible.

References

1. Bowling, Peter Charles L’enfant: Vision, Honor, and Male Friendship in the Early American Republic, Washington, DC, 2002 2. Build DC, MA-ICA, Washington DC 20003 3. Carpenter, Gray Iron and Ductile Iron Pipe – Some Historical Benchmarks Impacting Condition Assessment, ASCE ERWI Conference, Providence, RI, 2010 4. Cohen, The Solution to Pollution Is Still Dilution, Earth Island Institute. 5. Civil Engineering, “USGS: Potomac River Cleanest in Decades,” Civil Engineering, October 2010 6. Hatch, Mott, Macdonald, DC WASA – Water System Facilities Plan, June 2009 7. Penn State Public Broadcasting, Liquid Assets-The Story of Our Water Infrastructure, Documentary, 2008