Spring- Time to Flush the Pipes

 As part of the annual maintenance program for the regional water distribution systems in Virginia and Washington DC, on March 21st , 2022 Fairfax Water, the Washington Aqueduct, Loudoun Water and the City of Manassas will switch from chloramine to chlorine to disinfect their water. During this time, Arlington Department of Environmental Services, DC Water, the Prince William Service Authority, Loudoun Water and Fairfax Water will begin flushing their water distribution systems. Each spring these water distribution companies flush their water mains by opening fire hydrants and allowing them to flow freely for a short period of time.

Fairfax Water will disinfect with chlorine from March 21st  to June 13th and the water systems the flushing of the water mains in Fairfax and Prince William will occur during that time. Crews from the Service Authority and Fairfax Water will open hydrants throughout their service area in brief intervals in order to draw water more forcefully through the distribution system and scrub out the pipes. This helps to dislodge sediment that may have collected in water mains over the past year. In DC, Arlington and  Falls Church, the flushing will occur from March 23 through May 9th , 2022. Those jurisdictions purchase treated drinking water from the Washington Aqueduct. Loudoun Water also announced they will be starting their program on March 21st.

For most of the year, chloramines, also known as combined chlorine, is added to the water as the primary disinfectant. During the spring the water treatment plants for Fairfax Water, Loudoun Water and the Washington Aqueduct switch back to chlorine in an uncombined state, commonly referred to as free chlorine. This free chlorine reacts with sediments suspended during flushing and kills bacteria that may be in the bio-film that forms on the pipe walls. Many water chemistry experts believe this short exposure to a different type of disinfectant maintains a low microbial growth in the bio-film and improves the quality and safety of the water.

This change in disinfection is an annual program to clean the water distribution pipes and maintain high water quality throughout the year. The U.S. Army Corps of Engineers Washington Aqueduct provides water to the District of Columbia, Arlington County, and other areas in Virginia. Fairfax Water provides water to Fairfax County and parts of both Loudoun and Prince William County. WSSC does not switch their disinfectant.

You may notice a slight chlorine taste and smell in your drinking water during this time, this is not harmful and the water remains safe to drink. Depending on your location within the distribution system, it could take up to a week for your drinking water to transition from combined to free chlorine at the beginning of the flushing program, or from free chlorine to combined chlorine at the conclusion of the flushing program. You may want to use filtered water to drink or leave an open container of water in the refrigerator for a couple of hours to allow the smell to dissipate. Refrigerator filters remove chlorine so you do not have to worry about ice. Water customers who normally take special precautions to remove chloramine from tap water, such as dialysis centers, medical facilities and aquarium owners, should continue to take the same precautions during the temporary switch to chlorine. Most methods for removing chloramine from tap water are effective in removing chlorine. The annual chlorination is important step to remove residue from the water distribution system. Free chlorine is better suited to remove residue that may have collected in the pipes than chloramine and a coordinated opening of fire hydrants serves to flush the system and scrub the pipes.

Prince William County the Retirement Mecca that will Survive Climate Change

The climate of the earth is constantly changing. Scientific studies have indicated that over the past century the earth has warmed 1.3 degrees Fahrenheit. This warming is not particularly alarming in itself given our planetary history, but the speed of this temperature increase and the fact that the warming is projected to continue at an accelerated pace is worrisome. The planetary warming is forecast to cause sea levels to rise due to melting of sea ice in parts of the world, and changes in weather and patterns and precipitation. If carbon dioxide (CO2) concentrations in the atmosphere are the driving force in earth’s temperature that many scientists believe, then these trends are likely to continue. On a whole earth basis the climate models show at this point there is nothing that we can do to stop global warming and climate change.

As the concentrations of CO2 in the atmosphere increase, the warming produced by the greenhouse gas effect is strengthened. Computer modeling of the climate predicts that there will be feedbacks that significantly increase the impact from the increasing CO2. Even if the concentration of CO2 in the earth’s atmosphere were to stabilize at this level, the changes in the climate of the earth in response to the atmospheric CO2 levels would continue for hundreds of years. In reality, the global emissions of CO2 will not stabilize or decrease any time soon and will continue to rise for at least a generation. What is going to happen will happen, so we need to plan for change and make decisions for the next 30-50 years based on likely outcomes.

It is my plan to live for another 40 years. My relatives do pretty well and I am an optimist and a “real food” and exercise devotee. So when it came time to select a place to live in retirement, climate change was one of the factors taken into consideration- water availability, distance from the coast, elevation, along with proximity to family, medical service and an airport and several other factors. Now, I find myself in northwest Prince William County a place that the Washington Post recently described as becoming “a regional retirement mecca, a small-scale version of Florida on the outskirts of Washington.” I made my choices based to a large extent on general projections of climate released by various groups, not having the tools or resources to do much more.

Now, however, the Interstate Commission on the Potomac River Basin (ICPRB) has completed a study in water supply availability and the health of the Potomac Watershed for various climate scenarios. The focus of their study was the Potomac River, which supplies water to the Washington Aqueduct, Washington Suburban Sanitary Commission (WSSC), and Fairfax Water who all funded the study. The Potomac River supplies 78% of the regions drinking water and the water utilities of the region must plan for the future. In addition, there must be adequate flow of the Potomac below Little Falls to ensure that the balance of saline and fresh water for the health of the Chesapeake Bay estuary. So, on the water rate payer’s nickel I get to see what the future might look like here in in Prince William County.

The National Research Program of the U.S. Geological Survey (USGS) actually performed the study using six of the global climate models and three atmospheric CO2 scenarios to create 18 separate possible scenarios. The USGS then “downscaled” the 18 global climate predictions to the Potomac River basin and to other areas as part of a separate project on climate change being conducted by the Chesapeake Bay Program Office and the USGS’s Virginia Water Science Center (your tax dollars at work). In addition, the Chesapeake Bay Program’s Phase 5 Watershed Model was used to estimate the impact of changing temperatures and precipitation on Potomac basin stream flows.

The most advanced types of models currently being used to project future global climate are general circulation models (GCMs). A GCM is a numerical model which represents the important physical, chemical, and biological processes on the Earth’s surface, in the atmosphere, and/or in oceanic systems that affect climate. The USGS used models from the National Center for Atmospheric Research (USA), Norway, Australia, Russia and Japan as listed in the chart below.

From ICPRB publication

In addition, the three CO2 emissions scenarios were based on IPCC’s Climate Change 2007: Synthesis Report (IPCC, 2007c). The USGS used relatively low emissions (B1), medium emissions (A1B), and high emissions (A2) temperature forecasts for each model to create the 18 scenarios.

IPCC Climate Change 2007

There is tremendous uncertainty in projecting the future climate of the earth, especially at the regional scale. Though global climate models are continually being refined and improved, they do not capture complexity of the interrelations of earth’s land, water, and atmospheric systems that we do not yet fully understand. Local nuisances can be lost in the broad sweeps of mathematical modeling of a living system. Scientific confidence in global model projections is higher for temperature than for precipitation, higher for global scales rather than small regional scales, and higher for longer time frames than shorter ones. Nonetheless, with all those disclaimers, the USGS did get some predictions out of their 18 scenarios.

Though it is predicted by the climate models that precipitation will increase on a global scale, when dealing with only the Potomac River basin, the models differed on whether precipitation will increase or decrease. The models project that the total annual precipitation varies from plus 9% to minus 9% or that the rainfall/ snowmelt that averaged 42.2 inches during the reference period (1988-1999) may stay within 4 inches of that average. Though, it is to be noted, that year to year weather variations in rainfall in the region are large, precipitation has varied from over 80 inches to below 20 inches in the past. Also, in the 18 climate scenarios, the increase in annual average temperature by 2040 increases for the area from 1.3 to 4.1 degrees Fahrenheit when compared with the reference period of 1988 to 1999. The average increase, over all scenarios is 2.7 degrees Fahrenheit. (These temperature predictions were the basis of the energy savings and water savings projects for my home that were geared for a slightly warmer, drier climate, though I am still hoping for wetter.)

Though annual rainfall increases in half of the climate change scenarios, flow in the Potomac River falls in most scenarios. Changes in both temperature and precipitation affect stream flows. Changes in rain or snow affect the amount of water that runs off the land surface and enters streams during rainfall. Precipitation also affects the amount of water recharging groundwater aquifers, which are the primary source of stream flow during dry weather periods. Increasing temperatures will cause more rain to be lost to evaporation from the soil, streams, and will increase transpiration, the water released to the atmosphere by plants. These increases in evaporation and transpiration will tend to reduce flow in streams which in turn reduces flow in the Potomac. With rising population, this could require changes in water use and supply for the area and reduce groundwater availability for private well owners like me.

Average annual basin-wide evaporation and transpiration is predicted to increase by 6-8%. Groundwater recharge decreases under all but three of the climate scenarios, and as I watch the statistically low water level in the monitoring well up the road, I worry about my well water supply. According to study results, the seasonal pattern of groundwater recharge does not change significantly under climate change, with January, February, and March remaining the months of greatest recharge. However, the average annual amount of groundwater that provides base flow to streams and the water in my well, is predicted to decrease in 16 out of the 18 scenarios by as much as 34% in one case.

Results for the 18 climate scenarios fell into three categories: minor impact, moderate impact, and major impact. The biggest impact is the ability of the regional water utilities to continue to supply water on demand during droughts as the climate changes. Six of the scenarios are predicted to have little impact on the system during a moderate drought and the projected population of the region can be supplied with drinking water from the Potomac River and current systems and operations. Six of the climate change scenarios fall into the “moderate impact” category. Under these scenarios the region is predicted to experience more frequent and stricter water use restrictions, but no water supply shortages during a moderate drought. Reservoir levels are predicted to fall to significantly lower levels during a drought than would occur in the absence of climate change with the projected and assumed increase in population.

However, the remaining six climate change scenarios are scary. Under these dreadful six scenarios, unless we make changes in the water supply systems we run out of water. These scenarios predict that both mandatory and emergency water use restrictions would be imposed and most system reservoirs would become empty or close to empty during a moderate drought. In addition, these six scenarios predict on some days of the drought the Potomac River would fail to provide sufficient water to meet demand and environmental needs. Our regional water utilities: The Washington Aqueduct, Washington Suburban Sanitary Commission (WSSC), and Fairfax Water working together with the ICPRB can make changes to the structure and operation of the water supply system to make it more robust. The Potomac River will continue to supply water to the region, we will have to use it more wisely to ensure adequate water supply in the future, but there will be water.  Clearly though, development in the groundwater recharge zones (mostly the Rural Crescent in Prince William County) and open areas needs to be limited to protect the groundwater and stream base flow that supplies our water.

The Washington Aqueduct Searching for the Best Possible Drinking Water

The Washington Aqueduct is a federally owned and operated by the Army Corp of Engineers. The Aqueduct consists of the Dalecarlia Reservoir and Water Treatment Plant, the Georgetown Reservoir, and the McMillan Reservoir and Water Treatment Plant. The Washington Aqueduct draws water from the Potomac River and treats it to provide finished drinking water to the water distribution companies that buy water from them. Thomas Jocobus, a civilian employee of the Army Corp of Engineers is the General Manager and the Aqueduct produces an average of 155 million gallons of water per day which it sell to the District of Columbia (about 75%), Arlington County, Virginia (about 15%), and the City of Falls Church, Virginia (10%).

The Washington Aqueduct is a very conservative organization reflecting its structure, management, and response to events of the past. Water systems consist of three systems: The first is the water treatment systems that draw water from the source and treats it to meet the US EPA Safe Drinking Water Act standards (SDWA). The second is the water delivery system that moves the water from the finished water storage through the water mains and throughout the community so that there will be on demand water and adequate water for firefighting. The third is the plumbing systems in homes and building that deliver water to your sink, toilet or shower.

Somewhere in the past the Washington Aqueduct had begun to view their mission as providing finished water that met all EPA SDWA requirements. After all, (unlike most water utilities that are regulated by state regulators) EPA Region 3 was their direct regulator and they were attentive and responsive to the regulatory requirement and deeply concerned about the quality and cost of the finished water they sold.  All the costs of the Aqueduct operations are directly passed on to wholesale customers. In the 1990’s something happened to remind the Aqueduct that really they are in the public health (and fire safety) business and that their operations could not be viewed separately from the water delivery and plumbing systems that ultimately brought water to the households and businesses that bought water  from the distribution companies. What happened was chloramine.

from DC Water

In 1994 amendments to the Clean Water Act SDWA resulted in changing from chlorine to chloramine for disinfection. The EPA issued regulations concerning disinfectionby-products formed when chlorine (used for a hundred years) reacts with organic matter in drinking water; the EPA considered these byproducts to be a potential health threat. Chloramines do not produce disinfection byproducts. The treatment process for the Washington Aqueduct was changed to add ammonia after primary disinfection to react with the remaining chlorine to prevent the formation of disinfection byproducts (haloacetic acids and trihalomethanes). When planning the chloramine project as advised by  EPA guidance manual the Aqueduct considered the possibility that the disinfectant change would increase the level of nitrification in the distribution system. Such an increase could cause a lowering of pH in the distribution system, increasing the possibility of corrosion. The Aqueduct put a plan in place to minimize the potential for nitrification and monitored for nitrification for six months following conversion. Unfortunately, corrosion was not caused by nitrification.  Shortly after the change, increasing pipe failures and levels of lead began appearing in the homes of Washington DC residents. It turns out chloramine-treated water picks up lead from pipes and solder and does not release it, resulting in elevated levels and deterioration of the pipes. Extreme lead concentration began appearing in Washington DC homes and water delivery pipe and plumbing systems began to fail at an accelerated rate.

  

Dr. Marc Edwards a MacArthur Prize winning professor of engineering at Virginia Tech ultimately  identified the cause and solution of the increasing incidence of leaks in copper water pipes. The lead problem was addressed by the Washington Aqueduct adding additional treatment steps to add orthophosphate and tightly control the pH of the water.  Orthophosphate controls corrosion in pipes, service lines, and household plumbing throughout the distribution system. It works by building up a thin film of insoluble material in lead, copper, and iron pipes and fixtures. This thin film acts a barrier to prevent leaching of metals into the water, but only works in a narrow pH range. Calcium hydroxide (lime) is also added to adjust the pH of the water to ensure optimal performance of the orthophosphate. In addition, DC WASA spent $97 million to replace a portion of 15,000 pipes and 2,000 full pipe replacements.

The change in the water treatment process prevents the finished water from dissolving lead in the water mains, solder joints, and fixtures. The changes in the operation of the Washington Aqueduct were more profound. The Aqueduct had to rethink the management of their relationship with their customers, how had they made a change in the water treatment without testing the impact on all the other water systems? That is unlikely to ever happen again.  The Washington Aqueduct's customers (District of Columbia Water and Sewer Authority, Arlington County, and the City of Falls Church) entered into a memorandum of understanding with the U.S. Army Corps of Engineers that restructured the business relationship and created the Wholesale Customer Board and Technical Committee to oversee and approve Washington Aqueduct's operating and capital budgets and long term strategy.

The Washington Aqueduct’s official mission became to provide the “best possible” drinking water while: Minimizing any negative effects on the environment, being fiscally responsible to consumer who bear all the operating and capital costs through water rates, and anticipating and avoiding unintended negative consequences. The Aqueduct has been working with their Wholesale Customer Board to navigate the challenges that face drinking water utilities in our modern world; microbial water quality issues, trace chemicals and emerging contaminants in the source water, and water quality issues resulting from treatment and distribution.

Chemicals are everywhere in our modern world. The technology used for chemical analysis has advanced to the point that it is possible to detect and quantify nearly any compound known to human kind down to less than a nanogram per liter or parts per trillion (1/1,000,000,000,000). This enhanced analytical ability has allowed scientists to discover that trace levels of pharmaceuticals, potential endocrine disrupting compounds (EDC) and other emerging contaminants exist in surface water, have appeared in some groundwater and may persist in the water through conventional and some advanced treatment trains to appear in our finished drinking water. The Washington Aqueduct and its partners on the Wholesale Customer Board and technical working group expert panel from consulting, academia, EPA and other Water Utilities are working to develop a framework to make decisions and chart courses of action when faced with these challenges. The first and continuing challenge is to keep evolving the understanding of what is the “best possible” drinking water and remember to consider all consequences before taking any action. The Washington Aqueduct of today is unlikely to be the first water treatment operation to make any change, but is unlikely to be surprised by unanticipated consequences of any changes in treatment that are made in the future. 

Sediment Disposal from the Washington Aqueduct Water Treatment Plants

Drinking water systems may obtain their water supply either directly from the rivers, lakes, reservoirs for surface water or from wells for ground water or like DC Water, Arlington and Falls Church may purchase finished water from wholesalers like the Washington Aqueduct. Raw water is treated to produce finished drinking water. During the treatment of source water, water treatment plants, WTPs, remove contaminants by screening, sedimentation, flocculation and filtration. The waste streams generated from these steps are water treatment residuals. In a 2011 report the US Environmental Protection Agency, EPA, estimated that approximately 31% of the WTPs directly discharge to surface water, 7% transfer residuals to waste water treatment plants and the remainder is disposed of on land.

Solid residuals from water treatment plants include sludge, schmutzdecke (biological surface layer in slow sand filtration units), and spent treatment media. Residuals contain contaminants removed from the source water and treatment chemicals added by the WTP. Prior to final disposal residuals from the source water treatment operations can be treated on site by the WTP. Washington Aqueduct has a newly constructed residuals management facility that disposes of the solids by contract hauling.  The residuals from the Aqueduct are being used for reclamation and backfilling under a Maryland surface mining permit. The residuals are permitted to be used  offsite as clean fill. The volume and characteristics of the residuals depend on the source water, drinking water production rate, efficiency of source water treatment, and type of source water treatment used. The goal of all residuals treatment/ solids removal systems is to decrease the volume of water while increasing solids content. This process creates two waste streams the liquid and the solid.

EPA’s Filter Backwash Recycle Rule, FBRR, established requirements to ensure that WTPs do not compromise the quality of finished drinking water when recycling water from residuals management. The FBRR requires WTPs that reuse certain wastewater liquid residuals (filter backwash, thickener supernatant, and dewatering process liquids) the water must be returned to a point in the water treatment process where it will be treated by coagulation and filtration.

Water treatment residuals solids contain naturally occurring suspended and dissolved solids from the source water, as well as precipitated solids generated by chemical treatment as well as residual contaminants from chemical treatment. The naturally occurring solids include sediment and soils that are carried to the Potomac in run off from rain and snow melt. These solids are regulated under the Resource Conservation and Recovery Act, RCRA, regulations and are classified as hazardous or nonhazardous. A waste is characterized as hazardous or nonhazardous based on its ignitability, corrosivity, reactivity, and toxicity. Generally speaking, these wastes are not toxic and are often sold and used as soil amendments in agriculture or disposed of by contract hauling to a permitted disposal facility. The solids residual from water treatment generally contains the river sediment, traces of the algaecides and flocculants.

Sludge generated by water treatment plants is not subject to regulation under the Biosolids Rule. The Biosolids Rule (part of the Clean Water Act Amendments of 1987) was created to protect public health and the environment from any anticipated effects from recycling of sewage sludge Biosolids. The toxicity of solid residuals from sewage treatment is assessed by the Toxicity Characteristic Leaching Procedure (TCLP), which is a soil sample extraction method for chemical analysis. If contaminant concentrations in the TCLP leachate are below those listed in the Land Disposal Restrictions of RCRA, the solid residual is classified as non-hazardous and can be disposed at a municipal landfill or other location. There is tremendous controversy associated with potential impacts of Biosolids and the land disposal or reuse of Class B and even Class A Biosolids. I am not aware of any controversy associated with agricultural use of solids residual (predominately river silt) of water treatment plants.

The Dalecarlia Reservoir and Water Treatment Plant

from Army Corps of Engineers via Wikimedia

I went up to the Dalecarlia Reservoir and Water Treatment Plant on MacArthur Boulevard for a tour and to speak with Thomas Jocobus, the General Manager. The Dalecarlia operations are the main location for the Washington Aqueduct. The Washington Aqueduct consists of the Dalecarlia Reservoir and Water Treatment Plant, the Georgetown Reservoir, and the McMillan Reservoir and Water Treatment Plant. The Washington Aqueduct draws water from the Potomac River and treats it to provide finished drinking water to the water distribution companies that buy water from them.

The Washington Aqueduct is a federally owned and operated by the Army Corp of Engineers and Mr. Jacobus like all employees of the Washington Aqueduct is a civilian employee of the Army Corp of Engineers. The Aqueduct was initially built with federal funds, but since 1927 the operating budget and capital budget have been paid for by the Aqueduct’s customers. Today, the operating budget is around $46 million that is supplied by the wholesale water rates charged for the water delivered. The Aqueduct produces an average of 155 million gallons of water per day and sells that water to the District of Columbia (about 75% of the finished water), Arlington County, Virginia (about 15%), and the City of Falls Church, Virginia (10%). In total about one million people a day use water supplied by the Aqueduct.

The maximum capacity of the Aqueduct is 320 million gallons of water per day much more than even the peak demand for drinking water and fire fighting for their customers. Though water use peaked at an average of 180 million of gallons a day about a decade ago, the system was expanded in the 1950’s anticipating serving Montgomery and Prince George counties, but the Washington Suburban Sanitary Commission (WSSC) instead built what is today the WSSC's principal water supply facility, the Potomac River Filtration Plant in western Montgomery County to supply their needs.

The Washington Aqueduct dates back to 1853 when congress appropriated $5,000 to develop the first portion of the system. The first portions of the system were the Dalecarlia Reservoir and Georgetown distribution reservoir. That portion of the system was designed to run on gravity, so that the system did not require pumps until much later when the system and the city expanded and demand for water required the expansion of the system. Even today the energy used is reduced because of the utilization of natural elevations in the design of the system. The Aqueduct first began delivering water in 1862. The Lydecker Tunnel and McMillian Reservoir and water treatment plant were added in 1905. The McMillian slow sand water treatment plant was the first treatment plant in the system and was built to address the increasing outbreaks of typhoid fever that were caused by contaminated drinking water. This was followed by a rapid sand filtration system at Dalecarlia to address the continued population growth after World War I.

Today the water for the Washington Aqueduct continues to be drawn from the Potomac River at the Great Falls and Little Falls intakes. This duel intake location about 10 miles apart allows for some degree of management of the water quality at intake if there should be a fuel spill or other water quality disturbance. On its way from the river intakes to the Dalecarlia reservoir, raw water passes through a series of screens designed to remove debris such as twigs and leaves and whatever trash finds its way into the Potomac River. Then copper sulfate and sodium permanganate are added as algaecides. All water drawn for the system enters the Dalecarlia Reservoir. While the water moves slowly through Dalecarlia Reservoir, much of the sand and silt settles to the bottom. This is called pre-sedimentation. After screening, the addition of the algaecides and pre-sedimentation the water is either pumped to the Dalecarlia or McMillan treatment plants.

The treatment plants filter and disinfect water from the Potomac River to meet safe drinking water standards. The treatment process is not identical at both plant, but it is very similar and includes sedimentation, filtration, fluoridation, pH adjustment, primary disinfection using sodium hypochlorite, secondary disinfection with chloramine through the addition of ammonia, and corrosion control with orthophosphate.

From the Army Corp of Engineers

The raw water from the Potomac River contains suspended solids, sediment, bacteria, and microorganisms that must be removed to produce finished drinking water. These are removed by the water treatment processes of the Washington Aqueduct after the initial screening and pre-sedimentation water treatment consists of:

Coagulation - A coagulant, aluminum sulfate (alum) and powdered activated carbon, is added to the water as it flows to sedimentation basins. Coagulants aid in the removal of suspended particles by causing them to consolidate and settle. Alum contains positively charged atoms called ions which attract the negatively charged particles suspended in water causing them to gather into clumps of particles heavy enough to settle. The activated carbon controls odor in the water.

Flocculation – The water is gently stirred with large paddles to distribute the coagulant; this causes particles to combine and grow large and heavy enough to settle. This process takes approximately 25 minutes. Cationic polymer and nonionic polymer are added.

Sedimentation – The water flows into quiet sedimentation basins where the flocculated particles settle to the bottom. After about four hours, approximately 85% of the suspended material settles out. Until recently, the sediment recovered was returned to the river, now the sediment residuals are collected from Dalecarlia, McMillan and Georgetown locations and then pumped to a central processing facility at Dalecarlia.  Residuals processing, including gravity thickening and dewatering, occur at the newly constructed Residual Management building. Following processing, trucks haul the residuals off-site to permitted land-disposal areas.

Filtration – Water at the top of the basins flows to large gravity filters, where the water flows down through filter media consisting of layers of small pieces of hard coal (anthracite), sand, and gravel placed in the bottom of deep, concrete-walled boxes. Filtered water passes through to a collecting system underneath. The filters are back washed every four days.

Disinfection – Chlorine in the form of sodium hypochlorite is added with precision equipment to kill pathogenic microscopic life such as bacteria or viruses. Ammonia is then added. The chlorine and ammonia combine to form chloramine compounds. This is the most recent significant change in the water treatment process and was required by changes in the Safe Drinking Water Act in the 1990's. The concentration of chloramines in the water is closely monitored from the time it is added at the treatment plants to points near the furthest reaches of the distribution systems.

The Dalecarlia operation has an EPA certified laboratory to perform the tens of thousands of analysis required each year under the Safe Drinking Water Act. One of the coolest features of the tour was seeing the surveillance of the water treatment train. In one of the laboratories is a trough sink with 15 spigots continually running. Each spigot continually draws water from one step in the treatment process. If a problem arises water at every point can be checked to make adjustments.

Fluoride, in the form of hydrofluorosilicic acid, is added to the finished water to reduce tooth decay; this is especially beneficial for children. Orthophosphate is added to control corrosion in pipes, service lines, and household plumbing throughout the distribution system. It works by building up a thin film of insoluble material in lead, copper, and iron pipes and fixtures. This thin film acts a barrier to prevent leaching of metals into the water. Calcium hydroxide (lime) is also added to adjust the pH of the water to ensure optimal performance of the orthophosphate.

After the water has completed its path through the treatment process, it is referred to as finished water and meets all requirements under the Safe Drinking Water Act. Because the Washington Aqueduct is in Washington D.C. it is directly regulated by the US EPA Region 3 office. The Washington DC regulators do not have primacy. Unlike most large urban water systems the Aqueduct does not have state regulators to answer to and its customers are the three water distribution systems DC Water, Arlington and Falls Church section of Fairfax County. Falls Church has come to an agreement to turn over their distribution system to Fairfax Water who will continue to buy water for that portion of the system from the Aqueduct. The Washington Aqueduct does not currently engage in any advanced water treatment, but is studying the options.  

The History of Drinking Water in Washington DC

In the first decade of the nineteenth century a group of residents of Washington DC were granted permission to pipe water from the city spring to their neighborhood in the 600 block of Pennsylvania Avenue. Shortly thereafter the city built a pipe to convey water from a city spring to the northwestern Pennsylvania Avenue vicinity, between 9th and 14th streets. These, were the first instances of water deliveries in Washington DC and the beginning of the water system in our nation’s capital. The city-wide delivery of fresh water was still another fifty years away and would arrive with the Washington Aqueduct.

The original portions of the Washington Aqueduct were planned and built by Lieutenant Montgomery C. Meigs of the Army Corp of Engineers. The Dalecarlia Reservoir was completed in 1858 and water first reached the District through the Washington Aqueduct system on January 3, 1859. Initially the reservoir provided water to the city from the adjacent Little Falls Branch, but this soon was inadequate and flow from the Potomac River was added in 1864. At that time the city government believed, the Washington Aqueduct system would be sufficient for all the future water needs of the city. Today the Washington Aqueduct is a division of the Baltimore District, U.S. Army Corps of Engineers. The Aqueduct is a federally owned and operated public water supply agency that produces an average of 180 million gallons of water per day at two treatment plants located in Washington DC and sells the water to the District of Columbia, Arlington County, Virginia, and the City of Falls Church, Virginia.

 After the initial construction of the Washington Aqueduct the surge in population of Washington DC during the Civil War, quickly created a human waste problem in the city and there were epidemics of smallpox, malaria, and typhoid from human waste contaminating the water supply which took many thousands of lives during the war years. Dr. John Snow had discovered and proved the connection between cholera and contaminated water during the 1850’s in London, England. Nonetheless, the general belief was that if water looked, tasted and smelled fine it was good and though the Potomac River provided dilution disease survived. The Washington Aqueduct was originally built as a water transportation system, to bring the river water into the city. However, in 1895 the flow from Little Falls Branch was diverted away from the Dalecarlia Reservoir to prevent disease in conjunction with development of the sanitary sewer system. Despite these steps it was clear that, the Washington Aqueduct needed to be expanded and have a filtration system. The Washington Reservoir, which is now called the McMillan Reservoir, was built in 1902 to increase supply and in 1905, a 75 million gallon per day slow-sand filtration system was added at that reservoir and the Bryant Street high-lift pumping station was built.

After World War I an 80 million gallon per day rapid-sand filter was added at the Dalecarlia Reservoir to address the problems created by continued population growth and the sheer amount of raw sewage that was being pumped into the river. Primary waste treatment began for Washington DC at Blue Plains sewage treatment plant in 1937. The continuous population growth of Washington DC during World War II made it necessary to continue to expand and improve the water supply system. In February 1946, Congress approved comprehensive plans from the Army Corp of Engineers and the City Engineer to construct, improve and add to the existing water system. For more than thirty years, implementation of the plan underwent periodic modifications through changing requirements and increases in necessary funding by Congress. This awkward and inefficient oversight and funding was still in effect when I briefly lived in the District in the early 1970s when the water and sewage agency was known as the District of Columbia Department of Environmental Services. Later, in 1985, the District Government established a new Department of Public Works, of which the Water and Sewer Administration was a part of until 1996.

In 1996, the District Government initiated the creation of the District of Columbia Water and Sewer Authority (DC WASA re-branded DC Water in 2010), an independent authority of the District of Columbia providing water delivery and sewage services to the region. On April 18, 1996, following a 30-day Congressional review period, the District Council enacted DC Law 11-111, "The Water and Sewer Authority Establishment and Department of Public Works Reorganization Act of 1996." This allowed DC WASA to have a separate and dedicated source of funding-water and sewer rates. It was envisioned that DC WASA would then be able to use that funding to meet its statutory obligation to provide sanitary sewer services and deliver potable water to the Washington Metropolitan Area. The Washington Aqueduct remains   federally owned.

Today, the Aqueduct draws water from the Potomac River at the Great Falls and Little Falls intakes and treats the water at two treatment plants, Dalecarlia and McMillan. The Aqueduct filters and disinfects water from the Potomac River to meet current safe drinking water standards. The treatment process includes sedimentation, filtration, fluoridation, pH adjustment, primary disinfection using free chlorine, secondary disinfection with chloramine through the addition of ammonia, and corrosion control with orthophosphate. The EPA sets national limits on residual disinfectant levels in drinking water to reduce the risk of exposure to disinfection byproducts formed when public water systems add chemical disinfectant for either primary or residual treatment. These levels are known as Maximum Residual Disinfectant Levels (MRDLs). The EPA also sets EPA sets limits on the contaminants regulated under the Safe Drinking Water Act to ensure that the water is safe for human consumption. These limits are known as Maximum Contaminant Levels (MCLs). During calendar year 2011, no MRDL nor any MCL violations occurred in the Washington Aqueduct system.

By 1996 some portions of the water delivery system were 100 years old and the sewage system was almost the same age. The water and sewage rates in place in the Washington Metropolitan Area covered the costs to deliver the water and treat the sewage and replace 0.33% of the system each year, an unrealistic and irresponsible repair and replacement rate.  DC Water averages between 400 and 500 water main breaks per year, and they thought that a plan to replace the system over a 300 year time span was meeting their statutory obligations. 

Water delivery systems have a long life span, they are just pipes, pumps and valves, but the life span is not infinite. We reward short sighted behavior. In order to have cheaper water and sewer, a replacement cost schedule was not built into the customer rates for the past 78 years which coincidentally is the current average age of a water main in Washington DC. There are water pipes north of the White House that are reported to have been laid before the Civil War. This past Spring DC Water announced that they have tripled the replacement rate to 1% (with of course the increase in water rates) so that in 100 years the system will be replaced. Sewage rates were increased to finance the District’s portion of the $7.8 billion Blue Plains improvement program called the Clean Rivers Project that will meet the reduced total nitrogen released requirements of their operating permits and increase the control of the system during rain storms in addition sludge treatment will be improved and sewer piping improved in many areas. In truth, according to an interview with the General Manager, George Hawkins on National Public Radio, DC Water has gotten so far behind that they cannot to catch up- it will take decades. It is likely, given the age of the water system in Washington DC the increase in replacement rate was probably necessary to address what was failing each year. One hundred years is longer than the predicated life of a water distribution system, piping systems are rated at 80 years and the average water main in Washington DC is 78 years old. The water pipes in DC are old. They leak. DC Water is trying to use a predictive modeling to determine which pipes need to replace first to keep the good quality* water they are buying from the Washington Aqueduct flowing to the homes and businesses in the District.

Washington DC (and most of America) has always thought about the cost of water wrong, there should have always been a plan for maintenance, upgrade and replacement of the system and the care and protection the water resources; instead we have all taken water (and sewage) for granted. Every pipe should have been on a schedule to be replaced before it exceeded its life and broke. The water rates need to cover these capital replacement and maintenance costs. If we do not maintain our infrastructure we will not have on demand water. DC Water sees persuading customers to pay for the maintenance and improvement of the water and sewer system as their biggest challenge. The investment into water and sewer infrastructure is simply one of the best investments that any community can make.

* Dr. Marc Edwards a professor of engineering at Virginia Tech discovered while doing research in the mid-1990s to identify the cause of an increasing incidence of pinhole leaks in copper water pipes, that chloramine was causing the accelerated pipe deterioration and extreme lead concentrations in DC drinking water. Chloramine-treated water picks up lead from pipes and solder and does not release it, resulting in elevated levels and deterioration of the pipes. The change to chloramine was made after the EPA issued regulations concerning disinfection by-products formed when chlorine reacts with organic matter in drinking water; the EPA considered these byproducts to be a potential health threat. Chloramines do not produce disinfection byproducts. The lead problem was addressed in 2004 by the Washington Aqueduct adding additional treatment steps to the water to prevent the chloramine from dissolving lead in the water mains, solder joints, and fixtures. In addition, DC WASA spent $97 million to replace a portion of 15,000 pipes and 2,000 full pipe replacements. Then after the dust settled on this re-branded themselves as DC Water.