Opportunity
Early in the 19th century, the federal government constructed a pipeline to carry drinking water from a natural spring to residents of Pennsylvania Avenue between 9th and 14th Streets. About fifty years later, in 1858, the Dalecarlia Reservoir was completed, and in 1859 the Washington Aqueduct began providing citywide water service.
Outbreaks of smallpox, cholera, and typhoid during the Civil War caused the city to expand the aqueduct and provide a filtration system. In 1937, the Blue Plains sewage treatment began treating the city’s wastewater.
Today, DC Water delivers about 100 million gallons per day (GPD) of drinking water to more than 600,000 residents, 700,000 people employed in the District of Columbia, and 17.8 million annual visitors. The water system includes about 1,320 miles of mains, 8 storage reservoirs and tanks, 43,600 valves, and 9,400 public fire hydrants.
As in many older East Coast cities, DC’s aging water and sewer infrastructure demands ongoing monitoring and maintenance as well as major renovation of physical resources and data systems.
Solution
Mott MacDonald has provided DC Water with its services as an engineering program management consultant under a series of multiyear contracts.
In support of DC Water’s ongoing capital improvement program, we provide overall program management of the water distribution system, including project planning, engineering design, and strategic planning services, as well as review of the master plan and operations.
We prepared the water systems facilities plan update, a master planning document used to select and prioritize projects under the capital improvement program. DC Water’s CIP includes 332 individual design and construction activities in the water service area with a total lifetime budget of more than $2.5 billion through 2030.
We delivered the updated and expanded water systems facilities plan. Using Primavera’s P6 software, Mott MacDonald provides project control tracking and management for DC Water.
In January 2014, DC Water announced it had selected us for a new five-year contract to support DC Water's ongoing capital improvement program, and to perform work pertaining to the design, construction services, and operations of the water transmission and distribution system.
Hydraulic modeling
- We imported an ESRI geodatabase into Bentley’s WaterGEMS software to create a hydraulic model that included all of the water system’s pipes in the eight pressure zones.
- Following an incident when the supply of high-pressure water was reported as inadequate to combat a major fire, DC Water called on our team to prepare a report called “Evaluation of Small Diameter Water Mains — Fire Flow Analysis.” Using the hydraulic model, the report was completed within one month.
Large main renewal and replacements
We are undertaking a systematic, prioritized approach to assessing all large-diameter water mains, leading to repair, rehabilitation, and/or replacement. This includes the following:
- Internal joint sealing installation
- Retrofitting of cathodic protection systems on steel mains
- Slip-lining rehabilitation with HDPE (high-density polyethylene) or fusible PVC pipe
- Replacement of segments with ductile iron pipe
- Identification, repair, and replacement of broken and malfunctioning valves
Small main renewal and replacements
Approximately 700 miles of DC’s distribution mains consist of unlined cast-iron pipe that is prone to be “tuberculated” with small mounds of corrosion products. This reduces hydraulic capacity and promotes the growth of microbes.
We have provided planning, design, design management, and other services in support of DC Water’s program to renew small water mains.
Pumping stations
We support improvements to modernize all three pumping stations, part of DC Water’s capital improvement program:
- 80 MGD Anacostia Pumping Station
- Rehabilitation of the Fort Reno Pumping Station
- 16th and Alaska pumping station upgrades
Storage facilities
We are managing a program to upgrade DC Water’s five underground storage reservoirs and three elevated water tanks. Based on inspections completed by Mott MacDonald and others, upgrades include the following:
- Ventilation improvements
- Installation of membrane covers
- Sample pump improvements
- Electrical improvements
- Improvements to SCADA (supervisory control and data acquisition) and instrumentation
- Rerouting of drain pipes
- Upgrades to dechlorination equipment
Fire hydrant upgrades
We assisted DC Water with its program to upgrade fire hydrants, meeting DC Water’s accelerated schedule and preparing documents for multiple contracts. More than 4,900 fire hydrants were replaced or upgraded throughout the district.
Lead service replacement program
The Washington Aqueduct converted to chloramination for water disinfection. Monochloramine is more stable than free chlorine, dissipating less rapidly and avoiding objectionable chlorine odors. However, chloramination can increase corrosion and therefore levels of lead in drinking water.
We provided assistance to DC Water in its effort to replace lead service lines, significantly exceeding the EPA’s requirement to replace 7% of lead service lines each year.
Design documents
In an accelerated manner, we provided design documents for these projects:
- Replacement of 3,500 feet of small water mains in the Capitol Hill area
- Replacement of 20,000 feet of water mains 12 inches or less in diameter
- Replacement of an additional 7,000 feet of small-diameter water main
- 5,100 feet of 16-inch tie-in to the McMillan Water Filtration Plant
- Fort Stanton Reservoir Site Work & Joint Seal Project
Outcome
For over a decade, we have successfully managed the capital improvement program for the water service area and achieved project control targets. In one year, total overall spending in the water service area was 99.8% of the baseline projection.
Notable benefits
- Our hydraulic modeling enabled DC Water to improve fire safety.
- We helped DC Water exceed the EPA’s requirement to mitigate the potential effects of lead in the water system.
- Our assessment and rehabilitation programs helped identify and repair leaks and broken valves in large mains, and assess the condition of tuberculated small mains.
- Our design for the Fort Stanton Reservoir helped safeguard a supply of drinking water, preserve the character of a historic park, and prevented erosion in an aesthetically attractive and environmental sustainable way.
- Our conversion of DC Water’s mapping inventory to an Esri geodatabase format will streamline monitoring efforts into the future.