THE PROBLEM

The Maryland Intercounty Connector (ICC) project has finally become a reality. Approved in May 2006, the project began in the fall of 2007 and is expected to be completed in 2012.
Since the project’s early beginnings nearly fifty years ago, environmental groups and local home owners have been concerned about the environmental impact of the project. Approval was given only after Maryland agreed upon mitigations to meet the environmental, economic, and community requirements.
The six-lane, 18-mile toll highway will cut through parkland and residential communities between the Interstate 270 and Interstate 95 corridors across Montgomery and Prince George's counties. The estimated cost is $2.4 billion and could rise to $3 billion with financing costs, making it the most expensive new highway project in the region, and one of the most expensive in the nation.
The ICC will link existing and proposed development areas between the I-270/I-370 and I-95/US1 corridors with a multi-modal east-west highway, limiting access and accommodating an efficient route for the movement of passengers and goods.
Within each of the major watersheds in the approximated 4,300 acres, state-of-the-art stormwater controls and stormwater management sites are in place to ensure Best Management Practices (BMPs) and prevent stormwater pollution. There are twenty-one special project sites, totaling 620 acres, designed to improve water quality, protect brown trout, and safeguard other environmentally sensitive elements in the Upper Paint Branch watershed.

Chesapeake Bay is a 303(d) listed impaired watershed for nutrients and sediment. For this project,  the Maryland Department of the Environment (MDE) has set a nephelometric turbidity unit (NTU) discharge limit of a 50--NTU monthly average, and a 150 NTU daily maximum.

OUR SOLUTION

After presenting to the Inter-Agency Working Group (IAWG) and a team from Rain for Rent along with the providers of StormKlear® water treatment laid out a solution to meet the specific needs of the stormwater treatment for this project.
Rain for Rent designed a 50 to 200 gpm system with a tube settler using a StormKlear chitosan injection as the first means of settling. Chitosan, an approved polymer made from crab shells, naturally neutralizes the negative surface charge of the dirt particles, causing them to settle. After the chitosan injection, the sediment flocculated, and the water was filtered through a sand media and bag system. Because the ICC project is directed through a wetlands area, pollution prevention was a huge concern and the stormwater pollution prevention plan was scrutinized. Turbidity requirements averaging a 50 NTU discharge rating were imposed, while allowing for out of compliance events to occasionally spike to 150 NTU. Each step of the filtration process was critical and enabled the project to stay in compliance with the turbidity requirements of the MDE. Figure 1 illustrates this operation.
ICC stormwater runoff was stored in ponds where turbid water is kept prior to treatment. Power Prime™ pumps moved the water from the ponds to the tube settler where the chitosan was injected. This process ensured that the water quality parameters were met and allowed for higher flow rates. Higher flow rates ensured that no off-specification water left the site—even during rain.
The tube settler works in conjunction with pumps and other filtration equipment as a result of:

  • The fluid stream is pumped from the pond using a 4-inch DV100 Power Prime™ pump. During the pumping operation, StormKlear chitosan is introduced into the fluid stream which starts the treatment process in the water. The treated water enters the tube settler where it flows through a tortuous path designed to slow the fluid down and allow more time for flocculation to occur. The process sends particulates down into a sump area where they can be easily removed.
  • After the settling process, the cleaned water is pumped into a 36-3 Sand Media Filter. This filter removes remaining suspended solids from the fluid stream to an approximate level of 20 to 25 microns.
  • The final step is to polish the water so that it meets the accepted turbidity level for the specific project. This is done using bag, and if needed, particulate filters to remove the remaining suspended solids down to as low as a ½ micron. Finer sub micron filtration is also available if needed.

The filtration process, the clean water is discharged into a channel which drains into the creek. This water is tested every 30 minutes to ensure the turbidity levels stay well below the required levels.

GREAT RESULT: Future of the Project

Because of the growth of the project, Rain for Rent has been asked by the contractor to build additional mobile treatment trailers. These mobile trailers allow the customer to meet its turbidity requirements while at the same time working safely within the designated highway project areas. System mobility is crucial on account of the multiple locations requiring treatment.