MANAGING CONTAMINATION FOR THE METROPOLITAN WASHINGTON AIRPORT AUTHORITY (MWAA) RAIL PROJECT

Transcription

1 MANAGING CONTAMINATION FOR THE METROPOLITAN WASHINGTON AIRPORT AUTHORITY (MWAA) RAIL PROJECT TRB-EEE SESSION 51 GREEN CLEANUP/GREEN RECYCLING IN THE TRANSPORTATION CONTEXT JUNE 9 TH, 2010

2 The Dulles Corridor Metrorail Project 23 miles of Metro from West Falls Church Station to Dulles Airport 11 new stations $2.6 Billion The Silver Line will connect National and Dulles Airports MM&A awarded Service contract to provide Environmental Containment, Management, Mitigation, Disposal and Remediation (CMMR) of Hazardous Substances

3 Discovery of TCE Impacted Groundwater Site Characterization and Phase I & II ESA s, followed by subsequent sampling, identified TCE impacted groundwater in subsurface work areas (tunnel and station) SITE ISSUES Heavily traveled 6-lane road Many surrounding businesses Tight project schedule with expensive delays Other construction in the area impacting the site

4 Groundwater Management System Design Requirements Minimize impact on traffic Minimal impact on surrounding businesses Maintain Schedule Reduce volume of hazardous waste (water classified as F-listed waste) Meet the Clean Water Act requirements Reduce impact to the environment from potential releases Minimize carbon foot print

5 Options? Groundwater Insitu Remediation not an option at this time because of property access issues Groundwater Recovery Sumps in construction area Vertical wells adjacent to construction area Horizontal wells under construction area Groundwater Management Off-site disposal On-site treatment with activated carbon filtration On-site chemical treatment (Fenton s)

6 Evaluation of Groundwater Recovery Options 1. Sumps in construction areas with vacuum truck water removal High carbon footprint High impact on traffic Large volume of Hazardous Waste Generate High potential for release Expensive! $85/hour for vehicle and driver Hose/equipment in construction area

7 Evaluated Groundwater Recovery Options (cont.) 2. Vertical Well Groundwater Recovery Impact on traffic during construction - need under the road piping to minimize impact during recovery Wells may have to be destroyed and re-installed to stay out of the way of construction activity Relatively inexpensive

8 Evaluated Groundwater Recovery Options (cont.) 3.0 Horizontal Well Groundwater Recovery Minimal to no impact on traffic No impact on businesses More screen therefore better recovery rates than vertical wells Not in the way of construction Expensive, and difficulty scheduling

9 On-site Treatment or Off-site Disposal? Groundwater a hazardous waste (F-listed, spent solvent) making off-site disposal expensive ($2/gallon) Carbon Footprint Vacuum Trucks, assuming round trip of 250 miles 80 metric tons CO2- equivalent/month On-site treatment, assuming 7.25 MWh per month usage on pumps 4 metric tons CO2 equivalent/month * The Emissions and Generation Resource Integrated Database (egrid) and MRR used for generating CO2 equivalents and for conversions from diesel fuel and power usage and to convert emissions

10 On-site Treatment Options Activated Carbon Filtration Inexpensive Generates hazardous waste Requires shut down of at least part of system or redundancy Potential for release due to breakthrough Chemical Oxidation Treatment (Fenton s) Expensive Generates no waste No shut-down required No potential for release from breakthrough Total treatment of water and sediment

11 Project Execution Design and built horizontal groundwater recovery and treatment system Obtain VPDES General Permit Construct chemical (Fenton s) addition, retention, treatment and discharge system

12 Project Execution

13 Project Summary Groundwater removed to allow project to proceed, on schedule Continuing to pump and treat > 25,000 gallons per day total of 2.7 million gallons Zero waste generated Energy usage and water usage monitored closely (treated and storm water used for non-potable needs) Surrounding business and traffic continue operation, uninterrupted

14 Thank you! Any Questions?