MEMORANDUM

TO:	Brian D’Amico and Eric Strassler, EPA/EAD

FROM:	Steve Strackbein and Mary Willett, ERG

DATE:	June 29, 2009

SUBJECT:	Washington Dulles Runway 1L-19R Construction Project Details
and Update

Project Details

The Metropolitan Washington Airports Authority (MWAA) has recently
constructed a fourth runway (Runway 1L-19R), associated taxiways, and an
approximately 30-acre deicing pad at Washington Dulles International
Airport (IAD).  The stormwater management system for the runway was
designed to detain stormwater for treatment through constructed wetland
Biological Treatment Units (BTUs).

Table 1 presents design specifications, costs, and material/construction
information identified for the runway project.

Table 1. Dulles Airport New Runway Design Specifications, Costs, and
Material/Construction Information.

Item	Description	Comments

Runway Length	9,400 feet

	Runway Width	150 feet

	Connector Taxiways	75 feet wide by

 3,100 feet long	Runway includes three (3) connector taxiways

Deicing Pad	700 feet x 1,870 feet	Capital costs not provided by MWAA

Project Cost	$356 million	Included $200 million in AIP funding

Clearing and Grubbing	675 acres

	Topsoil Stripping	525,000 cubic yards

	Excavation	2,300,000 cubic yards

	Cement Treated Base	883,655 square yards

	Concrete	610,000 square yards

	Asphalt Pavement	340,686 square yards	Equivalent to 24.2 miles of road

Underground Copper Cable	742,610 feet	Equivalent to 140 miles of cable

Drainage Pipe	22,051 feet	Equivalent to 4.17 miles of pipe

Reinforced Concrete Pipe	15,300 feet

	Box Culverts	13	Combined 4,700 linear feet

Fencing	22,000 linear feet

	Labor – Earthwork	500,000 man hours

	Labor – Paving	1,000,000 man hours

	

The project also included a $1.5 million investment for five new
constructed wetland BTU’s placed adjacent to the runway to provide a
cleansing effect to stormwater runoff in the area.  This treatment
technology utilizes a complex system of collection and distribution
pipes. This design allows even distribution of runoff to maximize
effective treatment across each unit before being discharged. 

Each BTU incorporates multiple layers of sand, stone and a special soil
mixture, topped with specific surface vegetation including cattails and
other plant species native to the mid-Atlantic region.  The vegetation
was selected for its tolerance to flooding, extensive root depth,
oxygen-carrying capacity of the root system, and poor wildlife habitat. 
Contaminated stormwater is piped to the BTU where contaminants are
absorbed by the plants’ root system, broken down by soil
microorganisms, or physically filtered by the media comprising each
layer.  The BTUs can be bypassed during clean stormwater flows.

Expected Performance for the BTUs

For IAD, fugitive glycol losses will now be more effectively managed by
diversion to the constructed wetlands for BTU treatment and discharge.

The two primary functions of the BTUs are to treat storm water runoff
that contains fugitive deicing fluids that occur outside the contained
centralized deicing areas and to remove total phosphorous from storm
water runoff.  Additional benefits to the environment will be a
reduction in the amount of BOD discharged to local streams.  The BTUs
are expected to produce effluent BOD concentrations of 100 mg/L and a
50% reduction in phosphorus discharges.  The BTUs work by degrading the
dissolved organic matter through microbial growth and respiration.  BTUs
have the capability of metabolizing toxic organic compounds and
degrading other stormwater contaminants including oil and grease,
suspended solids, and nutrients.  Table 2 presents the expected removal
efficiencies and effluent concentrations for the constructed wetland
BTUs at IAD.

Table 2. Expected BTU Removal Efficiency and Effluent Concentrations

Parameter	Removal Efficiency	Effluent Concentration

BOD	50 - 90%	2 – 100 mg/L

TSS	50 - 90%	2 – 10 mg/L

TN	40 - 90%	1 – 3 mg/L

TP	10 - 90%	<1 mg/L

Fecal Coliforms	80 - 99%	<100 – 1,000 col/100mL

Metals	50 - 90%	Below Detection

*Removal efficiencies and effluent concentrations are very dependent
upon influent concentration and hydraulic loading rate.

BOD – Biochemical Oxygen Demand

TSS – Total Suspended Solids

TN – Total Nitrogen

TP – Total Phosphorus

Current Status

Based on a June 11, 2009 call with Mr. Thomas Beatty of MWAA, the
constructed wetland BTUs are in place and going through start up.  Mr.
Beatty indicated that no performance data is yet available for the
units.

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