PORT OF SEATTLE

MEMORANDUM

DATE: December 2, 2011

SUBJECT: Department of Ecology NPDES Permit Agreed Order for the Seattle-Tacoma

International Airport

Amount of This Request: $0 Source of Funds: 2011 and 2012 Operating Budgets;

Future Individual Project Authorizations

ACTION REQUESTED:

Authorization for the Chief Executive Officer to execute an agreed order with the Washington

State Department of Ecology (Ecology), related to the Seattle-Tacoma International Airport’s

National Pollutant Discharge Elimination Systems (NPDES) permit, to conduct an

environmental investigation, and to implement corrective actions as needed, to address

The acceptable pH range is from 6.5 to 8.5. The elevated pH readings have ranged from 8.7 to

9.6. Although the pH of discharges to streams has at times been elevated, no measurable effects

have been found in the water quality of the streams.

The detention ponds associated with the elevated pH detain stormwater for extended periods of

time and then slowly release the water to local streams. The ponds have been very effective in

reducing erosive flows in our streams. However, the long-term water detention encourages the

growth of naturally occurring algae, which is likely modifying the pH of water.

Airport staff has worked with Ecology to define the scope of this agreed order. It provides that

December 2, 2011

Page 2 of 4

Execution of this agreed order will require an estimated expenditure of up to $90,000 through the

end of 2012, for which funds have been included within the 2012 operating budget. Depending

upon any necessary longer-term improvements, the ultimate cost of complying with the agreed

order could be up to $3,000,000. However, if necessary, those additional costs would not be

expected to occur until 2013.

BACKGROUND:

The Airport’s NPDES Permit authorizes stormwater discharges associated with industrial

surfaces that could otherwise increase erosion and flooding in local streams. Over the past 10

years, the Port has met this requirement through the construction of a series of stormwater

detention ponds and vaults.

Beginning in July 2009, discharge monitoring identified a recurring pattern of elevated pH from

three detention ponds located on the Airport’s west side. These ponds receive runoff from

runways and taxiways, and discharge directly to Miller and Walker Creeks. Staff immediately

reported these permit exceedances to Ecology and initiated preliminary investigations. These

investigations indicated that the elevated pH is not directly attributable to Airport operations and

that the pH of Miller and Walker Creeks remains in the acceptable range when the ponds are

discharging. Observations over this period noted increased algal growth in the west side ponds

results of these interim actions, both Port staff and Ecology agreed that additional investigations

are needed before the most appropriate solution can be identified and implemented.

As a result of this decision, Port staff and Ecology worked collaboratively to develop a plan to

further investigate and implement actions as needed to correct the pH exceedances. This plan is

represented in the Agreed Order No. 8755, issued to the Port on November 2, 2011. The agreed

order requires that the Port prepare and implement a study plan, submit interim and final reports,

implement operational corrective actions and implement structural and/or treatment controls as

needed. A compliance schedule for completing these efforts is contained in the order.

PROJECT JUSTIFICATION:

This authorization request will allow the Port to continue to collaboratively work with Ecology

December 2, 2011

Page 3 of 4

measures. The agreed order provides an achievable compliance schedule for completing the

investigation as well as time needed to define future actions as necessary, gain appropriate

approvals and complete a project in the event that structural and/or treatment controls are needed

to address the pH exceedances.

stormwater detention ponds. Port staff has completed this study plan and is prepared to

submit it to Ecology.

 Submit an interim progress report to Ecology no later than June 30, 2012.

 Implement operational corrective actions no later than July 31, 2012.

 Submit a final report to Ecology no later than October 31, 2012.

 Implement and construct necessary structural and/or treatment controls no later than

October 15, 2013.

FINANCIAL IMPLICATIONS:

Cost Estimate:

The study plan investigation and reporting costs are estimated to be $80,000. A minor

Although the need for these controls has not yet been determined, their cost has been estimated

to be less than $3,000,000.

Budget/Authorization Summary:

The study plan and potential operational corrective action have been anticipated and included in

the Aviation Environmental and Maintenance 2011 and 2012 operating budgets.

Additional funding may be required for the design and construction of potential structural and/or

treatment controls. Future Commission authorization will be requested in the event such controls

are required, or if the total anticipated project costs exceed $300,000.

ENVIRONMENT AND SUSTAINABILITY:

Implementation of the agreed order will allow the Port to determine if the elevated pH discharges

December 2, 2011

Page 4 of 4

compliance with the Airport’s NPDES Permit and provide an opportunity to improve water

quality in Miller and Walker Creeks.

BUSINESS PLAN OBJECTIVES:

The Aviation Division’s business plan seeks to lead the airport industry in environmental

innovation and minimize the Airport’s environmental impacts. Implementation of the agreed

order will allow the Port to characterize any potential impacts the elevated pH discharges may

have on the environment and identify appropriate corrective actions if needed.

TRIPLE BOTTOM LINE SUMMARY:

Implementation of the agreed order allows the Port to ensure its operations are protective of the

environment and that its actions are transparent and open to the regulatory agency review and

stormwater discharges. This alternative could result in the issuance of a unilateral Ecology

enforcement order to perform the work, which would eliminate Port control over the

investigation and assessment of necessary corrective actions. The imposition of penalties would

also be likely. This is not the recommended alternative.

Alternative 2

Execute the NPDES Permit agreed order and conduct the investigation and assessment of

necessary corrective actions. This alternative will provide a mechanism to adequately evaluate

the elevated pH and implement corrective actions as needed within an achievable compliance

schedule. This is the recommended alternative.