Incorporating Climate Change Adaptation in EPA Region 10 Programs:

An example based on a newly initiated pilot in the Office of Water and Watershed’s Total Maximum Daily Load program

David CroxtonU.S. Environmental Protection Agency

Watershed Unit Manager– EPA Region 10

What is a TMDL? A Total Maximum Daily Load (TMDL) is a calculation of the maximum amount of a pollutant that a water body (or segment) can receive and still meet the state/tribe’s water quality standards.

• TMDLs are required by the Clean Water Act when a water body’s designated uses are determined to be impaired or threatened.

• The pollutants causing or expected to cause the impairment are what are limited under a TMDL.

What is a TMDL? (cont’d)

A TMDL is the sum of the following:

• Waste load allocation (WLA). Total amount of the pollutant from existing point sources (e.g., sewage treatment plant, industrial facility, stormwater).

• Load allocation (LA). Total amount of pollutant from existing nonpoint sources and natural background (e.g., farm runoff, atmospheric mercury).

• Margin of safety (MOS). Expressed as an explicit factor (e.g., percent of total, such as 10%) or an implicit factor (e.g., conservative assumption in modeling).

Pilot Approach Underway• Will select a TMDL (or two) based on suggested criteria:

– Timing of model development (i.e., so that new thinking can be incorporated in next six months)

– Tribal involvement (i.e., clear role for EPA)– Watershed is in a location where analyses of potential changes

have been conducted (e.g., vulnerability assessments)– Connection with other priorities (e.g., salmon recovery, Puget

Sound)

• Identify commonly occurring variables that relate to TMDL assumptions in models, analyses (e.g., T, flow)

• Coordinate with EPA Region 1 on Lake Champlain phosphorus TMDL being revised to consider climate change.

From Washington Technical Advisory Group Built Intrastructure Report (Dec. 2010) – Appendix C

What will be Success for this Pilot?Overall our goal is to determine the science needs to

support potential future changes into TMDL analyses.• Learn/adapt

– Begin with one program to learn which impacts are most relevant and identify knowledge gaps; adapt this process for other programs

• Identify needed tools, data sources, models, etc., and where they are available – Federal partnerships in the region, e.g., C3, will be useful

– Climate Science Center and Climate Decision Support Center, Landscape Conservation Cooperatives

• Identify policy issues and decisions

Potential Policy Issues• Is climate change part of “background” conditions

that aren’t assigned to any source category to address (e.g., lower flows)?

• How much can the “margin of safety” be used to account for climate change uncertainty versus uncertainty of the models themselves?

• Can /should we leverage more stringent limits or move to watershed-scale permits for point sources, to get more investments in green infrastructure in the watershed?