Update: Mixing Zone proposal became effective for State purposes on March 23, 2006. EPA has initiated formal ESA consultations with the Services (FWS &NMFS). EPA has not formally approved of the regulation change as of 2-13-07.

In 2004, the Alaska Department of Environmental Conservation proposed several changes to the current mixing zone regulations. The Department received many comments, most of them expressing concern over mixing zones in fish spawning areas. As a result, DEC along with its partner State resource agencies Fish and Game and Natural Resources, reviewed the comments and together formulated a new and significantly different 2005 proposal for mixing zone regulations. The comments recieved on the 2004 proposal will not be considered under this 2005 public comment period. You are encouraged to review and comment on the 2005 proposal. Below is a list of commonly asked questions and information on the current public comment period.

What is a Mixing Zone?
Even with the best treatment technology, wastewater discharges from sewage treatment and industrial
facilities (i.e. mining, seafood processing, oil exploration or production, etc.) sometimes have low levels
of pollutants. Most wastewater discharges permitted in Alaska are to surface waters such as the ocean,
lakes, streams, or rivers. The area where treated wastewater is authorized by DEC to mix with a water
body is called a mixing zone. For more information on mixing zones, Click here.

How are Mixing Zones used in Alaska today?
Nearly every wastewater discharge to Alaska ’s surface waters has a permit that includes provisions
for a mixing zone. The most common are for municipal wastewater treatment systems. Click here to see
some examples of how mixing zones are currently used in Alaska.

What are the proposed changes?
DEC is proposing to repeal and adopt revisions that would: 1) expand the prohibition on mixing zones to include lakes; 2) create exemptions to the prohibition on mixing zones in fish spawning habitat; 3) reorganize the mixing zone regulations to improve clarity and reduce redundancy; 4) simplify some technical provisions including ones dealing with risk assessment, flow calculations, and mixing zone models; and 5) update a reference to federal technology-based effluent limitations. The proposal includes a new definition for shellfish and provides for consideration of measures that would mitigate the potential adverse effects of mixing zones on aquatic resources. Learn more about the changes in the factsheets below.

Mixing zone regulation comparisons:

How do other Pacific Northwest States deal with Mixing Zones in spawning areas?
Find out more on this factsheet.

Who bears the 'burden of proof' that a mixing zone will meet all regulatory requirements?
More information found here.

What is the State's fish protection policy? Click here.

Will DEC provide any guidance to the permit staff on implementation of the regulations? Yes, DEC has prepared draft implementation guidance reflecting the 2005 Proposed Regulations. While this Draft 2005 Guidance is not part of the public comment period on the 2005 Proposed Regulations, it has been provided for informational purposes only. DEC will revise the draft guidance, if necessary, to reflect the final regulations when they are adopted. Click here to see the draft guidance.