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Water quality: Model released for comments

by Wyoming Livestock Roundup

Casper – The Wyoming Department of Environmental Quality (DEQ) Water Quality Division designated all “waters not specifically listed in Table A of the Wyoming Surface Water Classification List” for secondary contact recreation in the 2007 revision of Chapter One. 

However, the Environmental Protection Agency (EPA) disapproved of this portion because the designation was made without conducting a use attainability analysis (UAA).

“Since the EPA rejected Wyoming’s draft of Chapter One of the Categorical Use Attainability Analysis for Recreation, all water bodies in Wyoming are protected as primary contact recreation waters by default,” said Bobbie Frank, executive director of the Wyoming Association of Conservation Districts (WACD).

Lindsay Patterson of DEQ explained the current UAA model and EPA’s concerns with it at the WACD Area IV meeting on Sept. 18.

In their current draft of Chapter One, the DEQ defines primary waters as those where recreational activities may result in immersion in and or ingestion of water. Due to insufficient data on water availability to support primary contact recreation in lakes, reservoirs and ponds, this UAA model does not address still bodies of water.

Secondary waters are those where contact with water is expected to be incidental or accidental and would not result in either full immersion or ingestion of water.

However, the UAA model created by the Department of Environmental Quality works to ensure the bodies of water in Wyoming are correctly classified.


The DEQ is currently working to define waters as primary due to flow, primary due to access or primary due to extension. 

According to Patterson, to qualify as primary under flow, the water source must have a mean average flow greater than six cubic feet per second. Based on mileage, this applies to 82 percent of streams in the hydrology data set in the state examined by the UAA. 

Primary classification due to access impacts water bodies near communities and recreation areas.

In populated areas, defined as census blocks of at least 55 people per square mile, a one-mile buffer is put into place. The buffer causes all water within that radius to be considered primary water because residents have easy access to it. 

“The one-mile buffer was determined because that is the distance kids are expected to walk to school, according to Department of Education policy, and we believed that was a reasonable distance, but not excessive,” Patterson said. 

All waters within national and state parks, historic sites and wildlife habitat management areas are considered primary waters. Campgrounds and Wyoming Department of Transportation (WYDOT) rest areas have a buffer zone of one-half mile of primary classification due to access.

As defined by the DEQ, streams classified as primary by extension are stream segments designated for primary contact that were extended to the nearest terminus, tributary or nearest primary segment to minimize the occurrence of short, isolated reaches. 

Frank said that this ensures that water can be managed from a practical standpoint. Primary by extension classification guarantees that all parts of the water body meet standards if the classification changes more than once.

Bacterial load

A water body is considered a primary water if there is a mean of 126 or more colonies of E. coli per 100 milliliters of water for summer recreation, which runs from May 1 through Sept. 30. The mean is determined by multiple samples taken throughout the recreation period.

E. coli levels are an indicator,” Frank explained. “The levels do not mean that the water is going to make recreationists sick if it is ingested, but it means that there is a chance.”

During the winter recreation season from Oct. 1 to April 30, E. coli populations shall not exceed a geometric mean of 630 colonies per 100 milliliters. This change in acceptable bacterial load is due to the expected reduction in recreation during the cooler months.

Single samples can be taken from the water bodies to determine bacterial loads. 

If the water body is determined to have high use, the colonies cannot exceed 230 colonies of E. coli per 100 milliliters, medium use has a limit of 298 colonies per 100 milliliters, and lightly used water bodies have a maximum for 410 colonies per 100 milliliters.

Infrequently used water bodies have the highest maximum allowance of 576 colonies per 100 milliliters. 

If water bodies exceed these maximums, they will be posted to the state’s 303(d) list, which indicates the colony load needs to be reduced, but the stream will not be listed as an impaired body.

Next steps

“Everyone who worked on this model has done a wonderful job,” Frank said. “It will take more fine tuning, but I am excited to get this model approved and on the books.”

Using the UAA model, interested parties can search water bodies, examine data collected by researchers and add or remove various layers to better understand the classification.

“We are trying to make sure that Wyoming water bodies are accurately being protected for uses, rather than presumed, and this model is very accurate,” Frank continued. “This will save time and money as the process continues.”

Frank said she does not see a mass delisting of waters happening with the implementation of the model or a significant impact on the agricultural industry other than water bodies that are improperly classified being listed correctly. 

The first draft is currently out for public comment, which closes on Sept. 30. After the comment period closes, DEQ will review the feedback, make changes if needed and send the draft back out for a formal 45-day comment period that is to be announced. 

Kelsey Tramp is the assistant editor of the Wyoming Livestock Roundup and can be reached at 

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