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Department of Environmental Quality

Office of the Secretary

Legal Affairs Division

Dissolved Oxygen Criteria for Barataria and Terrebonne Basins (LAC 33:IX.1105, 1113, and 1123)(WQ075)

Under the authority of the Environmental Quality Act, R.S. 30:2001 et seq., and in accordance with the provisions of the Administrative Procedure Act, R.S. 49:950 et seq., the secretary gives notice that rulemaking procedures have been initiated to amend the Water Quality regulations, LAC 33:IX.1105, 1113, and 1123 (Log #WQ075).

The dissolved oxygen criteria is being revised for 60 water quality management subsegments in the Barataria and Terrebonne Basins, and Table 3 of LAC 33:IX.1123 is revised accordingly. This rule also includes minor clarifications to the narrative dissolved oxygen standard in LAC 33:IX.1113. The proposed criteria are based on the results presented in the department's Use Attainability Analysis of Barataria and Terrebonne Basins for Revision of Dissolved Oxygen Water Quality Criteria, which was technically approved by EPA Region 6 on May 5, 2008. Nationally-recommended dissolved oxygen (DO) criteria of 5 mg/L for freshwater and marine and 4 mg/L for estuarine waters are the current criteria in Louisiana, except where site-specific revisions have been made. For many Louisiana water bodies, natural, physical conditions (such as lack of slope and re-aeration potential) prevent attainment of the current nationally-based DO criteria. The Barataria and Terrebonne Basins in southeast Louisiana constitute one such area where levels of dissolved oxygen in ambient surface waters are naturally low.

Because incorrect criteria can result in erroneous use impairment decisions that impact a multitude of the state’s water quality programs (e.g., total maximum daily load determinations, wastewater permitting, implementation of best management practices to reduce non-point source pollutant loads), it is critical to establish appropriate and protective DO criteria that are supportive of fish and wildlife propagation in these regions. Therefore, a Use Attainability Analysis (UAA) was conducted to support the development of ecoregion-based dissolved oxygen criteria for the Barataria and Terrebonne Basins.

According to the regulations, a UAA is defined as a structured scientific assessment of the factors affecting the attainment of a use which may include physical, chemical, biological, and economic factors (see 40 CFR 131.3(g) and LAC 33:IX.1105). The UAA process is described in 40 CFR 131.10 and LAC 33:IX.1109.B.3. It entails the methodical collection of data that is then scientifically analyzed and summarized and used to revise or establish uses and criteria. The results presented in the Barataria and Terrebonne UAA indicate the currently adopted dissolved oxygen criteria are inappropriate for some water bodies in the Barataria and Terrebonne Basins. The biological data collected supports that in these ecoregions diverse fish species are abundant in reference areas with naturally occurring, seasonal periods of low dissolved oxygen, and therefore, the fish and wildlife propagation use is supported. The basis and rationale for this proposed rule are to revise the dissolved oxygen criteria

for the Barataria and Terrebonne Basins, based on the Use Attainability Analysis. This proposed rule meets an exception listed in R.S. 30:2019(D)(2) and R.S. 49:953(G)(3); therefore, no report regarding environmental/health benefits and social/economic costs is required.

Title 33


Part IX.  Water Quality

Subpart 1.  Water Pollution Control

Chapter 11.Surface Water Quality Standards


* * *

Ecoregiona relatively homogeneous area of similar ecological characteristics such as climate, land surface form, soils, potential natural vegetation, land use, hydrology, and other ecologically relevant variables.

* * *

AUTHORITY NOTE:Promulgated in accordance with R.S. 30:2074(B)(1).

HISTORICAL NOTE:Promulgated by the Department of Environmental Quality, Office of Water Resources, LR 10:745 (October 1984), amended LR 15:738 (September 1989), LR 17:264 (March 1991), LR 20:883 (August 1994), amended by the Office of Environmental Assessment, Environmental Planning Division, LR 25:2401 (December 1999), LR 26:2545 (November 2000), LR 29:557 (April 2003), LR 30:1473 (July 2004), amended by the Office of the Secretary, Legal Affairs Division, LR 33:456 (March 2007), LR 33:827 (May 2007), LR 35:


A. – C.2.

3.Dissolved Oxygen. The statewide dissolved oxygen (DO) values represent minimum criteria for the types of water specified. (That is, a level below the criterion, as opposed to above the criterion, may indicate potential impairment.) These DO criteria are designed to protect indigenous wildlife and aquatic life species associated with the aquatic environment and shall apply except in those water bodies that have ecoregional-specific or site-specific criteria, or where exempted or excluded elsewhere in these standards. DO criteria for specific state water bodies are contained in LAC 33:IX.1123. Naturally occurring variations below the criterion specified may occur for short periods. These variations reflect such natural phenomena as the reduction in photosynthetic activity and oxygen production by plants during hours of darkness. However, no waste discharge or human activity shall lower the DO concentration below the specified minimum.
a.Fresh Water. For a diversified population of fresh warmwater biota including sport fish, the DO criterion is 5 mg/L. Fresh warmwater biota is defined in LAC 33:IX.1105.
b.Estuarine Waters. For estuarine waters, the DO criterion is 4 mg/L.
c.Coastal Marine Waters (Including Nearshore Gulf of Mexico). For coastal marine waters, the DO criterion is 5 mg/L.

C.4. – Table 1.A.Footnote f.   …

AUTHORITY NOTE:Promulgated in accordance with R.S. 30:2074(B)(1).

HISTORICAL NOTE:Promulgated by the Department of Environmental Quality, Office of Water Resources, LR 10:745 (October 1984), amended LR 15:738 (September 1989), LR 17:264 (March 1991), LR 17:967 (October 1991), repromulgated LR 17:1083 (November 1991), amended LR 20:883 (August 1994),

Louisiana Register   Vol. 34, No. 10   October 20, 2008

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