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The BMW Association is collaboratively working to develop pH TMDLs for Barr Lake and Milton Reservoir. Read this page to learn more about what TMDLs are and how the BMW Association is developing them.
What is a TMDL, anyway?
Under section 303(d) of the 1972 Clean Water Act, states, territories, and authorized tribes are required to develop lists of impaired waters that do not meet water quality standards. In Colorado, this list is called the 303(d) List. Law requires that states, territories, and tribes establish priority rankings for waters on the lists and develop total maximum daily loads (TMDLs) for these waters. Barr Lake and Milton Reservoir were included on Colorados 2004 303(d) List with medium priority for elevated pH.
As defined by the U.S. EPA, a TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards, and an allocation of that amount to the pollutant's sources. In mathematical terms:
TMDL = LA + WLA + MOS
where LA is the nonpoint source load allocation, WLA is the point source waste load allocation, and MOS is a margin of safety.
What goes into a TMDL?
The EPA identifies the following elements of a TMDL submittal:
1. Submittal Letter
Each TMDL submitted to EPA should be accompanied by a submittal letter stating that the submittal is a draft or final TMDL submitted under §303(d) of the CWA for EPA review and approval.
2. Problem Statement
Waterbody name and location.
A map including key features (i.e. watershed boundary or upper and lower bounds on the receiving stream segment) and the location of sources.
Waterbody §303(d) list status (including pollutant covered by the TMDL and priority ranking).
Watershed description (e.g., predominant land cover or land use, geology and hydrology).
3. Applicable Water Quality Standards and Water Quality Numeric Targets
Description of applicable water quality standards, including designated use(s) affected by the pollutant of concern, numeric or narrative standard, and the antidegradation policy.
If the TMDL is based on a target other than a numeric water quality standard, describe the process used to derive the target.
4. Pollutant Assessment
Source inventory with location of background, point, and nonpoint contaminant sources
Supporting documentation for the analysis of pollutants loads from each source. Assembling the TMDL
5. Linkage Analysis
Rationale for the analytical method used to establish the cause-and-effect relationship between the numeric target and the identified pollutant sources.
Supporting documentation for the analysis (e.g., basis for assumptions, strengths and weaknesses in the analytical process, results from water quality modeling).
6. TMDL and Allocations
Total Maximum Daily Load (TMDL) - The TMDL is expressed as the sum of the WLAs, the LAs, and the MOS
Seasonal Variation1 - Description of the method chosen to consider seasonal and interannual variation.
Critical Conditions - Critical conditions associated with flow, loading, designated use impacts, and other water quality factors.
7. Follow-Up Monitoring Plan
8. Public Participation
Description of public participation process used.
Summary of significant comments received and the responses to those comments.
9. Implementation Plan
Implementation plans are needed before TMDL approval if they are necessary to provide reasonable assurance that the load allocations contained in the TMDL will be achieved.
What happens after the BMW Association develops the TMDLs?
The BMW Association will develop individual pH TMDLs for both Barr Lake and Milton Reservoir. The group will submit these TMDL documents to the Colorado Department of Public Health and Environment (CDPHE) for review. If approved, the CDPHE will submit the TMDL document packages to the EPA. The EPA then has 30 days in which to approve or disapprove a state's TMDLs.
Is there a schedule for all this? Where is the BMW Association in this schedule today?
The BMW Association is working closely with the CDPHE to develop pH TMDLs efficiently and in a reasonable timeframe. The diagram below outlines the planned schedule for TMDL development and implementation. As of spring 2007, the BMW Association is on-schedule and has hired a consultant to begin watershed and reservoir water quality modeling. Click HERE to download a chart of the anticipated schedule.
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