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Wasteload Allocation Procedures

A Wasteload Allocation (WLA) is the portion of a receiving water’s assimilative capacity that is allocated to one of its existing or future point sources of pollution.

The Iowa Department of Natural Resources is responsible for maintaining and enhancing water quality in the state.  To that end, IDNR develops WLAs for facilities that discharge treated wastewater (for example, domestic sewage treatment plants and industrial plants) into waters of the state in order to assure that the permitted effluent limits meet applicable state Water Quality Standards.  The calculation of a WLA may be based on conservative assumptions to protect the water quality under worst case scenario conditions.  Facilities can submit site-specific information on both the receiving waterbody and the discharge characteristics for consideration.

The current rule reference document that outlines WLA methodology is as follows:
Basin Plan Support Document – Introduction
Basin Plan Support Document – Wasteload Allocations

IDNR is in the process of updating this rule reference document including renaming it Wasteload Allocation Procedures. 

WLAP and Copper BLM Stakeholder Meetings - June 10, 2015:
The DNR will be holding a meeting to further discuss some of the issues with proposed changes to the Iowa Wasteload Allocation Procedure (WLAP) raised during the first round of stakeholder meetings.   The purpose of the updated WLAP document is to provide the technical methodologies to develop wasteload allocations and water quality based limits to be protective of surface WQS as described in IAC 567 Chapter 61 – Water Quality Standards.  The proposed rule will document the current procedures and policies to increase transparency and also update the methodologies to reflect the current scientific research in calculating wasteload allocations that are used in wastewater permitting.

The DNR is also holding a stakeholder meeting to discuss the inclusion of the Biotic Ligand Model (BLM) in the determination of copper criteria, which allows for site-specific variations in the bioavailability and toxicity of copper.  Changes are proposed to allow the flexibility to use the existing copper criteria, or the ability to use the Biotic Ligand Model (BLM) to generate site-specific criteria based on known data from the site area.

These meetings will be held on the same day as many of the same stakeholder are invited to attend.  The Copper BLM will be held from 9:30 a.m. to 12:00 p.m. and the WLAP meeting will be held from 1:00 p.m. to 4:00 p.m. on June 10 in the Wallace Building. If you wish to attend, please contact Matthew Dvorak (e-mail:; ph:515-725-8397).

WLAP Rule Making Documents:
WLAP Stakeholder Meeting Presentation February 5, 2015
Draft Wasteload Allocation Procedures November 24, 2014

August 3, 2012 Technical Advisory Committee Meeting Agenda
Location:  502 E 9th St., Wallace Building, Des Moines, IA
Conference Rooms 3 East and West

Requesting a Wasteload Allocation:
To request a WLA, please fill in the WLA request form and send the WLA requests electronically to

WLA Request Form and Instructions Updated 11/2014
WLA Request Form and Instructions Updated 11/2014

Site Specific Data Collection

IAC 61.2(5)”d” – Implementation Strategy states that “A wastewater treatment facility may submit to the department technically valid instream data which provides additional information to be used in the calculations of their wasteload allocations and effluent limitations.  Facilities may choose to collect site specific information in lieu of the default pH and temperature data for calculating ammonia limits.   IAC 61.2(5)”d” and 61.2(4)”g””(4)”  also allow facilities to collect site-specific mixing zone study information.

Wastewater treatment facilities are encouraged to plan ahead when considering any data gathering effort.  Many of these efforts require seasonal data particularly collected during low stream flow conditions.  For more information please refer to the Site Specific Data Collection document.

Site Specific Data Collection 03/2011

DNR Contact:
Connie Dou