TIN/TDS Task Force

On December 19, 1995, a Task Force, composed of approximately 20 water, wastewater, and groundwater agencies in the Santa Ana Watershed, was formed to evaluate the impact of total inorganic nitrogen (TIN) and total dissolved solids (TDS) on water resources in the Santa Ana River Watershed. At that time, the Task Force established agreements between SAWPA and two consultants, Risk Sciences and Wildermuth Environmental Inc., to perform the consulting services for the Study . A separate agreement was formed between SAWPA and the State Water Resources Control Board (SWRCB) to obtain the Santa Ana Region RWQCB staff support in an advisory role.


On December 19, 1995, a Task Force, composed of approximately 20 water, wastewater, and groundwater agencies in the Santa Ana Watershed, was formed to evaluate the impact of total inorganic nitrogen (TIN) and total dissolved solids (TDS) on water resources in the Santa Ana River Watershed. At that time, the Task Force established agreements between SAWPA and two consultants, Risk Sciences and Wildermuth Environmental Inc., to perform the consulting services for the Study . A separate agreement was formed between SAWPA and the State Water Resources Control Board (SWRCB) to obtain the Santa Ana Region RWQCB staff support in an advisory role.

The task force work was divided into a series of phases. Phase 1A focused on the defining the watershed hydrology more precisely and the reaching consensus on TDS and nitrate thresholds for Beneficial Use Impairment. As part of the threshold development, the Task Force reached agreements on the interpretation of beneficial use impairment terms. The results of Phase 1A were presented in the Draft Reclamation Guidance Document (prepared by Risk Sciences, Inc.- Tim Moore). In mid-June 1997, Phase 1B of the Nitrogen TDS Study was commenced. Phase 1B covers tasks to describe analytical methodologies to investigate watershed hydrology and tasks to define the legal, scientific and economic implications of methodologies. In March 1998, Phase 2A, the major technical effort of this study, commenced with the objective of developing a nitrogen loss rater for surface water recharge, developing a new monitoring plan, developing an updated boundary maps for management zone, to estimate TDS and nitrate in groundwater and to computer new groundwater objectives for TDS and nitrate. The results of this major technical effort were incorporated into the Tim Moore’s Reclamation Guidance Document.

 In 1999, the Task Force moved into Phase 2B with the development of a wasteload allocation for TIN TDS along the Santa Ana River upstream of the Prado Dam. In addition, Wildermuth Environmental Inc. developed an outline for a Santa Ana Watershed Data Collection and Management Program which will establish the framework for collecting water quality data for monitoring the health of the watershed and to conduct future studies.

Work on the TIN TDS Task Force study is nearing completion. Wildermuth Environmental Inc. has prepared maps and tables for submittal to the peer reviewers for the proposed Basin Plan Amendment that will incorporate the results of the Nitrogen TDS study. Work also continues on additional modeling runs of the Santa Ana River Wasteload Allocation to recalibrate the river streambed recharge estimates from the new RIX and Riverside Basin modeling, the development of a mass balance table and charts, and the segregation of TDS and nitrate quantities by subbasin along the Santa Ana River to assist in POTW permitting.

Mr. Moore of Risk Sciences has completed the Reclamation Guidance Document for submittal to the RWQCB and is working with the RWQCB to prepare final language for the basin plan amendment (as of January, 2003). Final work is being prepared by outside parties for Maximum Benefit Analyses that may modify some of the final adopted TDS and nitrate objectives based on maximum benefit use as opposed to historical ambient. Upon acceptance of the TIN TDS results as a basin plan amendment, the proposed new basin plan will be submitted to the State Office of Administrative Law and EPA for review.

For further information about this project, please contact Mark Norton
Email: First name initial last name @sawpa.org
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