Page 19 - Yucaipa Valley Water District - Board Workshop

Workshop Memorandum 18-231

Date: October 9, 2018

From: Joseph Zoba, General Manager

Subject: Discussion Regarding the Draft Waste Load Allocation Model Update for the Santa
Ana River

The Regional Water Quality Control Board (“Regional Board”) establishes water quality objectives to
protect the designated beneficial uses of surface and ground waters in the Santa Ana River
watershed. These objectives are set forth in the Regional Water Quality Control Plan ("Basin Plan").
The Regional Board imposes effluent limitations or waste discharge requirements to ensure
compliance with the water quality objectives.

When issuing discharge permits, the Regional Board must take into consideration a wide range of
factors in order to determine the most appropriate effluent limitation. This includes, but is not limited
to:
• The water quality objectives;
• The current average water quality in the receiving water;
• The availability (or lack thereof) of assimilative capacity in the receiving water;
• The net effect of the regulated discharge on the receiving water (alone and in combination
with all other discharges to the same receiving water); and
• The volume and quality of other natural and man-made flows reaching the receiving water.

Theoretically, the Regional Board could simplify the permitting process by establishing effluent
limitations that prohibited pollutant concentrations from exceeding the applicable water quality
objective or the current average concentration in the receiving water (whichever was more
restrictive). However, such an approach, while administratively easier, would not be consistent with
water resource management since it would tend to discourage greater use of recycled water in the
region.

Working closely with stakeholders throughout the watershed, the Regional Board developed a more
sophisticated tool for deriving appropriate effluent limitations and waste discharge that will ensure
long-term compliance with the nitrogen and salinity objectives in the Basin Plan. This tool, the Waste
Load Allocation Model (WLAM), evaluates the cumulative effects of a large number of different
discharges, over a wide range of land use and planning conditions, on the surface and ground waters
of the region. The WLAM also takes into consideration the normal fluctuations in weather patterns
(e.g. extend droughts or El Niño winters) that also influence regional water quality. The WLAM
assists regulatory permit writers in the process of deriving appropriate effluent limitations and waste
discharge requirements.

The purpose of this workshop agenda item is to discuss the regional trends and future anticipated
regulatory issues for the Yucaipa Valley Water District.

Yucaipa Valley Water District - October 9, 2018 - Page 19 of 172