Maintaining Dry Creek Water Quality

DCVA Hires Water Experts

The Dry Creek Valley Association Board – through its alliance with the Clean Water Coalition – knew it was time to thoroughly understand how our precious water resources flow in and flow out of our watershed. We commissioned expert analysis from two hydro-geologists to model how the SWCA’s proposed projects change the water balance and thereby impact groundwater and surface water quality.

First, our experts collected a thorough set of data and documented sound water balance assumptions. Then each modeled the potential impact of the wastewater disposal project using different methodologies to calculate the water balance, salt budget and concentrations of total dissolved solids. Our primary concern is that the NSCARP project may concentrate the wastewater contaminants in our soils and groundwater and over time irreparably contaminate our drinking water supplies.

Using different methodologies and only addressing currently regulated compounds such as salts and nitrogen, the two scientists arrived at the same cautionary conclusions:

What we know: Over time and based on average calculations alone, the total dissolved solids (salts, etc.) from the NSCARP project wastewater could more than double the salinity of our groundwater aquifer to above drinking water standards. And, this impact may occur in less than 10 years.

Other contaminants, especially nutrients and metals, will concentrate in our groundwater aquifer over time. The extent and timing of this concentration will be dependent upon farming practices. Thus, if wastewater is applied when the vines do not need nutrients or if both fertilizers and wastewater are applied, then nutrients such as nitrate can build-up in the soils. When the winter rains come, the excess accumulated nutrients, salts, metals and organic chemicals are flushed from the soil directly into our groundwater.

Each year, the added chemical load results in an average increase in chemicals found in the groundwater, so that over time the concentration of groundwater contaminants becomes higher than that present in the wastewater itself.

Bottom line: Potential water quality impacts to local groundwater supplies as a result of NSCARP would significantly violate anti-degradation policies at both the State and Federal levels. To avoid such degradation of our soils, groundwater and surface water, the wastewater should be treated to groundwater recharge standards before application on land over our drinking water supply.

What we do not know: In addition to metals, nutrients, and salts, wastewater contains hundreds of unidentified organic compounds, including pharmaceuticals. The County does not even test for the presence of these other, potentially dangerous contaminants. Why? The County only relies on current standards, and our nation’s water quality regulations are about twenty years behind the times.

The organic compounds remaining in the wastewater are those that were not removed through tertiary treatment – this means these emerging contaminants are largely resistant to treatment by adsorption or microbial processes. As these emerging contaminants have little or no affinity for the soil and may not be taken up by plants, over time they too will concentrate in the groundwater, potentially reaching levels that are twice that found in the wastewater.

We do not know how these organic compounds and emerging contaminants interrelate with each other, so we cannot predict the impact they’ll have on our current safe, drinking water supply or our children’s health. What we can predict is that contamination of the aquifer supplying drinking water will require the SCWA to spend hundreds of millions to clean up its water supply later. So, we ask – why not clean the wastewater to groundwater recharge standards now and avoid such degradation of soils, groundwater and surface water.

The impacts could be greater than the averages used in the technical studies: The findings are based on averages over the entire groundwater aquifer. The models cannot predict localized impacts, and this raises other unanswered questions. Are there places in the drinking water aquifer where the contamination levels could be higher than the levels in the wastewater itself? What will the contamination levels be in wells down gradient from fields irrigated with wastewater?

The bottom line is that no one – not the County Water Agency and not our expert hydrologists – has satisfactory answers to these critical questions. And without reasonable assurances that our drinking water aquifer will not be damaged by NSCARP’s proposed project, it is imperative that the Sonoma County Board of Supervisors not certify the adequacy of the Water Agency’s EIR.

Judith Olney, Director

Dry Creek Valley Association

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