| The Off-Channel Surface Mining Ordinance (OCSMO) was adopted by the Yolo County Board of Supervisors on August 6, 1996, as part of the County’s Off-Channel Mining Plan (OCMP) development process. At that time, none of the four aggregate mining operators who elected to participate in the OCMP were proposing to dewater in conjunction with aggregate mining operations. Therefore, the County staff, in coordination with the participating aggregate producers, decided to prohibit dewatering rather than specifically analyzing the effects of allowing dewatering. Thus, the OCSMO, which implements the OCMP, was adopted with a prohibition of dewatering. That prohibition is found in Section 10-4.412 of the OCSMO, which provides:
Under no circumstances, shall any off-channel excavation use dewatering as a part of their surface mining operations.
“Dewatering” is not defined in the OCSMO. County staff have conservatively interpreted the term to mean lowering the water level in a wet (i.e. filled with water) mining pit by pumping water from the pit, or artificially lowering the water level, regardless of the purpose of the pumping.
The request by Teichert Materials to amend Section 10-4.412 of the OCSMO to allow for limited dewatering activities stems from an enforcement action (Attachment C). In April 2015, County staff received a complaint that Teichert was employing dewatering practices in the Mast pit at their Esparto off-channel mining facility. Teichert began pumping water from the Reiff pit to the processing plant in 2004. Prior to 2004, water was supplied to the plant via a well. Also in 2004, Teichert began discharging recycled wash water back into the Reiff pit instead of discharging into settling ponds adjacent to the plant site. The Central Valley Water Quality Control Board (CVWQCB) required this change because they no longer allowed discharge within the flood zone (the setting ponds are located in the flood zone). In summary, the CVWQCB prohibited Teichert in 2004 from discharging wastewater into the onsite detention/settling basins because the basins were located in a floodplain. Teichert then began discharging their wastewater into the Reiff pit (thereby containing it onsite in accordance with the CVWQCB). That water was then pumped back to the plant site for use in gravel washing and related industrial activities. Thus, the water was "recycled" within a closed system.
Teichert began mining in the Mast pit in 2004 and continued until 2009, when operations were put on hold due to the economic downturn. According to Teichert, when they resumed mining again in 2012/2013, they realized they needed to add water to the Reiff pond in order to continue use of the existing infrastructure (i.e., pump intake and conveyance pipeline). Thus, in late 2013 Teichert began pumping surface water from the Mast pit to the Reiff pit to provide make-up water (i.e. meet the water supply demands on the plant site).
After the initial complaint in April 2015 about Teichert’s dewatering activities, staff requested additional information and analysis from Teichert to determine the scope and scale of the pumping activities. In August 2015, County staff notified Teichert that the pumping activities were inconsistent with the OCSMO and resulted in a “condition of concern” pursuant to the Administrative Policy. Teichert began preparation of a Correction Plan and retained a Professional Geologist/Certified Hydrogeologist (Luhdorff and Scalmanini Consulting Engineers or LSCE) to prepare detailed analysis to determine if the operational change may constitute an increased risk to groundwater resources or imminent impacts to health, safety, or the environment. The County retained the services of a Professional Geologist/Certified Hydrogeologist (Baseline Environmental Consulting or BASELINE) to review all documents submitted by Teichert. Additionally, the information provided by Teichert was reviewed by the Cache Creek Technical Advisory Committee's hydraulic engineer.
After reviewing and analyzing all of the available information, BASELINE found that there is substantial evidence to support a determination that there is no imminent and substantial endangerment to the public health, safety, or environment related to the ongoing extraction of water from the on-site wet pits for use in the aggregate processing plant, as long as the water does not substantially exceed the amount used during the monitoring period (i.e., 160-acre-feet per year) and the washwater is returned to the Reiff or Mast ponds (so that the aquifer can be recharged).
The Correction Plan submitted by Teichert, and ultimately accepted by the County Administrator on April 15, 2016, contained a two prong approach to reach compliance (Attachment C). The Correction Plan proposed that Teichert apply for an amendment to Section 10-4.412 of the OCSMO to allow for dewatering under specified circumstances that do not result in adverse impacts to groundwater resources and, if such an amendment is approved, apply for an amendment of its existing mining permit to allow such dewatering. Therefore, should this proposed Ordinance amendment be approved, Teichert would still need to seek separate approval to amend its permit to allow dewatering activities, subject to the requirements of the amended Ordinance.
The proposed OCSMO amendment would allow for surface mining operations to use dewatering if site-specific analysis prepared by a qualified Professional Engineer or Professional Geologist demonstrates that such dewatering would not result in off-site impacts to groundwater or other water resources (e.g., creeks and wetlands). Also, the water from dewatering must be put to a beneficial use and cannot be discharged off-site. The volumes of groundwater pumped from wet pits must be recorded and reported to the County.
Under the proposed OCSMO amendment (Attachment A), monitoring of groundwater levels would be required prior to, and for the duration of, dewatering activities to ensure that dewatering activities do not result in adverse effects to groundwater or other water resources (e.g., creeks and wetlands). If monitoring reveals adverse effects on neighboring wells within 1,000 feet or on other water resources (e.g., creeks and wetlands), dewatering activities must cease or measures must be implemented to ensure that impacts on affected wells are mitigated. Such mitigation may include well modification, well relocation, or compensation for increased pumping costs.
In summary, the proposed amendment to the OCSMO provides a regulatory framework to ensure dewatering activities related to mining operations do not create adverse impacts. The Ordinance amendment would allow for limited dewatering activities so long as water generated from dewatering is beneficially used and discharged on-site, and site-specific technical analysis is performed by a qualified professional that demonstrates that the proposed dewatering will not adversely affect off-site wells with respect to groundwater level and quality. Under the proposed ordinance, mining operators would seek separate approval prior to initiating dewatering activities and would annually report groundwater monitoring measurements and the volumes of groundwater pumped from wet pits to the County for review.
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