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New Private Well, Potential to Contaminate Public Water Sources

 

Last updated 11/14/2022 at 2:41pm



In the process of approving a new residential well in the northern end of the Borrego Springs’ aquifer, problems of increased pollution in a nearby Borrego Water District well, moved the Borrego Water District (BWD) and the Watermaster staff to require the owner install non-impermeable materials such as clay to prevent potential leakage of agricultural runoff.

The Watermaster approved of the well, without the application of non-permeable materials, despite objections by BWD, and the Watermaster’s Technical Committee. Both contended that the well could add agricultural runoff; further polluting the BWD’s adjacent well that is used for residential water.

Rebecca Falk, chair of the Borrego Springs Sponsor Group, explained why the county’s community-planning group felt it needed to add its voice to that of the BWD in protesting the decision of the Watermaster.

“We wrote to the Watermaster because in addition to potential pollution of a residential well, this decision by the Watermaster is setting a precedent, which has serious implications for Borrego Springs’ future water quality, Falk said.

“The Borrego Valley Groundwater Basin adjudication, under which Borrego’s, state-mandated Sustainable Groundwater Management Act (SGMA) operates, requires the Watermaster to protect the water quality in the Borrego Valley. This decision, we believe, goes against that imperative.”

In the letter to the Watermaster, the Borrego Springs Community Sponsor Group, which represents the community in land use planning activities, wrote:

“It has come to the attention of the Sponsor Group that the Watermaster Board recently did not follow the recommendations of their staff (West Yost), as well as the recommendation as submitted by the Borrego Water District (BWD). This is regarding a well application for a domestic well located near the BWD well number ID4-18. The Sponsor Group is requesting that the issue be reconsidered to ensure that adverse cross-contamination within the aquifer be restricted,” Falk noted.

“Of specific concern is that the Watermaster Board did not require that the non-saturated well annulus of the subject well be filled with a non-permeable material, even though the owner of the well was willing,” added John Peterson, vice chair of the group, said. “It is well known that a well can provide an avenue for downward migration of shallow water and any contaminants it might contain. This is of special concern considering that recent water quality samples from the BWD well ID4-18 have shown a significant and substantial rise in nitrate levels.”

He added, referencing the letter, “The most likely cause of such an increase is the downward movement of irrigation return flows in the area. The completion of nearby wells, offering a preferential pathway for downward movement of degraded irrigation return flows, could further compound this problem.”

Peterson, is a California Professional Geologist, and a California Certified Hydrogeologist. He has 40 years of experience working within the basin, including 22 years’ experience working as the San Diego County Hydrogeologist.

Peterson reviewed the studies, and agreed that the suggested construction design, as requested by the BWD, is a reasonable and sensible approach to address the issue of potential cross-contamination of irrigation return flows.

“Due to these issues, the Borrego Sponsor Group is in support of the request as provided by the BWD; that the well be installed with a non-permeable well annulus to restrict the vertical migration of degraded shallow waters,” Peterson explained.

The debate that prompted the Sponsor Group letter to the Watermaster is about the well annulus, that portion of a well that lies between the production casing, which allows the pump and motor to be installed in the well, and the country rock that has been removed through the drilling process.

After the installation of the production casing, the annulus is filled below the saturated zone (“water table”), with very porous material such as sand and or gravel, which allows water movement into the screen section of the well. This water is then available to the pump and the motor. However, the unsaturated section “above the water table” of the annulus can be refilled with either permeable or non-permeable materials.

According to Peterson, examples of permeable materials would be sand or country rock; non-permeable materials would include neat cement or expandable clays, such as bentonite.

“If the annulus in the unsaturated portion above the water table is refilled with permeable materials this could allow for vertical migration, most frequently downward, of shallow vadose water. The unsaturated zone of an aquifer is the zone above the water table that allows for the transport of water from the surface to the water table. All recharged water, which includes natural groundwater recharge as well as irrigation return flows moving downward, must move through the unsaturated portions of a groundwater basin,” he said.

“Therefore, it is very important that the effects of water movement through the unsaturated (vadose) zone be included in the analysis of any hydrological system,” Peterson added.

The water that is applied to an agricultural crop is consumed in three different ways:

“Transpiration,” which is water that is required for plant growth. This water is ultimately lost to the atmosphere.

“Evaporation,” which is the loss of water directly to the atmosphere and is a function of the efficiency and design of an irrigation system.

“Irrigation Return Flow” is the quantity of water used to “flush” the overlying soils of excess salts and chemicals. This “excess” water is necessary so that those salts and chemicals can be removed from the root zone of crops. It will ultimately recharge the groundwater system; However, it is excessively laden with salts and chemicals that have been used on the agricultural crop. These waters moving through the unsaturated (vadose) zone are thus highly enriched with salts and excess agricultural chemicals.

“A well annulus that is refilled with permeable materials can provide for preferential pathway for the downward migration of degraded water containing irrigation return flows,” Peterson noted, adding that, “This is especially important given that the nearby BWD operational well (ID4-18) and the surrounding area are located in the northern agricultural fields of Borrego Springs.”

Borrego Springs Watermaster: The Watermaster is a committee of representatives of the parties to the Judgment. The Watermaster convenes monthly to conduct its business and prepares an annual budget and assessment to fund its operations and activities. The Watermaster maintains a website for the purpose of disseminating important documents and data to the parties, other stakeholders, and interested public, such as meeting agendas and minutes, production and water-level elevation data, guiding documents, and Watermaster forms.

Technical Advisory Committee: The Technical Advisory body is established to study technical aspects of the Basin and to issue recommendations to Watermaster based on technical study for the purpose of achieving Sustainable Groundwater Management in the Basin in an effective and efficient manner.

The Committee’s responsibilities include, without limitation, making recommendations based on best science and data collected regarding the Water Budget and the avoidance of “Undesirable Result,” determined by the TAC based on best available data, including without limitation information generated from BVHM model runs.

Assessments must consider all inflows and outflows from the Basin, including without limitation mountain front underflow and flux into the Borrego Springs Basin across the Coyote Creek fault and all other underflows, agricultural and recreational irrigation return flows; specific yield differences of the three aquifers (upper, middle and lower) within the different Management Areas of the Basin; and other matters approved by the Watermaster to improve upon initial assumptions regarding the Water Budget that will enable better Adaptive Management of the Basin.

The Environmental Working Group: The role of the Environmental Working Group (EWG) is to advise and further the mission of the Borrego Springs Watermaster to implement the Stipulated Judgment and comply with Sustainable Groundwater Management Act (SGMA) by focusing on the protection of human health and the environment. The activities of the EWG shall be approved by the Watermaster Board and will always include a nexus between environmental issues and the sustainable use of groundwater in the Borrego Springs Subbasin.

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