Environmental Management

Creighton Avila

(530) 621-5153
FACT SHEET – Investigation of Stormwater Drainage Containing Elevated pH Levels near El Dorado Trail

Placerville, CA - On January 28, 2016, the County of El Dorado Community Development Agency issued a press release advising the public to avoid contact with stormwater in the vicinity of the El Dorado Trail near the end of Stage Court due to high alkaline levels, which have been determined to be caused by water that contains calcium hydroxide (i.e. made up of calcium and hydroxide ions). The area of concern along the El Dorado Trail has been clearly posted with warning signs, caution tape and temporary fencing.

Staff continues to work closely with the Central Valley Regional Water Quality Control Board (CVRWQCB), other state agencies, and the County Public Health Officer on this issue. The County is evaluating potential mitigation measures for this issue and will continue to monitor and sample water in the area throughout the rain season.

According to Dr. Nancy Williams, El Dorado County Public Health Officer:

"Calcium hydroxide is not currently classified in any of the four toxicity categories used by U.S. EPA. As a highly alkaline substance, solid calcium hydroxide is considered to be a moderately caustic irritant to exposed skin. However, because calcium hydroxide barely dissolves in water, casual contact with the pooled water next to the El Dorado Trail is not likely to produce any harmful effects. It would take extended or repeated exposures to this water to irritate skin. Eyes are more sensitive and would be irritated sooner. It is always wise to avoid unnecessary contact with any substance you don't know is safe."

The County is not aware of public contact with the water in the posted area near the El Dorado Trail that has resulted in reported injury or illness. However, the County continues to warn the public to avoid contact with this water and encourages the public to report any injury or illness associated with this issue to the El Dorado County Health Officer.

The following are updated facts regarding the investigation into this matter:

  • The County’s Community Development Agency (e.g. Environmental Management and Stormwater Management programs) staff have conducted field and laboratory sampling (e.g. over forty samples to date) of stormwater in this area on multiple occasions since being made aware of the issue on January 12, 2016. As of February 5, 2016, all field and laboratory data, sampling locations, and an investigation timeline have been posted and are continually updated on the County’s website:

pH Levels

  • Field test results indicated a pH greater than 12.5 within a limited area of ponding water adjacent to the El Dorado Trail. Water tests farther down the drainage (e.g. approximately 200 feet downstream) from the ponding area produced pH levels of around 7, which are within the normal range for stormwater runoff.
  • While a pH of 12.5 or greater is considered hazardous as defined by state regulations, pH alone does not determine the degree of hazard to human health. The type of substance(s) in the water and the concentration of these substances must also be known in order to determine the degree of hazard.

Substance Type

  • Laboratory testing of the high pH water indicates the presence of predominately calcium and hydroxide ions. 
  • The cause of the high pH water is believed to be due to contact with residual processed lime from the former Diamond Lime Plant that operated in the area from approximately 1933 to 1977. 
  • Naturally occurring limestone (i.e. calcium carbonate) was processed at the former Diamond Lime Plant to produce calcium hydroxide. Calcium hydroxide is a dry powdery material also known as hydrated lime or "lime water" when mixed with water. Hydrated lime is commonly used in agriculture as a soil amendment, in cement, in food preparation, to balance pH in drinking water, and as an antacid.


  • The concentration of calcium and hydroxide ions in the water is very low and self-limiting. This means that while the pH may be high, the ability of calcium hydroxide solid to dissolve in water is low. The lower the concentration, the less potential health impact.
  • The pH of the water in the affected area has been compared by some to lye (i.e. Sodium Hydroxide) or Drano. The concentration of hydroxide ions in lye is significantly higher than the concentration of hydroxide ions in the ponded water. While lye and Drano will cause chemical burns on exposed skin, the water in the ponded area is more likely to cause minor skin irritation with prolonged contact.

Other Information

  • The CVRWQCB has had an open investigation since 2012 on the property where the bulk of the historic Diamond Lime Plant once existed. The CVRWQCB maintains regulatory jurisdiction over the investigation and remediation of this site. 
  • On February 19, 2016, the CVRWQCB issued an ORDER TO SUBMIT TECHNICAL REPORTS (Order) to the property owner of the former Diamond Lime Plant. 
  • The Order provides background information indicating that metals were detected in surface water samples. A review of the CVRWQCB laboratory reports provided to the County, thus far, indicates that the level of metals in the water meet California drinking water standards, which is consistent with the County’s testing results. The CVRWQCB also tested soil samples for total metals to evaluate for hazardous waste criteria. None of the metals detected in the analysis exceeded hazardous waste thresholds. The Order may be viewed on the County’s website provided above. 
  • The Order background information also states that soil samples of concentrated lime waste from above the surface at the historic Diamond Lime Plant were collected by CVRWQB staff in 2012 and staff, "exhibited burning of exposed skin and choking upon inhalation." The County was recently advised of the above health effects reported by CVRWQB staff. Following the 2012 soil samples, the area was subsequently graded and covered with soil, burying the surface lime waste. The County and CVRWQCB will continue to investigate the site and, if necessary, implement mitigation measures to ensure that this material is not exposed to surface water runoff or public contact. 
  • The County conducted additional lab testing of the high pH water and water upstream for other hazardous substances, such as heavy metals. Testing results indicate that the levels of metals in the water meet California drinking water standards. However, the County advises the public to avoid contact with the water. Test results are available for public review on the County’s webpage indicated above. 
  • The State Department of Fish and Wildlife has determined that there is no current impact on Weber Creek resulting from this issue and therefore is not currently investigating this matter. 

For additional information regarding the Order and investigation by the CVRWQCB please contact Walter Floyd, Project Manager, at (916) 464-4651. For questions about the current water tests in the El Dorado Trail area please contact the Environmental Management Division at (530) 621-5300.

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