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The Laboratory analyzes drinking water, wastewater, streams, ground waters, reservoirs, and soils. The Lab’s results are used to determine compliance with State and Federal water reclamation criteria, Safe Drinking Water requirements and other regulations. Lab results are used by District staff to determine treatment efficiency and needs. The Lab’s activities are divided into three main categories: wastewater, drinking water, and Alpine County monitoring (where the recycled wastewater is applied for irrigation). Indian Creek Reservoir (ICR) monitoring has increased to assess the efficacy of the hypolimnetic oxygenation system (HOS). 

Sampling and Testing

Sampling and testing of monitoring wells in Alpine County has increased. This will increase the time and supplies required by the Laboratory for sampling and testing. Thirteen new wells have been installed in Diamond Valley and seven more to replace or augment existing domestic wells throughout the land application areas.

A smiling person wearing a lab coat and gloves is handling a bottle and a syringe in a lab setting.

Monitoring for MTBE in water production wells continues. The Lab is testing sentinel-monitoring wells in drinking water production areas, wastewater treatment facilities, and Harvey Place Reservoir in Alpine County. VOC (including MTBE) tests are performed by commercial laboratories and require substantial funds for testing.

The Lab is still sampling MTBE treatment systems’ discharge to our sewer at underground storage tank (UST) sites. This program has decreased since many UST treatment systems are discharging to infiltration galleries or have remediated the contamination.

Microbiological monitoring is performed throughout the drinking water distribution system at: customers’ homes, businesses, all wells, water storage tanks, in new and repaired mains and tanks, and in response to customer concerns. The Lab performs Total Coliform, E. coli, and Heterotrophic Bacteria Plate Counts on the new water mains and all water tanks. The Lab also develops and maintains records of daily drinking water production.

The Lab continues collecting and testing drinking water samples for the Arsenic Treatment System (ATS). Arsenic tests are done on raw water and at various stages of the treatment process. The South Upper Truckee Well #3 Carbon Dioxide Removal System is also tested monthly for performance and State requirements.

Samples from small water systems in El Dorado, Alpine and Mono counties are routinely tested for coliforms, nitrates, and several other chemical tests. A fee is charged to cover all costs for these services.

The Lab will continue to automate sampling, analyses and reporting to increase the productivity of this division. A Laboratory Information Management System (LIMS) was purchased and was placed online in January 2013. The LIMS can schedule sample events, import electronic data from instruments and contract laboratories, ensure the quality of the test results by comparing to defined quality assurance criteria, link test results to GIS systems (District wells; storage tanks; mains, Alpine County sample sites) and customer databases, track test trends, alert personnel to outliers and violations, maintain history of instrument maintenance, track chemical inventory, and produce billing of tests. The LIMS enables laboratory staff to track all laboratory operations faster and easier.

Wastewater Treatment Plant

Each day samples are taken of the influent, effluent and the treatment processes. Close to 3,000 samples are collected and 17,000 tests run each year to assure the recycled water meets requirements. The treatment plant has been in 100% compliance since 1995.

A water treatment plant with basins, buildings, and a crane, set against a backdrop of mountains and trees.

Drinking Water

The Lab collects 20-40 samples each week from wells, storage tanks, dedicated sample taps and customers' homes. These samples are tested for bacteria, chlorine and temperature to assure that only safe high quality water is delivered to our customers.

Our wells are sampled every year and analyzed for all required tests and some unregulated ones, even though the state requires less frequent monitoring. Some of the tests performed are metals, minerals, uranium, radon, up to 60 volatile organic chemicals (ie: chloroform, MTBE, and benzene) and bacteria. Results of the annual testing on each of our wells can be found at the Water quality page (see the right of this page for more info).

Our consumer confidence report, giving the average and range of values for detected compounds in our distribution system and at the wells can be found on our documents page (see the right of this page). 

Why add chlorine? It makes the water taste funny: The District began adding chlorine to the drinking water in 1989. This is done to reduce contamination of your water by bacteria.

Alpine County Program

The purpose of the Alpine County monitoring program is to assess the effects of using our recycled water to irrigate Alpine County ranchlands. To accomplish this, extensive monitoring is performed on Alpine County ground waters, surfacewaters and soils. Samples of soils and well water are taken from all the ranches receiving recycled water for irrigation. Stream samples are taken from the West Fork Carson River, upstream, midstream and downstream of the areas irrigated with our water. The District also installed special monitoring wells at areas that could immediately show any groundwater impact from our recycled water. Some sites are outside the area receiving recycled water to act as study controls. The sample sites were chosen in cooperation with the Lahontan Regional Water Quality Control Board, National Resources Conservation Service, and District design engineers. Sample sites and types of analyses are periodically reviewed and modified.

Close to 10,000 tests are performed each year on Alpine County water and soil samples. Most of the analyses are conducted in our own laboratory. The tests include nutrients, minerals, solids, metals, algae, and bacteria. Analyses for some toxic metals and many organic chemicals are performed by independent state certified laboratories. The District Laboratory collects 30-40 samples each month from the following areas:

Sample Type# SamplesFrequency
Streams8 to 10Monthly
Irrigation Ditches5Monthly
Ranch Wells4Quarterly
Monitoring Wells26Quarterly
Harvey Place Reservoir1Monthly
Indian Creek Reservoir*6Monthly

* No longer used for recycled water

Indian Creek Reservoir

Indian Creek Reservoir (ICR) was built to receive tertiary treated reclaimed wastewater from the late 1960s till 1989. During that time it provided a home to rainbow trout and was a great year-round fishery. All reclaimed wastewater is now stored in our Harvey Place Reservoir during the winter months. ICR currently receives no reclaimed water, getting its water from the West Fork Carson River and Indian Creek stream. It still is a great year-round trout fishery.

Diamond Valley Rach - recycled water center with pickup truck, mountain backdrop, leafless trees, blue sky with clouds, and a fence.

Monitoring is done at ICR in response to Total Maximum Daily Loads (TMDL) planning and to assist Fish & Game with fishery management. The Lab performs profiling at ICR each month. An electronic data sonde is sent through the water column at three sites. The sonde records depth, temperature, pH, electrical conductivity and dissolved oxygen. The data is downloaded to a computer and the results tabulated and graphed. The results are then e-mailed to the California Dept of Fish & Game. Water samples are also taken at three depths and analyzed for nutrients, minerals, metals, chlorophyll, algae and bacteria. Graphs showing temperature and dissolved oxygen (DO) in winter and summer are shown below.

Quality Assurance

Quality assurance is a major part of the laboratory routine. Each time a test is run, 10 - 20 percent of the samples analyzed are standards, duplicates, and interference checks. Each test is subjected to a statistical evaluation of accuracy and precision. A test is re-done if the result falls below acceptable levels or is not within trend values. The analysts who perform the tests are certified by both the American Water Works Association and the California Water Environment Association. Our laboratory is certified by the California Environmental Laboratory Accreditation Program.

Laboratory Tests

The District's Lab uses both manual and automatic methods to analyze nutrients, metals, minerals, and solids. Many test methods (nutrients and metals) are capable of detecting in the parts-per-billion (ppb) range. The lab is equipped with several computer controlled instruments that can run un-attended. Some instruments can perform multiple analyses on up to 50 samples an hour. Automatic methods enable better quality control and reduces the amounts of hazardous waste that requires disposal. Bacterial tests for total coliform, E.coli, and fecal streptococci are also performed.

The parameters used most to determine recycled water influence on natural waters are nitrates, ammonia, phosphorous, chlorides, and total dissolved solids (TDS). The data is tabulated and plotted to determine any trends. The Laboratory is certified by the State of California to perform drinking water and wastewater tests. Some of the tests the Lab performs are listed in the table below.


Perfluorooctanoate (PFOA) and Perfluorooctanesulfonate (PFOS) are fluorinated organic chemicals that are part of a larger group of man-made chemicals referred to as per-and polyfluoroalkyl substances (PFAS). They have been used extensively in consumer products such as carpets, clothing, fabrics for furniture, paper packaging for food, fire-fighting foams, and other materials (e.g., cookware) designed to be water proof, stain resistant or non-stick. Certain PFAS chemicals (including PFOA and PFOS) are no longer manufactured in the United States. However, these chemicals are still produced internationally and are imported into the US in consumer goods such as carpets, apparel, textiles, paper, packaging, coatings, rubber and plastics.

These chemicals can get into drinking water when products containing them are used or spilled onto the ground or into lakes and rivers. The chemicals move easily through the ground, getting into ground water that may be used for water supplies or for private drinking water wells.

In 2014 and 2015 the District sampled for PFOA as part of the Unregulated Contaminant Monitoring Rule (UCMR-3). All of our drinking water wells were sampled, including those on standby. No PFOA’s were detected in any of the District’s drinking water wells.

MicrobiologyMinerals / DemandNutrientsPhysical TestsMetals
E. coliBoronKjeldahl NitrogenElectrical ConductivityBarium
Fecal ColiformsChlorideNitrateOdorCalcium
Fecal StreptococciChlorineNitritepHCopper
Plate countsHardnessPhosphate, orthoSuspended SolidsIron
SulfatePhosphorous, totalTurbidityLead
BOD Total Dissolved Solids
.COD ..

Look for the Lab's white truck. You'll see the technicians getting samples from the streams, fields, school, stores, and restaurants throughout South Lake Tahoe and eastern Alpine County. Stop by if you have any questions.

For more information, call us at 530-544-6474, ext 6231 or e-mail us with your