Hexavalent Chromium

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State Rescinds 2014 MCL for Hexavalent Chromium

 

2014 California Regulation for Hexavalent Chromium 

In 2014, the State of California created a new maximum contaminant level, or MCL, for hexavalent chromium, also known as chrome 6, or Cr+6. The new MCL was adopted at 10 micro-grams per liter, or 10 parts per billion (ppb). Previously, the State regulated Cr+6 through a MCL of 50 ppb for Total Chromium, which includes all forms of chromium, including Cr+6. California's 50 ppb MCL for Total Chromium has been in place for a number of years. The federal Environmental Protection Agency (EPA) has an established MCL for Total Chromium of 100 ppb. All of the states in the United States, with the exception of California, use EPA's MCL of 100 ppb for Total Chromium.  Neither the EPA nor any individual state, other than California, has an MCL specifically for Cr+6.

Cr+6 is a naturally occurring ionic form of the element chromium. It is found in the geologic soils throughout California, and is mined as an ore to be used in industrial processes. The ore is used in making stainless steel, textile dyes, wood preservatives, leather tanning, paints, inks, plastics, and various coatings. Cr+6 is a known carcinogen, primarily entering the body through the lungs inhaled as dust or in a vapor form due to high-heat industrial processes. Scientific studies have been inconclusive to date though as to whether Cr+6 is a proven carcinogen when ingested by drinking water containing trace levels of Cr+6. In creating the new MCL, the State was concerned that the risk of getting cancer could potentially be increased after decades of drinking large amounts of water containing elevated levels of Cr+6.

Five of the City's eleven municipal drinking water wells have Cr+6 at levels between 10 ppb and 24 ppb. The source of Cr+6 in Vacaville's deep groundwater wells is from the naturally occurring mineral deposits in the geologic formation of the Sacramento Valley. It is not a result of any industrial pollution. There are no known Cr+6 industrial pollution sites in Vacaville. Many other cities in the region, and throughout California, are also dealing with Cr+6 in their water supply wells. As a result of the 2014 regulations, Vacaville has been working with the State Water Resources Control Board's Division of Drinking Water (DDW) to design treatment systems or modify the five source water wells to produce drinking water with Cr+6 less than the new 10 ppb MCL by the lawful deadline of January 1, 2020.

DDW was careful to point out that the new 10 ppb MCL did not create an urgent drinking water crisis. Any potential health risks regarding Cr+6 in drinking water would require decades of drinking large volumes of drinking water with elevated levels of Cr+6. Therefore, DDW determined that communities with groundwater wells exceeding the new MCL could continue to use those wells while they implemented proposed system improvements to address Cr+6 under compliance plans approved by DDW. Vacaville has been working with DDW under such an approved compliance plan.

State Rescinds 2014 MCL for Hexavalent Chromium

In May 2017, the Superior Court of Sacramento County issued a judgment invalidating the new California MCL of 10 ppb for Cr+6. The court determined the State Water Resources Control Board (Water Board) failed to properly follow the requirements of the Safe Drinking Water Act for establishing the new MCL. The court ordered the Water Board to delete the new hexavalent chromium MCL from the California Code of Regulations. This change became effective on September 11, 2017. Therefore, as of September 11, 2017 the 10 ppb MCL for Cr+6 is no longer in effect. The regulation of hexavalent chromium in drinking water reverts back to the previous State of California MCL of 50 ppb for Total Chromium.

The Water Board has notified agencies, such as Vacaville, that were previously under compliance orders to address Cr+6 that the new 10 ppb MCL for Cr+6 is voided and no longer has to be met. The Water Board has determined that it will begin the process of adopting a new MCL for Cr+6, following Safe Drinking Water Act requirements. The Water Board will utilize scientific and economic data obtained during the past three years to establish a new Cr+6 MCL, but it is too early to project what that new MCL will be. The Water Board estimates it will take approximately two years to establish a new Cr+6 MCL.

The City of Vacaville continues to deliver the highest quality drinking water, meeting all federal and state drinking water requirements, to our customers.

 

To view a list of frequently asked questions about hexavalent chromium, scroll down the page or click here

To view the state website regarding chromium-6 drinking water MCL click here.

To view the City of Vacaville's 2016 Water Quality Report click here

To view the City of Vacaville's 2016 Triennial Water Report click here

 

HEXAVALENT CHROMIUM (Cr+6) INFORMATION/FAQs

Q. What is hexavalent chromium, also known as Cr+6?
A. Hexavalent chromium, or Cr+6, is a naturally occurring ionic form of the element chromium. It is found in geologic soils throughout California and is mined as an ore to be used in industrial processes. The ore is used in making stainless steel, textile dyes, wood preservatives, leather tanning, paints, inks, plastics, and various coatings.

Q. Does Cr+6 cause cancer?
A. Cr+6 is a known carcinogen that primarily enters the body through the lungs inhaled as dust or in a vapor form due to high-heat industrial processes. Scientific studies have been inconclusive to date, though, as to whether Cr+6 is a proven carcinogen when ingested by drinking water containing traces of Cr+6.

Q. How long has Cr+6 been in Vacaville ground water?
A. Cr+6 was first detected in Vacaville well water about 15 years ago. Prior to that, the City was unable to test for it. As science has improved, so too has the testing. Since the Cr+6 in Vacaville’s groundwater is from the naturally occurring Cr+6 in the soil, it is believed that Cr+6 has always been in the groundwater in Vacaville.

Q. Why did the state change the regulations on the maximum contaminant level (MCL) for Cr+6?
A. According to a press release from the California Department of Public Health: “California is the first and only state in the nation to establish a maximum contaminant level specifically for chromium-6 in drinking water,” said Dr. Ron Chapman, CDPH director and public health officer. “Establishing this maximum contaminant level (MCL) underscores California’s commitment to safe drinking water standards to protect the public health.”

The regulations set the MCL for hexavalent chromium in drinking water at 10 ppb and specifically regulate the hexavalent form of chromium. This is one-fifth the current total chromium standard of 50 ppb, which includes both trivalent chromium (Cr+3) and hexavalent chromium (Cr+6). The federal MCL for total chromium is 100 ppb. Cr+3 is less toxic than Cr+6 and actually an essential nutrient at low dosages, while Cr+6 may pose a risk of cancer when ingested.

Q. How many groundwater wells does the City of Vacaville operate?
A. The City operates 11 groundwater wells.

Q. What happens when water wells are found to exceed the MCL for Cr+6?
A. The City is required to notify the public when the annual average of quarterly samples is over the MCL for Cr+6. After a full year of required testing, 5 of our 11 wells require us to inform the public.

Q. Are the wells with elevated Cr+6 levels treatable at the City water treatment plant?
A. No. The groundwater wells with elevated Cr+6 levels are located too far from the Vacaville Water Treatment Plant, and therefore, must be treated at the wellhead. Also, the method of treating water to remove Cr+6 is a specialized technology that is not available at the Vacaville Water Treatment Plant.

Q. Where are the wells located?
A. For drinking water system security reasons we do not give specific addresses of the locations of the City’s wells. However, we can say that the wells are located in the eastern section of Vacaville.

Q. How long have these wells been in use?
A. Two of the five wells in question have been in service since the 1970s, two others since the late 1990s, and the other well was placed into service in 2005.

Q. What can be done to lower or remove Cr+6 from the water?
A. The City is looking at a variety of options at this point. The three newer wells have long service lives ahead of them. As a result, the City has been evaluating treatment solution pilot studies and is planning to install its first specialized Cr+6 treatment system at one of these wells in 2017. Additional treatment systems are planned over the next four years as part of the City’s compliance plan. The typical cost for these treatment systems is over $1 million each.

Q. Is there anything I can do at my home to remove Cr+6 from the water?
A. Home water carbon-based filtration systems and water filter pitchers are not specifically designed to remove Cr+6. However, reverse osmosis point-of-use water treatment is an effective, but pricey solution.

Q. How much water comes from the City’s wells?
A. The City’s water system produces about 15.5 million gallons of water a day during our busiest times. Of that amount, the North Bay Regional Water Treatment Plant is sending us 7.5 million gallons per day (5 million gallons from Putah South Canal or Lake Berryessa water and 2.5 million gallons is North Bay Aqueduct or Delta water); our own treatment plant at the Corporation Yard is producing 4 million gallons a day Monday through Friday (All Putah South Canal or Lake Berryessa water); and City wells make up the balance, about 5.5 million gallons per day, of the water produced. These production rates can change daily, weekly and monthly depending on water demand, seasons, water quality, water availability and other operational considerations. We have a very dynamic and reliable water system that produces high quality drinking water.

Q. My water tastes/smells funny. Is that from Cr+6?
A. No. Cr+6 is odorless, colorless and has no taste.

Q. So how come my water tastes/smells funny sometimes?
A. There are a number of reasons that this could occur. Most objectionable taste or odor in water is caused by chlorine added to the water to ensure that it is free from bacteria and is safe to drink. This off-taste can be removed by cooling the water in a pitcher, adding a lemon to the water, or passing the water through a water filter that contains granulated carbon.

Q. Is there Cr+6 in surface water?
A. Yes. The level of Cr+6 in surface water sources is about 1 to 2 parts per billion.

Q. Where can I get more information about hexavalent chromium?
A. The City has a page on its website dedicated to hexavalent chromium. It can be found at www.cityofvacaville.com/cr6.  That page has links to other sites with information about hexavalent chromium as well.

Q. Is there anyone I can call with the City who can answer my questions?
A. Yes. Please contact Mindy Boele, Water Quality Manager, at (707) 469-6400. E-mail Mindy at mindy.boele@cityofvacaville.com.