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   Monk Hill Water Treatment Plant   Revised June 30, 2011
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Located at 2696 Windsor Ave. in Northwest Pasadena near JPL, the Monk Hill Treatment Plant is operational as of late 2010 and PWP began service from the plant on July 6, 2011 (read the press release).

Funded by NASA and backed by the U.S. EPA, California Department of Toxic Substances Control and the Los Angeles Regional Water Quality Board, the state-of-the-art plant is part of an ongoing effort to remove perchlorate and volatile organic compounds (VOCs) from the groundwater near NASA-owned JPL, which was the site of Army rocket testing decades ago.

The Monk Hill basin is an aquifer that runs below Hahamongna Watershed Park in the Arroyo Seco. It will once again serve as a vital local groundwater resource when Monk Hill Treatment Plant comes online and rehabilitates water pumped from four nearby wells that tap the aquifer (Arroyo Well, Well 52, Ventura Well, and Windsor Well) .


Public Health Review of Monk Hill Treatment Plant

Arroyo Well, Well 52, Ventura Well, and Windsor Well are drinking water wells that were inactive for many years due to groundwater contamination that migrated from the Jet Propulsion Laboratory. The California Department of Public Health (CDPH) has classified these wells as "Extremely Impaired Sources." PWP and NASA collaboratively oversaw the design and construction of the Monk Hill Treatment Plant to remove perchlorate and VOCs from these four wells to make the water suitable for drinking once again.

Because of the nature of the contamination at these wells, PWP worked with the California Department of Public Health (CDPH) to complete a rigorous public health review, public comment and permitting process, in accordance with California health and safety codes, before serving water from these wells.

The review process included:

1. Examination by CDPH of the treated water that PWP intends to serve;

2. A public review and comment period where the public was invited to review CDPH and other documents;

3. A public hearing where concerns were heard and questions answered;

4. Permit issuance to PWP, upon CDPH approval of the health and safety standards of the water that PWP intends to serve.


Public Comment Period: February 11 - March 13, 2011

The California Department of Public Health issued a "permit to serve water" to PWP in March 2011after all public comments were reviewed and considered. For questions regarding the permit, please contact: Jeff O’Keefe, CDPH District Engineer, 500 N. Central Ave., Suite 500, Glendale, CA 91203, or send e-mail to:

Project documents are available for review here below and at these public libraries:

Pasadena Central Library
285 East Walnut Street
Pasadena, CA 91001-1556
(626) 7

Mon – Thu: 9am – 9pm
Fri – Sat: 9am – 6pm
1pm - 5pm
Altadena Main Library
600 East Mariposa Street
Altadena, CA 91001-2211
(626) 798-0833

Mon – Tue: 10am – 9pm
Wed – Sat: 10am – 6pm
Sunday: Closed


Public Hearing: February 24, 2011

On February 24, 2011, the California Department of Public Health held a public hearing tp gather comments from the public about its proposal to issue a permit allowing PWP to serve drinking water produced by Arroyo Well, Well 52, Ventura Well, and Windsor Well, and treated at the Monk Hill Treatment Plant

View the Power Point Presentation

Public Hearing Agenda

1.  Introduction from the Hearing Officer (7 - 7:10 pm)

2.  CDPH Presentation on the Permit Evaluation of PWP's Monk Hill Treatment System (7:10 - 7:30 pm)

3.  Public Comments on Monk Hill Treatment System (7:30-9 pm)

4.  Hearing Closed (9 pm)





Project Documents


Contact Us

Jeff O’Keefe, CDPH District Engineer, (818) 551-2004,

Gary Takara, PWP Principal Engineer, (626) 744-3729,


Frequently Asked Questions

What is perchlorate?

Perchlorate and its salts are used in solid propellant for rockets, missiles, and fireworks, and elsewhere (e.g., production of matches, flares, pyrotechnics, ordnance, and explosives).  Their use can lead to releases of perchlorate into the environment. Perchlorate's interference with iodide uptake by the thyroid gland can decrease production of thyroid hormones, which are needed for prenatal and postnatal growth and development, as well as for normal metabolism and mental function in adult. Perchlorate is a regulated drinking water contaminant in California, with a maximum contaminant level (MCL) of 6 micrograms per liter (µg/L, or parts per billion).  The recent sampling results show perchlorate levels ranging from 5 to 45 ug/L in these wells.


What is CTC?

Carbon tetrachloride (CTC) is a VOC which is found in the discharge from chemical plants and other industrial activities.  Some people who use water containing CTC in excess of the MCL over many years may experience liver problems and may have an increased risk of getting cancer.  CTC is a regulated drinking water contaminant in California, with a MCL of 0.5 ug/L.  Although historical results ranged from 0.2 to 15 ug/L, recent sampling results show non-detectable levels of CTC from these wells.


What is an “extremely impaired source”?

As defined in the CDPH Policy Memo 97-005, an extremely impaired source must meet one or more of the following conditions:

  • Greatly exceeds a drinking water standards

  • Contains a mixture of contaminants of health concern

  • Is threatened with contamination by nearby activities

  • Is designed to intercept known contaminants

Because both Arroyo Well, Well 52 greatly exceed the California perchlorate drinking water standard with the highest detected perchlorate levels more than 3 times the MCL, and has contained a mixture of contaminants (perchlorate and CTC), they have been classified as extremely impaired sources.


Why are “extremely impaired sources” used for drinking water?

The best quality sources available should always be used for drinking water.  However, when properly and reliably treated, extremely impaired sources are a valuable resource. Treatment of Arroyo Well, Well 52, Ventura Well, and Windsor Well will help clean up groundwater contamination and protect other nearby drinking water wells.  Additionally, use of these local wells will reduce PWP’s reliance on imported treated surface water, which is subject to cutbacks during drought conditions and not available during scheduled maintenance events, and may be vulnerable to natural disasters such as earthquakes.


What is the permitting process for “extremely impaired sources”?

Drinking water projects involving extremely impaired sources require intensive assessment by CDPH.  Before a permit can be issued, an extremely impaired source must be carefully evaluated.  The evaluation must include the following six elements:

·                    Source water assessment

·                    Full characterization of raw water quality

·                    Source protection measures

·                    Assessment of monitoring and treatment

·                    Assessment of human health risks

·                    Identification of alternatives

The evaluation for Arroyo Well, Well 52, Ventura Well, and Windsor Well is called the CDPH Policy Memorandum 97-005 Documentation, Raymond Basin, Monk Hill Subarea (or “97-005 Engineering Report”).  PWP has made this document available for public comment.

The project must also be reviewed for compliance with the California Environmental Quality Act (CEQA).  Once a project receives a permit from CDPH, extensive ongoing monitoring and evaluation, and regular reporting of these findings to CDPH, is required.


What are the proposed treatment processes for Arroyo Well, Well 52, Ventura Well, and Windsor Well?

PWP and NASA have chosen ion exchange and granular activated carbon (also known as GAC) treatment processes for the removal of perchlorate and VOCs (primarily CTC), respectively.  In the ion exchange process, water passes through vessels filled with ion exchange resin, and the perchlorate in the water binds to the resin in exchange for chloride ions on the resin.  In the GAC process, water passes through vessels filled with granular activated carbon, and the VOCs in the water are removed by adhering to the carbon.  Both treatment processes are considered Best Available Technology by CDPH, and have been reliably and successfully used to treat drinking water in several locations in Southern California, including Altadena and Baldwin Park.  The MHTS is designed to remove both perchlorate and VOCs from the drinking water to meet Federal and State drinking water standards.


What if the proposed treatment facility fails?

Several reliability and redundancy features have been incorporated into the system design to prevent the treatment system from failures.  All water will go through the ion exchange vessels followed by the GAC vessels.  All vessels will be in the “lead-lag” arrangement.  For the ion exchange process, the total flow will be divided into 4 pairs of ion exchange vessels.  Each pair of vessels will receive 25% of the total flow and water will first flow through the lead bed (1st bed) and then through the lag bed (2nd bed).  This increases the reliability since the bulk of the contaminant would be removed in the lead bed, and the lag bed is to provide redundancy in case the lead bed does not function properly.  The GAC would work similarly, but with 5 pairs of vessels, each pair treating 20% of the total flow.  The treatment facility is equipped with various instrumentation and alarm features to notify the system operators of any failure that may occur in the treatment process.  The operational status of each unit process can be monitored on site or remotely.  Also, PWP has experienced and competent operators to oversee operations and maintenance of the facility as well as to perform frequent monitoring and inspection of the facility. 


What is NASA doing about cleaning up groundwater contamination originating at JPL?

NASA has funded source area remediation of soil and groundwater on-site at the JPL facility to remove perchlorate and VOCs.  Groundwater remediation is ongoing using liquid-phase granular activated carbon to remove VOCs and a fluidized bed reactor to remove perchlorate.  Since its operation began in early 2005, about 1,500 pounds of perchlorate and 40 pounds of VOCs have been removed from the groundwater beneath the source area at JPL.  Soil remediation occurred from 1998 to 2005 using a soil vapor extraction system (SVE) which removed approximately 260 lbs of VOCs from the soil.  More information on the groundwater cleanup efforts for the JPL property is available on the NASA website:

In addition, NASA has funded a 2,000 gallons per minute (gpm) treatment plant to remove perchlorate and VOCs from two Lincoln Avenue Water Company (LAWC) drinking water wells in Altadena.  The treatment facility, which became operational in July 2004, allows LAWC to deliver water to its customer that meets all Federal and State drinking water standards.  NASA is also funding the MHTS (the subject of this Fact Sheet) with a 7,000 gpm capacity, to treat PWP’s four contaminated wells (Arroyo Well, Well 52, Ventura Well, and Windsor Well), that have been shut-down for many years due to the high levels of perchlorate and VOCs (primarily CTC).


How has the treatment facility been tested?

To demonstrate that the treatment facility (MHTS) will be able to reduce the perchlorate and VOC levels to below their respective MCLs, PWP has performed extensive start-up testing at the MHTS from December 2010 to February 2011.  All monitoring results show that the MHTS is capable of effectively removing perchlorate and VOCs from the four contaminated wells to meet all Federal and State drinking water standards.  


Is my tap water safe to drink?

Yes! The MHTS has been carefully designed and evaluated to ensure that the water produced by the treatment plant does not contain any perchlorate or VOCs.  In addition, PWP conducts extensive testing of the water as required by CDPH.  PWP prepares an annual water quality report summarizing the results of the mandated testing that is performed throughout the year. The annual report for 2009 is available at


Does this project comply with CEQA?

In compliance with the California Environmental Quality Act (CEQA), PWP prepared an Initial Study to determine whether this proposed project may have a significant effect on the environment.  Several mitigation measures were included as part of the project design and noted in the Initial Study to minimize potential significant effects on the environment.  These mitigation measures have been incorporated into the MHTS design, construction, and operational requirements.  With the incorporation of these mitigation measures, the Initial Study determined that the proposed project will have less than significant impacts on the environment. 

As the lead agency under CEQA, PWP prepared a Mitigated Negative Declaration (MND) for this project.  The document was distributed to the public and circulated through the State Clearinghouse (SCH# 2008061056) for a 30-day review period beginning on June 10, 2008 and ending on July 10, 2008.  Three written comments were received during the review period.  The project was approved by PWP on July 10, 2008 and a Notice of Determination (NOD) was filed by PWP through the Los Angeles County Clerk Office on July 11, 2008.