City of Palo Alto Advanced Mercury Source Control Study Page 1 of 22 

2006 Annual Report of Activity – February 2007 

Advanced Mercury Source Control Study 

2006 Annual Report of Activity 

City of Palo Alto Regional Water Quality Control Plant1

2501 Embarcadero Way, Palo Alto, CA 94303 

February 2007 

The City of Palo Alto Regional Water Quality Control Plant (RWQCP) is regulated under Waste 

Discharge Requirements Order No. R2-2003-0078 adopted on August 20, 2003 by the California 

Regional Water Quality Control Board, San Francisco Bay Region. In accordance with Provision 

4 of this Order, the RWQCP is submitting this annual report regarding our advanced mercury 

source control study. 

I. Background 

Provision 4 of the RWQCP’s August 2003 Discharge Order requires that the RWQCP partners 

achieve further mercury reductions by developing and implementing an Advanced Mercury 

Source Control Study. The project objective is to conduct additional mercury source control in 

two distinct areas: 

(1) Improve amalgam collection and pretreatment at dental offices, to reduce overall mercury 

loading from those sources. 

(2) Identify on-site RWQCP mercury uses, conduct a review of alternatives, and implement 

replacement with alternative materials, as appropriate, to reduce dependence upon mercurycontaining products at the facility. 

A study work plan was submitted to the Regional Board in November 2003 and approved in 

December 2003. The first annual update was provided, as required, in the Clean Bay Pollution 

Prevention Plan, submitted in February 2004. The second and third annual updates were 

provided as stand-alone document in February 2005 and February 2006. 

This latest document, dated February 2007, provides a summary of 2006 activity, along with 

projected next steps and schedule. 

 

1

 Questions or comments on this report should be directed to Karin D. North at 650.494.7629 or 

cleanbay@cityofpaloalto.org 
 

City of Palo Alto Advanced Mercury Source Control Study Page 2 of 22 

2006 Annual Report of Activity – February 2007 

Part 1 – Advanced Dental Office Source Control 

The objective of the Advanced Dental Office Source Control program is to develop and 

implement a program for the installation of amalgam separators at dental offices. This program 

and the associated ordinance language were developed in cooperation with the Mid Peninsula 

Dental Society (MPDS), California Dental Association (CDA) and other stakeholders. Staff 

coordinated with other jurisdictions that either had similar requirements in place or were 

developing similar measures: San Francisco; East Bay Municipal Utility District (EBMUD); 

Seattle, Washington; and Minneapolis/St. Paul, Minnesota. 

A. Requirements for Dental Offices 

The RWQCP partner cities, Palo Alto, Mountain View and Los Altos, passed an ordinance to 

require that all owners and operators of dental vacuum suction systems install an ISO 11143 

certified amalgam separator device by March 31, 2005. The installed device must be certified by 

ISO 11143 as capable of removing a minimum of 95 percent of amalgam. The RWQCP elected 

to use the same list of approved amalgam separators that is maintained by the City of San 

Francisco. The complete text of the ordinance is provided in the Appendix. 

In addition to the amalgam separator requirement, several best management practices (BMPs) 

that directly affect sewer discharges are now required: 

• Do not rinse chairside traps, vacuum screens, or amalgam separator equipment in a sink 

or other sanitary sewer connection. 

• Train staff in the proper handling and disposal of amalgam materials and fixer-containing 

solutions; training records must be available for inspection. 

• Do not use bleach or other chlorine-containing disinfectants to disinfect the vacuum line 

system. 

• Do not use bulk liquid mercury; use only precapsulated dental amalgam. 

• Store amalgam waste in accordance with recycler or hauler instructions. 

Other amalgam-related BMPs will continue to be encouraged. 

B. Outreach to Dental Facilities and Building Owners 

In 2006, the RWQCP focused on inspecting dental offices. The following outreach occurred in 

2006: 

 The RWQCP finished inspecting the remaining 43 percent of the 134 dental offices in the 

service area; results are listed in the inspection summary. 

 RWQCP submitted an article in the Mid Peninsula Dental Society Articulator 

highlighting the program and thanking the dentists for their participation. (See Appendix 

for article). 

 The RWQCP continued to update its web site, which includes electronic versions of the 

brochure, forms, ordinance text, list of approved separators (linked to list maintained by 
 

City of Palo Alto Advanced Mercury Source Control Study Page 3 of 22 

2006 Annual Report of Activity – February 2007 

City of San Francisco), inspection form, and answers to frequently asked questions: 

http://www.cityofpaloalto.org/cleanbay/dental.html

 

C. Outreach to wastewater agencies within the Bay Area 

In December 2006, staff from the RWQCP spearheaded the organization of a one-day training to 

share the dental amalgam programs within the Bay Area to other wastewater staff throughout the 

bay area and California. The workshop on “Creating a Dental Amalgam Program” was cosponsored by the Bay Area Pollution Prevention Group (BAPPG) and the California Water 

Environment. The overall goal of the workshop was to provide wastewater agencies with the 

tools and knowledge to start their own dental amalgam program, which included 

• Summary of the Mercury TMDL, 

• How to work with your dentists, 

• Information on setting up a program, 

• Compliance options, 

• Inspector training, and 

• Highlights and lessons learned from existing programs. 

Tom Mumley, from the Regional Board, set the stage for the workshop informing agencies that 

dental amalgam programs will be necessary to meet upcoming discharge limits outlined in the 

Mercury TMDL. Representatives from the City of Palo Alto and East Bay Municipal Utility 

District and San Francisco Public Utilities presented on lessons learned and the success of their 

Dental Amalgam Programs. Tom Barron, a consultant who specializes in dental programs, 

provided a detailed inspector training, which included examples of amalgam separators. 

The workshop was well attended by eighty-eight people who represented forty-five agencies and 

businesses in Northern California; 60% of the BAPPG agencies were represented at the 

workshop. The overall workshop received an excellent/ very good based on the evaluation forms. 

Attendees received a workbook, which included a CD that contained a literature review on dental 

programs locally and nationally. The “Creating a Dental Amalgam Program” CD contains the 

most complete reference material put together to date nationally on this subject. Staff from the 

Regional Water Quality Control Plant organized the contents of the workbook and CD. A copy 

of the table of contents of the CD is attached. 

D. Dental Inspections 

Based upon the information collected by the RWQCP in 2004, it was determined that 134 of the 

168 dental offices in the RWQCP’s service area are required to install amalgam separators. The 

other 34 dental offices are exempt from the ordinance because the removal or placement of 

amalgam fillings occurs at the facility no more than 3 days per year. Each of the 134 dental 

offices was asked to submit a “Self Certification of Amalgam Separator Installation” form by 

April 30, 2005, to indicate that they had met the compliance deadline of March 31, 2005 for 

installation of an amalgam separator. By April 30, 2005, 95 percent of the 134 dental offices had 

certified that their amalgam separators were installed. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 4 of 22 

2006 Annual Report of Activity – February 2007 

In July 2005, the RWQCP began inspecting the dental offices. Inspections were conducted only 

at those offices that were required to install an amalgam separator. The first offices to be 

inspected were those that had not supplied the RWQCP with the “Self Certification of Amalgam 

Separator Installation” form by April 30, 2005. A typical inspection lasted approximately 20 

minutes, and addressed the following issues: 

• Implementation of amalgam best management practices (BMPs); 

• Presence of an amalgam separator; 

• Review of separator maintenance records; and 

• Management of amalgam wastes and x-ray processing wastes. 

As of December 31, 2006, 134 dental offices had been inspected at least once. Three quarters 

(75%) of the 134 dental offices inspected were in full compliance with all requirements. These 

offices had installed amalgam separators, and were using all required BMPs at the time of their 

initial inspection. The remaining 25 percent of the offices still needed to implement one or more 

of the BMPs. Follow-up inspections were conducted at many of these sites, with the result that 

by December 31, 2006, most of the 134 offices were in compliance with their required BMPs. 

Amalgam Best Management Practices 

The initial inspections revealed that a number of sites required improvement in their amalgam 

waste collection, storage, and disposal BMPs (Figure 1). The best management practices that 

most frequently required attention included 

• Proper storage of amalgam waste (24%) 

• Train staff annually in proper handling and disposal of amalgam materials and fixercontaining solutions. (12%) 

• Keep training records (11%) 

• Do not rinse chair side traps, vacuum screens, and amalgam separator equipment in a sink 

or other sanitary sewer connection (13%) 

Suggested improvements were communicated to these sites during the initial inspection, and via 

a follow-up letter. Additional follow-up occurred during an additional inspection, three offices 

received notice of violation letters. To date, most of the 134 sites are now in compliance. 

Amalgam Separator Information

Most dental offices in the service area have their own vacuum system, and therefore have 

installed their own separator. However, in some buildings the landlord provides the vacuum 

system (and an amalgam separator) for the tenants to use. Sometimes the “landlord” is one of 

the following: 

• One of the dentists 

• All of the dentists together or 

• A separate individual 

There are twenty-one practices in the service area where a “landlord” provides and maintains the 

separator. 

Out of the 75 inspections completed by December 31, 2005, only two dental offices had not yet 

installed an amalgam separator. These offices mistakenly believed that they had an existing 
 

City of Palo Alto Advanced Mercury Source Control Study Page 5 of 22 

2006 Annual Report of Activity – February 2007 

amalgam separator in place. Three additional offices had installed separators, but were 

potentially not maintaining them according to manufacturer instructions. The separator at a sixth 

site could not be observed during the initial inspection because of a malfunctioning lock on the 

vacuum closet door. 

In 2006, the 59 remaining offices were inspected and the six offices mentioned above were reinspected. RWQCP staff confirmed that all dentists in our service area have now installed an 

amalgam separator (Figure 2). 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Do not rinse into sewer

Train staff

Keep training record

Proper storage

No bleach in vacuum line

Pre-measured amalgam

Ok Not Ok NA

Figure 1: Summary of Best Management Practices for 134 dental offices after the initial 

inspection. (RWQCP staff does not require the smaller dental offices to keep training 

records for staff.) 
 

City of Palo Alto Advanced Mercury Source Control Study Page 6 of 22 

2006 Annual Report of Activity – February 2007 

0% 20% 40% 60% 80% 100%

Certified separator

Flow rates

No bypass

Proper

maintenance

Correct hauling

Ok Not Ok

Figure 2: Summary of Amalgam Separators for 134 dental offices. (A landlord manages 

the separator at 21 of the 134 dental practices in the service area). 

E. Challenges 

A few challenges were identified during the 2004-2006 implementation. 

Vacuum line vs. dental office ownership In large dental/medical buildings, it is common for a 

vacuum system to be shared amongst multiple independent dental offices. In our ordinance and 

outreach materials, we were careful to note that in cases of shared vacuum systems, each dental 

office is legally responsible for ensuring that an approved amalgam separator has been installed. 

In some cases the dental office as well as the landlord had to be contacted in order to complete 

the inspection of that site. 

Scheduling Inspections Scheduling the inspections was time consuming. Each dental office was 

notified and an appointment time was scheduled. A follow up fax was sent to the office and a 

phone call reminder is made prior to the inspection. A few inspections had to be rescheduled for 

various reasons, such as site employees being on sick leave. 

F. Future Inspections and New Dental Offices 

In 2007, RWQCP will send the dentists a letter requesting that they submit an annual report 

certifying that they follow the BMPs and that the amalgam separator is maintained correctly. In 

addition to the annual report, RWQCP staff will continue to inspect 20% of the dental offices 

every year. The practices that will be re-inspected in the first year will be those offices that had 
 

City of Palo Alto Advanced Mercury Source Control Study Page 7 of 22 

2006 Annual Report of Activity – February 2007 

minor BMP issues during the initial inspection. Most of the dental offices that had major BMP 

issues were re-inspected in 2006. 

New dental offices will emerge occasionally within the service area. RWQCP plans on keeping 

track of new offices during the building permit review process and by noticing new dental 

offices while in the field. RWQCP will contact the new dental offices as they open. 

G. Program Evaluation 

The RWQCP’s dental program will be evaluated based on the following: 

1) Number of dental facilities in compliance with new ordinance 

2) Mercury concentration in a dental building cleanout and “dental area” trunk line before 

and after amalgam separator installations 

3) Mercury concentration/loadings in RWQCP influent, effluent, and biosolids 

Dental Facilities in Compliance with New Ordinance 

As discussed previously, inspections conducted at 134 of the 134 dental offices subject to the 

ordinance indicate that all dental offices have installed an amalgam separator. Therefore, we 

have confirmed 100% compliance with the amalgam separator requirement. 

Mercury concentration in a dental building cleanout and “dental area” trunk line before and after 

amalgam separator installations 

The RWQCP conducted sampling of a dental building cleanout and a sewer trunkline (in an area 

with numerous dental facilities and no residential inputs), in order to compare mercury 

concentrations before and after the installation of amalgam separators. The RWQCP selected 

two sites for this dental line sampling, as presented below: 

Sampling Locations Site Description 

Building cleanout on 

Welch Road, Palo Alto 

Large medical and dental building housing several dental offices as 

well as some medical clinic offices. The landlord provides shared 

vacuum systems for all the dental offices in the building. 

A trunkline on Welch 

Road, Palo Alto 

Manhole site is upstream from the building cleanout sampling 

location (due to safety concerns at the sampling location 

downstream of that address). This is downstream of numerous 

dental and medical facilities. There are no residential inputs to this 

sewer line. 

Wastewater samples were gathered at each of these locations via a standard 24-hour composite 

methodology – the same method used throughout the city for sanitary sewer pollutant analysis. 

Previously, we concluded that there was no significant difference in the mercury results pre- and 

post- sewer line cleaning. Therefore, there are two baseline data sets prior to the installation of 

amalgam separators. In order to compare the pre and post amalgam separator installation two 

more rounds of sampling occurred in September 2005 and November 2006, after the amalgam 

separators were installed. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 8 of 22 

2006 Annual Report of Activity – February 2007 

Figure 3 on the following page presents the sampling results. To interpret the data, first notice 

the logarithmic scale on the graph. 

Building Cleanout Results. The building cleanout results are represented by the open squares. 

There was a 90% reduction in the average mercury concentration in the building cleanout after 

amalgam separators were installed. This reduction was calculated by comparing an average of 12 

samples taken after separators were installed to an average of 24 samples taken prior to 

installation of separators. One would expect a very significant reduction, because the vacuum 

system at this building is a dry vacuum system. Wastes from dry vacuum systems do not pass 

through a vacuum screen before being discharged to the sanitary sewer, as is typical in a wet 

vacuum system. Therefore, at this monitoring site amalgam particles in the past were directly 

entering the sanitary sewer prior to installation of the amalgam separator. The new separator 

now captures these amalgam particles. Although the RWQCP’s industrial waste mercury local 

limit of 0.01 milligrams per liter is not applicable to dental offices, it is significant that all of the 

building cleanout sample results from the 2005-2006 sampling were lower than this value. 

Sewer Manhole Results. Mercury concentrations in samples collected from the sewer manhole in 

2005 and 2006 indicated a 37% reduction from the samples collected prior to amalgam separator 

installation. This reduction was calculated by comparing the average mercury concentration of 

15 samples after separators were installed to the average of 25 samples before this installation. 

Please note that this sewer manhole is located on the same street as the above building cleanout, 

but upstream of that building. 
City of Palo Alto Advanced Mercury Source Control Study Page 9 of 22 

2004 Annual Report of Activity – February 2005 

Palo Alto 2004-2006 Dental Cleanout and Manhole Data: 

Before and After Installation of Amalgam Separators

(Amalgam Separators Required March 31, 2005)

0.0001

0.001

0.01

0.1

1

1/14/2004 8/1/2004 2/17/2005 9/5/2005 3/24/2006 10/10/2006 

Sampling Date

[Hg], mg/L

Average residential line [Hg] = 0.00012 ppm

Average influent line [Hg] = 0.00038 ppm

IW discharge limit = 0.01 ppm

Pre Amalgam Separators Post Amalgam Se

Figure 3. Results of 2004-2006 Palo Alto Dental Cleanout and Sewer Trunkline Analyses (Raw data provid
 

City of Palo Alto Advanced Mercury Source Control Study Page 10 of 26

2005 Annual Report of Activity – February 2006 

Mercury in Influent, Effluent and Biosolids 

Figures 4 through 7 present RWQCP data on influent and effluent mercury mass loadings, 

influent and effluent mercury concentrations, and mercury concentrations in sludge cake prior to 

incineration. 

As shown in Figure 4, influent mercury loading decreased significantly in 2006. The 2006 

influent loading was 10 % lower than the 2005 influent loading and 38% lower than the 2004 

influent loading. Even though the 2006 influent loading had decreased within the past 5 years, 

even lower influent loadings were observed during some years in the late 1990s. Influent 

samples are collected on a weekly basis. 

With respect to influent data gathering, there is a data gap that needs to be acknowledged. 

Mercury amalgam particles are very dense, and are more likely to travel along the bottom of 

sewer pipes than to be suspended throughout the water column. Due to the configuration of the 

RWQCP influent sampling location, it is believed that some mercury amalgam particles would 

not be captured in the influent samples. These amalgam particles would not enter the RWQCP’s 

primary treatment process, but would be trapped in the “grit” channel at the headworks of the 

RWQCP. Because the grit is highly irregular, it is not feasible to conduct accurate, representative 

sampling. The grit is disposed of at a landfill, and its pollutant content has never been included in 

the various mass balances that have been conducted. Therefore, we recognize that there may be 

decreases in mercury content of that material that will continue to avoid detection. 

Figure 5 presents effluent mercury loading data. These annual average data are based upon 

monthly effluent samples. In 2005, the RWQCP’s effluent mercury loading dropped by 25% 

from the 2004 effluent loading. In 2006, the RWQCP’s effluent mercury loading continued to 

decline another 6% relative to 2005. The 2006 value represents the RWQCP’s lowest effluent 

mercury loading on record. 

Figure 6 presents effluent and influent mercury concentration data between 2000 and 2006. The 

concentration data display similar reductions to the loading data, as the RWQCP effluent flow 

rate was approximately equal in 2005 and 2006. 

Mercury concentrations in the RWQCP’s pre-incineration sludge cake are presented in Figure 7. 

These data are also based upon monthly samples displayed as 6 month rolling averages. Sludge 

cake mercury concentrations have declined since Fall of 2005. We expected a delay in the 

decline in the concentration in the sludge cake after the dental amalgam program. 

Overall, these data suggest that the RWQCP’s dental amalgam program is resulting in both 

influent and effluent mercury loading decreases. However, significant fluctuations in these 

loadings from year to year are common. Our analyses of 2007 data are expected to indicate 

whether the decreases observed in 2005 and 2006 can be attributed to the dental amalgam 

program. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 11 of 26

2005 Annual Report of Activity – February 2006 

0

10

20

30

40

50

198919901991199219931994199519961997199819992000200120022003200420052006

Year

Influent Loading (lbs/yr)

Figure 4. RWQCP Mercury Influent Loading: 1989-2005 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1996 1998 2000 2002 2004 2006

Year

Effluent Loading (lbs/yr)

RWQCP lab samples

independent ultraclean samples

Figure 5. RWQCP Mercury Effluent Loading: 1997-2005 

(effluent loading prior to 1997 are not shown, as loads were calculated using primarily non-detect data points)
 

City of Palo Alto Advanced Mercury Source Control Study Page 12 of 26

2005 Annual Report of Activity – February 2006 

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

19891990

19911992199319941995

1996

199719981999

2000200120022003

2004

20052006

Year

Hg Concentration ppb (Influent)

0.00

0.05

0.10

0.15

0.20

0.25

Hg Concentration ppb (effluent)

Hg Influent

Hg Effluent

Figure 6: RWQCP Mercury Influent and Effluent Concentrations: 1989-2006 

RWQCP Sludge Cake Mercury Concentration

(six-month rolling averages)

0

50

100

150

200

250

300

350

400

450

500

4/11/20018/11/2001

12/11/2001

4/11/20028/11/2002

12/11/2002

4/11/20038/11/2003

12/11/2003

4/11/20048/11/2004

12/11/2004

4/11/20058/11/2005

12/11/2005

4/11/20068/11/2006

Date

Mercury (ug/kg)

Due date for 

amalgam separator 

installation was 

3/31/05

Figure 7: RWQCP Sludge Cake Mercury Concentration: 2001-2006 (six-sample rolling 

average)
 

City of Palo Alto Advanced Mercury Source Control Study Page 13 of 26

2005 Annual Report of Activity – February 2006 

II. Part 2 – POTW Mercury Use Investigation 

A. Program Summary 

Pursuant to the August 2003 Discharge Order, the RWQCP was tasked with conducting a 

thorough investigation of the uses of mercury at the Plant. The investigation shall include the 

following: 

• An inventory of the mercury used at the Plant, focusing on switches and reagents, but 

including all uses 

• A listing of available non-mercury alternative products 

• Recommendations and a time schedule for action by Palo Alto where appropriate 

In accordance with the Santa Clara County Urban Run-off Program and associated stormwater 

discharge permit, the City of Palo Alto was required in 2002 to prepare an initial investigation of 

municipal mercury uses. This analysis included mercury uses at the RWQCP. The inventory is 

presented in Table 1, organized into three separate sections: lights, switches, and lab reagents. 

The list includes currently inventoried mercury-containing products, as well as the plan for 

action, as appropriate. 

 Figure 2. Some of the mercury alarm switches that were removed from service or pulled 

from storage at the RWQCP in 2002. All such switches are turned in to the City’s 

municipal hazardous waste collection for recycling. 

In 2005, the RWQCP reviewed these results and found no additional mercury-containing 

components to add to the list. If additional sources are identified in the future, the RWQCP will 

review applicability of alternative products and recommend any additional actions. 

As for previously identified products, the schedule is presented in Table 1. The primary items 

for which alternatives have been identified are mercury switches. In those cases, because there is 

no immediate pathway between the switches and the environment, the schedule involves 

removing mercury switches upon failure. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 14 of 26

2005 Annual Report of Activity – February 2006 

B. Program Evaluation 

Effectiveness of this program is measured by: 

• Numbers of switches collected and replaced 

• Adoption of a mercury-free alternative to the COD laboratory procedure 

• Further identification of other sources and alternatives 

RWQCP mercury replacement. Since 2002, RWQCP has replaced or removed 43 mercury 

switches (approximately 2.3 pounds) from the plant. Many of the switches that were recycled 

were not in service but were inventory in the shop and warehouse contributing to the large 

amount of mercury recycled in a short period of time. In 2005, the RWQCP replaced 6 switches 

within the plant that is approximately 100 grams of mercury. In 2006, there were no switches 

replaced within the treatment plant. 

COD laboratory procedures. There is a mercury-free method available, but it is not EPA 

certified. Due to this lack of federal certification, and possible chemical interferences, it may not 

be possible to use alternative methods. 

Identification of sources and alternatives. City staff identified an alternative float switch 

which is a non mercury bulb and is produced by the same manufacturers as the mercury 

switches. For other applications, such as temperature or pressure switches, there are a variety of 

techniques for replacement, usually by digitizing the signal and using logic to control a switch. 

In addition the RWQCP uses a Programmable Logic Controller (PLC) system to make contacts 

when necessary while monitoring a signal. These are usually a case by case modification rather 

than a universal replacement. Other situations arise where the switch is an integral part of an 

existing system that does not retrofit, such as the torque alarms on the clarifier sweeps. Nothing 

short of redesigning the sweep arms can replace the mercury switches; these will not be replaced. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 15 of 26

2005 Annual Report of Activity – February 2006 

Table 1. Inventory Results and Current Plans 

Product Use at 

RWQCP? 

Plan for Seeking 

Alternatives 

Lights 

Fluorescent Yes – 

common 

Now using low mercury 

lights – formally initiated in 

2001 

Metal halide (high intensity discharge lamps w/bluewhite light) None found 

High pressure sodium (yellow-white lights used for 

street lamps & outdoor security) 

Yes, common No current plan 

Mercury vapor lamps Yes – 

uncommon 

use (2-3 

only) 

No current plan 

Switches 

“Silent” wall switches (prior to 1991) None found Will replace any overlooked 

upon failure 

Wall-mounted office thermostat Yes – 6 to 10 Will replace upon failure 

Airflow/fan limit controls None found 

Building security systems None found 

Pressure control None found Will replace, upon failure, 

any overlooked devices and 

replace with Hg-free 

Torque-arm alarm switches Yes – about 

12 to 16 

Will not replace; integral 

part of existing torque arm 

Float control (used for sump pumps) Yes Will replace with Hg-free 

upon failure. 

Lab Reagents 

Pre-mixed test tubes for monitoring chemical oxygen 

demand (COD) 

Yes There is a mercury-free 

method available, but it is 

not EPA certified. Due to 

this lack of federal 

certification, and possible 

chemical interferences, it 

may not be possible to use 

alternative methods. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 16 of 26

2005 Annual Report of Activity – February 2006 

III. Future Tasks and Schedule 

Table 2 presents future tasks and schedule. Table 3 presents the required reporting schedule. 

Periodic updates and a final report shall be made to the Bay Area Pollution Prevention Group, 

the Regional Board, the Mid-Peninsula Dental Society and other stakeholders. A key feature of 

such reporting shall include effectiveness measures including mercury reductions achieved and 

lessons learned. 

Table 2: Schedule for Future Tasks 

Task Target Timeframe 

OUTREACH and INSPECTIONS 

Request maintenance records of amalgam separator March 2007 

Inspect 20% of dental offices each year June 2007 

PROGRAM EVALUATION 

Review biosolids, influent and effluent data pre- and postamalgam separator requirement November 2007 

POTW MERCURY USE 

Continue replacing mercury switches, upon failure. Continuing 

Table 3. Reporting Schedule 

Task Deadline 

Work plan. The Discharger shall submit a schedule and detailed 

work plan for the Advanced Mercury Source Control Program. 

Within 90 days 

after permit 

adoption 

Implementation of the workplan will begin within 30 days of the 

Executive Officer’s approval of the workplan. 

Progress Reports –For February 2006, this current document, 

submitted concurrently with Clean Bay Plan, is considered the 

progress report.

Annually, on 

February 28 

Final Report. The Discharger shall submit a final report 

presenting the results of the Advanced Mercury Source Control 

Program. 

December 15, 2007 
 

City of Palo Alto Advanced Mercury Source Control Study Page 17 of 26

2005 Annual Report of Activity – February 2006 

IV. Appendices 

 Ordinances from Cities of Mountain View and Palo Alto 

 Article in Articulator 

 Self-certification Forms 

o Form #2: Self-Certification of Amalgam Separator Installation 

 Table of Contents for Creating a Dental Amalgam Program CD-rom 

 Inspection Checklist 

 Raw sampling data 
 

City of Palo Alto Advanced Mercury Source Control Study Page 18 of 26

2005 Annual Report of Activity – February 2006 

Mountain View Dental Ordinance, Chapter 35, MVCC 

(R) Requirements for Dental Facilities that Remove or Place Amalgam Fillings. 

(a) Definitions. For the purposes of this section the following words and phrases shall be as 

defined herein. 

(1) “Amalgam separator” is a device that employs filtration, settlement, centrifugation, or ion 

exchange to remove amalgam and its metal constituents from a dental office vacuum system 

before it discharges to the sewer. 

(2) “Amalgam waste” means and includes non-contact amalgam (amalgam scrap that has not 

been in contact with the patient); contact amalgam (including, but not limited to, extracted teeth 

containing amalgam); amalgam sludge captured by chairside traps, vacuum pump filters, screens, 

and other amalgam trapping devices; used amalgam capsules; and leaking or unusable amalgam 

capsules. 

(3) “ISO 11143” is the International Organization for Standardization’s standard for amalgam 

separators. 

(b) All owners and operators of dental facilities that remove or place amalgam fillings shall 

comply with the following waste management practices: 

(1) No person shall rinse chairside traps, vacuum screens, or amalgam separators equipment in a 

sink or other connection to the sanitary sewer. 

(2) Owners and operators of dental facilities shall ensure that all staff members who handle 

amalgam waste are trained in the proper handling, management and disposal of mercurycontaining material and fixer-containing solutions, and shall maintain training records that shall 

be available for inspection by the fire chief or his designee during normal business hours. 

(3) Amalgam waste shall be stored and managed in accordance with the instructions of the 

recycler or hauler of such materials. 

(4) Bleach and other chlorine-containing disinfectants shall not be used to disinfect the vacuum 

line system. 

(5) The use of bulk mercury is prohibited. Only pre-encapsulated dental amalgam is permitted. 

(c) All owners and operators of dental vacuum suction systems shall comply with the following: 

(1) An ISO 11143 certified amalgam separator device shall be installed for each dental vacuum 

suction system on or before March 31, 2005; provided, however, that all dental facilities that are 

newly constructed on and after the effective date of this ordinance, shall include an installed ISO 

11143 certified amalgam separator device. The installed device must be ISO 11143 certified as 

capable of removing a minimum of 95 percent of amalgam. The amalgam separator system shall 

be certified at flow rates comparable to the flow rate of the actual vacuum suction system 

operation. Neither the separator device nor the related plumbing shall include an automatic flow 

bypass. For facilities that require an amalgam separator that exceeds the practical capacity of 

ISO 11143 test methodology, a non-certified separator will be accepted, provided that smaller 

units from the same manufacturer and of the same technology are ISO-certified. Alternative 

materials and methods may be proposed to the fire chief or his designee for approval. 

(2) Proof of certification and installation records shall be submitted to the fire chief or his 

designee within 30 days of installation. 

(3) Amalgam separators shall be maintained in accordance with manufacturer recommendations. 

Installation, certification, and maintenance records shall be available for immediate inspection 

upon request by the fire chief or his designee during normal business hours. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 19 of 26

2005 Annual Report of Activity – February 2006 

Palo Alto Dental Ordinance, Section 16.09 

16.09.112 Requirements for dental facilities that remove or place amalgam fillings. 

(a) Definitions. For the purposes of this section the following words and phrases shall be as 

defined herein. 

(1) “Amalgam separator” is a device that employs filtration, settlement, centrifugation, or ion 

exchange to remove amalgam and its metal constituents from a dental office vacuum system 

before it discharges to the sewer. 

(2) “Amalgam waste” means and includes non-contact amalgam (amalgam scrap that has not 

been in contact with the patient); contact amalgam (including, but not limited to, extracted teeth 

containing amalgam); amalgam sludge captured by chairside traps, vacuum pump filters, screens, 

and other amalgam trapping devices; used amalgam capsules; and leaking or unusable amalgam 

capsules. 

(3) “ISO 11143” is the International Organization for Standardization’s standard for amalgam 

separators. 

(b) All owners and operators of dental facilities that remove or place amalgam fillings shall 

comply with the following waste management practices: 

(1) No person shall rinse chairside traps, vacuum screens, or amalgam separators equipment in a 

sink or other connection to the sanitary sewer. 

(2) Owners and operators of dental facilities shall ensure that all staff members who handle 

amalgam waste are trained in the proper handling, management and disposal of mercurycontaining material and fixer-containing solutions, and shall maintain training records that shall 

be available for inspection by the superintendent or designee during normal business hours. 

(3) Amalgam waste shall be stored and managed in accordance with the instructions of the 

recycler or hauler of such materials. 

(4) Bleach and other chlorine-containing disinfectants shall not be used to disinfect the vacuum 

line system. 

(5) The use of bulk mercury is prohibited. Only precapsulated dental amalgam is permitted. 

(c) All owners and operators of dental vacuum suction systems, except as set forth in subsections 

(d) and (e) of this section, shall comply with the following: 

(1) An ISO 11143 certified amalgam separator device shall be installed for each dental vacuum 

suction system on or before March 31, 2005; provided, however, that all dental facilities that are 

newly constructed on and after the effective date of this ordinance shall include an installed ISO 

11143 certified amalgam separator device. The installed device must be ISO 11143 certified as 

capable of removing a minimum of 95 percent of amalgam. The amalgam separator system shall 

be certified at flow rates comparable to the flow rate of the actual vacuum suction system 

operation. Neither the separator device nor the related plumbing shall include an automatic flow 

bypass. For facilities that require an amalgam separator that exceeds the practical capacity of 

ISO 11143-test methodology, a non-certified separator will be accepted, provided that smaller 

units from the same manufacturer and of the same technology are ISO-certified. Alternative 

materials and methods may be proposed to the superintendent for approval, pursuant to 

16.09.165. 

(2) Proof of certification and installation records shall be submitted to the superintendent within 

30 days of installation. 

(3) Amalgam separators shall be maintained in accordance with manufacturer recommendations. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 20 of 26

2005 Annual Report of Activity – February 2006 

Installation, certification, and maintenance records shall be available for immediate inspection 

upon request therefor by the superintendent or designee during normal business hours. 

(d) Facilities with vacuum suction systems that meet all of the following conditions may apply to 

the superintendent for an exemption to the requirements of subsection (c) of this section: 

(1) The systems was installed before October 1, 2003. 

(2) The system is a dry vacuum pump system with an air-water separator. 

(3) The sedimentation tank is non-bottom draining, with the drain above the anticipated 

maximum level of accumulated sludge. 

(4) Evidence of regular pump outs (a minimum of once a year, or more often if either directed by 

the manufacturer or necessary to keep solids from exiting through the drain) is maintained and 

open to inspection by the superintendent during normal business hours. 

(5) The system has no direct discharge pipe to the sewer on the bottom of the sedimentation tank. 

An owner or operator whose facility meets conditions (1) through (5) may apply for this 

exemption by written letter to the superintendent. The superintendent or designee will review the 

system and, if the exemption is approved, shall provide a written letter of exemption. An 

exemption obtained pursuant to this subsection (d) shall expire upon installation of a new 

vacuum system. Upon expiration of the exemption, the facility shall comply with subsection (c) 

of this section before commencing further operation. 

(e) The following types of dental practice are exempt from this section 16.09.112, provided that 

removal or placement of amalgam fillings occurs at the facility no more than 3 days per year: (1) 

Orthodontics; (2) Periodontics; (3) Oral and maxillofacial surgery; (4) Radiology; (5) Oral 

pathology or oral medicine; (6) Endodontistry and prosthodontistry. 
 

City of Palo Alto Advanced Mercury Source Control Study Page 21 of 26

2005 Annual Report of Activity – February 2006 

Dentists Help Reduce Amount of Mercury Entering the Bay! 

The Regional Water Quality Control Plant (RWQCP) would like to thank dentists in East Palo 

Alto, Los Altos, Mountain View, and Palo Alto for their compliance with the new amalgam 

separator requirements. For the past six years the RWQCP, in cooperation with the MidPeninsula Dental Society and the California Dental Association, worked to identify ways to 

decrease the amount of amalgam entering the treatment plant. Based on research and 

collaborative discussions, the RWQCP required dental offices to implement a set of Best 

Management Practices and to install an amalgam separator by March 31, 2005. 

As of November 2006, inspections 

have confirmed that all dentists in our 

service area have installed an 

amalgam separator (see figure to the 

right). Since the installation of 

amalgam separators, the RWQCP has 

measured a 94 percent reduction in 

the average mercury concentration 

from a local dental office and a 64 

percent reduction in a city sewer line 

downstream of multiple dental 

offices! Most importantly, the 

RWQCP has seen decreases in the 

mercury concentrations in its plant 

influent, its sludge cake prior to incineration, and its effluent to the Bay. Sludge cake mercury 

concentration (see figure below) is the best indicator of mercury decreases at the treatment plant, 

because the great majority of the mercury in the treatment plant is associated with solids that 

become sludge. 

The RWQCP is delighted with the success of the program, and we owe our thanks to the local 

dentists. Dentists should be proud that their amalgam management program has reduced the 

amount of mercury entering the 

Bay. Thanks again for the good 

work! 

For more information about 

mercury in the environment, 

amalgam waste haulers, or on-site 

collection devices, see: 

http://www.cityofpaloalto.org/publi

c-works/cb-dental.html, or contact 

Karin North, RWQCP Amalgam 

Program Manager at (650) 494-

7629 or Karin.north@cityofpaloalto.org

Mercury in RWQCP Sludge Cake

(six-month rolling average)

0

50

100

150

200

250

300

350

400

450

500

4/11/2001

10/11/2001

4/11/2002

10/11/2002

4/11/2003

10/11/2003

4/11/2004

10/11/2004

4/11/2005

10/11/2005

4/11/2006

10/11/2006

Date

Mercury (ug/kg)

Progress over time with amalgam 

separator installation

0

20

40

60

80

100

120

Before 2003

In 2004

Jan-05

Feb-05

Mar-05

Apr-05

May-05

Jun-05

Jul-Dec 2005

In 2006

# amalgam separators 

installed

0.00%

20.00%

40.00%

60.00%

80.00%

100.00%

Percent Compliance

# separators

installed

Percent

compliance
 

City of Palo Alto Advanced Mercury Source Control Study Page 22 of 26

2005 Annual Report of Activity – February 2006 

 

SAMPLE OF "FORM #2" TO INDICATE 

INSTALLATION OF AMALGAM SEPARATOR

Self-Certification of Amalgam Separator Installation 

Return completed form within 30 days of installation 

V. SECTION 1 – BUSINESS NAME AND ADDRESS 

Name of dental practice: 

Site address: 

SECTION 2 – AMALGAM SEPARATOR EQUIPMENT 

Manufacturer Name: 

Equipment Model: 

ISO Standard 11143 Certification Number: 

Installation Date: 

Maintenance Frequency: 

A. CERTIFICATION 

I certify under penalty of law that the information provided above fully describes the dental amalgam 

separator used by the dental practice at the present time. 

I certify that this document and all attachments were prepared under my direction or supervision in 

accordance with a system designed to ensure that qualified personnel properly gather and evaluate the 

information submitted. Based on my inquiry of the person or persons who manage the system, or those 

persons directly responsible for gathering the information, the information submitted is to the best of my 

knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for 

submitting false information, including the possibility of fine and imprisonment for knowing violations. 

Printed Name Title 

Signature Date 

Return completed form to: 

Amalgam Recovery Program, RWQCP, 2501 Embarcadero Way, Palo Alto, CA 94303 
 

City of Palo Alto Advanced Mercury Source Control Study Page 23 of 26

2005 Annual Report of Activity – February 2006 

SAMPLE of "Inspection Checklist" 

Contact Person for this office: 

Address: Phone: 

Who is the responsible party for amalgam separator? 

Who is the responsible party for waste silver hauling? 

Inspector: Date: 

Business Name 

(Corporation) Dentists At Office 

Share an 

Amalgam 

Separator

Share Silver 

Hauling 

 

(Continue on back) 

1. Amalgam Waste Management Data 

Required Waste Management Practices Applicable Not Applicable [Explain] 

Does Office Comply? 

Yes No 

 [1] Do not rinse chairside traps, vacuum screens, and amalgam separator 

equipment in a sink or other sanitary sewer connection. [Sewer Ordinance 

16.09.112(b)(1)] 

 [2a] Train staff annually in proper handling and disposal of amalgam materials and 

fixer-containing solutions.

 [2b] Keep record of this staff training. [16.09.112(b)(2)] 

 [3] Store amalgam waste in accordance with instructions of the recycler or hauler. 

For example, a practice may use a large well-sealed plastic container to hold used 

chairside traps, vacuum screens, amalgam separator wastes, used capsules, and 

other amalgam wastes for recycling. [16.09.112(b)(3)] 
 

City of Palo Alto Advanced Mercury Source Control Study Page 24 of 26

2005 Annual Report of Activity – February 2006 

 [4] Use a vacuum line disinfectant that does not contain bleach or other chlorinecontaining disinfectant. [16.09.112(b)(4)] 

 [5] Use pre-measured amalgam capsules. Use of bulk mercury is prohibited. 

[16.09.112(b)(5)] 

Comments Regarding Amalgam Waste Management Practices 

 

Required Amalgam Separator Applicable Not Applicable [Explain] 

Manufacturer: Model: 

Vendor: Date Installed: 

Separator Location: Maintenance By: 

Amalgam Waste Hauler: Separator Waste Hauler: 

Does Office Comply? 

Yes No 

 [7a] Install an ISO-11143 Certified Amalgam Separator Device in the office vacuum 

system. This device is certified as removing a minimum of 95% of amalgam. 

[16.09.112(e)(1)] 

 [7b] The amalgam separator system is certified at flow rates comparable to the 

actual flow rate of the office's vacuum suction system. [16.09.112(e)(1)] 

 [7c] Neither the separator device nor the related plumbing include an automatic 

flow bypass. [16.09.112(e)(1)]

 [8] Amalgam separator is maintained in accordance with manufacturer's 

recommendations. [16.09.112(e)(3)] 

 [9] Amalgam waste is hauled offsite in accordance with state hazardous waste 

laws. 

Comments Regarding Amalgam Separator 
 

City of Palo Alto Advanced Mercury Source Control Study Page 25 of 26

2005 Annual Report of Activity – February 2006 

 

B. 2. Photographic Waste Management Data 

Describe how x-ray processing wastes are disposed of (Check all that apply): 

 Scrap Used Fixer 

 Film Fixer Rinse 

• • • [1] Placed in a container for pick up by recylcer 

• • • [2] Placed in a container & taken to household hazwaste

• • • [3] Treated on-site

• • • [4] Discharged to sewer

• • ••• [5] Placed in trash

• • • [6] Other: 

Amount of fixer waste generated last year: gal 

Name of waste hauler that takes fixer: 

Comments Regarding Photographic Wastes 

 
 

City of Palo Alto Advanced Mercury Source Control Study Page 26 of 26

2005 Annual Report of Activity – February 2006 

Mercury Sampling at Dental Facilities, Palo Alto, 2004-2006

Sampling method: standard 24-hour composite sampling method, the same method used for trunkline 

measurements through the service area. 

Pre Amalgam Separators Post Amalgam Separators 

Date 

Dental Building 

Cleanout (mg/L) 

Dental Area 

Manhole (mg/L) Date 

Dental Building 

Cleanout (mg/L)

Dental Area Manhole 

(following sewer line 

cleaning) (mg/L) 

3/8/2004 0.06 0.0019 9/19/2005 0.0006 0.0005 

3/9/2004 0.012 0.00025 9/20/2005 0.00023 

3/10/2004 0.019 0.0015 9/21/2005 0.0028 0.0007 

3/11/2004 0.0053 0.0006 9/22/2005 0.0086 0.0004 

3/12/2004 0.049 0.00041 9/23/2005 0.00026 

3/16/2004 0.0087 0.0018 9/24/2005 

3/17/2004 0.353 0.0028 9/25/2005 0.00026 

3/18/2004 0.06 0.0021 9/26/2005 0.0024 0.0007 

3/22/2004 0.059 0.0011 9/27/2005 

3/23/2004 0.016 0.0009 9/28/2005 0.0049 0.00035 

3/24/2004 0.012 0.0012 9/29/2005 0.00049 

3/25/2004 0.039 0.004 11/13/2006 0.016 0.0006 

6/14/2004 0.02 0.0022 11/14/2006 0.0031 0.00038 

6/15/2004 0.026 0.00038 11/15/2006 0.0006 

6/16/2004 0.0062 0.00048 11/17/2006 0.0036 0.0007 

6/18/2004 0.051 0.0005 11/27/2006 0.017 0.0029 

6/21/2004 0.05 0.0005 11/28/2006 0.0033 0.0031 

6/22/2004 0.0049 0.001 11/29/2006 0.0031 0.00037 

6/23/2004 0.0043 0.001 11/30/2006 0.016 

6/24/2004 0.014 0.0022 

6/25/2004 0.45 0.00045 

6/28/2004 0.116 0.0006 

6/29/2004 0.04 0.0022 

6/30/2004 0.161 0.001 

7/1/2004 0.0011 

Average 0.068183 0.0012868 0.006783333 0.000818667

St dev 

0.110055 0.000916778

 0.006059078 0.00089965

2005 Influent Data (for comparison 

purposes) 

Date mg/L 

January-05 0.00026

February-05 0.00021

March-05 0.00019

April-05 0.00023

May-05 0.00027

June-05 0.00024

July-05 0.00027

August-05 0.0002

September-05 0.00025

October-05 0.00021

November-05 0.0021

December-05 0.00018

Average 0.000384167

Std Deviation 0.000541