Massachusetts MassDEP
Massachusetts environmental lab certification, MassDEP and the CAM.
How MassDEP certifies labs under 310 CMR 42.00, how reciprocity and PFAS rules work, and the calibration criteria the Compendium of Analytical Methods sets for cleanup data.
At a glance
How environmental lab certification works in Massachusetts.
Massachusetts is not a NELAP state. MassDEP certifies water labs under its own regulation, and its Compendium of Analytical Methods sets data quality expectations for site cleanup data under the Massachusetts Contingency Plan.
State program (non-NELAP)
- Program
- Laboratory Certification Program, Division of Environmental Laboratory Sciences, MassDEP, at the William X. Wall Experiment Station
- Legal basis
- 310 CMR 42.00, Certification and Operation of Environmental Analysis Laboratories
- Matrices
- Potable water (drinking water supplies) and non-potable water analyzed under 40 CFR Part 136. Chemistry and microbiology for both.
- NELAP status
- Not a NELAP accreditation body. MassDEP applies 310 CMR 42.00 with the EPA methods.
- Out-of-state labs
- Certificates may be issued in a comparable classification, without an inspection, to labs certified by EPA or by their resident state under standards at least as stringent as 310 CMR 42.00 (310 CMR 42.16). MassDEP guidance from June 2020 accepts NELAP accreditation for PFAS only when the resident state does not certify PFAS.
- Cleanup data
- The Massachusetts Contingency Plan (310 CMR 40.0000) and the Compendium of Analytical Methods (CAM) set analytical and calibration expectations for site cleanup data
- PFAS in drinking water
- Interim policy BWR/DWP 2024-01 accepts EPA Method 533 and 537.1 results only from labs EPA has approved under UCMR 5, and states NELAP accreditation is not an acceptable alternative. It expires when MassDEP amends 310 CMR 22.07G.
The accreditation cycle
The Massachusetts certification cycle.
The steps below summarize 310 CMR 42.00 and MassDEP’s current PT policy.
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Apply by analyte and method
Apply for certification in potable or non-potable water for each analyte and method your lab reports.
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One-year certificate
Certificates are valid for one year (310 CMR 42.09).
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Proficiency testing
At least one PT per calendar year for each certified analyte by each method, with results due by December 31 (policy WES-2026.001, effective June 3, 2026).
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Inspections
At MassDEP’s discretion (310 CMR 42.07).
Initial calibration
What auditors check in your initial calibrations.
Massachusetts sets calibration expectations in two places: the certification regulation for water labs, and the CAM for data used under the Massachusetts Contingency Plan.
A range that brackets what you report
The lowest standard should sit at or below your reporting limit and the highest at or above the top concentration you report. Results outside the calibrated range need to be qualified.
Error at the low end, not r² alone
A correlation coefficient of 0.999 can still hide a low standard that back-calculates 30 percent off. Auditors look at relative error, especially at the lowest levels.
Records that rebuild the curve
Raw responses, the model and weighting used, any excluded points with the reason, and the verification that followed. An auditor should be able to reconstruct every initial calibration from the record.
Calibration criteria in the CAM
For VOCs by GC/MS, CAM II A sets “%RSD <20 (average RFs), r >0.995 (linear regression), or r2 >0.99 (non-linear regression),” with continuing calibration %D below 20 for most analytes.
Source: MassDEP CAM II A, VOCs by GC/MS, Revision 2
310 CMR 42.08 also requires that instruments be calibrated immediately prior to analysis using a blank and at least three standards that bracket the expected concentration range, unless the method says otherwise. For PFAS by EPA 1633, CAM X A requires at least six standards when average response factors are used.
Self-check
Are your initial calibrations ready for a Massachusetts assessment?
Tick what your lab could show an auditor today. Nothing you select is saved or sent anywhere.
6Checks to work through
Select each item your lab could show an auditor today.
A self-assessment to help you prepare, not a compliance determination.
Massachusetts specifics
The CAM puts the calibration criteria on paper.
For cleanup data under the Massachusetts Contingency Plan, the Compendium of Analytical Methods spells out what a defensible calibration looks like, method by method. A lab that meets the CAM’s performance standards and documents it can support a claim of presumptive certainty for its data.
The criteria are familiar, but they are explicit: RSD limits for response factor calibrations, correlation thresholds for linear and nonlinear fits, continuing calibration limits, and minimum standard counts for newer methods like EPA 1633. Every one of them is something a data reviewer can check against your raw data.
MassDEP updated the CAM through 2026, with a revised overview effective June 30, 2026, Revision 1 of the PFAS module for EPA 1633 (CAM X A, January 29, 2026), and a new private well PFAS module for EPA 533 (CAM X B, September 30, 2026). It also issued a new chemistry PT policy effective June 3, 2026.
How WLTR helps
Calibration evidence ready for MassDEP and MCP data review.
WLTR independently reviews the calibration your instrument software produced. Your analyst still makes the final call. What changes is that the evidence is complete, consistent across analysts, and ready before the auditor asks for it.
- Each analyte reviewed one at a time in the instrument software.
- The model and weighting are whatever the batch was processed with.
- r² is the number most people look at, even though it does not measure error at the low end.
- QA signs off without an independent check on the curve.
- Every analyte and every candidate model side by side in the Calibration Intelligence dashboard.
- Diagnostics run automatically and the best fit curve is identified, with the reasons recorded.
- Relative error at every level, including the lowest standard, shown on one screen.
- A traceable record your QA manager can review, sign and hand to a MassDEP reviewer.
See how your curves measure against the CAM and against every candidate model, with the low end on the same screen.
Questions
Massachusetts accreditation FAQs
Is Massachusetts a NELAP state?
No. MassDEP certifies labs under its own regulation, 310 CMR 42.00, and is not a NELAP accreditation body.
What does MassDEP certify?
Chemistry and microbiology for potable water and for non-potable water analyzed under 40 CFR Part 136.
Can an out-of-state lab be certified in Massachusetts?
Yes. Under 310 CMR 42.16, MassDEP may certify a lab in a comparable classification without an inspection if the lab is certified by EPA or its resident state under standards at least as stringent as 310 CMR 42.00. MassDEP guidance from June 2020 accepts NELAP accreditation for PFAS only when the resident state does not certify PFAS.
What is the CAM?
The Compendium of Analytical Methods is MassDEP’s set of analytical and quality control requirements for data used under the Massachusetts Contingency Plan, including initial and continuing calibration criteria for each method.
What calibration criteria does the CAM set for VOCs?
CAM II A sets less than 20 percent RSD for average response factors, r above 0.995 for linear regression or r² above 0.99 for nonlinear regression, and continuing calibration percent difference below 20 for most analytes, with higher limits for designated difficult analytes.
Sources
Primary sources for this page.
- MassDEP, certified laboratories (opens in a new tab)
- MassDEP Compendium of Analytical Methods (CAM) (opens in a new tab)
- MassDEP memorandum on the revised 310 CMR 42.00 (June 2020) (opens in a new tab)
- 310 CMR 42.00 (opens in a new tab)
- MassDEP CAM I, overview (effective June 30, 2026) (opens in a new tab)
- MassDEP CAM II A, VOCs by GC/MS (opens in a new tab)
- MassDEP policy BWR/DWP 2024-01, PFAS drinking water testing (opens in a new tab)
- MassDEP policy WES-2026.001, chemistry proficiency testing (opens in a new tab)
This page summarizes public program information to help labs prepare. Requirements change, and the agency’s current rules and guidance always take precedence. WLTR is not affiliated with or endorsed by the Massachusetts Department of Environmental Protection. Spot something out of date? Tell us at admin@wltr.tech.
Before your next assessment
See your Massachusetts ICALs the way a data reviewer will.
Bring a recent initial calibration. We will walk you through every analyte and candidate model in the Calibration Intelligence dashboard, the best fit, and the record your QA manager would sign.
Request a demoHow the methodology works
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