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GSA7 min readUpdated June 7, 2026

SIN 541620: Environmental Consulting Services Guide for GSA MAS

A Refresh 32 guide to GSA MAS SIN 541620, Environmental Consulting Services, including category fit, NAICS/PSC context, max order, TDR/OLM status, and offer preparation notes.

Built for
Contractors mapping offerings, pricing support, catalog files, labor categories, or Add SIN modifications to official GSA MAS scope
By the end
Understand where SIN 541620 fits and what evidence to prepare before using it in an offer or modification.
Field guide

When SIN 541620 fits

Scope fit
A close-looking SIN can still be wrong if the subcategory, PSC, NAICS, or deliverable story points elsewhere.
Signal
541620 Services include providing advice and assistance to businesses and other organizations on environmental issues, such as the control of environmental contamination from pollutants, toxic substances, and hazardous materials; endangered species, wetland, watershed, and other natural resource management plans; Archeological and/or cultural resource management plans. This includes identifying problems (e.g., inspect buildings for hazardous materials), measure and evaluate risks, and recommend solutions. Multi-disciplined staff of scientists, engineers, and other technicians with expertise in areas, such as air and water quality, asbestos contamination, remediation, ecological restoration, and environmental law such as Planning and Documentation Services for the development, planning, facilitation, coordination, and documentation of and/or for environmental initiatives. NOTE: Services under this SIN cannot include architect-engineer services as defined in the Brooks Act and FAR Part 2, or construction services as defined in FAR Parts 2 and 36 (GSA Class Deviation RFO-2025-36).
Response
Compare the buyer's requirement to the official SIN language before forcing the opportunity into a familiar lane.
Service proof
Service SINs can create labor-category, qualifications, worksite, and rate-support questions.
Signal
The SIN supports service work, labor categories, deliverables, and pricing support.
Response
Prepare labor category descriptions, service narratives, past performance, FCP Services Plus data, and pricing support.
Modification path
Adding a SIN can affect catalog files, service descriptions, pricing support, and buyer-facing records.
Signal
The contractor wants to add this SIN after award or adjust offerings tied to it.
Response
Use the Add SIN and Add Product/Labor Category modification pages to plan scope, price, and evidence changes.
Refresh 32

SIN 541620 quick facts

A compact view of the official SIN record from the user's Refresh 32 MAS offerings workbook.

Category
Professional Services
Environmental Services
NAICS
541620
NAICS codes associated with the SIN in the workbook.
PSC
F999
Product Service Code mapped to the SIN.
Max order
$1,000,000
Ordering threshold for seeking additional price reductions.
Part 1

What SIN 541620 covers

541620 Services include providing advice and assistance to businesses and other organizations on environmental issues, such as the control of environmental contamination from pollutants, toxic substances, and hazardous materials; endangered species, wetland, watershed, and other natural resource management plans; Archeological and/or cultural resource management plans. This includes identifying problems (e.g., inspect buildings for hazardous materials), measure and evaluate risks, and recommend solutions. Multi-disciplined staff of scientists, engineers, and other technicians with expertise in areas, such as air and water quality, asbestos contamination, remediation, ecological restoration, and environmental law such as Planning and Documentation Services for the development, planning, facilitation, coordination, and documentation of and/or for environmental initiatives. NOTE: Services under this SIN cannot include architect-engineer services as defined in the Brooks Act and FAR Part 2, or construction services as defined in FAR Parts 2 and 36 (GSA Class Deviation RFO-2025-36).

The official record maps this SIN to NAICS 541620 and PSC F999. Those codes are not the whole strategy, but they help explain how the offering is categorized for buyers and reviewers.

Part 2

How to prepare the offer story

For service-oriented SINs, keep the service description, labor categories, pricing support, and past-performance examples aligned. A reviewer should be able to see what work is being sold, who performs it, and why the rate story is defensible.

If the SIN is being added through eMod, write down what changes operationally: new scope, new pricing, new files, catalog impact, and who owns maintenance after approval.

Part 3

Buyer and SEO language to keep straight

Use the SIN number, title, category, and subcategory together: SIN 541620 - Environmental Consulting Services - Professional Services - Environmental Services. That combination helps a buyer understand the lane quickly and helps the page avoid becoming a vague keyword page.

When writing capability language, explain the actual deliverables and evidence. Do not make the SIN carry the whole message by itself.

Examples

What this looks like in practice

Real-world checkHow to test SIN 541620 before building files

Start with the official title and description: Environmental Consulting Services sits under Professional Services > Environmental Services. Then compare your actual commercial offering to that scope, not only to the NAICS code.

If the fit still looks strong, build the proof stack: offering description, pricing support, past performance or product support, and any SIN-specific files the current GSA instructions require.

  • Confirm scope language.
  • Check NAICS and PSC signals.
  • Match the pricing file to the offering type.
  • Keep the support package reviewer-friendly.

Frequently asked questions

Is SIN 541620 part of TDR?

The Refresh 32 workbook marks TDR as Y for this SIN. GSA states that TDR became mandatory across MAS SINs with Refresh 31, so contractors should still verify current contract reporting instructions in official GSA sources.

Can order-level materials be used with SIN 541620?

The workbook marks OLM as Y. OLM treatment should always be verified against the current MAS solicitation, mass modifications, and contract-specific instructions.

Should I pick a SIN only because the NAICS matches?

No. NAICS helps, but SIN selection should be based on the actual offering, official SIN description, category/subcategory, pricing files, and buyer acquisition path.