Our recommendation: treat the park as a park that sits on top.

40 CFR 761.61(c) Risk-Based Pathway

40 CFR 761.61 governs the cleanup and disposal of PCB remediation waste under the Toxic Substances Control Act. It provides three pathways:

• (a) Self-implementing — risk-based cleanup using numerical standards keyed to land use. No EPA pre-approval; notification required. The regulation constrains how this can be used at or adjacent to high-occupancy areas such as parks, playgrounds, and day care centers.
• (b) Performance-based — specific numerical cleanup standards. For high-occupancy areas, PCBs must be reduced to levels specified in the regulation, typically with cap and deed-notice conditions above the unrestricted level.
• (c) Risk-based disposal approval — any method the EPA Regional Administrator finds will “not pose an unreasonable risk of injury to health or the environment.” Requires written EPA approval before cleanup activity begins.

The regulation itself is the primary source above. The working application skeleton at raw/moonshots.boston/research/homeworld-bio/761-61c-application-skeleton.md is credible-secondary; it is an internal research memo, not a filed document.

What 761.61(c) does

Section 761.61(c) allows EPA to approve an alternative method for PCB remediation waste on a case-by-case basis. The statutory test is “unreasonable risk.” EPA has discretion to approve or deny. The Parker Street / McCoy Field approval in New Bedford, Massachusetts (issued by EPA Region 1 in 2005) is the closest Massachusetts precedent for a 761.61(c) approval, and it was for conventional excavation with institutional controls, not for bioremediation.

See regulatory pathway for the formal claims drawn from the regulation, each of which carries an LCS level.

What 761.61(c) does not do

• It does not delegate PCB authority to states. Massachusetts has an Executed Cooperative Agreement with EPA for many hazardous waste programs, but PCB authority under TSCA Section 6(e) is non-delegable. PCB cleanup decisions are federal.
• It does not guarantee approval. EPA may request additional information, impose conditions, or deny. There is no shot clock on a 761.61(c) decision.
• It does not authorize bioremediation as a pre-approved method. As of 2026-04-13 there is no known precedent for a 761.61(c) approval using bioremediation as the primary remedy for PCBs. A Gold Star application would be first-of-kind on that dimension.
• It does not replace Massachusetts Contingency Plan obligations, Chapter 21E liability, or MassDEP oversight of non-PCB fractions of the contamination (lead, PAHs, metals). Those remain in force in parallel.

What the pathway would require if pursued

From the regulation itself (paraphrased into a checklist; see the skeleton memo for the longer treatment):

1. A written application to the EPA Regional Administrator in Region 1.
2. Nature of contamination and description of contaminated materials.
3. Summary of sampling procedures and analytical methods.
4. A cleanup site map showing PCB concentrations across the site.
5. Description of the cleanup plan, including schedule, disposal technology, and approach.
6. Written certification signed by the property owner and the cleanup party.
7. Any additional information EPA believes necessary to evaluate the application.

These requirements are drawn from the regulation. Nothing in the 761.61(c) concept article should be read as a claim that any of the above exists for Gold Star Mothers Park. None of the listed items has been drafted in final form, and no application has been filed.

Posture for Gold Star Green

The coalition’s current posture (see coalition investor model and the partner-facing coalition proposal) is that a feasibility study could, at most, produce the evidence package that would let a counsel and engineer of record decide whether a 761.61(c) application is even advisable. The decision to file belongs to the City of Cambridge as property owner, not to any coalition partner. Nothing about the project is authorized to act as a filer of record.

Related

• regulatory pathway — the claims form with LCS levels.
• gold star mothers park — the site case file.
• park roof typology — the architectural concept that would, under one scenario, sit on top of any 761.61(c)-approved in-situ chamber.

Coalition Investor Model

Gold Star Green describes itself as a coalition project, not a funding round. The distinction matters because as of 2026-04-13 there is no authorized remediation, no filed 40 CFR 761.61(c) application, no revocable access license granted by the City of Cambridge, and no current offering of securities. The coalition model is the public vocabulary for how a project in this state invites participation.

The coalition model is designed to underwrite Santa Prosper’s recommended path — the Lid Park — but it is not locked to that single option. Six other community-surfaced futures for Gold Star Mothers Park live at /options on thelittledig.org, and the coalition structure described here could underwrite any of them if Cambridge chooses a different path. The model is about how a civic project in pre-authorization state invites participation, not about which specific design ends up on the site.

This article describes the model at the concept level. The full coalition proposal lives under partners/coalition-proposal.md and is currently private-review pending counsel review. Nothing below should be read as an offer of a security or a commitment to raise funds.

Four tracks

The April 12 diff pack (see source) describes four participation tracks for the public campaign:

1. Residents and neighborhood supporters — sign and follow.
2. Scientific and engineering partners — universities, labs, and consultants who can contribute methodology review.
3. Foundation and agency partners — foundations, agencies, and programs that fund environmental work.
4. Investor interest — a separate, explicitly non-solicitation track that uses Reg CF Rule 206 testing-the-waters language, with no SAFE, no commitment tier, and a required disclosure legend.

Only the first three are public-facing in the v1 coalition language. See cambridge coalition graph for the entity graph and epa region 1 and tufts cee for specific entity stubs.

Reg CF Rule 206 posture

The April 12 reframe replaced an earlier “SAFE Commitment” investor tier with a “Non-Binding Indication” tier and added the required 17 CFR 227.206 disclosure:

No money or other consideration is being solicited, and if sent in response, will not be accepted. No offer to buy the securities can be accepted and no part of the purchase price can be received until the offering statement is filed and only through an intermediary’s platform. A person’s indication of interest involves no obligation or commitment of any kind.

This is a testing-the-waters posture under Regulation Crowdfunding. It is not a safe harbor that authorizes sales. See the contamination data, regulatory pathway, and engineering feasibility claims articles for what is and is not currently supported by primary sources.

Revocable access license

The proposed structure for field access to Gold Star Mothers Park, should a pilot ever proceed, is a revocable access license from the City of Cambridge to a qualified operator — not a lease, not a sale, not an SBIR-style engagement. A term sheet draft exists in raw/moonshots.boston/research/homeworld-bio/revocable-access-license-term-sheet.md; no license has been proposed to or granted by the City as of 2026-04-13.

What this concept does not claim

• No entity has committed funds to Gold Star Green.
• No foundation has approved a grant for the project.
• No city agency has authorized or endorsed the project.
• No securities offering is open or pending.
• No investor has signed anything.

All entity relationships described in cambridge coalition graph are either “historical” (research the entity has already published), “proposed” (a conversation or outreach has occurred), or “active regulator” (the entity has jurisdiction regardless of the project’s posture).

Related

• park roof typology — the architectural frame the coalition is asked to underwrite.
• 761 61c pathway — the regulatory pathway the coalition would need to help fund a feasibility study for.
• observable land — the accompanying data-governance concept.

Observable Land

“Observable land” is the concept that the same data posture the Proffer platform applies to commitments — visible, time-stamped, independently checkable, with source traceability — should apply to a contaminated parcel that the public actually lives next to.

The thing being observed

At Gold Star Mothers Park, the primary observables are:

• Soil sampling data as released by the City of Cambridge Department of Public Works. See contamination data for the re-extracted table, and the verified-against list in that article for the PDF sources.
• Groundwater sampling data as released by Cambridge DPW (see raw/pdfs/groundwater-summary.pdf and raw/pdfs/groundwater-full-data.pdf).
• The regulatory status of the site under TSCA and under Massachusetts Contingency Plan filings (RTN 3-52413 for the overall park and RTN 3-52198 for the basketball court). See regulatory pathway.
• The City of Cambridge public communications log — community notices, flyers, and the October 16, 2025 community meeting slide deck (all in raw/pdfs/).

Each observable in the KB is cited back to a primary source file under kb/gold-star-green/raw/. No contamination number enters the KB without a verified-against PDF path.

Why observability is the concept and not transparency

“Transparency” describes a property of a document. “Observability” describes a property of a system: a set of signals, a sampling discipline, a publish cadence, and a shared schema that lets anyone reproduce a conclusion.

For this project the implication is concrete:

• Raw source files are ingested into raw/ and never modified.
• Numeric values are re-extracted from PDFs before they are placed in a claim article, not transcribed from earlier working documents. See the contamination data article body for discrepancies that this rule surfaced during compilation.
• Every claim article in claims/ carries a confidence value and (where applicable) an lcs legal-confidence level.
• Disagreements between sources are preserved in article bodies, not resolved silently.

Connection to the Proffer platform

The Proffer platform is, in one framing, a mechanism for making commitments observable. Applying the same mechanism to a parcel of land is a small move: the observables are samples instead of commitments, but the discipline is the same. See kb/proffer/wiki/concepts/protocol-v2-roadmap.md for the broader observability theme in the Proffer KB. This article is a narrow specialization of that theme to contaminated urban land.

What this concept does not claim

• Observability is not a remediation method. It does not clean the site.
• Observability is not a regulatory pathway. It does not substitute for the 40 CFR 761.61(c) process or for MCP filings.
• Observability does not imply the City has adopted this posture. The City of Cambridge has published primary data; that is the City’s action, not a Gold Star Green action.

Related

• contamination data — the re-extracted numeric record.
• regulatory pathway — the legal record.
• cambridge coalition graph — the entity record.
• park roof typology — the architectural record.

Park-Roof Typology

Park-roof is the pattern of placing a public park on the roof of a structure the city cannot or will not move out of the way. The park is the visible civic surface; the structure underneath is the honest acknowledgement that whatever sits there is not going away soon.

The shape of the pattern

A park-roof project has three layers, in order from the sky down:

1. A public park surface — trees, benches, play area, paths, planting beds.
2. A structural slab that carries park loads and separates the park from whatever is below.
3. A zone below the slab that does a job the neighborhood cannot tolerate as an open pit: active rail, a highway trench, an underground remediation chamber, a utility corridor, or contaminated fill that has not yet been removed.

Park-roof is a typology because the same diagram recurs whether the thing below is active freight (Millennium Park in Chicago), a sunken highway (Klyde Warren Park in Dallas), a decommissioned elevated rail (The High Line in New York), or urban fill awaiting remediation (the concept examined here for Gold Star Mothers Park in Cambridge).

See high line, millennium park, and klyde warren park for case-specific treatment.

Why it applies to Gold Star Green

Gold Star Mothers Park sits on fill left in place after the 1963 Squire’s meatpacking fire. The City of Cambridge has appropriated $1M from Free Cash and described a total excavation estimate of roughly $10M (see gold star mothers park and contamination data). Excavation cannot begin until EPA completes its review of the PCB-bearing fraction of the work under TSCA.

The park-roof frame allows the project to say two things at once:

• The park comes back. The community gets a usable surface sooner than a full excavate-and-replace schedule would allow.
• The work below the slab is decoupled from the schedule above it. If the City excavates, the dig becomes the basement of the structure. If the City chooses a risk-based pathway under 40 CFR 761.61(c) instead, the treatment chamber sits under the slab. In both cases the park is built.

This is a conceptual frame, not an engineered design. No structural drawings exist for Gold Star as of 2026-04-13. See engineering feasibility for confidence bounds on any feasibility claim.

What park-roof is not

• It is not a claim that excavation is unnecessary. The decision between excavation and an in-situ pathway belongs to the City and to EPA Region 1.
• It is not a claim that any specific engineering configuration has been approved by any agency. See 761 61c pathway for the regulatory posture.
• It is not a substitute for site characterization, treatability studies, or public review.

Related

• observable land — the accompanying concept for how data about the site is shared.
• coalition investor model — how the project is financed without pretending a funding round has occurred.
• 761 61c pathway — the regulatory pathway that makes an in-situ option legally conceivable.