Colorado · Area of Critical Environmental Concern
American Basin ACEC
BLM found a natural system and a scenic value here, and its plan calls for special management. BLM's records place at least 1 active mining claim inside the line today, and a grazing allotment covers part of it. It covers 1,605 acres and was designated February 5, 1993, in the 1993 Gunnison Resource Area RMP. In the plan's name, RMP stands for resource management plan.
One of the 1,120 places the Bureau of Land Management has designated an Area of Critical Environmental Concern. This page shows its line, what BLM found there and what sits inside it.
The line
Who holds the claims
At least 1 claim sits inside this line: 1 active, 1 with a holder BLM names. BLM lists 1 as Active. The claim wasn't located before the area was designated.
- BULL RUN MINING LLC1claim
BLM's mining rules list designated ACECs among the places where mining that disturbs the surface beyond casual use needs a plan of operations BLM approves. Exploration of five acres or less can go ahead on a notice instead.
Grazing allotments
A grazing allotment covers part of this line. Its permittee isn't named here yet.
- Grizzly Gulch15,082acres
The nearest areas
- Redcloud Peak ACECColorado · 6,093 acres · 3 grazing allotments covering part of it7miles
- Slumgullion Earthflow ACECColorado · 1,317 acres · 5 rights of way, 3 grazing allotments covering part of it14miles
- Sapinero Mesa ACECColorado · 17,242 acres · at least 39 active mining claims, 2 rights of way, 5 grazing allotments covering part of it37miles
- San Miguel River ACECColorado · 21,657 acres · at least 16 active mining claims and 1 more BLM lists as Under Review, 12 rights of way, 16 grazing allotments covering part of it38miles
- Fairview South (BLM Expansion) ACECColorado · 608 acres · a grazing allotment covering part of it39miles
More from BLM's Colorado office
Every area BLM's Colorado office holdsThe proposed rule
A proposed rule, RIN 1004-AF53, would change how BLM drafts every land use plan, and how it designates ACECs like American Basin ACEC. The comment window hasn't opened: the proposed rule wasn't in the Federal Register at our last check. The Watch sends one email the day it prints.
The rule's abstract
The purpose of this rulemaking is to establish in regulations an updated process for the approval of the development, revision, amendment, and maintenance of land use plans, as provided for by the Federal Land Policy and Management Act of 1976, for public lands administered by the Bureau of Land Management (BLM). Additionally, this rulemaking will provide clarification of the process the BLM uses for designating Areas of Critical Environmental Concern.Unified Agenda entry for RIN 1004-AF53, Publication ID 2026, reginfo.gov (OMB OIRA), read Oct 18, 2026