The Risk Assessment Code (RAC) in EM 385-1-1.

What a RAC Is

The manual defines the RAC as the conversion of the probability and severity of a given hazard into a specific risk level based on the residual risk. The levels are extremely high (E), high (H), medium (M), and low (L) (paragraph 2-2.u). Residual risk is the level of risk remaining after controls have been identified and countermeasures selected (paragraph 2-2.t), so the RAC describes the risk after your controls, not before them.

The tool for getting there is the risk matrix, which evaluates severity (catastrophic, critical, moderate, or negligible) and probability (frequent, likely, occasional, seldom, or unlikely) to find the RAC for each work element and the overall RAC for the activity, task, or definable feature of work (paragraph 2-2.w). The manual describes severity as "an approximate amount of potential harm, damage, or injury occurring" and probability as the "likelihood of something happening."

RACs on the AHA

Every AHA assigns a RAC to each job step to show the residual risk that remains after controls, and an overall RAC for the AHA that must not be lower than the highest job step RAC (paragraph 2-6.d(4)(e) and (f)). If a single layer of control can't bring a hazard to an acceptable level, additional controls go in, aiming for low or medium where possible (paragraph 2-6.d(4)(d)).

Who Accepts the Risk

Residual risk has to be communicated and accepted by the proper authority before the activity begins, and activities that require an AHA don't begin until the AHA with its RAC has been reviewed, accepted, and signed. Prime contractors set up an internal process naming the acceptance authority for each level of residual risk and include it in the APP. The manual notes that USACE does not accept contractor risk (paragraph 2-6.c).

When the RAC Changes

If a change to the AHA raises the initial RAC, the AHA is resubmitted for acceptance before work starts. Changes that don't raise the RAC don't have to be resubmitted (paragraph 2-6.d(5)(a) and (b)). A well-written RAC is also a planning tool: if a revision would push a step from medium to high, that's a signal to look for another control before the paperwork goes back in.

The RAC and Your SSHO

The residual RAC also decides staffing. Level 2 and Level 3 SSHOs cannot be assigned to projects with a residual RAC of high or extremely high (paragraph 2-2.x(2) and (3)), and a Level 1 SSHO must be assigned and on site at every project with a residual RAC of high or extremely high (paragraph 2-8.b(2)(f)). Where an activity with multiple sites has been rated low or medium, an SSHO of any level may be appointed for remote sites more than 45 minutes from the primary Level 1's site (paragraph 2-8.b(2)(e)).

Read EM 385-1-1 AHA requirements for the rest of what goes in an AHA, or send yours for an activity hazard analysis review.