36.11.423    WATERSHED MANAGEMENT - CUMULATIVE EFFECTS

(1) The department shall include an assessment of cumulative watershed effects on projects involving substantial vegetation removal or ground disturbance. Using the analysis, the department shall ensure that the project will not increase impacts beyond the physical limits imposed by the stream system for supporting its most restrictive beneficial use(s), when considered with other existing and proposed state activities for which the scoping process has been initiated. The analysis shall identify opportunities, if any exist, for mitigating adverse effects on beneficial water uses.

(a) The department shall determine the necessary level of cumulative watershed effects analysis on a project level basis. The level of analysis shall depend on the:

(i) extent of the proposed activity;

(ii) level of past activities; and

(iii) beneficial uses at risk.

(b) The department shall complete a coarse filter screening on the following projects:

(i) upland timber harvest and salvage harvest of more than 15 acres or 50 mbf;

(ii) RMZ harvest of green timber;

(iii) salvage harvest within the RMZ of one or more acres of dead and dying timber;

(iv) new road construction greater than 0.5 miles;

(v) new road construction located within an RMZ; or

(vi) construction of any length of new road that includes the installation of new Class 1 stream crossings.

(c) The department shall complete a preliminary watershed analysis on projects when coarse filter evaluations determine there is anything other than low potential for cumulative impacts.

(d) The department shall complete a detailed watershed analysis when coarse filter screening or preliminary analysis predict or indicate the existence of unacceptable cumulative watershed effects as a result of the proposal.

(e) The department shall establish threshold values for cumulative watershed effects on a watershed level basis.

(f) The department shall determine thresholds for cumulative watershed effects by taking into account such items as:

(i) stream channel stability;

(ii) beneficial water uses; and

(iii) existing watershed conditions.

(iv) The department shall set threshold values at a level that ensures compliance with water quality standards and protection of beneficial water uses with a low to moderate degree of risk.

(g) The department shall set threshold values for cumulative effects associated with projects proposed in the watershed of a water quality limited water body at a level that provides for protection of beneficial water uses with a low degree of risk.

(2) Whenever feasible, the department shall cooperate with other landowners in watersheds with mixed ownership to minimize cumulative watershed effects within acceptable levels of risk.

History: 77-1-202, 77-1-209, 77-5-201, 77-5-204, MCA; IMP, 77-5-116, 77-5-204, 77-5-206, 77-5-207, MCA; NEW, 2003 MAR p. 397, Eff. 3/14/03; AMD, 2020 MAR p. 2239, Eff. 12/12/20.