(1) The department shall establish a riparian management zone (RMZ) adjacent to the minimum width of the SMZ required under ARM 36.11.302 when forest management activities are proposed on sites with high erosion risk or on sites that are adjacent to fish bearing streams or lakes.

(2) The department shall determine the presence of high erosion risk from:

(a) established soil surveys;

(b) existing inventories; or

(c) site-specific field evaluations.

(3) When the department proposes forest management activities on sites determined to have high erosion risk:

(a) the department shall establish an RMZ with a minimum of 100 feet when activities are located on slopes greater than 25% but less than 35%;

(b) the department shall establish an RMZ with a minimum of 150 feet when activities are located on slopes greater or equal to 35%, but less than 50%;

(c) the department shall establish an RMZ with a minimum of 200 feet when forest management activities are located on slopes greater or equal to 50%; and

(d) the department may modify and shorten RMZ widths established for high erosion risk when topographic breaks, existing roads or other factors are present that reduce erosion risk and provide suitable sediment delivery filtration.  Modified or shortened RMZ's must still meet the minimum width of the SMZ required under ARM 36.11.302.

(4) The following restrictions apply to forest management activities conducted within an RMZ established for high erosion risk:

(a) The department shall limit new road construction within an RMZ to situations in which:

(i) a stream crossing is required;

(ii) potential impacts can be adequately mitigated; or

(iii) alternative locations pose higher risk of resource impacts.

(b) The department shall restrict ground based equipment operations within the RMZ.

(i) The department shall not allow the operation of wheeled or tracked equipment within an RMZ when it is located on slopes greater than 35%.

(ii) The department shall not allow the operation of wheeled or tracked equipment within an RMZ when it is located on slopes less than 35%, unless the operation can be conducted without causing excessive compaction, displacement or erosion of the soil.

(iii) The department may allow the use of wheeled or tracked equipment inside of that portion of an SMZ or RMZ when operated from an established road on the side of the road away from the stream pursuant to ARM 36.11.304.

(c) The department shall restrict cable yarding of logs within and across an RMZ to cable systems and operations that do not cause excessive ground disturbance within the SMZ or RMZ.

(5) The department shall design harvest prescriptions conducted in SMZ's and RMZ's located adjacent to fish bearing streams to retain adequate levels of shade and potential large woody debris recruitment to the stream channel by:

(a) establishing an RMZ that when combined with the SMZ has a minimum slope distance equal to the site potential tree height of the proposed harvest stand at age 100 years;

(b) determining site potential tree height from site index curves developed for local or regional forest types; and

(c) determining site index of a stand by measuring tree height and age directly from suitable index trees located at the approximate minimum SMZ width.

(6) The department shall determine adequate levels of shade retention on a project level basis.

(a) Adequate levels are those levels that maintain natural water temperature ranges.

(7) The department shall determine adequate levels of large woody debris retention on a project level basis.

(a) Adequate levels are those levels that maintain stream channel form and function.

(8) The department shall retain all bank edge trees on timber harvests conducted adjacent to streams.

(9) Timber harvests within the SMZ and RMZ of a stream, lake, or other body of water supporting bull trout or any other fish or aquatic species listed under the Endangered Species Act, 16 U.S.C Sections 1531 through 1544, the department shall act pursuant to ARM 36.11.427.

(10) The department shall use existing roads in the SMZ or RMZ only if potential water quality impacts are adequately mitigated and beneficial uses are fully protected.