(1) Area 4 description.

(a) Tri-Cities northwest buffer zone. An area including all lands lying within a boundary line beginning at the northwest corner of Section 25, T10N, R26E; thence north two miles along section lines to the northwest corner of Section 13, T10N, R26E; thence east one mile along the section line to the northeast corner of Section 13, T10N, R26E; thence north approximately one-half mile along the section line to the United States Department of Energy Hanford Site south boundary line; thence easterly approximately ten miles and south approximately two and one-half miles along the south boundary line to the south section line of Section 27, T10N, R28E; thence west approximately six and three-fourths miles along section lines to the southwest corner of Section 27, T10N, R27E; thence north one mile along the section line to the northwest corner of Section 27, T10N, R27E; thence west four miles along section lines to the point of beginning.

(b) Tri-Cities northeast buffer zone. An area including all lands lying within a boundary line beginning at the intersection of the Esquatzel Diversion Channel drain and the Columbia River; thence east along the Esquatzel Channel to its intersection with Road 68; thence southeasterly approximately one mile along Road 68 to its intersection with Fraser Drive near the northeast corner of Section 24, T10N, R28E; thence south approximately four miles along section lines and portions of Fraser Drive and Dent Road to the southwest corner of Section 6, T9N, R29E; thence east approximately eight and one-half miles along section lines and a portion of Foster Wells Road to its intersection with the Bonneville Power Administration power line in Section 4, T9N, R30E; thence southeasterly approximately seven miles along the power line to its intersection with SR 124 in Section 32, T9N, R31E; thence easterly approximately two and one-half miles along SR 124 to the east section line of Section 34, T9N, R31E near the intersection of SR 124 and the Union Pacific Railroad; thence south approximately three miles along section lines to the southeast corner of Section 15, T8N, R31E; thence west approximately one-fourth mile along the section line to the Union Pacific Railroad; thence southerly approximately four and one-half miles along the railroad to its intersection with U.S. Highway 12 near the Boise Cascade paper mill; thence northwesterly along Highway 12 to its intersection with Interstate 182; thence westerly along I-182 to the west shoreline of the Columbia River; thence northerly approximately six and one-half miles along the Columbia River to the U.S. Department of Energy Hanford Site south boundary line in Section 14, T10N, R28E; thence east approximately one-half mile across the Columbia River to its east shoreline; thence northerly approximately one-half mile to the point of beginning.

(2) Area 4 restrictions.

(a) Application by air of use restricted pesticides as defined in WAC 16-230-810 may be made by written permit only.

(b) The use or application of low volatile ester formulations of use restricted herbicides is prohibited: Provided, That hormone sprays may be applied by aircraft to orchards for the prevention of fruit drop.

(c) On and after April 5th through October 31st of each year all applications of use restricted herbicides are prohibited daily from three hours prior to sunset until two hours after sunrise the following morning: Provided, That applications of use restricted herbicides are exempt from the sunset and sunrise restrictions when using an application rate of forty gallons of water carrier or greater per treated acre and conforming to the manufacturer's specified combination of nozzle type/size and pressure in pounds per square inch (psi) at the nozzle that produces a spray droplet size that falls within the very coarse (or larger) range as defined by the ASABE standards: Provided further, That applications of granular and pellet formulations of the use restricted herbicides are exempt from the sunset and sunrise restrictions: Provided further, That applications of the use restricted herbicides on small experimental plots for research purposes are exempt from the sunset and sunrise restrictions.