(1) (a) The commission shall, from time to time as adequate factual data become available, determine designated groundwater basins and subdivisions thereof by geographic description. If factual data obtained after the designation of a groundwater basin justify, the commission may alter the boundaries or description of that designated groundwater basin by adding lands to the basin. After a determination of a designated groundwater basin becomes final, the commission may alter the boundaries to exclude lands from that basin only if factual data justify the alteration and the alteration would not exclude from thedesignated groundwater basin any well for which a conditional or final permit to use designated groundwater has been issued. The general assembly hereby finds, determines, and declares that allowing alterations to exclude lands from a designated groundwater basin only under such circumstances as set forth in this paragraph (a) reaffirms, rather than alters, the general assembly's original intent that there be a cut-off date beyond which the legal status of groundwater included in a designated groundwater basin cannot be challenged, and that such cut-off date was intended to be the date of finality for the original designation of the basin. After this cut-off date has passed, any request to exclude wells that are permitted to use designated groundwater from an existing groundwater basin shall constitute an impermissible collateral attack on the original decision to designate the basin.

(a.5) Nothing in Senate Bill 10-052, enacted in 2010, shall affect litigation brought under this section that is pending on January 1, 2010.

(b) In making such determinations the commission shall make the following findings:

(I) The name of the aquifer within the proposed designated basin;

(II) The boundaries of each aquifer being considered;

(III) The estimated quantity of water stored in each aquifer;

(IV) The estimated annual rate of recharge;

(V) The estimated use of the groundwater in the area.

(2) If the source is an area of use exceeding fifteen years as defined in section 37-90-103 (6), the commission shall list those users who have been withdrawing water during the fifteen-year period, the use made of the water, the average annual quantity of water withdrawn, and the year in which the user began to withdraw water.

(3) Before determining or altering the boundaries of a designated groundwater basin or subdivisions thereof, the state engineer shall prepare and file in his office a map clearly showing all lands included therein, together with a written description thereof sufficient to apprise interested parties of the boundaries of the proposed basin or subdivisions thereof. The commission shall publish the same and hold a hearing thereon. Following such hearing, the commission shall enter an order to either create the proposed designated groundwater basin, to include modification of the proposed boundaries, if any, or dismiss the original proposal, according to the factual information presented or available.

(4) (a) The commission shall not, after May 23, 1983, determine as part of any designated groundwater basin any groundwater within the Dawson-Arkose, Denver, Arapahoe, or Laramie-Fox Hills formations which was located outside the boundaries of any designated groundwater basin that was in existence on January 1, 1983.

(b)

(I) However, the commission may determine as a part of any designated groundwater basin any groundwater in the Crow Creek drainage area in Weld county, upstream from the confluence of Crow Creek and Little Crow Creek, within the Laramie-Fox Hills formation when the Laramie-Fox Hills formation is not overlaid by the Dawson-Arkose, Denver, or Arapahoe formations.

(II) If, upon receipt by the state engineer of the findings of the Laramie-Fox Hills study, as authorized by Senate Bill 250, 1985 legislative session, that the upper Crow Creek drainage area in Weld county, upstream from the confluence of Crow Creek and Little Crow Creek, within the Laramie-Fox Hills formation when the Laramie-Fox Hills formation is not overlaid by the Dawson-Arkose, Denver, or Arapahoe formations should not be a designated groundwater basin, this paragraph (b) is repealed.