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Wattenberg Lakes Amendment, Exhibit D—Mining Plan May 2023 EXHIBIT D - MINING PLAN 1.0 GENERAL The Wattenberg Lakes Mine property is located within unincorporated Weld County on land owned by the City of Westminster and Holcim. The geographic coordinates of the main entrance area are 400 00' 40.82" North, 1040 50' 21.43"West. Sand and gravel will be the primary product produced from a small portion of the Wattenberg Lakes site. The principal intended use for the sand and gravel is for construction aggregates. Agricultural and mining uses surround the property, with residential uses extending farther from the site including the community of Wattenberg north of the property. The majority of the site is immediately west of the South Platte River between Weld County Road (WCR) 2 and WCR 6. Although a small northeastern section of the property straddles the South Platte River, the mining operation will not disturb the river. Mining was completed previously for most of the property, with only a small amount of additional mining planned (6.2 acres) to create the area required to complete Pond 1 (also known as the Struck Pond). The primary changes in the current DBMS permit amendment mining plan compared with the 2004 DBMS permit mining plan include the following (changes to the reclamation plan are noted in Exhibit E): • Mining has been completed in most of the permit area, with only a minimal amount of mining planned in two small areas in the Pond 1 (Struck Pond) area; Area 1 (see Exhibit C) was not previously included in the 2004 mining plan. • The Huett Seep/Ditch was re-routed immediately east of Pond 3 as part of the activities permitted in 2004. • A decreased area of mining occurred in the west boundary area of Pond 3, resulting in a straightened western pond boundary and a decrease in the disturbance during mining compared with the 2004 permit. The total DBMS permit amendment area covers 420.8 acres. The permit boundary and affected area are the same for this amendment. Within the site, 6.2 acres of the land will be mined as shown for Area 1 (3.2 acres) and Area 2 (3.0 acres) in Exhibit C, Map C-1; the remaining areas will be used for temporary earthwork and other material movement (minor grading) as part of reclamation activities. Area 1 and Area 2 are planned for mining concurrently. In June and August 2022, a survey was conducted within the permit area for wetlands and other waters of the U.S.; the delineation report is included in the vegetation exhibit (Attachment J-1) and wetlands are shown in Exhibit C, Map C-1. Holcim is working with the U.S. Army Corps of Engineers (USACE)to amend an existing permit to cover the wetland mitigation required to satisfy USACE 404 requirements. Please see Exhibit J for vegetation information. The proposed plan does not include mining in areas with existing wetlands. The saleable aggregate material to be removed from Area 1 and Area 2 will amount to approximately 158,000 cubic yards (221,000 tons at 1.4 ton/cy), based on exploratory logs from the previous investigation for adjacent Pond 3. The overburden and growth medium materials excavated as part of the mining operation, along with overburden previously placed in the west half of Pond 1 (Struck Pond), will total approximately 900,000 cubic yards. Overburden and growth medium will be stockpiled for use as backfill and reclamation within the permit area; excess overburden will be hauled off site for other uses. Based on routine groundwater elevation monitoring in the Wattenberg Lakes site, Area 1 and Area 2 groundwater is typically expected at approximately 2 ft below ground surface but can be less than 1 ft during seasonal highs. Additional information on groundwater at the site is presented in Exhibit G (Water Information). OTETRA TECH Page 114