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Home My WebLink About20252521.tiffEpvirownept, Ipc. LARRY E. O'BRIAN FOUNDER STEVAN L. O'BRIAN PRESIDENT September 5, 2025 via e-mail CTB@weld.gov Weld County Clerk to the Board Board of County Commissioners Office 1150 "O" Street Greeley, Colorado 80631 Re: L.G. Everist, Inc. - Ft Lupton Sand and Gravel M-1999-120 Adequacy Response - 04 Packets Dear Sir/Madam: 7985 VANCE DRIVE, SUITE 205A ARVADA, COLORADO 80003 303-423-7297 FAX 303-423-7599 We are delivering to you here with a copy of the Adequacy Response and supporting exhibits for the L.G. Everist, Inc, - Ft. Lupton Sand and Gravel mine application filed with you on November 19, 2024. Please place this packet with the original book. The original -s on file with the Division of Reclamation, Mining & Safety. This copy of the permit application adequacy response is delivered to you pursuant to 34-32.5-112(9)(a), Colorado Revised Statutes 1995, as amended, which states in part: .... the applicant shall place a copy of such application for public inspection at the office of the Board and Office of the County Clerk and Recorder of the County in which the affected land is located. This packet must be kept with the book for public review until the application has been approved by the Division. Please acknowledge receipt of the copy cf the permit adequacy response by date stamping this cover or signing in the appropriate space provided below and returning one copy of this letter to environment-incstartmail. com . Thank you, ENVIRONMENT, INC. Stevan L. O'Brian enclosure RECEIVED SEP 0 5 2025 WELD COUNTY COMMISSIONERS 1 PAGE OF DOCUMENT INCLUDED IN PAPER FILE. REMAINDER RETAINED ELECTRONICALLY IN TYLER. 703\ic:Rivilup ce):7LLDtImmph-ii4miocADAts-u-ttG}(C.KI 9)10115 2025-2521 Epviromvept, LARRY E. O'BRIAN FOUNDER STEVAN L. O'BRIAN PRESIDENT September 5, 2025 via e-mail nikle.gagnon@state.co.us Ms. Nikie Gagnon Division of Reclamation, Mining & Safety 1313 Sherman St., #215 Denver, CO 80215 Dear Nikie; 7985 VANCE DRIVE, SUITE 205A ARVADA, COLORADO 80003 303-423-7297 FAX. 303-423-7599 RE: L.G. Everist, Inc. Fort Lupton Sand and Gravel, Permit # M-1999-120 Adequacy Response #4 On behalf of my client L.G. Everist, Inc., I will respond to your August 25, 2025, adequacy review letter, as needed, in the order and number format presented in those documents. We have copied each inquiry into this document for ease of review. I have also revised the Reclamation Cost Estimate (Exhibit L) to add the groundwater drains to Table Llln. 1. Please commit to installing two drains within the permit area. • A north -south drain along the western edge of the Heins West slurry wall. • An east -west drain along the southern edges of the Southern Complex (Funakoshi, Parker 1-4, and Parker -Adams phases). L.G. Everist, Inc. commits to installing 2 groundwater drains as recommended by Schnable Engineering in the revised Heins Ground- water Model memo (dated 08/12/25). A north -south groundwater drain is proposed to be installed along the west side of the Northwest Phase; and an east -west groundwater drain is proposed to be placed on the southern side of the Parker #4 Phase in the approximate locations shown on Exhibit C-1 -Mining Plan and Exhibit F - Reclamation Plan Maps. Environment, Inc. M-1999-120 - AM -03 Adequacy Response #4 Page 2 September 5, 2025 2. Please revise and resubmit the mining and reclamation plans and maps in Amendment 3 as necessary to include the installation of the two groundwater drains. This should include a discussion of the timing for the drain installations. Attached are revised Map Exhibit C-1 Mining Plan and Map Exhibit F - Reclamation Plan map that have been updated to add the approximate location of both groundwater drains. We added text to Exhibit D - Mining Plan and Exhibit E - Reclamation Plan as requested. Full copies of all Exhibits are attached for the file. I also sent along pages from both exhibits showing what was changed. 3. Prior to any mining disturbance within the Heins West and Southern Complex (Funakoshi, Parker 1-4, and Parker -Adams) phases, please commit to submitting the engineered designs and configura- tions for the required drains through a Technical Revision to the Division. L.G. Everist, Inc. commits to filing a Technical Revision (TR) containing an engineering design and configuration for the groundwater drains located west of the Northwest phase and south of the Parker #4 phase. The TR and the designs will be filed prior to any mining disturbance occurring in either Phase. 4. Beginning with the 4th quarter 2025, please commit to submitting the monthly water level data for the active monitoring wells in and around the mining operation to the Division quarterly. The Division will review the quarterly data and determine if additional mitigation measures are needed to maintain hydraulic gradients, prevent excessive buildup, and ensure groundwater movement. Consistent with previous reporting, please highlight any values that are outside the historic high/low baseline range and provide a discussion of the observations. L.G. Everist, Inc. commits to submitting the monthly water level data for the active monitoring wells in and around the mining operation to the Division on a quarterly basis. Any values that are outside the historic high/low baseline range will be high- lighted and a discussion of the observations will be provided. Exhibit L - Reclamation costs Attached is a revised Exhibit L - Reclamation Cost Estimate which incorporates the new information needed to add a cost estimate of the groundwater drain on Table Llln for the Northwest phase. This will have no effect on the current bond calculation since mining on those Phases will not start until sometime in the Environment, Inc. M-1999-120 - AM -03 Adequacy Response #4 Page 3 September 5, 2025 future. A Technical Revision will be filed to address the groundwater drain design, location, and any bonding changes. List of attachments to this response: Exhibit C-1 - Mining Plan Map revised Exhibit b - Mining Plan revised Exhibit E - Reclamation Plan revised Exhibit F - Reclamation Plan Map Revised Exhibit L - Reclamation Cost Estimate revised Heins Groundwater Model memo (dated 8/12/2025) I hope these responses have addressed the adequacy questions you had. I will place a copy of this packet with the Weld County Clerks' office as required and send you a copy fo the proof of placement. If you have any questions please call me. Sincerely, Environment, Inc inQe., e Stevan L. O'Brian President cc L.G. Everist, Inc. Weld County Clerk file enclosures Exhibit D MINING PLAN Existing Conditions. The methods described and approved in the original mining and ✓ eclamation plans for the Fort Lupton Sand and Gravel Mine (FLS&G) 1999 permit, and the 2012 amendment applications will remain un- changed unless discussed in this text. The Mining Plan described in the 2004 amendment will continue be used with the only change being the direction of mining. The other change is that mining will continue to the north into the newly added areas before moving t o the southern end of the permit area. The future intent is to eventually remove the southern area from this permit into a new application that is being prepared. Map Exhibits C -Current Conditions, C -1 -Mining Plan, C -2 -Structures and F -Reclamation Plan have been provided in this packet. In the 2012 amendment, LGE combined the Fort Lupton Sand and Gravel Mine (M-1999-120) with the Lupton Meadows Reservoir (M-2002- 104) and added 7 parcels north, south and west of the existing mines. From that time until 2023 the mining Phases in the middle o f the permit area have been mined and reclaimed. The area that has been released has created a 2 -part mine as shown on the maps. The two (2) new areas to the permit boundary will increase the permit area by approximately 202.26 acres ±. EXHIBIT C -CURRENT CONDI- TIONS MAP shows the area being added to the permit and will reflect any changes to the Mining and Reclamation Plan in the existing area. There is very little change to the south area reclamation plan for the existing area except some of the oil and gas facili- t ies have been removed which will allow for an expansion of some of t he future reservoirs shapes. Nineteen of the twenty mined areas shown on the maps will be slurry wall lined and developed as a series of water storage reser- voirs ranging from 10.26 to 70.00 acres ±. The exceptions are the Deep Lake Phase that will be reclaimed as a pond and the southern e nd of the Sandstead Phase that will be backfilled with fines 2 t eet above ground water and revegetated. The north end of the Sandstead Phase may become a lined reservoir. TABLED -1 - MINING TIMETA- BLE on Page 9 is a list of the mining phases that will be referred t o in the following text. This timetable has been updated to ✓ eflect changes to existing Phases. EXHIBIT B -VICINITY MAP shows the parcels that will be added while the Mining and Reclamation Plan Maps show how the site will be developed. The total number of phases added to the Fort Lupton Sand & Gravel Mine is four and the new area will add approximately 7-15 years to the life to the mine. It is estimated by adding the new area, along with remaining reserves, that the life of the mine will be from 15 to 25 more years. This life span is subject to fluctua- t ion depending on market conditions. The current bond for Ft. Lupton S&G is $2,002,400.00. The bonds include surety for 20,134 feet of slurry wall and construc- t ion of 16,650 feet of bank sloping. At this time the applicant has a contract with the City of Aurora to develop 5 water storage ✓ eservoirs on the northern parcels of the property. This includes 256.59 acres of the existing permit area, south of Weld County Road 18. The Sandstead Phase, the new north areas as well as the south- e rn area, will be marketed by L.G. Everist, Inc. as they are devel- oped. L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 3 Revised -September, 2025 MINING PLAN EXHIBIT D WONT) The areas being added have been used primarily as agricultural land. The Northwest Phase is broken into 3 use areas, farm yard with a house, wetland/creek area and agricultural production. The house will be removed prior to mining. Mining will take place on t he yard and agricultural area in this Phase. The Northeast Phases are mostly grass land with 2 irrigation ditches crossing the site and a small farm yard near the northwest corner. LGE will maintain 50 foot setbacks along the diagonal ditch corridor that has the Meadow Island #1 and the east lateral of the Lupton Bottoms Ditch. If practical, the north/south leg of the Lupton Bottoms ditch will be moved to the east side of Northeast Phase #3 so it can be com- bined with Northeast Phase #2 as show in Option B. The applicant will bond the amended property in phases, and wishes to retain the option to seal each reservoir with either a slurry wall or a compacted liner, until just prior to bonding that particular phase. At the current time, slurry walls have been constructed around the active mining areas and the reservoir slopes are built by backfilling and grading or are in the process of being completed. TABLED -1 - MINING TIMETABLE has a current list of all certi- fied liners or lined areas being tested. At any given time, mining and reclamation may be occurring in o ne or more bonded phases to accommodate blending of materials and ✓ elocation of the processing plant and settling ponds. There will be times when reclamation is being completed in one phase while mining begins in another phase. Mining will progress from the e xisting permit area into the Northeast Phases then move to the Northwest Phase leaving the Ft Lupton West Phase as the last area t o be mined. The arrows on the EXHIBIT C-1 - MINING PLAN MAP show how mining will progress through the mine area at this time. The order o f mining in the south area will start on the west side and mine to t he east jumping from Phase to Phase. The last area to be mined will be the future Plant Site area, see Exhibit C-1 -Mining Plan Map. Optional Mining and Reclamation Plans. Due to the constantly expanding and changing development nature of the oil and gas and other utility operations in this area, L.G. Everist is submitting these Optional Mining and Reclama- t ion Plans with this amendment to guarantee the flexibility to make changes to mining areas and reservoir shapes throughout the life of t he mine. During the current run of mining and reclamation we have seen many changes to the Oil and Gas(O&G) facilities that are ✓ eflected on the current version of the maps and mining areas. We continue to stay abreast of, and in contact with, the oil and gas and utility companies about future structure and easement changes, including plans to relocate some of their facilities, plans to ✓ emove some of the older wells and facilities, and plans for oil and gas companies to add new structures as their permitting allows. For example, between 2012 and 2024 many of the wells and t acilities on the south area have been removed and the reservoir areas adjusted to show those changes. Many additional changes are e xpected in the future similar to this example. As mining progresses through the mine and into a new area it may be to our advantage - or we may be required by law to allow oil and gas companies or ditch companies to exercise their rights - to L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 4 Revised -September, 2025 MINING PLAN EXHIBIT D WONT) ✓ evise the shapes of the reservoirs due to changes to their facili- t ies, gaslines, wells or drilling pads or ditches. These changes may affect reservoir shapes, combine or split reservoirs, add or subtract oil and gas operations areas, gas lines, easements, etc. Therefore, we are presenting these optional plans to cover the possibilities with the understanding that the mining and reclama- t ion methods will remain unchanged, but the configurations and areas of the mined and reclaimed areas may change. Optional Mining Plan. Option A - The mining areas shown on the large map on EXHIBIT C-1 MINING PLAN MAP is Option A. This option shows the most conservative (and current) mining plan and it assumes no further changes to the location of ditches, oil and gas wells, gas lines or facilities before mining ends. Option B - The smaller map inset in the upper corner is Option B and is a more optimistic plan showing removal or relocation of numerous wells, gaslines and facilities to allow removal of more g ravel and increase the amount of water storage on the site. For Option B, the South Area remains as originally planned in 2012 but t he new north area may have the ditch moved between Northeast P hases #2 and #3 to create one large reservoir. Mining Methods overview The working face will be mined near vertical to maximize ✓ emoval of material from the mine. At the widest point, the longest working face will be approximately 1,700 feet long. If mining ended prematurely, this slope will be reclaimed using a cut/fill sloping method instead of backfilling. As mining reaches a setback limit, backfilling will commence within 3 to 6 months maximum so as to leave a 3:1 slope along the mine exterior, oil and gas facilities and the ditches. No more than 2,000 linear feet of side slope h ighwall area will need backfilling at any -one-time. This can be done because we plan to start backfill sloping whenever a new area is stripped so the material only has to be handled once. The mining setbacks will vary from 15 to 275 feet from the permit boundaries, structures and river as allowed by each use agreement of geotechnical analysis for said structures. No mining will be done in the setback areas but they may be disturbed as mining and reclamation progresses thru a phase. For example, around o il/gas wells we will maintain an eighty (80) foot radius around e ach well head when mining, but leave a 150 foot radius when recla- mation is complete. EXHIBIT C-1 - MINING PLAN MAP shows how this will look. Around the rest of the mine, the setback line will be to the o uter edge of the slurry wall or the top of the excavation limits. The temporary topsoil stockpiles placed within the setbacks will also limit noise and visual impacts to off site areas. In some cases, the setbacks will be used as a place for roads to access the mine exterior, ditches and access for the oil and gas facilities. The setback areas will be reclaimed if disturbed. The following information is a recap of the methods currently used at the mine and will continue to be used as mining progresses t hrough the areas added by this amendment. This mine will be operated as a dry -mine. Slurry walls will be constructed to the L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 5 Revised -September, 2025 MINING PLAN EXHIBIT D WONT) Division of Water Resources specifications around the perimeter of e ach additional mine area prior to commencement of mining in the new phases. This isolates each mining area from the surrounding ground- water table and allows for dry -mining of each mine area. However, if a slurry wall is not feasible, the Applicant will utilize a compacted liner to seal the reservoir areas for the end use as water storage. Design of the liner will follow the Division of Water Resources Guidelines also. Slurry wall design documents were submitted and deemed adequate to the Division in 1999. Slurry walls installed using this design, have been constructed successfully on t he 5 lined areas currently completed (and the 6 already released from the permit) . Prior to mining the phases, a groundwater drain will be in- stalled along the west side of the Northwest phase (AKA Heins West) and along the south side of the Parker #4 phase (AKA Southern Complex). The approximate locations of both proposed drains are shown on the Mining and Reclamation Plan maps. The drains will be installed in conjunction with the liner installation in that section o f the phase. A Technical Revision will be filed containing an e ngineering design and drain configuration for each drain prior to mining activities starting in the 2 phases affected. Additional monitoring wells have been installed along the western, eastern, and northern sides of the new areas in the amend- ment area. Ground water monitoring, and ground water quality t esting plans are included in EXHIBIT G - WATER for the amendment areas. Prior to mining moving into those areas just north of WCR 14.5, t he Plant Site will be moved to the Parker #4 Phase in the southern area, adjacent to the access road that now serves the agricultural areas. Mining operations within each new phase area will include t opsoil and overburden stripping, and excavation of dewatering t renches, and settling ponds. Raw materials will be excavated with e xcavators, front-end loaders, scrapers and/or bulldozers. As areas are cleared and stripped, previously mined slopes will receive backfill material to establish the permanent design side slopes. A conveyor is used to transport the raw material from the areas north o f WCR 18 to the Plant Site in the existing mine. Explosives will not be used at this operation. The reservoir access roads will be placed in the 25 foot wide setback between the slurry wall and the top of the slope into the ✓ eservoir. The disturbed areas from the setback line to the top of bank armoring, will be left as a gravel surface instead of being ✓ esoiled and seeded. The slope area between the top of slope and highwater line will be resoiled and revegetated. Adequate amounts o f the stripped topsoil and overburden will be stockpiled for later use in reclamation in the areas that will be seeded. Topsoil and overburden stripped from subsequent mine areas may be placed di- ✓ ectly on the seed bed in previous mine areas so it only has to be handled once and the disturbed areas will be concurrently reclaimed. The exact location of topsoil and overburden piles are unknown at t his time, so we have shown the approximate location on EXHIBIT C-1 - MINE PLAN MAPS . Mining within each phase will begin once topsoil and overburden has been removed from that phase area. Excavated materials (pit run) will be removed via front-end loaders, or excavators and may be L.G. Everist, Inc. 6 M-1999-120 Ft. Lupton Sand and Gravel Revised -September, 2025 MINING PLAN EXHIBIT D WONT) loaded onto a field conveyor and transported back to the processing plant, or loaded into off -road haul trucks for transport to the plant site. Mined slopes will range from near vertical to 0.5:1, or as required by the Slope Stability Analysis and Setback Agreements (see EXHIBITS - STRUCTURES from the 2004 submittal (included in this packet) . As soon as mining limits have been reached in one phase area, ✓ eclamation of the pit edges within that phase area will begin. This will allow for concurrent backfilling of the pit perimeter with previously stripped overburden and/or material stripped from the next phase area to be mined. Access roads built during slurry wall construction and mining will be left as access roads around the ✓ eservoirs or for access to oil and gas wells on the site. Slurry walls have been installed around Swingle North, Swingle South, Ft. Lupton West, Parker-Panowicz and the Blue Ribbon Phases. Testing is complete and certified for all but Blue Ribbon and Swingle South. A slurry wall is planned for the small lake on the north end of Sandstead. We anticipate slurry wall construction will begin soon after permit approval on the Northeast Phases. River setback and Bank armoring The only place the South Platte River is within 400 feet of the mining area is along the east sides of Northeast Phases #1 & #3 in t he amendment area and along the east side for the Parker #4 Phase in the south area. Along these stretches the slurry wall will be installed at least 200 feet from the edge of the river bank. Along t he South Platte River in Northeast Phases 1 and 3, mining will take place within 300 feet of the river bank and the bank slopes will be backfilled to 3:1. In the Parker #4 Phase the mining limit will be 70 feet west of the Lupton Bottoms Ditch and the bank will be ✓ ebuilt so the top of the slope into the reservoir area will be 250 f eet from the top of the river bank. This will be done by backfill- ing from the 1/2h:1v 1v mining face to the top -of -slope (TOS) line using shale and other quality -tested compactible material from the floor ✓ f the mined area. On the working face of non river side banks no more than 1,700 f eet of 1/2:1 cut/fill sloping and 2,000 feet of 1/2:1 backfill sloping in any one phase will be needed and no more than 2000 feet will need armoring. Armoring will be done, using the technique, and materials described in the BANK ARMORING PLAN in the APPENDIX of this applica- t ion packet. Water Diversions and Impoundments The entire site will be graded in phases to direct storm -water runoff towards interior ditches and dewatering systems. A CDPS permit for the existing mine operations is in place from the Colo- ✓ ado Department of Public Health and Environment (CDPHE) for the current dewatering operations. This permit will be modified, if necessary, to accommodate the additional parcels. As the slurry walls are installed, they will be constructed around the perimeter of each new phase prior to commencement of mining. This will seal off each individual phase area, and prevent- ing infiltration of groundwater into the mining area. Once the initial groundwater quantities within each mine area are pumped out, L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 7 Revised -September, 2025 MINING PLAN EXHIBIT D WONT) continued dewatering will not be required except on an as -needed basis after significant weather events. Description of Overburden, Deposit and Underlying Stratum Across the entire amendment area, approximately 3 feet of overburden (including approximately 6 to 18 inches of topsoil) will be removed from the mine areas and stockpiled for plant -growth material in surface reclamation or used as backfill for the pit slopes. An average thickness of approximately 33 feet of sand and gravel exists across the amendment area. Mining Timetable The continuing uncertainty of economic conditions in the construction materials industry precludes an accurate forecast of demand for materials during the life of the mine. This pit will be operated year -around by L.G. Everist, Inc., weather permitting. There may be periods up to 18 months or more when the demands for material are slow and no mining will take place, creating an "inter- mittent operation" situation. We therefore, can only estimate the mining timetable based on an average year and may expect a specific year to vary widely from the average. Table D-1: Mining Phases (6-2025) Phases Years ACRES ± Total Mined Slurry length wall Slurry status tified wall (cer- date) Fort Lupton Sand and Gravel - North Area Parker-Panowicz 1-2 43.51 20.60 3,540 2/5/14 Swingle North 1-2 42.02 31.88 5,220 11/30/22 Fort Lupton West 2-3 47.81 41.25 4,320 10/13/04 Swingle South 1-1 67.45 52.31 6,400 Pending Sandstead done 50.05 36.64 2,945 Proposed Blue Ribbon done 55.55 37.77 5,675 Pending Deep Lake done 7.90 5.75 0 NA South Area Funakoshi 1-3 42.97 27.39 4,770 Proposed Parker #1 1-2 43.17 22.17 4,230 Proposed Adams -Parker 2-3 72.92 43.83 11,755 Proposed Parker #2 1-3 33.27 26.83 4,545 Proposed Parker #3 1-2 43.12 32.71 7,860 Proposed Parker #4 2-3 56.94 44.24 6,235 Proposed New areas Northeast #1 3-4 70.87 57.17 7,350 Proposed Northeast #2 2-3 67.00 45.43 6,880 Proposed Northeast #3 1-1 12.12 5.21 2,925 Proposed Northwest 1-2 52.33 27.47 6,220 Proposed Totals 19-34 809.00 558.65 L.G. Everist, Inc. Ft. Lupton Sand and Gravel 8 M-1999-120 Revised -September, 2025 Exhibit E RECLAMATION PLAN Overview Unless specifically discussed below, the methods described and approved in the original Reclamation Plan will remain un- changed. This will remain a dry mining operation. All of the map exhibits have been labeled North area and South area for e asier review. When referring to a map exhibit it is inferred t hat both should be reviewed. EXHIBITS C - CURRENT CONDITIONS MAP show the current permit area and the area being added to the permit. The current post mining land uses are listed as developed water storage surrounded by access roads, gravel surface areas and ✓ evegetated areas. The following information makes change to the ✓ eclamation around the reservoirs. The plan is to reduce the ✓ esoiling and revegetating. Instead of revegetating to the water line, a gravel surface will be created from the mine setbacks to t he top of slope around the reservoirs. Resoiling and reveg- e tation will be done from the tops of slope to the highwater line, e xcept on bank armoring areas where no cover will be placed on the armoring. A gravel access road will be placed around the reser- voir. Including the slopes into the reservoirs there are three areas that will need revegetation, The scale house triangle in t arker-Panowicz, the area south of and around the Sandstead Reservoir and Deep Lake. All other disturbed areas will have a gravel surface. More detail is provided in the following Reclama- t ion Plan text and a typical cross section showing this is pro- vided on the EXHIBIT F - RECLAMATION MAP . As with the currently permitted mine area, the new properties will be reclaimed as lined water storage reservoirs. Each of the additional properties will either be sealed with a slurry wall or clay liner. Prior to mining, two of the phases will have ground- water drains installed in conjunction with the installation of the liner - proposed locations are shown on MAP EXHIBIT F - RECLAMATION PLAN MAP. In the Northwest Phase it will be along the west side and in t he Parker #4 phase it will be along the south side. Information o n the engineering design and drain configuration will be avail- able for review in the Technical Revisions filed prior to mining beginning in each phase. The applicant proposes to bond each phase prior to mining and t o determine the type of lining prior to posting a bond for that phase. Please refer to TABLE E-1 RECLAMATION TIMETABLE for information o n each Phase of Reclamation. Reclamation Plan Currently, the undisturbed and amendment areas of the mine site are primarily irrigated agricultural land. The area is broken into 6 different use areas. Please refer to the VEGETATION MAP in EXHIBIT I/J - SOILS AND VEGETATION for the location of each area described. The current uses are, mining operations area; non - irrigated pasture; irrigated crop areas; ditch & river corridors & wetland area, oil/gas operations areas and high capacity gas pipeline ROW's. The agricultural uses will continue as mining progresses until an area is taken out of agricultural production L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 9 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) and prepped for mining. There is no native vegetation present on t he agricultural areas because of the intensive agricultural practices that have taken place on the land. In most cases the o il/gas operations areas have little vegetation and the high pressure gasline ROW's have been farmed for many years and vegeta- t ion cover on those areas is consistent with farmed areas. The narrow band along Little Dry Creek/Slate Ditch and the Meadow Island Lupton Bottoms ditches have been constantly disturbed by ditch maintenance leaving only the river corridor, that will not be disturbed, with vegetation that may be considered native. The t ypical vegetation descriptions that have been submitted in EXHIBITS & J - SOILS AND VEGETATION in previous permitting packets will match t hese agricultural uses as the crops rotate throughout the years. The EXHIBIT F - RECLAMATION PLAN MAP shows a cross section sketch of t he proposed sloping plan and reclamation activities that will surround reservoirs in this plan. Under the contract with City of Aurora for the water storage ✓ eservoirs, the applicant has to turn over to Aurora, for contin- ued development, any reservoirs that have been significantly ✓ eclaimed. It has been agreed that this condition will exist once a reservoir liner has been certified by the Division of Water Resources, sloped, the surround gravel surface is complete. The change to graveling the band between the setbacks and the tops of slope into the reservoirs (or armored areas) eliminates the concerns that during Aurora's development, any revegetated areas would be disturbed, destroying any grass planted. Where mining will take place within 400 feet of the river, a setback of 300 feet on the north area and 250 feet on the south area will be maintained. At which point the slope into the ✓ eservoir will be backfilled and sloped. In these areas no more t he 500 feet will need backfilling nor will it be left open for more than 12 months. Where needed armoring will begin as soon as bank sloping is complete on each 500 -ft section. This will also e nsure, that if mining ceases before the resource is exhausted, o nly a minor amount of work would have to be done to finish ✓ eclamation on the disturbed area Armoring in the Northeast Phases #1 and #3 will progress with sloping, so approximately 2,000 feet will need to be completed at any time. No armoring will be done in the Parker #4 phase on the south area since there is armoring on the river bank anywhere the ✓ iver is within 400 feet of the area to be mined. The BANK ARMOR- ING PLAN is in the APPENDIX and explains how and where the armor- ing will be placed. LGE will be working with the Town of Ft. Lupton for direc- t ions on Flood Plain development. This facility is not in an Urban Area, not near public land, or facilities where public safety is a concern so, inlet/outlet structures for private ✓ eservoirs are not needed. There are no plans to install Inlets o r Outlets for the reservoirs. Those will be the responsibility o f the reservoir developers. The following approved seed mix will be used to seed areas where reclamation calls for revegetation. This mix will place L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 10 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) approximately 41.2 seeds per pound per sq-ft as prescribed by the NRCS planting guidelines. APPROVED SEED MIX Species Lbs. PLS/Acre Western Wheatgrass (Aribba) Big Bluestem (Champ) Blue Grama (Hachita) Switchgrass (Blackwell) TOTALS 5.00 2.50 0.60 1.75 9.85 The reclamation timetable shows the types and amount of land use in each Phase when reclamation is complete. Approximately 12.2% of the area in the permit will not be disturbed by mining, e ither because it is setbacks around well facilities, gaslines ROW's, along the ditches or areas too small to mine that will be kept in their natural state. As mining progresses, the perimeter slopes will be backfilled and graded at or near 3h to lv as discussed in the MINING PLAN . This will insure that when mining ceases only a minor amount of work will have to be done to finish reclamation in the disturbed area. The placement of the temporary soil stockpiles around the setback/perimeter of the mined area would be there if needed. Since the area between the liner, the water line and/or top of the armoring will be a graveled surface area, no resoiling will be needed. The graveled surface will mean the above -water -line areas simply have to be shaped and graded. We expect to salvage sufficient topsoil to meet reclamation ✓ equirements. Of the 809.0 acres ± in the permit area, only 42.1 acres ± or approximately 5.7% will need resoiling and revegetated and remaining above water gravel surface will cover 146.5 acres or 18.1% of the area to be reclaimed. The remaining area will be ✓ eservoir area, covered with water or undisturbed area. Observations at the site show that topsoil on the property has a salvageable depth of 6 to 12 inches, averaging 8 inches e xcept in isolated locations. There appears to be more than adequate soils to meet the demand for this site. Setback areas will not be stripped, and the disturbed areas inside the setbacks will not be resoiled. Gravel surface maintenance roads will be built around each reservoir and left around each gas/oil well where no seeding or resoiling will take place. This will provide ✓ oom around each well or reservoir to service it as needed by the well or reservoir owners. Some inert fill (as defined in Colorado Department Public Health and Environment regulations) may be imported for recycling and resale or in rare cases for reclamation purposes. On -site generated inert material will be used for bank sloping, buried in bank areas around the lakes or will be recycled/sold. An inert fill Notice and Affidavit are included in the Appendix for this mine. Existing soils in place have been capable of producing a fairly dense cover of irrigated crops and dryland grasses and should be suitable for use when revegetating the areas where L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 11 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) seeding will be done. These areas will be returned to at least t heir present vegetative condition when reclamation is complete. Under normal conditions, the operator will strive for a 30 to 40 percent cover rate on the revegetated areas when reclamation is complete. Under normal weather conditions, an adequate moisture reserve will be present for establishment of the proposed seed mixture. No irrigation will be used during reclamation since the plan is to e stablish a vegetation cover that is not dependent on irrigation t o survive. Optional Reclamation Plan. We are submitting two options for final configuration of the ✓ eservoir areas as well. Option A - The reservoir configurations for Option A are show on the large EXHIBIT F - RECLAMATION PLAN MAP . Option B - The inset map shows the reservoir configura- tions under Option B. The methods used to reclaim the reservoirs will be the same for both options. The difference may be an increase/decrease in t he volume of developed water storage and an increase/decrease in t he amount of graveling and revegetation necessary. We do not know when the Mining Option B or the Reclamation Option B or some part(s) of either or both will be implemented, but we are including these optional plans to increase the flexi- bility of this permit and account for the inevitable changes when mining the site. Whenever any part(s) of the Option B plans become feasible, we will file a Technical Revision(s) to the Division to provide revised Mining and/or Reclamation Map(s) that will show the changes. The Technical Revision(s) will discuss any changes needed to implement the optional changes, including a d iscussion on changes in disturbed areas, slurry wall lengths and ✓ evegetated areas. Deep Lake Option Mining has ended in Deep area around the existing lake ✓ evegetated. The town of Ft. o nce it is reclaimed and will augmentation plan. Lake and it will not be lined. The will be graded, shaped and Lupton will receive this property assume responsibility for a water RECLAMATION PERFORMANCE STANDARDS The property will be mined in compliance with the Reclamation P erformance Standards of Rule 6. Grading will be performed to create a final topography that is compatible with the intended final land use. The slopes will vary depending on the final use proposed in a particular area, reservoirs or grassed areas; the ✓ emainder of the area will retain its present drainage pattern. The RECLAMATION PLAN MAP shows how the area will be reclaimed. L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 12 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) The pit will be reclaimed so that a suitable grade for drainage exists, all surface runoff will be directed into the ✓ eservoirs created by mining. Settling ponds may be silted in from wash water, this type of backfilling tends to firm up and stabilize during the first 18 months after being placed. All grading will be done in a manner to control erosion and t o protect areas outside the affected land from slides or other damage. Backfilling and grading will be completed as soon as feasible after mining is completed in a given area. There are no drill or auger holes on the land. Maximum slopes will be within t he limits set forth in the Rules and Regulations of the Board and will be capable of being traversed by machinery. All refuse will be hauled away or disposed of in a manner t hat will control unsightliness and protect the drainage system from pollution. There are no acid-forming or toxic materials involved in this operation. The minimal amounts of petroleum products stored at the site will be stored as prescribed by applicable laws. The storage tanks will be surrounded by a berm o r secondary containment such as storing the tank in a larger metal container adequate to retain any fluid should a tank rup- t ure. In addition, there is adequate absorbent materials on site t o contain any spills that would occur. The operator does not expect prevailing hydrologic conditions t o be disturbed. L.G. Everist, Inc. will comply with applicable Colorado water laws and regulations (as the operator understands t hem) governing injury to existing water rights in order to minimize any disturbance, which might occur to the prevailing t ydrologic balance of the affected land and surrounding areas and t o the quality of water in surface and ground -water systems both during and after the mining operation and during reclamation. In addition, the operator expects to comply with applicable Federal and Colorado water quality laws and regulations. Any water used in the operation of the processing plants and gravel pit will come from water owned by L.G. Everist, Inc. or purchased from an o utside agency suitable for that use. EXHIBIT G -WATER contains specific information concerning impacts and uses of water at this mining operation. This is not a dredge facility, so there are no temporary siltation structures involved in this operation and no mining will be done within the confines of the river. If a U.S. Army Corps of Engineers Permit is required for mining in waters of the U.S., it will be obtained prior to disturbing those areas. Settling ponds will be constructed on the site to collect and recycle water from t he washing operation. There will be no earthen dams on the mined area. The mining and reclamation plans consider existing wildlife use of the site and final reclamation will enhance the area for continued wildlife use. However, creation and management of wildlife habitat is not a specific part of the reclamation plan. Topsoil in the area is good quality and deep enough to salvage what is needed for reclamation. When topsoil is removed t o reach the mineral deposit, it will be segregated and stock- piled. If the topsoil piles remain undisturbed for more than 180 L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 13 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) days, the approved seed mix will be planted on the piles or other means will be employed to preserve the topsoil from wind and water e rosion. This will keep it free of contaminants so that it ✓ emains useful for sustaining vegetation when reclamation begins. The stockpiles will be located in areas where disturbances by o ngoing mining operations will be at a minimum, i.e. along set- backs on the pit perimeter. The topsoil will be handled as little as possible until it is replaced onto areas where needed for ✓ eclamation. We will take measures necessary to insure the stability of the replaced topsoil on graded slopes and ensuring t hat it is spread as evenly as possible. Fertilizer and other soil amendments will be used, only if needed, in accordance with NRCS recommendations. Reclamation will begin once enough area has been opened so t hat any reclamation completed will not be disturbed as mining progresses. This may take one or more years depending on economic conditions and the amount of material mined. By the time mining is completed 75 to 90% of the total mined land will be reclaimed. As mining ends in each reservoir area, only backfilling, grading and shaping of the final mined slopes, bank armoring if needed, g raveling the surface as needed. Where needed, the proposed seed mix will be planted during the next planting season after ✓ esoiling is completed. The area will be monitored for success of ✓ evegetation until accepted by the Division for release. If ✓ evegetation failures occur prior to release, an analysis of the site will be made and the area will be revegetated again as necessary. Reclamation Timetable The numbers presented below represent our estimate of the various area of disturbance in the mine area. They may change as t he actual mining progresses through the site. L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 14 Revised -September, 2025 RECLAMATION PLAN EXHIBIT E (CLINT) Table E-1: Reclamation Phases (7-2025) Phases Years ACRES ± TOTAL LAKE GRAVEL REVEGE- ROAD MI SC . AREA SURFACES TAT ION (DITCHES, UND I S - TURBED AREAS f ETC. Fort Lupton Sand and Gravel - North Area Parker-Panowicz 3-5 43.51 20.45 9.49 6.28 5.97 2.99 Swingle North 3-5 42.02 29.53 6.86 2.46 1.35 3.33 Fort Lupton West 3-5 47.81 41.39 3.47 2.45 1.54 0.29 Swingle South 3-5 67.45 48.70 12.48 1.39 1.77 4.85 Sandstead 3-5 50.05 10.35 0.00 32.94 2.11 4.65 Blue Ribbon 3-5 55.55 37.04 7.69 2.64 1.54 8.17 Deep Lake 3-5 7.90 3.62 0.00 3.98 0.00 0.30 South Area Funakoshi 3-5 42.97 26.77 4.23 1.79 1.25 10.18 Parker #1 3-5 43.17 20.31 4.86 1.97 1.13 16.04 Adams -Parker 3-5 72.92 47.84 14.76 4.05 3.55 6.27 Parker #2 3-5 33.27 24.77 3.98 2.12 10.22 2.40 Parker #3 3-5 43.12 29.21 8.08 2.58 2.08 3.25 Parker #4 3-5 56.94 43.43 7.92 0.20 1.68 3.60 New areas Northeast #1 3-5 70.87 53.26 8.98 2.48 1.97 5.73 Northeast #2 3-5 67.00 49.45 6.42 7.02 1.84 4.11 Northeast #3 3-5 12.12 3.81 2.58 0.99 0.70 4.33 Northwest 3-5 52.33 22.44 6.10 5.03 1.56 18.76 Totals 809.00 512.37 107.90 80.37 40.26 99.25 L.G. Everist, Inc. Ft. Lupton Sand and Gravel 15 M-1999-120 Revised -September, 2025 EXHIBIT L RECLAMATION COSTS The bond currently held by the Division for the existing mining operation is adequate to do the reclamation needed at the existing stages in mine at this time. Since the plan is to add a liner to the Sandstone pond in the future and start liner construction in the Northeast #1 Phase this fall, we have revised the cost estimate to include those two liners and associated work and costs to reclaim the existing stages in their current state of disturbance. Tables L-ln to L -8n and Tables L -9n to L-lln show the areas and cost to reclaim each P hase in the northern permit area. Current bond information: Fort Lupton Sand & Gravel Mine $ 2,002,400.00 The following recap explains the changes to the site that we have d iscussed in detail throughout this amendment application. These changes may affect the reclamation bond. The current conditions d iscussion following this section has tables showings the remaining activities to be used in estimating the financial warranty needs at t his time. The applicant asks the Division to include the following items in its Circes© bonding calculations for this amendment: Bonding Decrease Reclamation Work completed (noted as of 10/21/2024) • Swingle North (2022,)Parker-Panowicz Parker-Panowicz (2014) and Ft. Lupton West (2004) areas - slurry walls certified by the DWR (13, 080') ; • Swingle -South - installed slurry wall (certification test in progress, 6400 ft) • Blue Ribbon - installed slurry wall (certification test in progress, 5675') • Backfilling, sloping and grading is done on Blue Ribbon, Swingle North and parts of Swingle South and Parker-Panowicz. Possible Bonding Increase Installed slurry walls • Sandstead - bond to install slurry wall (2945 ft) • Northeast #1 - bond to install slurry wall (7350 ft) In conjunction with the installation of the new slurry walls, t here were necessary surface disturbances including (a) the working platform that is built for the equipment that is constructing the slurry wall, (b) areas where the material was t aken from to construct the platform, and haul roads between the slurry wall platforms and the material gathering areas. These areas will need only grading and seeding. Mining in Existing area All of the areas currently in the mine are bonded for surface disturbance, liner installation and reclamation. Mining is complete in Parker-Panowicz, Swingle North, Deep Lake and Blue Ribbon and all sloping is done. In Swingle South and Ft. Lupton West mining continues. Current Conditions This reclamation cost estimate is based on the assumption that at the current time no more then 300.00 acres will need some form of L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel Revised -July, 2025 88 RECLAMATI❑N COSTS EXHIBIT L (C❑NT) ✓ eclamation at any -one-time. Of this, 45.78 acres will be gravel surface area needing only grading, 78.82 acres requiring resoiling and seeding and there is 157.97 acres of future reservoir area that needs n o work to reclaim. There is sufficient amounts of growth medium in Swingle South to place 8 inches on the above water area in Parker- t anowicz, the above water area in Swingle South, the backfilled area in Sandstead, Deep Lake and on the Plant Site. The Tables Ll, L2, and L3 contain all the base information used t o calculate this estimate. The disturbed areas include, the plant site; roads; slurry wall construction pads and staging areas; gravel surfaces on the above water areas around certified reservoirs and Blue Ribbon. Also the active mining areas that are stripped, partially mined or partially reclaimed areas. There are three Division of Water Resources (DWR) certified slurry walls. There are two installed slurry walls (12,075 ft total) which are being tested at this time and we assume they will pass certification standards within the next few months. and both are covered by the SWSP water; and We have included a factor of 20% for the 12,075 feet in those phases to cover remedial work on the completed liners until the DWR certification is received. Finally, there are 2 slurry wall (Sandstead & Northeast #1) that will be installed in the n ext 2 years. Both of the new slurry walls will be fully bonded as they are not installed yet. The slurry wall depths to bottom of the key t rench and as built lengths are shown in the Table L3. We have included a factor of 20% for the 12,075 feet in those phases to cover remedial work on the completed liners until the DWR certification is received. The total potential water surface area in Swingle South, is e stimated to be 37.3 acres at this time. Interior sloping is completed o n the Blue Ribbon, and approximately 50% of the Swingle South ✓ eservoir. The dewatering calculation for Swingle South is shown in Table L2, Blue Ribbon would not need dewatering as all slopes are done in that phase. Ft. Lupton West is a certified reservoir, so the slopes could be built using the cut/fill method as the below water slope are d ry at this time. We rounded the pumping time for Swingle South to the n ext day and used 72,300 gal/day as a transmissivity number to figure inflow from the aquifer. This figure is then used in the calculations for the bond amount. In this estimate we would have to complete bank backfilling on 3,040 linear feet at an average of 41.67 cyd/linear feet in Swingle South. The volume of concrete contained in the foundations of the scale and the processing plant is 125 yards. The conveyor is temporary and portable so only removal of 100 yards of concrete foundations for the g rade crossing over WCR 18 is included in the cost estimate. A 627C Cat motor scraper or similar equipment will be used to ✓ esoil the areas needing to be soiled and revegetated. A 140G Cat motor grader or similar equipment will be used to shape the seed bed, t he resoiled areas, grade the graveled surfaces and rip the Plant Site. A D8N Cat dozer or similar equipment will be used to reconstruct the slopes around the perimeter of the reservoirs. Cut/fill sloping is n eed in the Plant Site active mining area as mining has not reached the ✓ eservoir area sides, The tables below outline, the various areas of disturbance at t his time. As mining moves into the amendment area, the total d isturbance will begin to reduce as reclamation is completed in the 7 stages in the existing active mine area. L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel Revised -July, 2025 89 Declination MN MN8°01'E Name: FORT LUPTON Date: 06/17/25 Scale: 1 inch = 1,000 ft. LOCATED IN PARTS OF , SECTIONS 19, 30 & 31, T -2-N, R -66-W, AND PART OF SECTION 25 & 36, T -2-N, R -67-W, 6TH P.M., WELD COUNTY, COLORADO i; C) Copyright 2016, Tribe 4 a'ation ted L.G. EVERIST, INC. FT. LUPTON SAND AND GRAVEL MINE FIGURE L - SLURRY WALLS L.G. Everist, Inc. Ft. Lupton Sand and Gravel 90 M-1999-120 Revised - July 2025 RECLAMATION COSTS EXHIBIT L (CONT) TABLE LI CALCULATION FACTORS Explanation Quantity Units Soil depth 8.00 Inches Lake South) bank sloping re -construction (Swingle 41.67 cy/Lft Lake (Northeast bank sloping #1) re -construction 74.05 cy/lft Slurry wall installation cost $6.25 sq-ft Non certified Slurry wall bond factor 20% Swingle South slope construction time 267 days Weed control costs $5,000.00 Per year TABLE L2 DEWATERING DATA (Swingle South only) Description Amount Units Area 100% of lake depth 28.65 acres maximum depth 33 feet length of '/%:1 slopes 3,400 feet Unit volume of water on 1/2:1 slopes 156.25 cft/Lft length of 3:1 slopes 3,040 Ift Unit volume of water on 3:1 slopes 937.5 cft/Ift Gallon conversion factor 7.48 gal/cft Transmissivity # 72,300 gal/day Pump rate minimum 6,000 gpm CALCULATED VOLUMES AND TIMES Slope water volumes 1/2 :1 slope capacity 6,9963,880 gal 100% depth 383,018,863 gal Total pumping volume 452,982,743 gal Pumping time Dewater lake 45.14 Days Slope construction time 13.06 Days Recharge sloping time factor and for inflow Dewatering during 0.49 Days TOTAL PUMPING TIME* 59.00 Days *NOTE: pumping time rounded to next full day L.G. Everist, Inc. M-1999-120 Ft. Lupton Sand and Gravel 91 Revised -July, 2025 RECLAMATION COSTS EXHIBIT L (C❑NT) TABLE L3 - CURRENT CONDITIONS (revised 6/2025) RECLAMATION ACTIVITY STAGE Parker Panowicz Swingle North Fort Lupton West Swingle South Blue Ribbon Sandstead Deep Lake Northeast #1 TOTALS GRAVEL SURFACE GRADE (ac) 9.49 6.86 12.48 7.96 8.98 45.78 REVEGETATE & GRADE (ac) 6.28 2.46 35.14 19.83 2.64 32.94 3.98 2.48 105.75 RESOIL VOLUMES @ 8 inches 6,754 2,646 37,795 21,328 2,839 35,430 4,281 2,667 113,740 1/2 :1 SLOPE CUT/FILL SLOPING (yds) 39,440 126,67 31,391 197,508 1/2 :1 SLOPE BACKFILL SLOPING (yds) 74,050 74,050 Bank Armoring (In) 1,030 1,030 DEWATER (hrs) 59.00 59.00 BACKFILLING SETTLING POND (yds) 72,146 72,146 SLURRY WALL LENGTH (Lft) certified certified certified 6,400* 5,675* 2,945 7,350 10,295 SLURRY WALL COLOR (Figure L) BLUE BLUE BLUE YELLOW YELLOW ORANGE ORANGE SLURRY WALL DEPTH (ft) 33.0 43.0 30.00 38.00 CONCRETE DEMOLITION (yds) 25 100 100 225 ROADS (ac) 5.97 1.35 1.77 1.54 1.54 2.11 0.70 14.98 ate * slurry walls complete but not certifie L.G. Everist, Inc. Ft. Lupton Sand and Gravel M-1999-120 Revised -July, 2025 RECLAMATION COSTS EXHIBIT L (CONT) ESTIMATED UNIT COSTS FOR RECLAMATION ITEMS: Unit Cost 1. Revegetation includes grass seed mix and labor to drill . . . . . . . . . . . . . . . . . 2. Re -spreading soil and/or growth media with 627-E Motor Scraper, Haul distance less than 900 . . 3. Rip seed bed in plant site, 140G motor grader . . 4. Grade and shape gravel surfaces, 140G motor grader 5. full service rental of fuel, maintenance and . • Pumping costs includes, self contained pump, servicing daily. 6. Cut/Fill 1 1 slope Less than 120 feet . 7. Backfill 1 1 slope Less than 120 feet . Backfill Sandstead 8. 9. 10. 11. 12. 13. 14. . . . areas . . . areas . . . . . . . . . . . . . D8N Dozer push distance • . . . . . . . . . D8N Dozer push distance . • • . . $1,700.00/AC. . . . . . $1.929/YD 3 . . . . $193.69 ac. . . . $193.69 ac . . . . • . . . . . . . . . . . . . . . . . . Settling Pond. Slurry wall construction Slurry wall repair bonding Bank Armoring Place Materials Concrete demolition & on -site disposal Conveyor crossing foundation demolition. Secondary Revegetation seeding only . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RECLAMATION COSTS 1. Revegetation, 105.75 ac @ $1,700.00/ac 2. Resoiling, 113,740 x 1.12 @ $1.929/yd3 3. Rip plant site & seed beds 105.45 ac @ $193.69/ac. 4. Grading gravel surface & Seedbeds 158.54 ac. @ $193.69/ac 5. Dewatering, 59 days @ $221.67/day 6. Cut/fill and compact side slopes, 197,508 yds @ $1.08/yd3 7 Backfill and compact side slopes, 74,500 yds @ $1.25/yd3 8. Backfill settling pond, 72,146 CYD @ $2.22/yd3 22/yd 3 9. Slurry installation fee. 367,650 sq-ft @ $6.25/ft 10. Slurry contingency fee. 455,225 sq-ft @ $1.25/ft 11. Bank Armoring 2,421 cyd @ $2.22/cy 12. Demolition & on -site disposal 225 yds@ $8.30/yd3. 13 Secondary revegetation 105.75 x 25% x $1,262.00/ac 14 Weed control costs Mobilization Liability insurance @ 2.02% Contingency @ 3.00% Profit @ 10% Engineering and Management Bond Processing Fee Reclamation Management @ 4.0% Engineering @ 5.23% Direct Cost Total Indirect Costs Total Indirect costs Total bond estimate Request Bond be set at $4,345,000.00 Equipment listed in this estimate is used for the calculations and actual reclamation activities at the mine. . $221.67/day** $1.08/YD3 . $1.25/YD3 . $2.22/YD3 . $6.25/sq-FT . $1.25/sq-FT . $2.70 /Yd . $8.30/Yd. . $8.30/yd $1,262.00/ac $179,775.00 $219,404.46 $20,482.72 $30,707.61 $13,078.53 $213,308.86 $92,562.50 $160,163.42 $2, 187, 687.50 $305,031.25 $6,535.35 $1,867.50 $33,364.13 $5,000.00 $3,468,968.82 $6,406.48 $70,073.17 $104,069.06 $346,896.88 $521,039.12 $500.00 $138,758.75 $181,427.07 $4,345,003.28 similar types may be used in * Estimate for services from Rain for Rent, Ft. Lupton, CO (970) 535-4963 the L.G. Everist, Inc. Ft. Lupton Sand and Gravel 93 M-1999-120 Revised -July, 2025 L.G. Everist, Inc - Ft. Lupton Sand and Gravel RECLAMATION COST ESTIMATE 07/22/2025 EXHIBIT L (CONT) Permit # M-1999-120 Table L-ln Task Parker/Pano Pano Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 43.51 TOTAL MINED 20.60 WATER AREA 20.45 Undisturbed (AC) 2.99 001 Revegetate (AC.) 6.28 $1,700.00 $10,676.00 002 Resoil (AC.) 6.28 0.67 6,754 900 $1.929 $13,029.41 003 Rip seed bed (AC.) 6.28 $193.69 $1,216.37 004 Grading and Shaping (AC.) includes and graveled resoiled areas 15.77 $193.69 $3,054.49 005 Dewatering (per day) 0.00 $221.67 $0.00 006 Cut Fill Sloping (CYD) complete $1.08 0 007 Backfill (Cuyds) sloping complete 500 $1.25 0 008 Slurry wall SQ-FT.) (LINEAR Certified 28 $6.25 0 010 Concrete Demo Plant (Cuyds) 25 $8.30 $207.50 011 Secondary seeding (AC.)@250 1.57 $1,262.00 $1,981.34 012 Annual Weed Control $500.00 013 Backfill Setteling Pond (Cyd) 0.00 $2.22 $0.00 014 Reservoir armoring (Feet) 0 2.35 0 500 $2.70 $0.00 015 Underdrain Instalation (Feet) 0 $82.03 $0.00 Phase total project Table L -2n $30,665.11 Task Swingle North Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 42.02 TOTAL MINED 31.88 WATER AREA 29.53 Undisturbed (AC) 3.33 001 Revegetate (AC.) 2.46 $11700.00 $4,182.00 002 Resoil (AC.) 2.46 0.67 2,646 900 $1.929 $5,103.88 003 Rip seed bed (AC.) 2.46 $193.69 $476.48 004 urausny anu bnapiny (AC.) includes resoiled Anti p.aa.I r17 a.1 A .Z r,A A 13.14 $193.69 $2,545.09 006 Cut Fill Sloping (CYD) Complete $1.08 0.00 007 Backfill sloping (Cuyds) Complete 500 $1.25 0.00 008 Slurry wall (LINEAR SQ-FT.) Certified 38 $6.25 0.00 011 Secondary seeding (AC.)@25% 0.62 $1,262.00 $776.13 012 Annual Weed Control $500.00 Phase total project $13,583.57 L.G. Everist, Inc. Ft. Lupton Sand and Gravel L-1 M-1999-120 Revised - July 2025 L.G. Everist, Inc - Ft. Lupton Sand and Gravel RECLAMATION COST ESTIMATE 07/22/2025 EXHIBIT L (CONT) Permit # M-1999-120 Table L -3n 3n Task Swingle South Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 67.45 TOTAL MINED 52.31 WATER AREA 48.70 Undisturbed (AC) 4.85 001 Revegetate (AC.) 19.83 $1,700.00 $33,711.00 002 Resoil (AC.) 19.83 0.67 21,328 900 $1.929 $41,142.23 003 Rip seed bed (AC.) 19.83 $193.69 $3,840.87 004 Grading and Shaping (AC.) includes resoiled and graveled areas 32.31 $193.69 $6,258.12 005 Dewatering (per day) 59.00 $221.67 $13,078.53 006 Cut Fill Sloping (CYD) 3040 41.67 126,677 200 $1.08 $136,810.94 007 Backfill sloping (Cuyds) 0 $1.25 $0.00 008 Slurry wall SQ-FT.) (LINEAR complete 33 $6.25 $0.00 009 Slurry wall Contingency fee 20% (LINEAR SQ-FT.) 6,400 33 $1.25 $264,000.00 011 Secondary seeding (AC.)@250 4.96 $1,262.00 $6,256.37 012 Annual Weed Control $500.00 Phase total project Table L -4n $505,598.06 Task Ft Lupton West Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 47.81 TOTAL MINED 41.25 WATER AREA 41.39 Undisturbed (AC) 0.29 001 Revegetate (AC.) 35.14 $1,700.00 $59,738.00 002 Resoil (AC.) 35.14 0.67 37,795 900 $1.929 $72,906.60 003 Rip seed bed (AC.) 35.14 $193.69 $6,806.27 004 Grading and Shaping (AC.) includes resoiled and graveled areas 38.61 $193.69 $7,478.37 006 Cut Fill Sloping (CYD) 3400 39,440 200 $1.08 $42,595.20 007 Backfill sloping (Cuyds) 0 500 $1.25 0.00 008 Slurry wall (LINEAR SQ-FT.) Certified 33.00 $6.25 0.00 010 Concrete Demo Plant (Cuyds) 100 $8.30 $830.00 011 Secondary seeding (AC.)@256 8.79 $1,262.00 $11,086.67 012 Annual Weed Control $500.00 Phase total project $201,941.11 L.G. Everist, Inc. Ft. Lupton Sand and Gravel L-2 M-1999-120 Revised - July 2025 L.G. Everist, Inc - Ft. Lupton Sand and Gravel RECLAMATION COST ESTIMATE 07/22/2025 EXHIBIT L (CONT) Permit # M-1999-120 Table L -5n 5n Task Blue Ribbon Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 55.55 TOTAL MINED 37.77 WATER AREA 37.04 Undisturbed (AC) 8.17 001 Revegetate (AC.) 2.64 $1,700.00 $4,488.00 002 Resoil (AC.) 2.64 0.67 2,839 900 $1.929 $5,477.33 003 Rip seed bed (AC.) 2.64 $193.69 $511.34 Grading and Shaping 004 (AC.) includes resoiled 10.33 $193.69 $2,000.82 and graveled areas 006 Cut Fill Sloping (CYD) 0 $1.08 $0.00 007 Backfill sloping (Cuyds) 0 500 $1.25 $0.00 008 Slurry wall SQ-FT.) ( LINEAR complete p 43.00 $6.25 $0.00 Slurry wall 009 Contingency fee 20% 5,675 43.00 $1.25 $7,093.75 (LINEAR SQ-FT.) 010 Concrete Demo Plant 100 $8.30 $830.00 (Cuyds) 011 Secondary seeding 0.66 $1,262.00 $832.92 (AC.)@250 012 Annual Weed Control $500.00 Phase total project Table L -6n $21,734.16 Task Sandstead (Dodge) Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 50.05 TOTAL MINED 36.64 WATER AREA _ 10.35 Undisturbed (AC) 4.65 001 Revegetate (AC.) 32.94 $1,700.00 $55,998.00 002 Resoil (AC.) 32.94 0.67 35,429 900 $1.929 $68,342.16 003 Rip seed bed (AC.) 32.94 $193.69 $6,380.15 004 Grading and Shaping (AC.) includes and graveled resoiled areas 32.94 $193.69 $6,380.15 005 Dewatering (per day) 0.00 $221.67 $0.00 008 Slurry wall ( LINEAR SO -FT.) 2, 945 30.00 $6.25 $552,187.50 011 Secondary seeding (AC.)@25% 8.24 $1,262.00 $101392.57 ' 012 Annual Weed Control $500.00 013 Backfill Setteling Pond (Cyd) 72,146 $2.22 $160,163.42 Phase total project $860,343.94 L.G. Everist, Inc. Ft. Lupton Sand and Gravel L-3 M-1999-120 Revised - July 2025 L.G. Everist, Inc - Ft. Lupton Sand and Gravel RECLAMATION COST ESTIMATE 07/22/2025 EXHIBIT L (CONT) Permit # M-1999-120 Table L -7n Task Deep Lake Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 7.90 TOTAL MINED 5.75 WATER AREA 3.62 Undisturbed (AC) 0.30 001 Revegetate (AC.) 3.98 $1,700.00 $6,766.00 002 Resoil (AC.) 3.98 0.67 4,281 900 $1.929 $8,257.49 003 Rip seed bed (AC.) 3.98 $193.69 $770.89 004 Grading and Shaping (AC.) includes resoiled and graveled areas 3.98 $193.69 $770.89 005 Dewatering (per day) 0.00 $221.67 $0.00 011 Secondary seeding (AC.)@25O 1.00 $1,262.00 $1,255.69 012 Annual Weed Control $500.00 Phase total project Table L -8n $18,320.95 Task Northeast # 1 Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 70.87 TOTAL MINED 56.82 WATER AREA 53.68 Undisturbed (AC) 6.25 001 Revegetate (AC.) 2.48 $1,700.00 $4,216.00 002 Resoil (AC.) 2.48 0.67 2,667 900 $1.929 $5,145.37 003 Rip seed bed (AC.) 2.48 $193.69 $480.35 004 Grading and Shaping (AC.) includes resoiled and graveled areas 11.46 $193.69 $2,219.69 005 Dewatering (per day) 0.00 $221.67 $0.00 006 Cut Fill Sloping (CYD) 1,695 18.52 31,391 $1.08 $33,902.71 007 Backfill sloping (Cuyds) 1,000 74.05 74,050 $1.25 $92,562.50 008 Slurry wall ( LINEAR SQ-FT.) 7, 350 38.00 $6.25 $1,745,625.00 011 Secondary (AC.)@25O seeding 0.62 $1,262.00 $782.44 012 Annual Weed Control $500.00 014 Reservoir armoring (per foot) 1,030 2.35 2,421 $2.70 $6,535.35 ' Phase total project $1,891,969.41 L.G. Everist, Inc. Ft. Lupton Sand and Gravel L-4 M-1999-120 Revised - July 2025 L.G. Everist, Inc - Ft. Lupton Sand and Gravel RECLAMATION COST ESTIMATE 08/05/2025 EXHIBIT L (CONT) Permit # M-1999-120 Table L -9n Task Northeast # 2 Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 67.00 TOTAL MINED 56.47 WATER AREA 49.45 Undisturbed (AC) 4.11 001 Revegetate (AC.) 7.02 $1,700.00 $11,934.00 002 Resoil (AC.) 7.02 0.67 7,550 900 $1.929 $14,564.72 003 Rip seed bed (AC.) 7.02 $193.69 $1,359.70 004 Grading and Shaping (AC.) includes resoiled and graveled areas 13.44 $193.69 $2,603.19 006 Cut Fill Sloping (CYD) 1,398 7.82 10,932 $1.08 $11,806.95 007 Backfill sloping (Cuyds) 1,000 31.3 3,130 500 $1.25 $3,912.50 008 Slurry wall (LINEAR SO -FT.) 6,880 38.00 $6.25 $1,634,000.00 012 Annual Weed Control $500.00 Phase total project Table L -10n $1,680,681.07 Task Northeast # 3 Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 12.12 TOTAL MINED 4.52 WATER AREA 4.22 Undisturbed (AC) 4.33 001 Revegetate (AC.) 0.99 $1,700.00 $1,683.00 002 Resoil (AC.) 0.99 0.67 1,065 900 $1.929 $2,054.00 003 Rip seed bed (AC.) 0.99 $193.69 $191.75 004 Grading and Shaping (AC.) includes resoiled and graveled areas 2.58 $193.69 $499.72 006 Cut Fill Sloping (CYD) 730 31.3 22,849 $1.08 $24,676.92 008 Slurry wall ( LINEAR SO -FT.) 21925 35.00 $6.25 $639,843.75 012 Annual Weed Control $500.00 014 Reservoir armoring (per foot) 970 2.35 2,280 500 $2.70 $6,154.65 Phase total project $675,916.14 Table L -11n Task Northwest Acres Length Average Depth (FT) CYD/FT Volume (Cyds or Sqft) Push/Haul Distance Unit Cost Total cost TOTAL AREA 52.33 TOTAL MINED 27.47 WATER AREA 22.44 Undisturbed (AC) 18.76 001 Revegetate (AC.) 5.03 $1,700.00 $8,551.00 002 Resoil (AC.) 5.03 0.67 5,410 900 $1.929 $6,957.32 003 Rip seed bed (AC.) 5.03 $193.69 $974.26 004 Grading and Shaping (AC.) includes resoiled and graveled areas 11.13 $193.69 $2,155.77 006 Cut Fill Sloping (CYD) 695 12.86 8,938 $1.08 $91652.72 007 Backfill sloping (Cuyds) 500 500 70.42 44.95 57,455 500 $1.25 $71,818.75 008 Slurry wall (LINEAR SO -FT.) 6,220 35.00 $6.25 $1,360,625.00 012 Annual Weed Control $500.00 013 Backfill Setteling Pond (Cyd) 0 $2.22 $0.00 014 Reservoir armoring (per foot) 0 2.35 0 500 $2.70 $0.00 015 Ground water Drain Instalation (Feet) 2,540 $82.03 $208,356.20 Phase total project $1,671,177.98 Schnabel ENGINEERING TO: COMPANY: ADDRESS: FROM: T 303.651.1468 / F 303.651.1469 600 5. Airport Road, Suite A-205 / Longmont, CO 80503 schnabel-eng.com TECHNICAL MEMORANDUM Lynn Mayer Shults DATE: August 12, 2025 L.G. Everist, Mountain SUBJECT: Hens Property Groundwater Model Division Revision 2 7321 E. 88th Ave., Suite 200, PROJECT L.G. Everist Heins Property Henderson, Co 80640 NAME/NO.: 20C26026.06 Sampson Ash, PG CC: Susan Rainey, PE Victor deWolfe, PE, PG INTRODUCTION This memorandum discusses the groundwater impact analysis at the proposed Heins Property mine site. The purpose of the analysis is to provide information related to the potential impacts to the groundwater table in the vicinity of the site. This includes mounding upgradient and shadowing downgradient of the proposed slurry walls at the site. The site is located approximately three miles north of the town of Fort Lupton, Colorado. The mine plan for the site consists of two main mining areas (North and south) divided by the Meadow Island Ditch and, when constructed, the relocated east branch of the Lupton Bottom Ditch. There is a possible third or West cell. Slurry walls will be constructed around the perimeter of each of the planned cells to cut off groundwater, as shown on Figure 1. A standard offset of 200 feet from the river, and 15 feet from property lines, rights -of -way or utilities were used for the proposed slurry wall alignments. Groundwater modeling was conducted to evaluate the impact of the proposed slurry walls on groundwater levels. The objectives of the groundwater modeling are to: 1. Approximate the existing hydrogeologic conditions pre -slurry wall using available data. 2. Simulate the hydrogeologic effects of the slurry walls by predicting potential groundwater mounding upgradient of the property and shadowing downgradient. To satisfy these objectives, two steady-state (equilibrated) groundwater models were constructed for: 1. Pre -slurry wall conditions 2. Post -slurry wall construction conditions This modeling memorandum presents the geologic setting; a general site conceptual model of the aquifer system; the groundwater modeling software used; construction of the model; calibration of the model in terms of target residuals and mass balance; and finally, a discussion of the predictive simulations and conclusions. The groundwater modeling was conducted in general conformance with ATM standards for groundwater modeling.. LG. Everist Heins Property Groundwater Modeling GEOLOGIC SETTING Geotechnical Investigations The general subsurface lithology at the Heins Property consists of one to two feet of overburden at the surface, underlain by alluvial sand and gravel deposits ranging between 21.5 and 45.5 feet thick, followed by weathered Laramie Formation bedrock measuring about two feet thick, and finally less weathered Laramie Formation bedrock. The bedrock consisted of claystone, shale, and fine-grained cemented sandstone which are fine-grained rock types and therefore have a low hydraulic conductivity. The total depth to bedrock for the site was estimated to vary from about 23.8 to 47.5 feet deep or elevations 4812 to 4848 feet, respectively. The groundwater depths on the property range between 0.2 to 10 feet below ground surface or between elevations 4883 to 4869 feet, and the aquifer had a saturated thickness ranging between 16 to 30 feet. Subsurface lithology data was obtained from the geotechnical investigation on the property, consisting of 26 borings, performed by Schnabel Engineering between September 23, and October 10, 2024. These boring locations are shown on Figure 1. The information from this investigation was used along with existing data from other projects in thedomain to create the bedrock contours used in the groundwater model. Site Conceptual Model The site conceptual model of the South Platte Alluvial Aquifer as shown in Diagram I below consists of two layers, the unconfined sand and gravel of the South Platte Alluvial Aquifer and the Laramie Formation. The overburden was removed from the model for simplification. Even though this material has a lower hydraulic conductivity it is insignificant in the contribution of the model. The highly conductive Alluvial Aquifer has an estimated hydraulic conductivity of 500 ftiday (0,17 cm/sec) (CDWR, 2024) and is bounded on the bottom by the fine-grained rock of the Laramie Formation. The Laramie Formation has an average hydraulic conductivity of 3.2x10-3 ft/day (1 IA 0-6 cm/sec) as determined by packer testing during the geotechnical investigation. The rocks that comprise the Laramie Formation have a low hydraulic conductivity. In the model it acts as a no -flow boundary due to the orders of magnitude of difference in hydraulic conductivity between the two layers. WEST Edge of .Alluvial Aquifer South Platte Alluvial. Aquifer - Sands and Gravels tur-r-'. Laramie Formation - Claystone. Shale, and Fine Grained Cemented Sandstone a Diagram I — Site Conceptual Model _yr EAST South Platte River of to Scale Project 20C26026.06 it August 12, 2025 Page 2 Schnabel Engineering L.G. Everist Heins Property Groundwater Modeling The primary sources of inflows into the alluvial aquifer are: 1. Subsurface inflow from the upgradient end of the aquifer and tributary valleys 2. Infiltration of precipitation and irrigation 3. Seepage from unlined ditches or reservoirs (depending on time of year) The primary sink or area of outflow from the alluvial aquifer is theSouth Platte River because it is a gaining stream. However, water outflow from the aquifer also includes: 1. Seepage into unlined reservoirs or mines 2. Seepage into unlined ditches (depending on time of year) 3. Well withdraws 4. Subsurface outflow at the downgradient end of the aquifer The model domain encompasses the South Platte River alluvial floodplain between Weld County Road 14 in the south and Weld County Road 24 in the north. The domain is set between the confluences of Big Dry Creek and Little Dry Creek within the South Dlatte River valley (Figure 2). The western boundary is set at the extent of the Alluvial Aquifer which is correlated to Elevation 4900 feet. The South Platte River is the primary surface discharge for groundwater in the area and is set as the eastern boundary of the model. The ditches and unlined ponds are drains in the model domain that can add or remove water to the aquifer depending on the head differences. Drains with outflow, for example, Little Dry creek, return outflows to the South Platte River by surface flow and/or seepage into the aquifer. The topography slopes gently down from south to north along the valley. The project area exhibits widespread aggregate mining where slurry walls and/or clay liners (low permeable barriers) have been installed. These low permeability features act as hydraulic barriers and redirect groundwater flow, creating mounding on the upgradient sides and shadows on the downgradient sides. Land use in the area consists of mining and agricultural uses. ANALYSIS APPROACH — STEADY-STATE GROUNDWATER MODELING Overview The Heins groundwater model was developed using a combination Geographic Information System (GIS) database and GIS data analysis techniques (E RI, 2024) as well as Leapfrog geologic modeling to create model layers (Leapfrog Geo, 2024). That data was then imported into the software Groundwater Vistas Version 7.0 (Rumbaugh & Rumbaugh, 2015), a graphical user interface for MODFLOW. Groundwater Modeling Software The MODFLOW-2005 computer code was used to simulate groundwater flow by solving the 3 -dimensional groundwater flow equation using a finite -difference method where the model domain is subdivided into a grid of cells, and the hydraulic head is calculated at the centroid of each cell (Harbau h, 2005). Groundwater flows into and out of the model via head -dependent flux boundaries. These flows are calculated in the same manner for each simulation. Pre- and post -processing of MODFLOW-2005 files were completed using Groundwater Vistas. Groundwater Vistas is a graphical Project 20O260 6.06 it August 12, 2025 Page 3 schnabel Engineering L.G. Everest Heins Property Groundwater Modeling user interface that facilitates model construction, runs MODFLQW, data analysis and data presentation. It summarizes results as contours, shaded contours, velocity vectors and detailed mass balance analyses. This section discusses the modeling assumptions, limitations, solution techniques, and the way that they affect the models. When analyzing the groundwater flows in the model, as implemented, MODFLOW-2005 simulates the system as an unconfined aquifer with one value of hydraulic conductivity. One limitation is that cells can go "dry" or "flood". If the calculated head is above the top of the aquifer (ground surface) at any model cell, then that cell is flooded and will be treated as if the aquifer is confined (i.e., the saturated thickness will equal the top -elevation minus the bottom -elevation). If the calculated head falls below the bottom of the aquifer, that cell is dry and will be assigned a zero value for hydraulic conductivity. The preconditioned conjugate -gradient with Newton (PC N) solver package of MODFLOW-2005 was used to solve the groundwater flow equations for the model. It combines the efficiency of the conjugate gradient method with Newton-Raphson iteration to handle nonlinearities commonly found in unconfined aquifers and head -dependent boundary conditions. The solver uses preconditioning techniques to improve convergence speed and stability, making it well -suited for large,complex, and nonlinear models where traditional solvers like PCG or SOR may struggle. This package defines the number of outer and inner solver iterations, as well as criteria for both maximum head and residual change between iterations before allowing convergence. Tolerances for the maximum change in head and flow residual between iterations were specified as 1x1 0-3 feet and 100 cubic feet per day (cfd), respectively. These tolerances result in a mass balance of less than 0.001 %, indicting model convergence and solution accuracy. Steady-state conditions were simulated because the maximum water level rise is of principal interest and the time required to reach steady state is not of concern. Model Geometry and Spatial Discretization The model was constructed by importing shapefiles made in GIS representing aquifer parameters and boundary conditions into Groundwater Vistas. The model domain is a rectangular area 12,760 feet wide by 23,120 feet long (Figure 2). The domain was divided into a grid of cells measuring 10 feet on each side. Active cells contain values representing the following parameters: 1. The elevation of the top of the aquifer 2. The elevation of the bottom of the aquifer 3. The hydraulic conductivity of the aquifer 4. The recharge applied to the cell 5. The initial groundwater head within the aquifer 6. The boundary conditions for the model Layer Construction The maximum top of the alluvial aquifer is represented by the topography of the ground surface. Topographic data used for this model input are from a 1 -meter digital elevation model (DEM) obtained from the Colorado Hazard Mapping & Risk Map Portal (CWCB, B, 2024). Project 20C26026.06 / August 12, 2025 Page 4 Schnabel Engineering L.G. Everist Heins Property Groundwater Modeling The bottom of the aquifer and model is the low permeability Laramie Formation bedrock. Therefore, the model contains an elevation map of the bedrock surface. To create this surface, bedrock elevation data was obtained from the geotechnical investigation described previously in this memo, data from previous projects done for L.G Everist in the area, and publicly available data from Colorado's Decision Support Systems (CDWR, 2024). The bedrock elevations were contoured in AutoCAD. Overall, the spatial reliability of the bedrock data is considered good and deemed appropriate for the scope of this groundwater model. The DEM and the resulting bedrock elevation contour map were imported into Leapfrog to create the top and bottom of the alluvial aquifer. Due to the 10x10 g foot grid size used, the topographic and rock elevation data were averaged within that area resulting in some variation between model elevations and contoured ground/rock elevations. Aquifer Properties The horizontal hydraulic conductivity (Kx and Ky) of the alluvial aquifer used in the model was input between the range of 500 feet per day (fpd), and areas with known wash fine fill had an input of approximately 50 fpd. This value is based on average values from the Colorado Decision Support Systems GIS map and our experience in the area. We assumed an anisotropy ratio of 0.5 (Kv/Kr), meaning that the value in the vertical direction (Kv) is half the value in the radial direction (Kr). A groundwater elevation contour map for the alluvial aquifer provided the starting heads for the finite difference solution and was used to define general head boundary values. This surface was developed using the groundwater level data collected from monitoring wells in the area. This consists of wells owned by LG Everist on -site and off -site. Boundary Conditions The boundary conditions listed below define the sources and sinks for the water budget of the model. The system is assumed to be in equilibrium under pre slurry wall conditions. The model domain is inactive outside of the defined boundary conditions. These boundaries are shown on Figure 2. Exterior Boundary Conditions The exterior or the outer boundary conditions used for the model include three general head boundaries, two no -flow boundaries, and the river boundary: General Head Boundaries 1. Subsurface inflow from the upgradient portion of the alluvial aquifer (Southern Boundary). 2. Subsurface outflow from the downgradient portion of the alluvial aquifer (Northern Boundary). 3. Subsurface inflow from the tributary valley of Little Dry Creek (Part of the Western Boundary). These edges of the aquifer were chosen to be modeled by the MODFLOW General -Head boundary package to allow groundwater to flow into and out of the model and to permit groundwater elevations to change at the boundaries in response to aggregate mining. Project 20C26026.06 / August 12, 2025 Page 5 Schnabel Engineering L.rG. Everist Heins Property Groundwater Modeling No -Flow Boundaries 1. The edge of the South Platte Alluvial Aquifer (Part of the Western Boundary). 2. The contact between the South Platte Alluvial Aquifer and Laramie Formation (Bottom Boundary). The base and most of the western side of the model are simulated using the no -flow boundary (inactive cells) to represent the contact between the low -conductive Laramie Formation and the alluvial aquifer. River Boundary 1. The South Platte River (Eastern Boundary). The elevations of the river were determined using river gauges near the site to estimate starting and ending elevation. The South Platte River was simulated using the MODFLOW River package, which contributes water to or releases water from the aquifer at adjacent cells as determined by the hydraulic gradient between the aquifer and the river and as a function of streambed conductance. The unlined reservoirs or ponds within the model domain were also modeled as river boundaries. interior Boundary Conditions interior boundaries or inner boundaries included 6 drains, and 8 no -flow boundaries. Drains The ditches, unlined ponds, intermittent stream (Little Dry Creek), and the drain at the Zadel Pit within the model were simulated using the MODFL0W Drain Package which removes water from the adjacent cells as determined by the hydraulic gradient between the aquifer and the ditches and stream as a function of drain conductance. No -Flow Boundaries Aggregate mines that have installed slurry walls and/or clay slope liners around their properties were simulated using the no -flow boundary (inactive cells) as their contributions to the aquifer are negligible. CALIBRATION Calibration Process Model Calibration is an iterative process of adjusting model parameters (aquifer properties) and boundary conditions to obtain a reasonable match between field measurements and model -computed values. Calibration was conducted for the steady-state models, which is assumed to represent conditions observed during the months of August 2024 and March 2025. August 2024 was used to calibrate flows from the Lupton Bottom West Branch Ditch and measured piezometric heads while the March 2025 calibration was used to calibrate the model to piezometric heads recorded after the installation of the Zadel Pit Drain. The calibration targets for the two different models include the measured groundwater elevations observed in 34 monitoring wells (Figure 2) measured during the month of March 2025, and from 22 groundwater measurements taken during the geotechnical investigation described above, Project 20026026.06 it August 12, 2025 Page 6 Schnabel Engineering �. . Everist Heins Property Groundwater Modeling The monitoring wells were the primary targets as they were recorded on specific dates, offering high reliability and spatial relevance; while the geotechnical borings and publicly available data were secondary targets as they included data outside the time frame of calibration, which while useful for broader context is considered less reliable due to potential inaccuracies and differences in aquifer conditions. The model was calibrated primarily to the project -specific data, with the secondary dataset used to support regional trends and assess model robustness. Model calibration acceptability is subjective, but the following general guidelines for judging calibration sufficient for this model included: overall calibration quality is determined through statistical comparison of model results with field measurements and observations. This model includes only water elevations. • The primary statistic used in gauging and reporting "best fit" was the squared error of the measured and computed groundwater elevations. • Calibration continued until the coefficient of determination (R2) between the measured and observed groundwater elevations was within 10% of 1. The goals of the predictive simulation targets are: 1. To show how field measured groundwater heads differ from those in the steady-state simulation 2. To show how pre -slurry wall groundwater heads differ from those in the predictive simulations. Calibration Results The model is simple and homogeneous, containing heads that are well constrained by measured values for boundary conditions as well as a reasonable estimate of hydraulic conductivity. The calibration targets used for the pre -slurry wall condition steady state model illustrate that the input groundwater heads are generally within five feet of the measured values throughout the entire model. However, near the site where the mounding is expected the modeled heads are within two feet of the observed heads. Calibration plots for the two calibrated models show the residuals (Observed Head Values Vs. Modeled Head Values) for the site specific and publicly available data in Figure 3. The calibrated models both resulted in an R2 value of 0.99 at the end of the calibration process. In Figure 4 the groundwater elevation contours for the steady state calibrated model are shown. Figure 5 shows the data in terms of groundwater depth below ground. The contours with zero labels show where groundwater is at or near the ground surface. These locations generally match the locations of unlined pits as well as ditches and drains cut into the land. This illustrates the model is well calibrated to the internal boundary conditions. There is a long zero contour south of the existing slurry wall complex that was not modeled as a drain. This area is along Little Dry Creek, which, along with the South Platte River, flooded in 2013. At this location the floodwaters breached both Suburban and Weast Meadows reservoirs and deposited eroded sediment from the floodplain in the vessels. The resulting erosion scarps formed basins flowing breach repairs. These depressions match the flood topography and are four to six feet deep. Onsite observations suggest that the water level in the upper "fingers" of the depressions is about a foot deep. This means that the water level in a 4 -foot depression would have been 3 feet deep prior to the flood erosion. We understand that flood control studies are being conducted for Little Dry Creek. Project 20O260 6.06 August 12, 2025 Page 7 Sebnabel Engineering �. . Everist Heins Property Groundwater Modeling The mass balance reported by MODFLOW for the steady state pre -slurry wall model in March 2025 is as follows: March 28, 2025 Inflows = 1,214,888.2 cfd Outflows = 1,222A61.4 cfd Difference = - 715732 cfd (-0.6%) This illustrates that the initial steady-state model is accurately solved. Because the pre -slurry wall groundwater table represents data from measured groundwater levels, and the mass balance is accurate, this suggests the model is sufficiently calibrated to be used for predicting water levels after construction of the slurry walls. PREDICTIVE SIMULATIONS Using the steady state model for pre -slurry wall condition as the base model, predictive simulations were performed for groundwater mounding after the proposed slurry walls are constructed. Predicted Unmitigated Groundwater Mounding To understand the magnitude and extent of potential groundwater mounding upgradient of the Heins slurry walls, a steady state simulation including slurry walls was performed. The pre -slurry wall model was changed by inputting the Heins slurry walls as no -flow boundaries. All other aquifer parameters and boundary conditions remained unchanged, Initial heads were the model simulated heads from the pre -slurry wall steady state model. The steady state model for the post -slurry wall conditions generally produced higher groundwater elevation heads than those produced for the pre -slurry wall steady state condition. The groundwater elevations from the predictive simulation are shown in Figure 6. The difference between the pre- and post -slurry wall groundwater surfaces are the predicted mounding levels shown on Figure 7. For each of the predictive simulations, positive residuals are reported as values of groundwater mounding (warm colors) and negative values represent groundwater shadowing (cool colors). For this predictive simulation the magnitude of the maximum groundwater mounding is approximately 2.5 feet west of the Heins West and Zadel Pit. For the Southern Slurry Wall Complex in this predictive simulation, the magnitude of groundwater mounding ranges from 1 foot on the southern side to maximum groundwater shadowing of 3 feet in the middle of the complex near Little Dry Creek on the north side. The groundwater depth is closest to the surface on the west side of the Heins west cell as well as on the west side of the southern slurry wall complex as shown in Figure 8. A comparison of depths -to - groundwater on Figures 5 and 8, along with an inspection of Figure 7 shows that the existing shallow groundwater in the eroded depressions south of the complex is in a groundwater shadow (blue colors on Figure 7) for the predictive simulation. The zero contours still follow Little Dry Creek, but groundwater mounding is shifted to the south of the proposed slurry walls. Project 20026026.06 it August 12, 2025 Page 8 Schnabel Engineering �. . Everist Heins Property Groundwater Modeling CHANGE IN DISCHARGE TO ACCRETION BOUNDARIES The installation of slurry walls around the site can impact groundwater flow dynamics, resulting in changes to discharge at accretion boundaries. By reducing horizontal hydraulic connectivity of the aquifer, the slurry walls have modified the natural flow regime, limiting groundwater movement into and out of the enclosed area. As a result, discharge patterns at accretion boundaries have shifted, particularly along downgradient zones where the walls intersect historic flow paths. Thesechanges were incorporated into the groundwater model by updating boundary conditions and representing the slurry walls as zones of low permeability or no -flow barriers. The model was subsequently recalibrated using observed groundwater levels and flow data to ensure it reflects post -construction conditions. A summary of the changes in flow at accretion boundaries is provided in Table f below. Table I — Change in Discharge to Accretion Boundaries Name Discharge into Boundaries Accretion i Difference ( FD) Difference (CF.) Difference (GPM) Construction Prior to After Constuction South Platte 243,4019 231, 489.7 -12,218.2 -0.1 -63.5 Little Dry Creek 199258.9 55169.3 -144,089.6 -1.7 -748.5 Lupton Bottom West Branch Ditch 0.00 0.00 0.0 0.0 0.0 Lupton Bottom F:a≥t Branch Ditch 89, 028.5 148,144.0 59,115.5 0.7 . 307.1 ivied GI ow Ditch 0.00 153,656.0 153,656.0 1.8 798.2 Oot- i1 Ridge 0.00 1,806.9 1,806.8 0.0 9.4 Unlined Pits 393,839.4 293,221.8 -100,617.5 -1.2 -522+7 Alluvial (Groundwater U'nderflow Flow) 153,275.1 121,287.2 -32,007.9 -0+4 466.3 Totals 1, 078, 809.8 883,187.8 I 58,270.5 0.67 302.7 As shown, there is a small increase of about 300 gpm (5%) in the discharge to accretion boundaries with Heins slurry walls installed. The results illustrate that construction of the proposed slurry walls has a negligible impact on groundwater accretion to the South Platte River. Additionally, the outflows reported for Little Dry Creek flow into the South Platte River outside (downstream) of the model domain. CONCLUSIONS This groundwater impact analysis was performed to evaluate the mounding and shadowing effect the construction of slurry walls has on the local groundwater table. The model accurately replicated the conditions of the South Platte River alluvial aquifer based on data available from recent geotechnical investigations. Model construction was facilitated by using an extensive GIS to inventory, analyze, and present the data. The steady-state models reasonably simulated the equilibrated hydrogeologic changes caused by construction of the slurry walls. The predictive simulation during irrigation season showed that the magnitude of the maximum groundwater mounding and shadowing for proposed slurry walls can cause mounding as high as about 2..5 feet, and a minimum depth to groundwater of about 0.5 feet, before a Project 20C26026.06 if August 12, 2025 Page 9 Schnabel Engineering L.G. Everist Heins Property Groundwater Modeling drain is installed. The simulation also indicates that the maximum shadowing effect caused by the construction of the slurry walls is almost three feet and is located along Little Dry Creek in the middle of the Fort Lupton Pits. The groundwater flow pathways for return flows to the river have been lengthened due to slurry wall installation, the differences between flow paths can be compared in Figure 4 and Figure 6. These lengthened flow paths can increase the timing it takes for groundwater to return to the South Platte River. However, as the results show, the change in outflows to the South Platte River is negligible between pre - and post -slurry wall conditions. RECOMMENDATIONS The installation of the Heins North and Heins South cells on the eastern side of the property have minimal effect on the surrounding groundwater. No drain installation is recommended for these areas at this time. The site wells will be monitored approximately monthly. if the depth to groundwater, following the construction of the slurry wall(s) in any exterior well approaches three feet below ground surface, we recognize that a drain may need to be installed. The Heins West cell of the Northern Heins complex as well as the Southern complex have shown to cause a minimal amount of mounding. To mitigate potential groundwater mounding caused by the reduced flow through the slurry walls, a subsurface drain may be required. If groundwater levels rise to approximately three feet below the ground surface along the exterior of the proposed slurry wall complex, drains may be necessary to maintain hydraulic gradients, prevent excessive buildup, and ensure continued groundwater movement. The drains would help relieve pressure, reduce the risk of seepage or surface expression of groundwater, and maintain th.e effectiveness of the overall groundwater control system. The red groundwater mounding colors on Figure 7 show locations to target with drains. These are primarily 1) along the western edge of the Heins West slurry wall and 2) along the southern edges of the Southern Complex. A north -south drain along the Heins West wall would help Little Dry Creek drain water away from the reservoir complex. An east -west drain along the eastern half of the southernmost slurry walls would help drain mounding groundwater towards the South Platte River. We recommend such drains are installed as infiltration galleries with subsurface discharge. Essentially these drains are composed of slotted pipe in collection areas and discharge areas and operate using the hydraulic gradient to transfer and spread mounding groundwater closer the river. The pipes are buried at the depth required to maintain a groundwater depth threshold of 3 feet and bedded in a filter material to maintain good hydraulic connection with the aquifer materials. The below -grade discharge system ensures that groundwater is never consumed. LIMITATIONS These are steady-state models and cannot be used to evaluate groundwater return flow timing. The results of the groundwater modeling and conclusions drawn from them represent approximations and are based on the best available data and engineering judgement. Conservative assumptions were made during the calibration process so that groundwater mounding was not under -predicted. Givent_he unknown heterogeneity of the aquifer in the field and variations in ground surface from the topographic data used, the groundwater mounding and/or drainage mitigation may deviate from the model simulation. Project 20C26026.06 / August 12, 2025 Page 10 Schnabel Engineering L.G. Everist Heins Property Groundwater Modeling There is a possibility that mounding may be higher than predicted, although the conservative assumptions of this work make the deviation toward a lower mound in the field a more likely possibility. REFERENCES CDWR. (2024, November 19). Map Viewer. Retrieved from Colorado's Decision Support systems: https://maps.dnrgis.state.co.usidwrilndex.html?viewer=mapviewer CWCB. (2024, November 20). Colorado Hazard Mapping & Risk MAP Portal. Retrieved from Colorado Hazard Mapping: https://coloradohazardmapping_cornllidarpownioad ESRI. (2024, November 20). Retrieved from ArcGls Pro: htips://www.esriscom/en- usiarcgis/products/arcgis-pro/overview Harbaugh, A. W. (2005). MODFLOW-2005, The USGS Modular Ground -water Model - - the Ground - Water Flow Process. Rumbaugh, J. O., & Rumbaugh, D. O. (2015). Guide to Using Groundwater Vistas. Seequent, The Bentley Subsurface Company. (2024, November 20). Leapfrog Geo. Retrieved from https://www. seeq uent. comlprod ucts-sol utionslleapfrog-geo/ Project 20O26026.06 / August 12, 2025 Page 11 Schnabel Engineering O: Loncmont 2020\2QC26012C.06 Heins Pro 'e Relocated Lupton Botton Ditch East South Platte River Drain Boundary Model Domain Heins Property Groundwater Model Model Domain and Boundary Conditions 4895 4890 4885 4880 64875 -4870 4865 4860 4855 4850 Calibration 08-28-2024 0 a e ta O 4• a e s • a a I • i • • 0m•4 • • s 4 e s 4850 Note:. r M b 0 r • • a w • • • a • 0 0 s • e a 0 • • • V • • • -r • • • • y = 1.0088x - 42.743 R2 = 0.988 1 1 I I 4855 48(,() 4865 4870 4875 4880 4885 4890 4895 • EiSchnabel ENGINEERING Observed Values (Co HEINS PROPERTY GROUNDWATER MODEL Calibration Plot DA I 06/10/2024 FIGURE NO.. 3 i Schnabel Engineering, LLC. 2024 All Rights Reserved 0 C o cri t U) a O I i I u) C r O 44 U 2 0 1 C t co a C L 0 Co fC 4 Co, (N f � � '4..J C pcN C= C E a, LI) a C Legend Groundwater Elevation Contour (0.1. = 5ft) Lupton Ditch — South Platte River Zadel Drain Ditch Drains Model Domain Slurry Walls _l Lakes Graund at lo low Directio '.ler` 2,000 4,000 Feet Iiii!:11 FNGINFFRING Schnabei HEINS PROPERTY GROUNDWATER MODEL Existing Conditions Steady State Results 7/16/2025 PROJECT NO. 20C26026.06 FIGURE #4 CI Schnabel Engineering, 2025. All Rights Reserved. 8/7/2025 O:1t_ongmont\2020\20 26026 06 Heins Property\0 E_Products\07-GI \Heins Property 060025.apr Depth to Groundwater (.I. Lupton Ditch South Platte River Zadel Drain Ditch Drains HEINS PROPERTY GROUNDWATER MODEL Existing Conditions Depth to Groundwater Schnabel Engineering, 2025. All Rights Reserved. x Ltd CN rn C0 CD C CL a 0 w I C 1.0 C r O Co O 2 !Z LL w C:] t m O a, CN C I Cfl C] Cc 0 C 6 PCN E a, 0 a LID CD Monitoring Wells Groundwater Elevation (0.1. = 5ft) Lupton Ditch South Platte River Zadel Drain 0 ter r tion Ditch Drains Model Domain Slurry Walls Lakes 7 2,000 4,000 Feet Schnabe! FNGINFFERING HEINS PROPERTY GROUNDWATER MODEL Predictive Simulation Results 7/16/2025 chnabel Engineering, 2025. All Rights Reserve it 1.6 C� ( O CL C 0 C. I C 2 C) C 9 N- O ClJ 2 nS✓ ee1' III cp CIL M� tl Ce) t C CA) C ,5 I C� 'C 0 pcN 0 C C a, LI) CN 1 — Legend Lupton Ditch South Platte River Zadel Drain Ditch Drains Model Domain Lakes Slurry Wails Change Contours (C.1. = lft) Change from Existing Results (Feet) 3 HEINS PROPERTY GROUNDWATER MODEL Predictive Simulation Change from Existing chnabel Engineering, 2025. All Rights Reserved. Legend Depth to Groundwater (0.1. ft) Lakes Lupton Ditch C= SlurryWall South Platte River Depth to Groundwater Zadel Drain (Feet) Ditch Drains 70 Model Domain 0 VEINS PROPERTY GROUNDWATER MODEL Predictive Simulation Depth to Groundwater 8/812025 PROJECT NO. 20C26026.06 FIGURE #8 CI Schnabel Engineering, 2025. All Rights Reserved. Hello