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HomeMy WebLinkAbout1.05 Appendix E - Impacts Analysis-Wetlands-Dewatering IHC SCOTT RIFLE PIT #1 IMPACT ANALYSIS REPORT RIFLE PIT #1 IHC SCOTT (SCOTT CONTRACTING INC.) MARCH 2021 Prepared by 118 West Sixth Street, Suite 200 Glenwood Springs, CO 81601 970.945.1004 970.945.5948 fax IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 i TABLE OF CONTENTS 1.0 Rifle Pit #1 Impact Analysis 1 1.1 Adjacent Land Use 1 1.2 Site Features 2 1.3 Soil Characteristics 8 1.4 Geology and Hazard 8 1.5 Groundwater and Aquifer Recharge Areas 8 1.6 Environmental Impacts 9 Long-term and Short-term Effects on Flora and Fauna 9 Determination of the Effect on Designated Environmental Resources, including Critical Wildlife Habitat 9 Wildlife and Domestic Animals 10 Potential Radiation Hazard 10 1.7 Nuisance 10 1.8 Hours of Operation 11 LIST OF FIGURES Figure 1. Properties within 1,500 feet of Rifle Pit #1 3 Figure 2. Topography and Existing Conditions of the Rifle Pit #1 Property 4 Figure 3. Waterbodies near the Rifle Pit #1 Property 5 Figure 4. Soils at the Rifle Pit #1 Property 6 Figure 5. Proposed Condition (Reclaimed) of Rifle Pit #1 Property 7 IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 1 1.0 Rifle Pit #1 Impact Analysis This report documents the existing conditions and the potential changes created by the Rifle Pit #1 project and describes how IHC Scott (Scott) [formerly Scott Contracting, Inc. (SCI)] will ensure that impacts will be mitigated, and standards will be satisfied. The following sections address the information required in the Land Use Development Code (LUDC) Section 4-203.G. 1.1 Adjacent Land Use Per Garfield County submittal requirements, a list of landowners and mineral rights owners within 200-feet of the proposed project parcel is included with this submittal. Adjacent landowner addresses were obtained from the Garfield County Assessor’s web-based database. There are four adjoining properties with corresponding surface landowners: · North – Colorado River Ranch, LLC · West – Rex Robinson Ranch, LLC; Swanson Colorado Trust; Ilgen, Carrol Jeanne; Rosa, Linda Jane; Robinson, James Dean · South – Colorado Department of Transportation (CDOT) · East – Shidelerosa LLP This information was obtained from the Garfield County Colorado Land Explorer (Garfield County, March 2021). North Side: The parcel adjacent to the north is owned by Colorado River Ranch, LLC and is currently zoned Rural. There aren’t any compatibility issues with the proposed project since the current use is agricultural. West Side: The Rex Robinson Ranch, LLC, currently owns the property to the west. This property is zoned Rural. There is currently an oil & gas pad on this property which isn’t currently being used. The current use of this property is compatible to the proposed mine project.. South Side: The property to the south is currently owned by CDOT (I-70 N Frontage Road, also referred to as County Road 346) and is parallel to the property. East Side: The property to the east is owned by Shidelerosa LLP and is zoned Rural. This property is currently used for agricultural purposes and there is one residential driveway approximately 0.45-mile from the proposed mine property. All landowners have been notified of the proposed development. The proposed use is consistent with the predominant existing uses in the surrounding area. Figure 1 depicts the existing use of the adjacent properties within a 1,500-foot radius of the Rifle Pit #1 property. IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 2 1.2 Site Features Figures 2 through 4 depict the existing conditions of the waterbodies, topography, and vegetation cover of the property. Figure 5 depicts the proposed condition of the property. IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 3 Figure 1. Properties within 1,500 feet of Rifle Pit #1 IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 4 Figure 2. Topography and Existing Conditions of the Rifle Pit #1 Property IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 5 Figure 3. Waterbodies near the Rifle Pit #1 Property IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 6 Figure 4. Soils at the Rifle Pit #1 Property IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 7 Figure 5. Proposed Condition (Reclaimed) of Rifle Pit #1 Property IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 8 1.3 Soil Characteristics According to the USDA NRCS Web Soil Survey, most of the soil map units in the permit area are ranked as fair gravel sources and one soil unit (Olney loam) is ranged a poor. All the soils except the Kim loam is rated as fair condition for sand sources. Approximately 50% of the permit area has soil units that are rated as fair to good for reclamation material. Where/when applicable, the top 4 - 6 inches of topsoil will be salvaged and stored for later reclamation uses. The soils within the subject parcel are mapped by the NRCS as soil units: · Halaquepts, nearly level · Kim loam, 3 to 6% slopes · Olney loam, 1 to 3% slopes · Wann sandy loam, 1 to 3% slopes Note this property is being considered for gravel extraction as a result of the presence of these soils. The post-developed condition of the property will result in an 18.4-acre pond while the surrounding land around the pond will be restored to its natural condition. Scott plans to reclaim the property as each mining stage commences. Areas disturbed during development shall be restored with natural-appearing landforms that blend with the adjacent undisturbed topography within 90 days of completion. Details regarding reclamation processes and revegetation can be found in Section 2.12.7 of the Land Use Permit. See Figure 5 for the post-mining site conditions. 1.4 Geology and Hazard No natural geologic nor manmade hazards exist on the property that would influence the proposed use of the site. 1.5 Groundwater and Aquifer Recharge Areas The Colorado River borders the property to the north. A berm will be constructed to minimize the influence of the Colorado River on the proposed land use and operations. The height of the berm will be 5 feet and was determined by conducting floodplain modeling. See Land Use Permit for additional information on the floodplain modeling and floodplain analysis. The principal aquifer properties at the site are: · Saturated thickness (b) – the thickness of the saturated porous medium measured as the difference between the static water level and the base of the aquifer, measured in feet. Average saturated thickness of 18 feet at the site. · Hydraulic conductivity (K) – a measure of the capacity of a porous medium to transmit a volume of water through a unit cross-sectional area, typically expressed in units of feet per day. The aquifer at the site is assumed to have a uniform hydraulic conductivity of 1,000 feet per day. · Storage coefficient or specific yield (Sy) – the volume of water released from a unit volume of saturated aquifer per unit decline in head, expressed as a fraction. The aquifer at the site is assumed to have a uniform value of 0.2 for specific yield. · Transmissivity (T) – a measure of the capacity of a porous medium to transmit a volume of water through the entire saturated thickness, expressed in units of feet2 IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 9 per day. Transmissivity is obtained by multiplying the hydraulic conductivity by the saturated thickness (T = K x b). Transmissivity is approximately 18,000 feet2 per day. The proximity of the property to the Colorado River, the proposed dewatering activities and excavation of the site for mining does not allow for a subsurface wastewater facility. The A vault and haul waste system will be sited away from the perimeter of the property to eliminate the potential for a discharge to the ground and surface waters. Trash receptacles will also be sited away from the perimeter of the property to minimize the influence of trash from being discharged from the site. The Land Use Permit document includes a dewatering modeling analysis and Wetlands report, that outlines the existing and proposed vegetation conditions of the site. 1.6 Environmental Impacts The determination of the existing environmental conditions on the parcel to be developed and the effects of development on those conditions specific to flora and fauna, wildlife and domestic animals, and radiation hazards are described in the following sections. Long-term and Short-term Effects on Flora and Fauna Vegetation in the subject parcel is dominated by partially irrigated pasture lands, which are subjected to an inconsistent and uneven application of irrigation water via flood irrigation and subsurface seepage. The mixture of mesic and hydric soil conditions supports a mosaic of upland pasture areas and wet emergent meadows, with the water table so elevated in some portions that the wet meadows contain areas of open surface water. Some small areas contain sparse riparian woodland, dominated by non-native Russian olive (Elaeagnus angustifolia) with a sparse overstory of cottonwood (Populus deltoides). The wetlands will be avoided during Stage 1 and Stage 2 mining activities. The project occurs in mesic wet meadows and pastures. Most of the affected area has seen extensive development activities associated with grazing management, including trenching, disking, irrigation, and fence construction, and the habitats are already significantly disturbed. Animal species that are tolerant of, or habituate to, human activity persist in the area, and use the property on an intermittent and seasonal basis. The level of human disturbance is sufficiently great to preclude permanent occupancy of the parcel by wildlife species of concern. Determination of the Effect on Designated Environmental Resources, including Critical Wildlife Habitat Mining will remove vegetation in phases allowing incidental use of the site by wildlife, if needed. Wildlife will likely avoid the parcel entirely once mining development commences, and the existing level of casual use will be displaced to adjacent unimpacted habitats along the southern bank of the Colorado River. It is expected that the itinerant species will continue to utilize surrounding habitats given the small area of the mine. However, the existing mosaic of meadows and riparian woodland will not be recovered, and the property will support a much less complex environment dominated by agricultural cultivars. This could continue to provide winter grazing habitat for elk and mule deer, although the habitat quality would be low due to a lack of woody cover vegetation. Wild Turkey would likely abandon the parcel. Bald eagle foraging is concentrated along the Colorado River, and would be minimally impacted by the proposed development. Most small mammal and passerine bird IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 10 species will be able to resume use of the area once reclamation is complete; the longest- term potential habitat detractor will be persistence by noxious weeds. The area is seasonally used by the following species (based on CPW & COGCC RSO/SWH habitat data): · Bald Eagle (Winter Forage, Winter Range) · Elk (Severe Winter Range, Overall Range) · Mule Deer (Resident Population Area, Severe Winter Range, Winter Concentration Area, Winter Range, Overall Range) · Wild Turkey (Winter Concentration Area, Winter Range, Overall Range) Wildlife and Domestic Animals There are no significant wildlife resources on potentially affected lands. The site supports seasonal, low-level big game use, and typical use patterns of mesic shrublands and pasturelands. The impact to area wildlife should be minimal as a result of this project. A 5-foot tall berm will be constructed around the perimeter of the site therefore some wildlife may experience a slight change in traveled corridors to maneuver around the mine area. See Section 2.10.2 of the Land Use Application for more detailed discussions regarding Wildlife Habitat Areas. Potential Radiation Hazard The Colorado Department of Public Health and Environment (CDPHE) has posted a statewide radon potential map on their website based on data collected by the EPA and the U.S. Geological Survey. Garfield County and most of Colorado has been mapped as being within Zone 1 – High Radon Potential or having a high probability that indoor radon concentrations will exceed the EPA action level of 4 picocuries per liter (pCi/L). Radon is not expected to be a significant problem at the proposed site since the mine will not include any permanent structures, personnel will not be onsite for extended periods, and the site will not be developed with structures containing basements or substructures with radon can accumulate. 1.7 Nuisance Scott understands that all gravel operations proposed to mine areas greater than 30 acres shall be designed in multiple phases in order to minimize the visual impact of the gravel pit primarily by logical “sequencing” and “overall layout” of the pit’s design. Section 1.1.7 and Figures 3 and 4 describe and depict the mining stages for Phase 3 of this project. This approach integrates the use of berms along the perimeter of the site. These berms will be placed inside of a 25-foot set back area from the property line. These berms will be roughly 5-feet in height and 23-feet wide at the bottom built at 2H:1V slope. The berm will support noise mitigation during operations and provide a screen to buffer visual impacts. The berm will be constructed prior to commencing any mining activity by phase. Site preparation activity such as removal of overburden shall be allowed prior to the construction of the visual screening if material will be used for the creation of the necessary screening. IHC Scott – Rifle Gravel Pit #1 Impact Analysis Report March 2021 11 The location of the mining equipment in the bottom of the pit will also support mitigation of the mining noise and dust. All stockpiling of material at this point also be done at this level. 1.8 Hours of Operation The Rifle Gravel Pit #1 will operate from 7 a.m. to 7 p.m. Monday through Friday, and weekends, as needed. Scott will limit winter operations between the hours of 7 a.m. and 5 p.m. Approximately 3 to 5 employees will be on site during the mining operations. No nighttime activities are anticipated. Occasional equipment repair, or maintenance may be conducted at night, but lighting will be kept to a minimum and directed inward; the site will not have ambient lighting. 4 Figures Figure 1. NWI Wetlands Map. Figure 2. Initial Wetlands Mapping by SGM (July 17, 2019). www.sgm-inc.com EXHIBIT F June 26, 2020 1 Wetlands Delineation Finding Fill and dredging within Waters of the U.S. and tributary wetlands are regulated by the US Army Corps of Engineers (USACE) under Section 404 of the Clean Water Act (CWA). The National Wetlands Inventory (NWI) provides the user with information to conduct an initial desktop assessment and generate maps of the potential extent of jurisdictional waters for any area of interest. As a national-level dataset, the NWI is not and cannot be entirely accurate at a local level and should always be evaluated against a field-based study of conditions on the site. The NWI for the Rifle Pit #1 property (Property) indicates that the area consists of a mosaic of upland areas interspersed with wetland zones dominated by herbaceous emergent vegetation (Figure 1). A site visit and delineation performed by SGM on July 17, 2019 generally confirmed that this parcel contains large areas of wetlands dominated by cattail and bulrush emergent communities, although these areas are not as extensive as suggested by the NWI (Figure 2). The wetland areas are concentrated on the west end of the property and are well-developed and relatively high-quality from a biological and functional perspective. The east end is mesic pasture meadow rather than jurisdictional wetlands, and development of the gravel resources in this area could be accomplished without Section 404 permits or impacts to Waterbodies protected by the Garfield County Land Use Development Code (LUDC).The Last Chance Ditch enters the Property from the east; this is an artificially-excavated, gated and controlled irrigation ditch and as such is explicitly excluded from consideration as a protected Waterbody in the LUDC. The Last Chance Ditch and its laterals discharge tailwaters onto the surface of the Property, at numerous locations. Parcel Geology Boring logs (HP Geotech, 2008) and direct observation indicate that the entire Property is underlain by a consistent subsurface column consisting of (a) silty clay loam from the surface to a depth of 3 feet, (b) an impermeable clay aquitard layer at a depth of approximately 3 feet, (c) dry gravel to a depth of approximately 7 feet, and (d) saturated gravels in direct contact with the water table starting at a depth of 7 feet (see Land Use Permit Application, May 2020). The site visit and supplemental subsurface documentation suggests that the wetlands are supported entirely by irrigation tailwater discharge onto the Property, which pools on the shallow clay aquitards and forms a perched zone of saturation above dry gravel. There is no indication of natural surface hydrology on the Property: surface water reaches the property exclusively via artificially-excavated channels off the Last Chance Ditch, including the large lateral/tailwater ditch that bisects the property from east to west, and several smaller ditches that discharge underneath the interstate and onto the southern boundary of the property (Figure 3). The available drilling data consistently show that the water table is approximately 7 feet below the surface, and that 3 or 4 feet of dry gravel intervene between the zone of surface saturation and groundwater. Based on this understanding of the hydrology, if the tailwater discharge onto the property are stopped (by closing headgates, re-routing and/or piping the ditches, or other similar methods), the primary water source for the wetlands will be removed. Groundwater modeling also suggests that pit dewatering activities in adjacent upland areas (east) will significantly and rapidly depress groundwater levels throughout the Property, further isolating the wetlands from groundwater hydrology (See attached Letter Report, Hahn Water Resources, LLC, August 2, 2019 and July 8, 2020). 2 The combination of pit dewatering adjacent to the wetlands, and removal of irrigation-derived water discharges onto the property, are expected to remove the hydrology supporting the wetlands throughout the Parcel. It is expected that the areas currently mapped as wetlands per the USACE and LUDC criteria (Figure 2) will cease to display wetland hydrology and/or hydrophytic vegetation within two growing seasons and will no longer meet the criteria as wetlands under USACE jurisdiction or as Waterbodies under LUDC definitions. Army Corps Section 404 Permitting Considerations The USACE regulates the discharge or dredging of sediment into wetlands, including activities such as the commercial development of gravel resources, however wetlands supported entirely by irrigation water (a.k.a. agriculturally induced wetlands) are not regulated. The eastern portion of the Parcel does not contain jurisdictional waters or wetlands, and development can proceed in this area without further Section 404 permitting considerations. SGM’s site investigation completed on July 17, 2019 will be formalized in a wetland delineation report to provide confirmation of regulatory compliance, once development of the gravel operation is approved and the precise extent and nature of the initial development activities are determined. In addition, groundwater pumping is not regulated by the USACE, nor are indirect impacts to wetlands due to an adjacent pit dewatering operation (USACE, T. Morse, pers. comm.). Therefore, although initial gravel pit dewatering in the eastern portion of the property will depresses groundwater in adjacent wetlands and contribute to a loss of wetland conditions, that activity is not regulated and does not require a permit under Section 404. Dewatering permits from the Colorado Department of Public Health and Environment (CDPHE) – Water Quality Control Division (WQCD) and the Division of Water Resources (DWR) are required for dewatering operations. The NWI mapping, which shows much of the western portion of the Parcel as wetlands, means that prior to developing those areas, the burden of proof is on Scott Contracting to prove to the USACE that the wetlands are either (a) supported entirely by irrigation water and therefore non-jurisdictional, or (b) no longer meeting the regulatory definition of wetlands. In general, no more than 0.5 acres of direct wetland impact can be permitted without going through the extensive USACE Individual Permit process, therefore seeking a permit for impact to the wetlands is incompatible with effective development on the Parcel. However, documenting that the Parcel no longer contains wetland characteristics will allow full development on the site. Based on the underlying hydrology and geology described above, Scott Contracting believes that by removing irrigation tailwater discharge from the Property and rerouting the Last Chance Ditch and laterals, will remove the sole water source for the wetlands and result in the loss of wetland characteristics. Scott will monitor and document the change in wetland conditions and will seek formal confirmation of the findings from the USACE via an Approved Jurisdictional Determination. Once the USACE has formally recognized that the removal of irrigation water has resulted in the loss of wetland criteria, indicating that the wetlands are agriculturally induced, Scott Contracting will proceed to develop the remaining portion of the Property. Garfield County Wetland Impact Considerations Garfield County’s definition of “wetland” relies on the same fundamental criteria as the USACE: the presence of continuous or reoccurring saturation/inundation, the development of chemical signatures in the 3 soil that indicate anaerobic conditions typical of long-term saturation (i.e. “hydric soils”), and the dominance of plant species that depend on saturated soils (i.e. “hydrophytic vegetation”). Therefore, the wetland delineation performed for the Property (Figure 2) accurately describes the extent of wetlands/Waterbodies under the LUDC, as well as under the CWA. However, unlike the CWA the LUDC does not distinguish between wetlands supported by natural hydrology and those that are agriculturally-induced, and in fact the LUDC explicitly requires the disclosure of impacts to wetlands, regardless of “whether or not they are jurisdictional as defined by the Corps of Engineers [USACE]” (Article 14-401.T). Based on this reading of the LUDC, Figure 2 should be taken to indicate the extent of proposed impacts to wetlands, as required by Article 4-203.G. The proposed gravel pit operation on the Property would result in development within wetland areas and within the 35-foot buffer zone around Waterbodies, and therefore a waiver for this development is requested. The waiver request is based on the following factors: · Hydrologic studies, drilling logs, and site observations indicate that the wetlands on the site are supported by irrigation water rather than natural hydrology. · The proposed gravel operation is not logistically feasible without re-routing the current tailwater ditches and initiating groundwater pumping to dewater the pit, which would remove the irrigation water supporting the wetlands. · The development of the initial phase of the gravel operation, confined to the eastern portion of the Property outside of wetland areas, is expected to result in the loss of wetlands from the remainder of the Property. · The proposed gravel operation is financially feasible only if most of the Property is developed, including the areas of agriculturally induced wetlands. · The reclamation of the site would produce habitat value that would replace the lost values to some extent, since the gravel pond would support a wetland fringe on its periphery. These wetlands would be supported by natural groundwater rather than irrigation tailwaters, and therefore would be protected under the CWA. Recommended Monitoring & Development Based upon the wetland and groundwater modeling evaluations performed to date, Scott Contracting will proceed with the two-pronged approach to remove the hydrology which supports wetlands on the Parcel, while remaining in compliance with the CWA and the LUDC: 1. Remove all irrigation water discharge onto the property by rerouting the Last Chance Ditch to the northern boundary of the Property (See Drawings attached to NTC Letter) 2. Maintain dewatering in the initial pit development, to be in the upland eastern portion of the Property, which will depress groundwater throughout the Property. SGM will monitoring wetland conditions on a quarterly basis, using the standard USACE wetland delineation protocols to track the response of the hydrology and vegetation to the altered hydrology. Quarterly reports will contain conditions assessments and maps of the evolving extent of wetland areas, and the results will be shared with the USACE on a regular basis. Physical boundary indicators (such as earthen berms or silt fence) will be maintained to prevent any inadvertent transgression into areas that retain wetland characteristics during the initial phases of development. The quarterly reports will allow Scott Contracting 4 to document that all ongoing activities follow Section 404 regulations and would also document the point at which wetlands disappear from some or all the Property. At the point when monitoring indicates an unambiguous loss of wetland characteristics from the Property, Scott Contracting will submit the revised delineation results to the USACE and request an Approved Jurisdictional Determination (AJD), which would formally recognize that the NWI wetlands are no longer present, and that development of the remainder of the property can proceed without Section 404 permitting. Figures Figure 1. NWI Wetlands Map. 5 Figure 2. Initial Wetlands Mapping by SGM (July 17, 2019). 6 Figure 3. Location of Irrigation Laterals, Ditches, and Other Drainages. From: Alex Nees Sent: Monday, July 6, 2020 2:02 PM To: Morse, W Travis CIV USARMY CESPK (USA) Subject: RE: Scott Contracting's "Rifle Pit #1" project Thanks Travis, The contact info for the client is as follows (this will match what is provided on the GarCo permit application): Scott Contracting Inc. - Chris Hurley 9200 Mineral Avenue Centennial, CO 80112 (720) 889 - 4402 churley@scottcontracting.com Best, Alex -----Original Message----- From: Morse, W Travis CIV USARMY CESPK (USA) <w.travis.morse@usace.army.mil> Sent: Monday, July 6, 2020 12:26 PM To: Alex Nees <alexn@sgm-inc.com> Subject: RE: Scott Contracting's "Rifle Pit #1" project Hi Alex, The plan sounds reasonable; however, a formal JD may be unnecessary. Can you send me the contact info of your client/potential applicant (POC, company, mailing address, email, telephone) so that I can assign this action a file number? Sincerely, Travis Morse Senior Project Manager Colorado West Section U.S. Army Corps of Engineers 400 Rood Avenue, Room 224 Grand Junction, Colorado 81501 (970) 243-1199 ext. 1014 ***In response to COVID-19, Regulatory Division staff are teleworking from home or other approved location. We will do our best to administer the Regulatory Program in an effective and efficient manner. Priority will be given to health and safety activities and essential infrastructure. Action on your permit application or other request may be delayed during this emergency. We appreciate your patience over the next several weeks.*** Please provide us with your feedback by filling out a customer survey at http://corpsmapu.usace.army.mil/cm_apex/f?p=regulatory_survey For more information about our program, you can visit our website at http://www.spk.usace.army.mil/Missions/Regulatory.aspx -----Original Message----- From: Alex Nees [mailto:alexn@sgm-inc.com] Sent: Monday, July 6, 2020 11:40 AM To: Morse, W Travis CIV USARMY CESPK (USA) <w.travis.morse@usace.army.mil> Subject: [Non-DoD Source] Scott Contracting's "Rifle Pit #1" project Hi Travis, As we discussed briefly on the phone last week (July 2), Scott Contracting is proceeding with their plans to develop a gravel pit at Mamm Creek, between the Interstate and the Colorado River (KMZ of the site attached). The property is Parcel 217908300103. Scott is in the process of submitting their development permit application to Garfield County; this will be a Major Impact Review per GarCo guidelines. As part of that review process, Glenn Hartmann noted that GarCo would send the application to you for review, and asked that we notify you. The application includes a memo that addresses that differences between USACE jurisdiction and GarCo Waterbody protections, and discusses in detail the information I summarize below. * Based on a delineation I completed in the summer of 2019, significant portions of the western end of the property have surface water and display conditions consistent with wetland character (map attached). As we discussed, Scott has completed hydrologic modeling and reviewed existing drill core data which strongly indicate that the surface water is perched on a clay plan no deeper than 3 feet, and is underlain by approximately 4 feet of dry gravel before groundwater is encountered at a depth of approximately 7 feet. The only known source of surface water on the property is the Last Chance tailwater ditch and associated laterals, which currently discharge onto and/or traverse the property. Therefore the assumption is that the surface water is derived from agricultural sources. * Scott proposes to begin development of the gravel mine in the eastern portion of the property, outside the areas of wetland vegetation. They will reroute the Last Chance Ditch and all laterals to cease the discharge of tailwater onto the property. Tailwaters will be transported around the perimeter of the property to the existing tailwater ditch and thence to the Colorado River. Scott expects that the combination of (a) stopping the surface discharge of irrigation water onto the site, and (b) depressing groundwater by pit dewatering will remove all feasible sources of water from the wetlands on the site, resulting in an immediate loss of wetland hydrology and a subsequent loss of hydrophytic vegetation, thus providing evidence of the agriculturally-induced nature of these wetlands. * Scott proposes to monitor the wetland conditions on a quarterly basis once initial development begins (essentially completing repeated delineations), to track the response of the wetlands to the development activity. These quarterly monitoring reports would be completed by SGM and shared with Scott and the USACE. If conditions respond as is expected, and the wetlands lose jurisdictional character, Scott would request a formal Jurisdictional Determination from the USACE, and then expand the mining area to include the majority of the parcel. Please let me know if you have any questions/concerns, or would like any additional information pending the finalization of Scott’s land use change application to GarCo. Best, Alex Nees Senior Ecologist <Blockedhttp://www.sgm-inc.com/> <Blockedhttps://www.facebook.com/#!/SGM.Inc> <Blockedhttps://www.linkedin.com/company/1673955?trk=prof-exp-company-name> PHOTO LOG Project Name:Site Location:Date: Photo Point 1 (P1) Photo Point 2 (P2) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 2: Origin of PPL. Inland salt grass, sand dropseed, poverty weed, small amounts of tall wheat grass, etc. Clearly grazed, no hydrology. PPL Option 2: Fenceline ditch conditions. No evidence of significant maintenance or use of tailwater ditch on Shideler property. Ditch shows no evidence of flow, and is dominated by smooth wheat grass and English plantain (Plantago lanceolata). Maintained ditch on opposite side of fence is on Colorado River Ranch property. Outside of ditch boundaries, vegetation is typical mesic pasture, with no potential for wetland occurrence. PHOTO LOG Project Name:Site Location:Date: Photo Point 3 (P3) Photo Point 4 (P4) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 2: Problem Area #1, a small ponding site supporting patches of reedgrass and Juncus balticus. The green vegetation is predominantly smooth brome. The only possible wetland zone is the pooling area and small patches of reedgrass and Juncus. PPL Option 2: Potential crossing site b/w problem areas. This has no potentially-jurisdictional features. Note gap between two patches of Juncus, connecting upland saltbrush scrub in immediate foreground with upland saltbrush scrub in near background. PHOTO LOG Project Name:Site Location:Date: Photo Point 5 (P5) Photo Point 6 (P6) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 2: Crossing of old ditch channel with upland character. No hydrology, vegetation dominated by tall wheatgrass, rabbitbrush, greasewood. PPL Option 2: Problem area #3 has ponding water supporting reedgrass and Russian olive, plus a small amount of cattail in the ditch. Also many fences and gates to maintain. PHOTO LOG Project Name:Site Location:Date: Photo Point 7 (P7) Photo Point 8 (P8) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 1: Representative conditions on the shoulder of the frontage road. Clearly upland/pipeline right-of-way reclamation vegetation. Note existing Ursa Energy pipeline. Vegetation is drill-seeded reclamation grasses, dominated by tall wheatgrass, with smaller components of dropseed and saltgrass. PPL Option 1: Note hydrophytic vegetation within pasture fence and extending slightly beyond pasture fence, including Juncus and milkweed. Note right-of- way/reclamation upland species on viewer's right. PHOTO LOG Project Name:Site Location:Date: Photo Point 9 (P9) Photo Point 10 (P10) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 1: Problem Area #4 has Phragmites growing across the right of way. Initial investigation suggests minimal likelihood of wetland occurrence. No apparent source of hydrology, but the vegetation has clearly reestablished after the installation of the earth the gas pipeline. WWDF datapoint "DP-2" indicates presence of hydric soils but no clear hydrology. PPL Option 1: Ditch lateral (Last Chance Ditch?) has clearly has been bored by previous pipeline installation. Ditch prism dimensions are 46 inches at the top, 12 inches at the bottom, 18 inches deep. Significant sediment accumulation in the prism in some areas are reducing the total capacity. PHOTO LOG Project Name:Site Location:Date: Photo Point 11 (P11) Photo Point 12 (P12) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 1&2: Problem Area #5 is a ponding area, pretty clear that water source is derived from discharge of tailwater Ditch at immediate far right. Could be skirted on the southeast. PPL Option 1&2: Lateral ditch, running alongside Fenceline. Note ditch elevated above the pasture field at left and the ROW at right. Ideally pipeline would be installed in shoulder on either side of ditch to take advantage of elevated topography. Ditch prism as previously recorded, 42" x 18" x 12" PHOTO LOG Project Name:Site Location:Date: Photo Point 13 (P13) Photo Point 14 (P14) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment PPL Option 1&2: Pipeline could also be installed next to ditch in the pasture. Note that powerlines would interfere with installing pipeline in the south shoulder of the ditch. Best option may remain routing through right-of-way on viewer's right PPL Option 1&2: Conditions of proposed discharge point. Artificial ditch, artificial turn-out, then ditch transitions immediately downstream to an excavation in native soil. Ditch prism is 46" x 18"x16" at bottom. 6" vertical wall rises from the top of the prism. Discharges into a splitter that is 24” x 24" square. Splitter discharges into lateral pictured in P12 and P13, and to an earthen ditch that is approximately 2 feet deep and 5 feet wide (viewer's far right foreground). PHOTO LOG Project Name:Site Location:Date: Photo Point 15 (P15) Photo Point 16 (P16) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment Existing ditch is clearly artificially excavated and subject to ongoing use and maintenance. Note ditch excavation material piled on viewer's right. Double crossing of wetland channels. Near-view crossing is culverted, far crossing is a low- water crossing (with visible open water). PHOTO LOG Project Name:Site Location:Date: Photo Point 17 (P17) Photo Point 18 (P18) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment Culverted road crossing, with wetland channel on both sides. Pipeline could be installed in the road bad using existing culvert. Road bed is non- wetland, due to elevation approximately 6 feet above surrounding wetland areas. Clear evidence of naturally occurring shallow ground water, visible in exposed gravel beds. Strong evidence that other wetland areas on the property are supported by natural ground water as well, and therefore jurisdictional. PHOTO LOG Project Name:Site Location:Date: Photo Point 19 (P19) Photo Point 20 (P20) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment Typical conditions along Colorado River, within the Shideler property. No indication of any artificial turn-out, headgate, or discharge structures. Relic highwater channel. No indications of recent flow from Colorado River, no identifiable ordinary high watermark, no defined channel or change in vegetation. But topography and sand deposits indicate at least occasional flow here. PHOTO LOG Project Name:Site Location:Date: Photo Point 21 (P21) Photo Point 22 (P22) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment Typical conditions along the western portion of riverbank on Shideler property. Generally, upland conditions extend to the edge of the ordinary high watermark. There is no natural or artificial discharge from the Shideler property into the river at any point. This feature appears to be a naturally-occurring slough drainage, supported by shallow groundwater derived from the River's water table. Surface water flow evident at the time of investigation. Photo taken looking generally east from the Shideler property line. PHOTO LOG Project Name:Site Location:Date: Photo Point 23 (P23) Photo Point 24 (P24) Nov 3, 2020Shideler Property, CO HWY 346, Silt, CO 81652Rifle Pit #1, Dewatering PPL routing assessment Muskrat dam has plugged an existing culvert on what appears to be the Bernudy Ditch. Dam is currently diverting water away from Bernudy Ditch on the Colorado River Ranch property, and into the unnamed native channel shown in P22. This appears temporary; Bernudy Ditch appears to be used/maintained by Colorado River Ranch. Powerline access road, taken looking south. The access road corridor is free from wetlands until the culvert crossings are reached (shown in P16 & P17). Proposed PipelineOption #1Put Pipeline between fenceand CR 346 DP-1 DP-2 Problem Area #1 Problem Area #2 Problem Area #5 Problem Area #3 Problem Area #4 Ditch currently being used Potential Crossing Proposed PipelineOptionBury Pipeline along existingTwo-Track Road Proposed PipelineOption #2 ERPESTAD,GARY L &JOAN H SHUSTER,PATRICK L& TONI M KANCILIA, H D& LESLIE MARIE SCOTTCONTRACTINGINC REX ROBINSONRANCH LLC & SHIDELEROSALLLP GYPSUMRANCHCO LLC ISLANDPARK LLC COLORADORIVERRANCH, LLC WILLEY,JOSEPH O WARD, CODY& AMANDA SHIDELEROSALLLP NORTH HANGSRANCH LLC STATE OF COLORADODIVISION OFWILDLIFE ASPIRIENTERPRISESLLC RisingSunDitch Colorado Ri v er Last Chance Ditch Last Chanc e Dit c h P2 P12 P7 P20 P10 P18 P21 P4 P13 P1 P8 P24 P22 P23 P19 P17 P16 P3 P15 P5 Legend SCI PropertyGarfield County ParcelsProposed Pipeline Location Option #1Proposed Pipeline Location Option #2Ditch currently being used Flow DirectionPhoto PointPotential Crossing Problem Area WoUS Data PointNHD Artificial Path Canal/DitchStream/River Ephemeral Stream Intermittent StreamPerennial Stream Proposed PipelineOption #1Put Pipeline between fenceand CR 346 DP-1 DP-2 Problem Area #1 Problem Area #2 Problem Area #5 Problem Area #3 Problem Area #4 Potential Crossing Proposed PipelineOption #2 SCOTTCONTRACTINGINC SHIDELEROSALLLP GYPSUMRANCHCO LLC COLORADORIVERRANCH, LLC SHIDELEROSALLLP P2 P12 P7 P10 P4 P13 P1 P8 P3 P5 Legend SCI PropertyGarfield County ParcelsProposed Pipeline Location Option #1Proposed Pipeline Location Option #2Ditch currently being used Flow DirectionPhoto PointPotential Crossing Problem Area WoUS Data PointNHD Artificial Path Canal/DitchStream/River Ephemeral Stream Intermittent StreamPerennial Stream DP-1 Ditch currently being used Proposed PipelineOptionBury Pipeline along existingTwo-Track Road COLORADORIVERRANCH, LLC SHIDELEROSALLLP NORTH HANGSRANCH LLC Colorado River P20 P18 P21 P24 P22 P23 P19 P17 P16 P15 Legend SCI PropertyGarfield County ParcelsProposed Pipeline Location Option #1Proposed Pipeline Location Option #2Ditch currently being used Flow DirectionPhoto PointPotential Crossing Problem Area WoUS Data PointNHD Artificial Path Canal/DitchStream/River Ephemeral Stream Intermittent StreamPerennial Stream SCOTTCONTRACTINGINC SHIDELEROSALLLP GYPSUMRANCHCO LLC COLORADORIVERRANCH, LLC SHIDELEROSALLLP ASPIRIENTERPRISESLLC DP-1 DP-2 DP-3 DP-4 DP-6 DP-5 Test pit dry Possibleoutfall? Test pit dry P13 P19 P1 P8 P23 P22 P24 P12 P7 P2 P5 P15 P16 P17 P3 P20 P10 P18 P21 P4 Legend Data PointPhoto/CommentWaters Proposed Pipeline Alternative Pipeline RouteWetlandProblem Area Wetland Slough/Ditch Complex SCI PropertyGarfield County Parcels Hahn Water Resources, llc MEMORANDUM June 3, 2020 TO: Angie Fowler, SGM FROM: Bill Hahn, P.G. SUBJECT: Rifle Pit Estimate of Pit Inflows Angie, Following are my findings on the probable rates of pit inflow / dewatering requirements related to dewatering of a proposed sand and gravel mine known as the Rifle Pit No. 1. My investigation was completed in August 2019 and summarized in a letter report to you. As you know, my investigation focused on the potential impacts of dewatering on adjacent wetlands rather than on the specific elements and design of the dewatering system. MODFLOW-2000 was selected as the modeling platform. MODFLOW is a three dimensional, finite-difference groundwater model developed by the U. S. Geological Survey. The model was used to estimate water level impacts from pit dewatering with an emphasis on water level change that would result from dewatering rather than on a specific dewatering system and its performance. Given the absence of site-specific information on aquifer properties, there is significant uncertainty in the inflow rates that were simulated by the model. With these facts in mind, the model predicted a pit inflow rate of about 7 cfs (3,000 gpm) under steady-state conditions. This rate will vary as a function of time, the pace of the mining, the depth and length of the dewatering trench (or if wells are used, the spacing and depth of the wells), the relative influence of boundary conditions, and several other factors.