Exhibit G: Weed Management and Revegetation Plan
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Exhibit G: Weed Management and Revegetation Plan THIS PAGE INTENTIONALLY LEFT BLANK Southeast Metro Natural Gas Project Weed Management and Revegetation Plan PREPARED Public Service Company of Colorado FOR: COPY TO: Environmental Planning Group, LLC PREPARED Matt Kizlinski, Hemlock Environmental Consulting, LLC BY: DATE: December 2019 Introduction Public Service Company of Colorado (PSCo), dba Xcel Energy, is proposing to replace approximately 5.2 miles of 20-inch diameter steel natural gas transmission pipeline. The Southeast Metro Natural Gas Project (SEMNGP, the Project) consists of installing and operating a new pipeline between an existing regulator station, F917, near the intersection of East Caley Avenue and South Troy Circle in the City of Centennial, and an existing valve set near South Yosemite Avenue and East Hampden Avenue in the City and County of Denver. This section of pipeline is an integral portion of the larger 20-inch diameter pipeline system that provides natural gas to the southeastern Denver metropolitan area. This pipeline would traverse land managed or owned by U.S. Army Corps of Engineers (USACE), Colorado Parks and Wildlife (CPW) – Cherry Creek State Park (the Park), the City and County of Denver, City of Aurora, unincorporated Arapahoe County, City of Greenwood Village, and the City of Centennial (Figure 1). This replacement section is part of an existing natural gas pipeline constructed in the 1950s that delivers natural gas between the same two project end points. Vegetation Status Habitats within the Project area are typically dry upland grasslands with smaller inclusions of shrublands. The portion of the Project passing through undeveloped lands, i.e., south of I-225, will impact vegetation. The Project will impact vegetation on lands managed by Greenwood Village, Cherry Creek School District (CCSD), Cherry Creek State Park (the Park) both within construction areas and temporary use areas. The purpose of this memo is to assess the potential impacts and develop an approach to restore the plant community post-construction. Uplands are generally a mix of native and non-native grasses while drainages present more diversity and hydric vegetation. Weeds are common. Table 1 presents common vegetation within the Park. That portion of the Project crossing CCSD athletic fields will be restored in coordination with CCSD. Of the approximate 3.6 miles of pipeline through the Park, about 2.2 miles pass through active black-tailed prairie dog (Cynomys ludovicianus) colonies. Predation by raptors and coyote have been observed; however, prairie dog populations are generally unchecked. As a consequence, vegetation within and adjacent to the colonies has been heavily impacted. Some areas exhibit very low to no vegetative cover. G-1 Table 1 Common Plant Species Scientific Name Common Name Trees/Shrubs Chrysothamnus viscidiflorus Viscid Rabbitbrush Eleagnus angustifolia Russian Olive Populus deltoides Plains Cottonwood Rhus trilobata Shunkbush Sumac Ribes aereum Golden Current Robinia pseudoacacia Black Locust Salix exigua Coyote Willow Yucca glauca Great Plains Yucca Forbs/Grasses Asclepias speciosa Showy Milkweed Bromus inermis Smooth Brome Bromus tectorum Cheatgrass Carduus nutans Musk Thistle Circium arvense Canada Thistle Conium maculatum Poison Hemlock Convulvulus arvensis Field Bindweed Dipsacus fullonum Teasel Euphorbia esula Leafy Spurge Glycyrrhiza lepidota Wild Licorice Hordeum jubatum Foxtail Barley Juncus balticus Baltic Rush Lathyrus polymorphus Manystem Pea Melilotus officinalis Yellow Sweetclover Opuntia polyacantha Plains Pricklypear Oxytropis lambertii Purple Locoweed Pascopyrum smithii Western Wheatgrass Penstemon sp Penstemon Poa bulbosa Bulbus Blue Grass Poa pratensis Kentucky Blue Grass Rumex crispus Curly Dock Thalaspi arvense Field Pennycress Typha angustifolia Narrowleaf Cattail Verbascum thapsus Mullein G-2 The Park performs regular surveys of weed species, mapping both individuals and larger populations. The Project received the most recent weed data from the Park to determine which species are relevant1. Table 2 presents those weed species populations crossed by the Project and are show on Figure 1. In most instances, these mapped weed patches are collocated with prairie dog colonies. Table 2 Weed Species Within the Project Area Scientific Name Common Name Colorado Status1 Bromus tectorum Cheatgrass C Carduus nutans Musk Thistle B Cirsium arvense Canada Thistle B Convolvulus arvensis Field Bindweed C Descurainia sophia Flixweed NL Dipsacus fullonum Teasel B Elaeagnus angustifolia Russian Olive B Linaria dalmatica Dalmation Toadflax B Rumex crispus Curly Dock NL Verbascum thapsis Common Mullien C 1List B species are those with discrete statewide distributions that are subject to eradication, containment, or suppression in portions of the State designated by the commissioner in order to stop the continued spread of these species. List C species are those that are widespread and well established for which control is recommended but not required by the State, although local governing bodies may require management. NL species are not listed by the state but tracked by CPW. Project Disturbances During construction, a 75-foot wide construction corridor will be used to install the pipeline. This corridor narrows through drainage crossings. Though the entire corridor will not be excavated, it is presumed the entire corridor will be disturbed by vehicle, equipment, and foot traffic and require reclamation. Construction is anticipated to begin late summer 2020 and continue through the winter, concluding in summer 2021. Construction may be active at multiple locations at once, with different segments in differing stages of construction. Guidance CPW provided the Cherry Creek State Park Revegetation/Reclamation Seed Mixes and Specifications (CPW Specifications, undated), and is the primary guidance document relating to weeds and revegetation. Colorado Department of Health and the Environment (CDPHE) will 1 Personal Communication. Steve Williams, CPW Invasive Species Mapping & Management, email to Matt Kizlinski, Hemlock Environmental Consulting. Re: Cherry Creek State Park Weed Data. August 28, 2019. G-3 administer the Stormwater Management Plan (SWMP). The SWMP will require post-construction restored vegetation to reach 70 percent of pre-construction coverage. General Practices The Project will enact the following measures throughout the construction period to promote successful revegetation. Pre-Construction Information will be gathered to document existing conditions This information is either already documented or is to be collected immediately prior to construction, as listed below: 1. A Reclamation Line List will be developed, containing a summary of per parcel information including land use type, irrigation system, soil composition, surface cover, noxious weeds, and a summary of side agreements with the landowner. This will serve as the baseline from which reclamation success will be measured. 2. The SWMP contains pre-construction information regarding surface flow direction as well as numerous site photos. 3. The Environmental Observer will perform a pre-construction site assessment for each parcel. This information will be recorded according to the Pre-construction Condition Sheet and will include numerous site photos. This form will provide a baseline that the post- construction condition can be checked against. Assessment comments regarding the site condition will also be added to the Reclamation Line List. Construction The construction portion of Reclamation Plan relates to the practices during construction to minimize construction impacts and promote faster and complete restoration. The practices are listed as part of the overall permitting requirements, including individual property owner reclamation specifications, Reclamation Line List prescriptions, vehicle and equipment washing requirements, included in topsoil handling practices, addressed as part of the Dewatering practices, addressed as part of the SWMP practices to minimize sediment transport, and measures taken as conditions arise requiring action. These growing practices are spelled out in the list below, which will be expanded/adjusted as appropriate as the project progresses: 1. ROW/disturbance limits to be physically and continuously delineated to prevent construction activity outside of the ROW. 2. Contractor to exit and enter construction ROW only at designated points. 3. When stripping back topsoil, contractor is to create a pronounced topsoil windrow with steep sides. This approach reduces moisture loss in the pealed soil, reduces surface exposure to minimize wind erosion, greatly reduces the likelihood of the soil furrow being driven over and needlessly compacted, it aids in clearly defining the construction limit, and, when on the down• gradient side, it acts as a SWMP BMP. 4. The topsoil stripping depth and locations will be determined in consultation with the land manager. 5. Topsoil and subsoil should never be mixed. Mixing may be prevented by removing all topsoil in the area of construction, stopping work, placing wood mats for construction traffic to drive on to distribute load, or other means to be approved. 6. In areas where all the topsoil has been stripped but the subsoil soils have become saturated, work is to stop or mats are to be placed to prevent rutting. The Environmental Observer has the authority to stop work when rutting is likely to impact the soil structure and increase soil compaction. The