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HomeMy WebLinkAboutNORTHERN INTEGRATED SUPPLY PROJECT - SPA210001 - SUBMITTAL DOCUMENTS - ROUND 1 - EROSION CONTROL LETTER/REPORTTechnical Memorandum #3 Erosion Control/ Landscaping/ Tree Mitigation Site Plan Advisory Review Process Prepared for: City of Fort Collins Prepared by: Northern Integrated Supply Project Water Activity Enterprise May 14, 2021 Revision Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 1 Memorandum Date: May 14, 2021 To: City of Fort Collins Planning Department From: Bridget Mitchell, P.E. and Sydney Shell, P.L.A. - Pinyon Environmental Subject: Northern Integrated Supply Project (NISP) – City of Fort Collins Site Plan Advisory Review (SPAR) Erosion Control/Landscape and Wetlands Restoration Plan This memorandum presents Erosion Control and Landscape and Wetlands Restoration methods proposed for the Northern Integrated Supply Project (NISP or the Project) within the City of Fort Collins (“City”), in accordance with Fort Collins Land Use Code requirements. This memorandum documents proposed erosion control and landscaping within the portion of NISP inside the boundaries of the City of Fort Collins (“Project Area”) in support of the NISP Site Plan Advisory Review application to the City. The NISP Water Activity Enterprise (WAE) is the permittee and the entity that will retain a contractor to implement construction activities. Northern Colorado Water Conservancy District (Northern Water), acting by and through the NISP WAE, has contracted Pinyon Environmental, Inc. (Pinyon), to provide environmental compliance services during the pre-construction phase of the Project. The Project includes the Poudre River Intake Structure and approximately 18,000 linear feet of the Poudre River Intake Pipeline within Fort Collins city limits. This proposed pipeline is an approximately 32- and 36-inch- diameter waterline that will be installed approximately five feet underground. The typical trench section will be about six feet wide. Soil stockpiles, vehicle traffic, and surface disturbance will be limited to a working area of 100-ft width. Conventional excavation equipment, including diesel-powered hydraulic excavators and front- end loaders, will be used to construct the new waterline and intake. Disturbance area at wetland and water crossings will be limited to a working area of 60-ft width for crossings less than or equal to 500 feet in length and 80-ft in width for crossings greater than 500 feet in length. Major road crossings will be bored. The pipeline within the City will cross three irrigation ditches and three wetland areas. The intake structure will be constructed along the bank of the Poudre River. Except for the intake structure, proposed surface impacts are temporary. Disturbed areas will be restored to pre-construction conditions. More detail is provided below. The Project is located on City property and private land. Restoration will follow this plan, but specific techniques or the seed mix may be amended after coordination with the property owner. Erosion Control The Project will result in greater than one acre of land disturbance and therefore triggers a Colorado Department of Public Health and Environment (CDPHE) construction stormwater discharge permit. Erosion Control Plans (including report) will be developed in accordance with CDPHE permit requirements and City Erosion Control Guidance (specifically the City’s Stormwater Criteria Manual Chapter 2, Section 6). The Erosion Control Plan will identify potential Project pollutants and describe control measures to be implemented to prevent pollutants from leaving the site and entering sensitive resources. Table 1 identifies potential pollutants, their applicability to the Project, and potential control measures to mitigate impacts. Control measures proposed will meet City standards per the City’s Stormwater Criteria Manual. Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 2 Table 1. Summary of Control Measures Potential Pollutant Potential with this Project? Description of Activities Measures to Control Source Disturbed and stored soils Yes Brush Cutting, Clearing, Grubbing, Excavation, Grading Vegetation buffers, sediment control logs, construction fencing, silt fence, rock sock, inlet/outlet protection, surface roughening, seeding and mulching Vehicle tracking of sediments Yes Vehicles entering and exiting site Vehicle tracking control (VTC) Management of contaminated soils No None expected on-site None expected on-site Loading and unloading Operations Yes Material Deliveries Good housekeeping Outdoor storage activities Yes Material storage Good housekeeping, stabilized staging areas Vehicle and equipment maintenance and refueling Yes Fueling and maintenance on equipment Stabilized staging areas, good housekeeping Dust or particulate generating processes Yes Grading operations and the presence of bare soil A water truck may be used to manage dust generation during construction Activities involving fertilizers, pesticides, detergents, etc. Yes Soil amendments and/or fertilizers may be used during seeding operations Good housekeeping On site waste management practices Yes Portable toilets, sanitary waste Good housekeeping; siting and securing portable toilets Concrete truck/equipment washing Yes Delivering concrete Contractor will use portable, contained washouts Dedicated asphalt/concrete batch plants No None expected on-site None expected on-site Non-industrial waste sources Yes Construction waste Good housekeeping; trash containers Other areas where spills could potentially occur No None expected on-site None expected on-site Control measures will be placed prior to land disturbance activity. Vehicle tracking controls, sediment control logs, silt fence, construction fence, storm drain inlet protection, and rock socks will be installed and maintained during construction. A brief description of their proposed use is provided below: Vehicle tracking controls will be placed as a source control to prevent tracking of sediment from disturbed areas to adjacent paved areas.  Construction fence will be placed to protect sensitive resources and prevent public from entering construction areas where appropriate.  Erosion control logs and/or silt fence will be placed downgradient of disturbed areas to contain construction sediment.  Inlet/outlet protection will be placed over the top of culvert inlets and outlets within the project area. Inlet protection will also be installed at inlet grates and throats to prevent sediment from entering the stormwater drainage system. Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 3  Rock socks will be placed in paved areas immediately downgradient of disturbed areas as needed. Rock socks may also be used for inlet protection. Proposed stormwater control measure details are provided in Attachment 1 for reference. The proposed pipeline will cross wetland and streams. Additional stormwater control measures will be implemented in these areas to protect these resources. Refer to the preliminary details provided in Attachment 2. Permanent stabilization methods are discussed in the Landscape and Wetlands Restoration Plan section. Landscape and Wetlands Restoration Plan This section describes landscape and wetlands restoration methods proposed for use on City of Fort Collins Natural Areas properties and non-natural areas/other properties. This Landscape and Wetlands Restoration Plan has been developed in accordance with the City’s Land Use Code Section 3.2.1 requirements and includes methods of reclamation and proposed reseeding for temporarily impacted areas (including wetlands). Existing tree inventory, removal, protection, and mitigation is detailed in Attachment 3. Natural Areas During site excavation the Contractor will strip and stockpile topsoil based on the following:  Native vegetation areas will be excavated to a depth of 8 inches and stockpiled separately.  Non-native vegetation areas will be stripped, and the top 2 inches will be removed to remove non-native seed source. Then an additional 8 inches will be excavated and stockpiled separately. As soon as practicable following installation of the pipeline, the trench will be backfilled with native material. Back-filled trenches will be compacted to 95% Standard Proctor Density. Areas within the limits of disturbance that have been driven over, compacted, or rutted by equipment must be scarified to a depth of 8 inches (not exceeding 10 inches between intervals), and regraded to original grade and contours prior to seeding. After compaction to final subgrade (8 inches below finished grade), the top 6 inches of subsoil must be ripped (no more than 20 inches between intervals), and the previously stripped and stockpiled topsoil materials spread evenly over the excavated areas in the corresponding zones immediately following the completion of construction. Soils in backfilled, compacted, and topsoiled trenches must match the grade of the surrounding undisturbed areas. All topsoil, either imported or salvaged in the Project area, will be treated with a herbicide for noxious weeds prior to final seeding (herbicide application will be timed so that it does not impact seed germination). The Contractor will seed all disturbed and topsoiled areas with native seed mixes (see below). Seed will be mixed by a wholesale seed supplier in the proportions determined by the Project team and approved by the City in order to obtain the approved application rate. Seed will conform to current State and Federal regulations and will be subject to the testing provisions of the Association of Official Seed Analysis. Seed and seed mixes will be furnished in bags or containers clearly labeled to show the name and address of the supplier, the common, scientific, and variety name(s) of the seed(s), the lot number, point of origin, net weight, percent of weed content, and the guaranteed percentage of purity and germination. These labels will be submitted to the Project team for approval prior to seeding. Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 4 The following seed mixes are proposed for use in wetland, riparian, and upland areas. The Project will coordinate with the City’s Land Conservation Manager to review, approve, and potentially amend seed mixes for use on individual natural area properties within the Project area. Additional seed mixes and landscaping may be required to match existing landscape conditions. Table 2. Seed Mixes for Temporary Impact Areas Grasses Latin Name Common Name Mix % - PSS Mix % - RI Mix % - UM Pascopyrum smithii Western Wheatgrass 10 15 15 Elymus trachycaulus trachycalus Slender Wheatgrass 15 10 5 Panicum virgatum Switchgrass 10 10 10 Poa palustris Fowl Bluegrass 5 Spartina pectinata Prairie Cordgrass 15 10 Elymus canadensis Canada Wildrye 10 10 10 Nassella viridula Green Needlegrass 10 10 5 Sporobolus crytandrus Sand Dropseed 5 5 Schizachyrium scoparium Little Bluestem 5 10 10 Bouteloua gracilis Sideoats Grama 10 Bouteloua curtipendula Blue Grama 10 Sporobolus airoides Alkali Sacaton 10 Shrubs Latin Name Common Name Rhus trilobata Threeleaf Sumac 5 5 Chrysothamnus nauseosis Rubber Rabbitbrush 5 Rosa woodsii Wood's Rose 5 5 Amelanchier alnifolia Saskatoon Serviceberry 5 5 Cornus sericea ssp. Sericea Red Osier Dogwood 5 Prunus Americana American Plum 5 5 Total Percent = 100 100 100 Legend PSS - Wetland Scrub-Shrub RI - Riparian UM - Upland Meadow Note: Actual mixture of plant species, size, and density will be determined by the property owner based on availability at the time of planting and discretion of restoration ecologist. The Contractor will drill-seed into the soil to an approximate depth of ¼ to ½ inch, using a range drill (not a Brillion). Immediately following seeding the Contractor will roll the seeded areas with a sheep’s foot roller to Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 5 lightly compact and imprint the soil to remove air voids, provide better seed-soil contact, and create indentations in the soil that will capture moisture. All seeded areas will be hydromulched in accordance with the City’s Storm Drainage Design Criteria and Construction Standards. The Contractor will obtain and submit to the Project manager certifications from suppliers of hydraulic mulch that laboratory and field testing of their product has been accomplished, and that it meets requirements pertaining to wood cellulose fiber mulch. Vegetation cover will be inspected in accordance with the Project construction stormwater discharge permit until final stabilization is achieved. According to the discharge permit, “Final stabilization is reached when all ground surface disturbing activities at the construction site are complete; and, for all areas of ground surface disturbing activities, either a uniform vegetative cover with an individual plant density of at least 70 percent of pre-disturbance levels is established, or equivalent permanent alternative stabilization methods are implemented” (CDPHE CDPS, 2019). Non-Natural Areas and Private Properties During site excavation the Contractor will strip and stockpile topsoil separately from any subsoil. As soon as practicable following installation of the pipeline, the trench will be backfilled. After compaction to final subgrade the top 6 inches of subsoil will be ripped and the previously stripped and stockpiled topsoil materials spread evenly over the excavated area. Areas within the limits of disturbance that have been impacted will be restored to original grade and contours, and disturbed areas will be revegetated using the seed mixes in Table 2 (or as otherwise directed by the property owner). The Project will coordinate with the City or private property owners to review and approve the proposed plant material on individual properties within the Project area. At minimum, the proposed design shall replace landscape conditions in-kind. Stormwater Engineering Vegetation cover will be inspected in accordance with the Project construction stormwater discharge permit until final stabilization is achieved. According to the discharge permit, “Final stabilization is reached when all ground surface disturbing activities at the construction site are complete; and, for all areas of ground surface disturbing activities, either a uniform vegetative cover with an individual plant density of at least 70 percent of pre-disturbance levels is established, or equivalent permanent alternative stabilization methods are implemented” (CDPHE CDPS, 2019). The Project will not increase impervious area greater than 1,000 square feet, therefore no permanent stormwater features are proposed. Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Page 6 References Colorado Department of Public Health and Environment (CDPHE) Water Quality Control Division, “CDPS General Permit Stormwater Discharges Associated with Construction Activity Authorization to Discharge Under the Colorado Discharge Permit System (CDPS), CDPHE. Effective on April 1, 2019. Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Attachment 1 – Stormwater Control Measure Details (City of Fort Collins Stormwater Criteria Manual Appendix E) Silt Fence (SF) SC-1 November 2010 Urban Drainage and Flood Control District SF-3 Urban Storm Drainage Criteria Manual Volume 3 Sediment Control Log (SCL) SC-2 November 2010 Urban Drainage and Flood Control District SCL-3 Urban Storm Drainage Criteria Manual Volume 3 SC-2 Sediment Control Log (SCL) SCL-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 SC-5 Rock Sock (RS) RS-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 SC-6 Inlet Protection (IP) IP-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Inlet Protection (IP) SC-6 November 2010 Urban Drainage and Flood Control District IP-5 Urban Storm Drainage Criteria Manual Volume 3 SC-6 Inlet Protection (IP) IP-6 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 SM-3 Construction Fence (CF) CF-2 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Vehicle Tracking Control (VTC) SM-4 November 2010 Urban Drainage and Flood Control District VTC-3 Urban Storm Drainage Criteria Manual Volume 3 SM-4 Vehicle Tracking Control (VTC) VTC-4 Urban Drainage and Flood Control District November 2010 Urban Storm Drainage Criteria Manual Volume 3 Vehicle Tracking Control (VTC) SM-4 November 2010 Urban Drainage and Flood Control District VTC-5 Urban Storm Drainage Criteria Manual Volume 3 Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Attachment 2 – Preliminary Wetland and Stream Crossing Details Technical Memorandum NISP SPAR Erosion Control/Landscape and Wetlands Restoration Plan Attachment 3 – Tree Inventory and Mitigation Memorandum Technical Memorandum NISP SPAR Tree Inventory and Mitigation Plan Page 1 Memorandum Date: April 30, 2021 To: City of Fort Collins Planning Department From: Allison Haraminac, Pinyon Environmental, Inc. Subject: Northern Integrated Supply Project (NISP) – City of Fort Collins Site Plan Advisory Review (SPAR) Tree Inventory and Mitigation Memorandum Introduction This memorandum presents the tree inventory and mitigation measures for the Northern Integrated Supply Project (NISP or the Project) within the city limits of the City of Fort Collins (City), in accordance with Fort Collins Land Use Code requirements and in support of the NISP Site Plan Advisory Review application to the City. The NISP Water Activity Enterprise (WAE) is the permittee and the entity that will retain a contractor to implement construction activities. Northern Colorado Water Conservancy District (Northern Water), acting by and through the NISP WAE, has contracted Pinyon Environmental, Inc. (Pinyon), to provide environmental compliance services during the pre-construction phase of the Project. Pinyon, in conjunction with Precision Surveying, Inc., has conducted a tree inventory for the project. This Tree Inventory and Mitigation Memorandum documents the results of the tree inventory and mitigation requirements outlined by the City Forestry Division. Methods On March 18, 19, 23, and 24, Pinyon biologist Tim Merlino visited the site with Precision Surveying, Inc. to inventory trees within the Project area. The surveyor mapped tree locations using a sub-meter accurate Global Positioning System (GPS) unit and recorded the diameter at breast height (DBH) and species for each tree, with input from Mr. Merlino. On April 9, 2021, Mr. Merlino visited the site again with representatives from the City Forestry Division and Northern Water to view trees outside of City Natural Areas proposed to be impacted by the project. The City Forestry Division assessed the condition of each tree and determined mitigation requirements for trees outside of Natural Areas during this site visit. Results A total of 1,427 trees were inventoried within and near the project area. Of these, 77 trees are proposed for removal (Table 1; Attachment 1). Tree removals would be necessary where trees are present within the proposed excavation zone and are incompatible with project infrastructure. The project’s engineering team has conservatively estimated the trees that would be removed based on potential working space for equipment and excavation requirements. Northern Water is proposing mitigation for anticipated impacts by planting trees and shrubs, with input from the City Forestry Division for tree replacements on properties outside of Natural Areas (Table 1; Attachment 1). Technical Memorandum NISP SPAR Tree Inventory and Mitigation Plan Page 2 Table 1. Impacted Trees and Proposed Mitigation Label1 Species Common Name Species Scientific Name Diameter Mitigation 70275 Common Hackberry Celtis occidentalis 8 1.5 trees 70576 Siberian Elm Ulmus pumila 12 3 trees 70577 Siberian Elm Ulmus pumila 6 3 trees 70578 Siberian Elm Ulmus pumila 24 3 trees 70579 Siberian Elm Ulmus pumila 4 0 trees2 70580 Siberian Elm Ulmus pumila 12 3 trees 70581 Siberian Elm Ulmus pumila 35 3 trees 70582 Plains Cottonwood Populus deltoides 12 3 trees 70676 Plains Cottonwood Populus deltoides 26 3 trees 70677 Siberian Elm Ulmus pumila 24 3 trees 70678 Plains Cottonwood Populus deltoides 12 3 trees 70716 Narrowleaf Cottonwood Populus angustifolia 10 3 trees 70759 American Elm Ulmus americana 12 3 trees 70706 Willow Salix amygdaloides or Salix fragilis 84 10 trees for this cluster 70711 Willow Salix amygdaloides or Salix fragilis 40 70712 Willow Salix amygdaloides or Salix fragilis 48 70713 Willow Salix amygdaloides or Salix fragilis 52 70714 Willow Salix amygdaloides or Salix fragilis 24 70760 American Elm Ulmus americana 3 70761 American Elm Ulmus americana 6 70762 Plains Cottonwood Populus deltoides 48 70763 American Elm Ulmus americana 4 70764 American Elm Ulmus americana 4 70765 American Elm Ulmus americana 4 70766 American Elm Ulmus americana 24 70783 American Elm Ulmus americana 3 70784 American Elm Ulmus americana 3 70785 Green Ash Fraxinus pennsylvanica 4 70786 Green Ash Fraxinus pennsylvanica 4 70787 American Elm Ulmus americana 3 70788 Plains Cottonwood Populus deltoides 5 70789 Green Ash Fraxinus pennsylvanica 5 70851 Willow Salix amygdaloides or Salix fragilis 40 10 trees for this cluster 70852 Willow Salix amygdaloides or Salix fragilis 72 70918 American Elm Ulmus americana 4 Technical Memorandum NISP SPAR Tree Inventory and Mitigation Plan Page 3 Label1 Species Common Name Species Scientific Name Diameter Mitigation 70919 American Elm Ulmus americana 4 70920 Willow Salix amygdaloides or Salix fragilis 12 70921 Plains Cottonwood Populus deltoides 38 70922 Plains Cottonwood Populus deltoides 28 70923 Plains Cottonwood Populus deltoides 32 70936 Willow Salix amygdaloides or Salix fragilis 24 70937 Willow Salix amygdaloides or Salix fragilis 24 70938 Willow Salix amygdaloides or Salix fragilis 34 70944 Plains Cottonwood Populus deltoides 6 70949 Plains Cottonwood Populus deltoides 8 71149 Plains Cottonwood Populus deltoides 6 6 trees for this cluster 71150 Plains Cottonwood Populus deltoides 6 71151 Plains Cottonwood Populus deltoides 4 71167 American Elm Ulmus americana 10 3 trees 71181 Willow Salix amygdaloides or Salix fragilis 20 2.5 trees for this cluster 71182 Russian Olive Elaeagnus angustifolia 10 71183 Russian Olive Elaeagnus angustifolia 10 71291 Plains Cottonwood Populus deltoides 4 3 trees for this cluster 71292 Plains Cottonwood Populus deltoides 4 71296 Plains Cottonwood Populus deltoides 6 71297 Plains Cottonwood Populus deltoides 4 71298 Plains Cottonwood Populus deltoides 4 71303 Russian Olive Elaeagnus angustifolia 10 1.5 trees 71311 Willow Salix amygdaloides or Salix fragilis 12 2 large shrubs 71312 American Elm Ulmus americana 12 1.5 trees 74086 Unknown Unknown 5 0 trees2 74128 Chokecherry Prunus virginiana 6 3 trees 74129 Chokecherry Prunus virginiana 10 3 trees 74130 Plains Cottonwood Populus deltoides 20 3 trees 74131 Plains Cottonwood Populus deltoides 20 3 trees 74151 Siberian Elm Ulmus pumila 24 3 trees 74155 Siberian Elm Ulmus pumila 24 3 trees 74156 Siberian Elm Ulmus pumila 38 3 trees 70221 Green Ash Fraxinus pennsylvanica 8 3 trees 70220 Chokecherry Prunus virginiana 8 3 trees 70943 Willow Salix amygdaloides or Salix fragilis 86 3 trees Technical Memorandum NISP SPAR Tree Inventory and Mitigation Plan Page 4 Label1 Species Common Name Species Scientific Name Diameter Mitigation 74095 Russian Olive Elaeagnus angustifolia 10 3 trees 74096 Siberian Elm Ulmus pumila 30 3 trees 74097 Russian Olive Elaeagnus angustifolia 10 3 trees 74098 Russian Olive Elaeagnus angustifolia 10 3 trees 74099 Russian Olive Elaeagnus angustifolia 12 3 trees 74100 Russian Olive Elaeagnus angustifolia 10 3 trees Total Proposed Mitigation 120 trees, 2 large shrubs 1See Attachment 1, Landscape Plan 2Mitigation is not recommended or required for these trees due to their small size. Plantings will follow City of Fort Collins guidance and Land Use Code requirements. Replacement trees will have the following calipers:  Canopy Shade Trees: 2.0” caliper balled and burlapped  Ornamental Trees: 2.0” caliper balled and burlapped  Evergreen Trees: 8’ height balled and burlapped Please see the Landscape Plan (Attachment 1) for planting notes and details. Trees not slated for removal will be protected with temporary construction fencing to avoid impacts. Conclusions and Recommendations One hundred and twenty trees and two large shrubs will be planted to offset the tree removals proposed for the project (Attachment 1). Trees will be planted as close as possible to the proposed temporary easement area (and outside of the permanent easement area) for the pipeline. Final placements will be determined in coordination with the City Forestry Division and property owner. Attachments: Attachment 1 – Landscape Plan