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HomeMy WebLinkAboutR-4179890) N 14 4* 6 4* 6 TT MITIGATION PLAN Wetland Enhancement Due to required frontage improvements and stormwater infrastructure, the applicant is proposing to fill the entirety of Wetland A (1,585 square feet). Mitigation for the fill of Wetland A will be provided through on -site wetland enhancement of Wetlands B and D, totaling 4,865 square feet. The proposed wetland enhancement plantings and large woody debris will increase diversity and density of native plants within Wetlands B and D, while providing increased opportunities for wildlife habitat. Wetland B Enhancement Plan Prior to planting, invasive woody species including (but not limited to) Himalayan blackberry (Rubus armeniacus), English holly (Ilex aquifolium), and English ivy (Hedera helix) will be removed from the wetland. Any existing native plants within the wetlands shall be retained and protected. Only shrubs will be planted within Wetland B, as a dense native overstory and moderate native understory currently exist. In order to provide dense vegetative cover to compete with potentially encroaching Himalayan blackberry (Rubus armeniacus), spacing of shrubs is at 5 feet on -center. This will allow the thicket forming species (twinberry, rose, and salmonberry) to outcompete non-native species. Wetland B Enhancement Plan (1,765 square feet) Common Name Latin Name Size Spacing Quantity Twinberry Lonicera involucrata 1 gallon 5' 12 Pacific ninebark Physocarpus capitatus 1 gallon 5' 12 Red -osier dogwood Cornus sericea 1 gallon 5' 12 Nootka rose Rosa nutkana 1 gallon 5' 12 Salmonberry Rubus spectabilis 1 gallon 5' 12 Wetland D Enhancement Plan Prior to planting, invasive woody species including (but not limited to) Himalayan blackberry (Rubus armeniacus) will be removed from the wetland. Any existing native plants within the wetlands shall be retained and protected. In order to provide dense vegetative cover to compete with potentially encroaching Himalayan blackberry (Rubus armeniacus), spacing trees at 10 feet on -center and shrubs at 5 feet on -center. This will allow the thicket forming species (twinberry, rose, and salmonberry) to outcompete non-native species. Wetland D Enhancement Plan (3,100 square feet) Common Name Latin Name Size Spacing Quantity Sitka spruce Picea sitchensis 1 gallon 10, 15 Red alder Alnus rubra 1 gallon 10, 15 Sitka willow Salix sitchensis 1 gallon 5' 23 Twinberry Lonicera involucrata 1 gallon 5' 23 Nootka rose Rosa nutkana 1 gallon 5' 23 Salmonberry Rubus spectabilis 1 gallon 5' 23 Buffer Enhancement To compensate for minor impacts (240 square feet) to the buffer of Wetland B associated with frontage improvements, a total of 700 square feet of buffer located between Lincoln Ave NE and Wetland B will be enhanced with a variety of native vegetation and large woody debris. To compensate for minor impacts to Wetland D (134 square feet) and Wetland D's buffer (954 square feet) for installation of the pedestrian trail, a total of 1,536 square feet of buffer will be enhanced. The proposed buffer enhancement plantings and large woody debris will increase diversity and density of native plants within Wetlands B and D, while providing increased opportunities for wildlife habitat. Wetland B Buffer Enhancement Prior to planting, invasive woody species including (but not limited to) Himalayan blackberry (Rubus armeniacus) and English holly (Ilex aquifolium) will be removed from the buffer enhancement area. Any existing native plants within the buffer shall be retained and protected. As the overstory of Wetland B and surrounding buffer is dense with red alder and black cottonwood, a variety of native shrubs and herbaceous species will be planted in the understory. The following native shrubs and groundcover will be planted in the buffer enhancement area: Wetland B Buffer Enhancement (700 square feet) Common Name Latin Name Size Spacing Quantity Vine maple Acer circinatum 2" cal. (7-8' tall) 6' 8 Salmonberry Rubus spectabilis 1 gallon 6' 8 Salal Gaultheria shallon 1 gallon 6' 8 Snowberry Symphoricarpos albus 1 gallon 6' 8 Sword fern Polystichum munitum 1 gallon 4' 10 Low Oregon grape Mahonia nervosa 1 gallon 4' 10 Wetland D Buffer Enhancement Prior to planting, invasive woody species including (but not limited to) Himalayan blackberry (Rubus armeniacus) and English holly (Ilex aquifolium) will be removed from the buffer enhancement area. Any existing native plants within the buffer shall be retained and protected. The following native trees, shrubs, and groundcover will be planted in the buffer enhancement area and any disturbed areas will be seeded with the buffer grass seed mix specified below: Wetland D Buffer Enhancement (1,356 square feet) Common Name Latin Name Size Spacing Quantity Big -leaf maple Acer macrophyllum 1 gallon 9' 8 Grand fir Abies grandis 1 gallon 9' 8 Vine maple Acer circinatum 1 gallon 6' 6 Salmonberry Rubus spectabilis 1 gallon 6' 5 Salal Gaultheria shallon 1 gallon 6' 5 Snowberry Symphoricarpos albus 1 gallon 6' 5 Sword fern Polystichum munitum 1 gallon 4' 24 Low Oregon grape Mahonia nervosa 1 gallon 4' 23 Any disturbed areas within the buffer enhancement areas will be seeded with the buffer grass seed mix specified below: Buffer Grass Seed Mixture Common Name Latin Name lbs./1,000 SF Tall fescue Festuca arundinacea 0, Colonial bentgrass Agrostis tenuis 0.4 Annual ryegrass Lolium multiflorum 0-1, Red clover Trifolium repens 0.2 PLANTING NOTES Plant in the early spring or late fall and obtain all plants from a reputable nursery. Care and handling of all plant materials is extremely important to the overall success of the project. The origin of all plant materials specified in this plan shall be native plants, nursery grown in the Puget Sound region of Washington. Some limited species substitution may be allowed, only with the agreement of the landscape designer, wetland professional, and/or City staff. Pre -Planting Meeting Prior to control of invasive species or installation of mitigation plantings, a site meeting between the contracted landscaper and the consulting wetland professional shall occur to resolve any questions that may arise. During this meeting a discussion regarding plant spacing and locations of plant species including wetland verses buffer species shall occur between the landscape contractor and the consulting wetland professional. Handling Plants shall be handled so as to avoid all damage, including: breaking, bruising, root damage, sunburn, drying, freezing or other injury. Plants must be covered during transport. Plants shall not be bound with wire or rope in a manner that could damage branches. Protect plant roots with shade and wet soil in the time period between delivery and installation. Do not lift container stock by trunks, stems, or tops. Do not remove from containers until ready to plant. Water all plants as necessary to keep moisture levels appropriate to the species horticultural requirements. Plants shall not be allowed to dry out. All plants shall be watered thoroughly immediately upon installation. Soak all containerized plants thoroughly prior to installation. Storage Plants stored by the Permittee for longer than one month prior to planting shall be planted in nursery rows and treated in a manner suitable to those species' horticultural requirements. Plants must be re -inspected by the wetland professional and/or landscape designer prior to installation. Damaged plants Damaged, dried out, or otherwise mishandled plants will be rejected at installation inspection. All rejected plants shall be immediately removed from the site. Plant Names Plant names shall comply with those generally accepted in the native plant nursery trade. Any question regarding plant species or variety shall be referred to the landscape designer, wetland professional, or City staff. All plant materials shall be true to species and variety and legibly tagged. Quality and condition Plants shall be normal in pattern of growth, healthy, well -branched, vigorous, with well -developed root systems, and free of pests and diseases. Damaged, diseased, pest -infested, scraped, bruised, dried out, burned, broken, or defective plants will be rejected. Plants with pruning wounds over 1-inch in diameter will be rejected. Roots All plants shall be balled and burlapped (B &B) or containerized, unless explicitly authorized by the landscape designer and/or wetland professional. Rootbound plants or B&B plants with damaged, cracked, or loose rootballs (major damage) will be rejected. Immediately before installation, plants with minor root damage (some broken and/or twisted roots) must be root -pruned. Matted or circling roots of containerized plantings must be pruned or straightened and the sides of the root ball must be roughened from top to bottom to a depth of approximately half an inch in two to four places. Bare root plantings of woody material are allowed only with permission from the landscape designer, wetland professional and/or City staff. Sizes Plant sizes shall be the size indicated in the plant schedule in approved plans. Larger stock may be acceptable provided that it has not been cut back to the size specified, and that the root ball is proportionate to the size of the plant. Smaller stock may be acceptable, and preferable under some circumstances, based on site -specific conditions. Measurements, caliper, branching, and balling and burlapping shall conform to the American Standard of Nursery Stock by the American Association of Nurserymen (latest edition). Form Evergreen trees shall have single trunks and symmetrical, well -developed form. Deciduous trees shall be single trunked unless specified as multi -stem in the plant schedule. Shrubs shall have multiple stems and be well -branched. Timing of Planting Unless otherwise approved by City staff, all planting shall occur between November 1 and March 1. Overall, the earlier plants go into the ground during the dormant period, the more time they have to adapt to the site and extend their root systems before the water demands of spring and summer. Weeding Existing and exotic vegetation in the mitigation areas will be hand -weeded from around all newly installed plants at the time of installation and on a routine basis throughout the monitoring period. No chemical control of vegetation on any portion of the site is recommended. Site conditions The contractor shall immediately notify the landscape designer and/or wetland professional of drainage or soil conditions likely to be detrimental to the growth or survival of plants. Planting operations shall not be conducted under the following conditions: freezing weather, when the ground is frozen, excessively wet weather, excessively windy weather, or in excessive heat. Planting Pits Planting pits shall be circular or square with vertical sides, and shall be 6" deeper and 12" larger in diameter than the root ball of the plant. Break up the sides of the pit in compacted soils. Set plants upright in pits. Burlap shall be removed from the planting pit. Backfill shall be worked back into holes such that air pockets are removed without adversely compacting down soils. Fertilizer Slow release fertilizer may be used if pre -approved by City of Renton staff. Fertilizers shall be applied only at the base of plantings underneath the required covering of mulch (that does not make contact with stems of the plants). No soil amendment or fertilizers will be placed in planting holes. Staking Most shrubs and many trees DO NOT require any staking. If the plant can stand alone without staking in a moderate wind, do not use a stake. If the plant needs support, then strapping or webbing should be used as low as possible on the trunk to loosely brace the tree with two stakes. Do not brace the tree tightly or too high on the trunk. If the tree is unable to sway, it will further lose the ability to support itself. Do not use wire in a rubber hose for strapping as it exerts too much pressure on the bark. As soon as supporting the plant becomes unnecessary, remove the stakes. All stakes must be removed within two (2) years of installation. Plant Location Colored surveyors ribbon or other appropriate marking shall be attached to the installed plants to assist in locating the plants while removing the competing non-native vegetation and during the monitoring period. PLANTING NOTES CONT'D Arrangement and Spacing The plants shall be arranged in a pattern with the appropriate numbers, sizes, species, and distribution that are required in accordance with the approved plans. The actual placement of individual plants shall mimic natural, asymmetric vegetation patterns found on similar undisturbed sites in the area. Spacing of the plantings may be adjusted to maintain existing vegetation with the agreement of the landscape designer, wetland professional, and/or City staff. Inspection(s) A wetland professional shall be present on site to inspect the plants prior to planting. Minor adjustments to the original design may be required prior to and during construction. Woodchip Mulch All landscaped areas denuded of vegetation and soil surface surrounding all planting pit areas shall receive no less than 2 to 4 inches of certified woodchip mulch after planting. A layer of woodchip mulch will be placed around the base of each plant in a 3-foot radius and at a depth of 2 to 4 inches. The woodchip mulch shall not be allowed to contact plant stems in order to avoid plant decay and rot. PLANT INSTALLATION GUIDELINES Compacted topsoil water thoroughly Plan tWiCE C SHRUB PLANTING DETAIL No Scale TREE PLANTING DETAIL No Scale Prune diseased and broken branches Water basin with 3-4" of mulch Planting hole min. twice size of root ball 'rune diseased and )roken branches Lath stakes driven securely in to the ground Nater basin with 3-4" mulch Unglazed planting pit surface 1/2 topsoil, 1/2 native soil, water thoroughly, fertilize MAINTENANCE The mitigation areas will require periodic maintenance to remove undesirable species and replace vegetation mortality. Maintenance shall occur in accordance with the approved plans. Chemical control, only if approved by City staff, shall be applied by a licensed applicator following all label instructions. Duration and Extent In order to achieve performance standards, the permittee shall have the mitigation area maintained for the duration of the five-year monitoring period. Maintenance will include: watering, weeding around the base of installed plants, pruning, replacement, re -staking, removal of all classes of noxious weeds (see Washington State Noxious Weeds List, WAC 16-750-005) as well as Himalayan blackberry, and any other measures needed to ensure plant survival. The landscape designer and/or wetland professional shall direct all maintenance. Survival The permittee shall be responsible for the health of 100% of all newly installed plants for one growing season after installation has been accepted by the City of Renton. A growing season for these purposes is defined as occurring from spring to spring (March 15 to March 15 of the following year). For fall installation (often required), the growing season will begin the following spring. The permittee shall replace any plants that are: failing, weak, defective in manner of growth, or dead during this growing season, as directed by the landscape designer, wetland professional, and/or City of Renton staff. Installation Timing for Replacement Plants Replacement plants shall be installed between September 15 and January 15, unless otherwise determined by the landscape designer, wetland professional, and/or City of Renton staff. Standards for Replacement Plants Replacement plants shall meet the same standards for size and type as those specified for the original installation, unless otherwise directed by the landscape designer, wetland professional, and/or City of Renton staff. Replanting Plants that have settled in their planting pits too deep, too shallow, loose, or crooked shall be replanted as directed by the landscape designer, wetland professional, and/or City of Renton staff. Herbicides / Pesticides In general, chemical controls shall not be used in the mitigation area, sensitive areas, or their buffers. However, limited use of herbicides may be approved depending on site -specific conditions, only if approved by City of Renton staff. Irrigation / Watering Water shall be provided during the dry season (July 1 through October 15) for the first two years after installation to ensure plant survival and establishment. A temporary above ground irrigation system shall be installed within the Stream S buffer enhancement area and Wetland B buffer enhancement area to provide water. Water shall be applied at a rate of 1" of water twice per week for year one and 1" per week during year two. If the mitigation plantings meet 80 percent survival at the end of year two, the system may be removed. General The permittee shall include in general maintenance activities the replacement of any vandalized or damaged signs, habitat features, fences, or other structural components of this mitigation site. FENCING & SIGNAGE Per RMC 4-3-050(G)(3)(f)-(h) outlines fencing and signage requirements. Prior to construction, the outer extent of the approved critical area buffer and areas not to be disturbed shall be marked with high visibility orange construction fencing and silt fencing. Subsequently, permanent fencing of the native growth protection area containing critical area shall be installed, along with permanent signs (made of wood or metal, adhered to treated or metal posts). Sign locations and size specifications shall be approved by the city. RMC 4-3-050(G)(3)(h) recommends the following wording for signs, "Protection of this natural area is in your care. Alteration or disturbance is prohibited by law." SPLIT RAIL FENCE 5 ft. 2 ft. min. 4' DfPE _ (TRIANGUUPR) S, ROUGH CEDAR 8" 12" TO 16' . Q I � 6" MIN. 12" DIAMETER 4"X4" ROUGH CEDAR POST (TRIANGULAR) CRUSHED SURFACING TOP COURSE (CSTC) POSTS ARE PRE -DRILLED I FOR FENCE RAIL INSERTS 4" TO 6" ROUGH CEDAR RAIL NOTES: 1. POSTS AND RAILINGS ARE PRECUT FOR ASSEMBLY. 2. 3 RAILS ARE PERMITTED. 3. FENCES SHALL BE PLACED AT THE APPROVED BUFFER EDGE. DEVELOPMENT ENGINEERING msippo 05/10/2022 CRITICAL AREA PROTECTION AREA SIGN INSTALLATION GUIDELINES NOT TO SCALE 12"x 18" Aluminum sign with white reflective background. Install one per protected feature in a conspicuous place. Minimum of two galvanized or stainless steel wood lag bolts to firmly secure sign. 4' X 4' pressure treated wooden post with 1/2" chamfer at top. Magnetic locator pin (e.g., pipe, rebar, 20 penny nail, etc.) placed 8-12" from post along CAPA line. Quick -set concrete Compacted native material NOTES: 1. Sign placement shall be subject to the approval of the City of Renton. Alternative sign designs may be submitted to the City of Renton for approval. 3. All signs must be secure and permanent. RA 1 7989 � o � o Q Q co o w U) ao w N �Lo OU)rn�o ; Q M M _ COco co CO � j N N o w _J x Ln > w Q rnwu- wO � 5 w s=4 101 of 107