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HomeMy WebLinkAbout3193.4SELECTED COMPENSATORY MITIGATION APPROACH Site planning for the Evendell Residential Community has focused on the mandated hierarchy of wetland impact reduction: 1) avoidance, 2) minimization, and 3) compensation. These avoidance and minimization strategies included a site design to avoid all adverse impacts to onsite wetland systems, except those minor impacts required by King County to create SE 1361h Street. The total amount of King County jurisdictional wetland area to be modified by the development of SE 136"' Street equals 225 square feet (0.005 acres). As compensation for this unavoidable impact 550 square feet (0.012 acres) of degraded wetland area would be restored and enhanced through the planting of native trees and shrubs. In addition, Tract P would be added to the overall protective buffer established by this mitigation program. This compensatory action has been reviewed and approved by King County environmental staff. • Mitigation Benefits The restoration and enhancement of the northern tip of the existing Class 2 Wetland is designed to accompany site development. The primary benefits associated with the proposed restoration and enhancement includes the creation of a viable plant community composed of native shrubs and trees. The selected plant species would increase plant community and wildlife habitat diversity and complexity within the wetland area. The restored and enhanced wetland area would provide increased screening protections for the wetland area adjacent with the new public roadway. In addition, the addition of Tract P to the overall established buffer would provide increased protection for the onsite wetland and additional retained wildlife habitats. • Selected Mitigation Area IThe selected mitigation area is located at the northern tip of the onsite Class 2 Wetland. The plant community within the selected area is presently limited as a result of prior land use actions. DESCRIPTION OF THE MITIGATION PROGRAM 1. As compensation for the unavoidable filling of 225 square feet (0.005 acres) of identified King County Class 2 Wetland the area directly south of the impacted wetland area shall be restored and enhanced through the planting of a variety of native trees and shrubs. The area to be restored shall be a minimum of 550 square feet (0.012 acres) in size. The selected species shall increase plant community and wildlife habitats diversity and complexity. 2. As compensation for the reduced buffer caused by the development of SE 1361h Street along the northern edge of the identified King County Class 2 Wetland the existing forested area in the northeastern corner of the project site (Tract P) shall be added to the overall buffer area. 3. All onsite activities shall be monitored by the project biologist. Following the completion of onsite planting activities a "record -drawing" (i.e. "as -built") plan shall be prepared and submitted to King County. A five-year monitoring program shall be undertaken to assure the success of the compensatory mitigation program. 4. Temporary and long-term erosion control measures shall be implemented. These measures include silt fencing during site preparation and wetland planting, and seeding of all exposed soil areas. 5. The retained wetland and associated buffer shall be identified as separate tract. The outer boundary of this tract shall be fenced and posted with standard King County buffer boundary signs at a minimum interval of 50 feet. GOAL AND OBJECTIVE OF THE MITIGATION PROGRAM The GOAL of the compensatory mitigation program is to fully compensate for the unavoidable adverse impact to Wetland A caused by the required development of SE 136 h Street. The restoration and enhancement of a portion of the onsite wetland shall provide full compensation for unavoidable wetland impacts. Upon the completion of this mitigation plan there shall be no net loss of wetland functions or values. To achieve the defined GOAL, the following OBJECTIVES and PERFORMANCE CRITERIA have are defined: Objective A. The restored and enhanced compensatory mitigation area shall be a minimum of 550 square feet (0.012 acres) in total size. The restored and enhanced .compensatory mitigation wetland area shall exhibit a scrub/shrub and sapling tree vegetation classes within five years following initial planting: Performance Criterion #A1: As defined by plant count 100% of the trees and shrubs initially installed within the compensatory wetland area shall exhibit survival through the end of the first growing season following planting. Performance Criterion #A2: As defined by plant count 80% of the trees and shrubs initially installed within the compensatory wetland area shall exhibit survival through the end of the fifth growing season following planting. Performance Criterion #A3: As defined by aerial coverage, invasive non-native species shall not exceed 15% at the end of the fifth growing season following planting within the restored and enhanced compensatory wetland area. IMPLEMENTATION INSPECTION Essential to the success of the mitigation program is the accurate inspection of onsite activities immediately prior to and during the initial wetland restoration and enhancement phase. These activities include pre - implementation site inspection, onsite inspection and technical direction during wetland planting activities, and post -planting site inspection and evaluation. The pre -implementation site inspection allows the project team and the project biologist to evaluate and, if' necessary, undertaken minor adjustments in the onsite implementation steps. These steps include analysis of project site elevation features, project sequencing and timing, final grade analysis, unforeseen required minor modifications to the original establishment plan, and the establishment of environmental protections (silt fences, etc.) required during implementation. Onsite technical inspection during implementation and planting activities shall be implemented by the project biologist. The project biologist shall perform implementation oversight and address minor unforeseen implementation difficulties to assure that the intent of the compensatory mitigation program is met. The project biologist shall also be responsible for ensuring that the species and sizes of native plants selected and noted within the final planting plan are utilized during implementation. If selected native species become unavailable, the project biologist shall consult with King County for substitute plant species to assure that the intent of the compensatory mitigation program is met. Post -implementation site inspection/ evaluation shall include the preparation of a "record -drawings" which shall be submitted to King County. CONTINGENCY PLAN As a contingency, should the proposed compensatory mitigation program fail to meet the performance criteria, the project proponent shall undertake required remedial actions. Where plant survival is the failing component, the project proponent shall replant and ensure the success of this second planting which would be held to the same standard of success as measured by threshold criteria and monitoring processes. Where non-native, invasive vegetation exceeds 15% aerial coverage the project proponent shall undertake removal actions. Such removal actions shall be completed using hand tools or pulling the plants by hand to remove the invasive vegetation without disrupting the soil profile. All cut or pulled vegetation shall be removed. from the mitigation area and disposed in .an approved location. Herbicides shall only be used following approval by King County, All herbicide application shall be completed by a licensed professional. Should additional remedial actions be required, the project proponent shall meet with the King County to establish and define actions to be taken to meet the desired goal of this mitigation program. TEMPORARY IRRIGATION The project proponent shall ensure that a minimum of one (1) inch of water is supplied each week to the compensatory mitigation area between June 1 and October 1.5 for a least the first two years following initial planting. The calculated amount of required water shall include both natural rainfall and temporary irrigation. The need for additional years of irrigation shall be determined based on site conditions and overall plant survival. The amount of water supplied to the compensatory mitigation area shall be increased if onsite monitoring defines such a need. PLANTING NOTES With the exception of the identified grass seed mixtures, all plant materials utilized within the restore and enhanced wetland shall be native to the Puget Sound Region. The onsite biologist shall inspect plant materials to assure the appropriate plant schedule and plant characteristics are met. The project proponent shall IMPLEMENTATION SCHEDULE PROJECT TASK TASK SCHEDULE Onsite pre -implementation project meeting Completed by Aug. 15, 2004 Placement of protective fencing, final marking, and identification of work area. Seeding of disturbed areas. Completed by Aug. 30, 2004 Completed by Sept. 15, 2004 Irrigation of restored and enhanced wetland. As needed following seeding Planting of restored and enhanced wetland area. Completed by Nov. 15, 2004 Record -drawings report to County Completed by Dec. 5, 2004 PROJECT MONITORING Following the successful completion of the proposed wetland planting a five-year monitoring and evaluation program shall be undertaken. The purpose of this program is to ensure the, success of the selected mitigation as measured by an established set of performance criteria. This monitoring may also provide valuable information on the effectiveness of mitigation procedures. STANDARDS OF SUCCESS • Vegetation Sampling Methodology and Monitoring Schedule The monitoring program shall count each plant initially installed within the restored and enhanced wetland area. The evaluation of the success of the compensatory mitigation program shall be based on the selected survival rate for trees and shrubs. These defined performance criteria shall be applied at the times of yearly monitoring. The percent survival rate shall be based on combined counts of existing, volunteer plants, and planted species during vegetation monitoring. Sample location shall be shown on the "record drawings" (i.e. "as -built") plan, and shall correspond to identified photopoints. Trees and shrubs shall be visually evaluated to determine the rate of survivorship, health, and vigor of each plant. The categories to be used shall include live, stressed, tip dieback, basal sprouts, not found, apparently dead, and dead. • Vegetation Monitoring 1. As a part of each monitoring period the project biologist shall count the number of live plants initially planted within the representative sample plots. Plants shall be identified to species and observations of general plant condition (i.e., plant health, amount of new growth) shall be recorded for each plant. 2. Within the restored and enhanced wetland the project biologist shall count the number of undesirable invasive plants and estimate the aerial coverage (as if the observer were looking straight down from above) of these invasive plants. Undesirable plants include blackberries, Scot's broom, tansy ragwort, reed canarygrass, and plants listed in the Washington State Noxious Weed List. 3. Within the restored and enhanced wetland the project biologist shall count the number of desirable "volunteer" plants and estimate the aerial coverage of these plants. 4. The project biologist shall take photographs that show the entire compensatory mitigation area. During the five-year monitoring period photos shall be taken in the same direction and at the same location to provide a series of photos. These photos shall show plant growth, plant species, and plant coverage. 5. Upon the completion of each annual monitoring period the project biologist shall prepare a report defining methods, observations, and results along with the date the observations were completed. Each report shall be provided to the County. 6. The monitoring schedule is defined as: A. Twice a year for two years following the completion of initial onsite planting. For each monitoring year, onsite monitoring would be completed once early in the growing season (late March to mid -April) and once again near the end of the growing season (mid -September). For each onsite monitoring activity an annual report would be prepared and provided to King County within three weeks after the completion of the fall monitoring. B. Once a year for years three, four, and five following the completion of initial onsite planting. For each monitoring year, onsite monitoring would be completed once near the end of the growing season (mid- September)._E,or each onsite monitoring activity a report would be prepared and provided to King County within three weeks after the completion of onsite monitoring. Vegetation Monitorina Seauencina MONITORING YEAR PLANT COMMUNITY MONITORING SUBMITTAL OF MONITORING REPORT YEAR-1 On or about April 15, 2005 On or about Sept. 15, 2005 Report due Oct. 7, 2005 YEAR-2 On or about April 15, 2006 On or about Sept. 15, 2006 Report due Oct. 7, 2006 YEAR-3 On or about Sept. 15, 2007 Report due Oct. 7, 2007 YEAR-4 On or about Sept. 15, 2008 Report due Oct. 7, 2008 LYEAR-5 On or about Sept. 15, 2009 1 Report due Oct. 7, 2009 VEGETATION MAINTENANCE PLAN Maintenance of the restored and enhanced wetland may be required to assure the long-term health and welfare of the wetland's environmental functions. Such maintenance would be identified during the monitoring period and undertaken only following discussion and coordination with King County. The overall objective is to establish undisturbed plant communities that do not require maintenance. Activities may include, but are not limited to, the removal of invasive non-native vegetation and the irrigation of selected areas. Established maintenance activities include the removal of any trash within the wetland or buffer. REMOVAL OF INVASIVE NON-NATIVE VEGETATION As a contingency, should the removal of invasive non-native vegetation become necessary within the restored and enhanced wetland area, the project proponent shall contact King County to establish and define specific actions to be taken.. Resultant contingency plan activities shall be implemented when the ongoing vegetation monitoring program indicates that plants listed in the Washington State Noxious Weed List, blackberries, reed canarygrass, or Scot's broom are becoming dominant in the community or exceed 15% of the aerial coverage of the planting areas. SEEDING FOR EXPOSED AREAS Seeding for all exposed surfaces within the mitigation area shall be completed within two weeks following the exposure of the soil. Wetland Area Soil Moisture Conditions common name scientific name rcent by weight edtop grostis alba 50% ater foxtail to ecurus geniculatus 50% (apply at the rate of 120 pounds per acre) Upland Buffer Area Soil Moisture Conditions common name scientific name percent by weight Colonial bentgrass grostis tennis 15% Tall fescue estuca arundinacea 40% Perennial ryegrass olium perenne 30% Creeping red fescue estuca rubra 15% (apply at the rate of 120 pounds per acre) SE 136th STREET 4-PSI O UNAVOIDABLE WETLAND FILL TO CREATE PUBLIC ROADWAY (225sgft) / p scale in feet gp / 20 40 60 \ TRACT P \ ADDED BUFFER AREA CLASS 2 WETLAND \ \ 2-PIS 10-COS 20-SAS NUMBS COMMON NAME PROPbSED PROPOSED INDICATOR SCIENTIFIC NAME SPACIN SIZE STATUS I- oc 4 estern red cedar (THP) loft ft height FAC u°a licata m imum 2 itk pruce (PIS) loft 4 ft h' °ght FAC Picea itchensis minim 4 ouglas PSM) 10 ft 4 ft neigh FACU Pseudotsu menziesii minimum 12 estern craba le :7 8 ft 4 ft height FACW P rus fusca minimum 3 lack twinberry 4 ft 2 gal FAC+ Lonicera involucrata 6 acific ninebark 4 ft 2 gal FA W- Ph socar us ca itatus 10 ed osier dogwood 4 ft 2 gal FACW Corpus stolonifera 20 itka willow 4 ft 2 gal FACW ESTABLISHED BUFFER BOUNDARY ..�. f1FFIAIFII WFTI ANfI R(11 WI'14 R� Salix sitchensis 1 sb~ 4 \ , I. aTWO BACKFILU BOx'el"TING 504. Box I/ W�NNus COMPOff,. w ip ` HPAOUGHLY 2. FOR MULCH TtPE BEE CONIFER TREE S. ' LANDSCAPE NOTE W STAKE DRIVEN J. IF BM8 AND OURLAP INTO QRW INcYen�D N'Ulf tROREUR%Aei _ W/ Nk FORW SAUCER YAjH1111111101 "�On ""`�' D T OR ESTABLISHED M"NUOUS KW AAlE?OED BASE, R[FER ll�, TO LS NOTES FOR BUFFER ;E11 BkB: REMOVE Aa I� AND ROLL BURLAP BOUNDARY OFF of TOP OF LII IROOTBALL SCARIFY SIDES AND BOTTOM LOCAT!ON OF SILT FENCE MIXTURE INDICATED N NOTES, AND FINAL PROTECTIVE FENC FILL IN 0- LAYERS, WATER AND MP EVERGREEN TREE STA N TATO flEMOVE AIR PDDKM BUFFER SIGNS TO BE PLANTING DETAIL ATTACHED EVERY 25 FEET 1 REMOVE ALL WIRE WRAP AND PLASTIC WRAP. REMOVE BURLAP FROM 114LXCH TO DEPTH SPEC7f1fD IN NOTES TOQ OF ROOT BALL MULCH k -TOPSOIL OR FO 1 CON11NU00S As �oiEs BASE, REFER TO . -- — _ EN ease REMOVE E 01 � L"�1 � L— ' 6URLAP OFF OF TOP —/ BACKFILL W/ - __ _ - 11 III = OF ROOTBALL BACKFIL L M AS NOTES INDICATED IN NOTE k — — — — �- nN4 BAGcFlIL S' LAYERS WATER I I T 1. — M CIA AITAWR PoalcETs ur— 1L1. — I CQMPp T. MIXED TIHORCIUG IL MIraU, 1 X &, LU DIA. FOR MULCH TYPE SEE LANDSCAPE NOTES. r 3. IF P&B AND BURLAP 15 OREIN iii CQL4.Fi. REMOVE . .SHRUB PLANTING° nFTA11 p° ' Y BEFORE WALLING 7�CaHoLoQ�_o I REVISIONS BY O Q I O O C CID-, U R EO .� Np Date MAY 2004 Sale AS SHOWN Drawn T.DEMING Job 04065 Sheet 1 Of Sheets 11 24 a0tivitq®sTEDT5heopv* edgmponent shall replace all dead and unhealthy plants with plants of the same �' ,.� ', j ``� j -�( �F > �) $ �!i y � --q sperifications.