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HomeMy WebLinkAboutR-4192147N O V O V 0 W i MITIGATION NOTES EXECUTIVE SUMMARY THIS PLAN HAS BEEN PREPARED AS MITIGATION FOR TEMPORARY IMPACTS TO THE WETLAND C BUFFER, PER CITY OF RENTON MUNICIPAL CODE (RMC) 4-3-050C.3.19. THE IMPACTS TO THE WETLAND BUFFER ARE TO ACCOMMODATE THE CONSTRUCTION OF A NEW SCHOOL. THE CURRENT OWNER, CITY OF RENTON SCHOOL DISTRICT, SEEKS TO RESTORE AND ENHANCE THE WETLAND BUFFER TO IMPROVE FUNCTIONS. PREVIOUSLY DELMOLISHED AND REMOVED RESIDENTIAL STRUCTURES AND VEGETATION WILL BE PLANTED WITH A MIX OF NATIVE TREES AND SHRUBS. EXISTING CANOPY VEGETATION WILL BE ENHANCED BY PLANTING UNDERSTORY SHRUBS AND GROUNDCOVERS. THE PROPOSED PROJECT WILL RESULT IN 3,344 SQUARE FEET OF TEMPORARY IMPACTS TO THE WETLAND C BUFFER. THE EXISTING BUFFER FUNCTIONS IN THE AREA OF TEMPORARY CONSTRUCTION IMPACTS ARE DEGRADED DUE TO THE PRESENCE OF INVASIVE AND NON-NATIVE VEGETATION, WHICH HAS BEEN MAINTAINED THROUGH MOWING. TEMPORARY IMPACTS WILL BE RESTORED AT A RATIO OF 1:1 FOR A TOTAL OF 31344 SQ FT OF RESTORED BUFFER. ADDITIONALLY, 102,040 SF OF THE WETLAND C BUFFER WILL BE ENHANCED, EXCEEDING CITY REQUIREMENTS. ENHANCEMENT OF THE DEGRADED BUFFER WILL RESULT IN EQUAL OR BETTER FUNCTIONS AFTER CONSTRUCTION THAN EXISTING CONDITIONS. MITIGATION FOR UNAVOIDABLE TEMPORARY IMPACTS INCLUDE THE REMOVAL OF NON-NATIVE AND INVASIVE SPECIES AND THE INSTALLATION OF A NATIVE TREE, SHRUB AND GROUNDCOVER PLANT COMMUNITY. PROJECT IMPACTS AND MITIGATION ARE SUMMARIZED IN THE TABLE BELOW. WETLAND B, A CATEGORY IV WETLAND, IS ALSO LOCATED ONSITE. WETLAND B WILL BE FILLED AND MITIGATION BANK CREDITS WILL BE PURCHASED. TABLE 1. PROJECT IMPACTS AND MITIGATION SUMMARY Impacted Critical Area Impact Type Area' of Impact (SF) Wetland C Buffer Permanent Conversion Temporary 0 0 31344 Wetland B Permanent 12,181 Conversion 0 Temporary 0 TOTAL' Permanent: 12,181 SF Conversion: 0 SF Temporary: 3,344 SF MITIGATION APPROACH - MITIGATION SEQUENCING AVOIDANCE. THE DESIGN TEAM AND SCHOOL DISTRICT EVALUATED AND REJECTED MULTIPLE SITES IN THE SCHOOL SERVICE AREA, ULTIMATELY SELECTING THIS LOCATION FOR THE SCHOOL. THE CONSTRUCTION OF THE NEW ELEMENTARY SCHOOL CANNOT BE ACHIEVED ON THIS SITE WITHOUT INCURRING PERMANENT IMPACTS TO WETLAND B AND A SMALL AREA OF TEMPORARY IMPACTS TO THE WETLAND C BUFFER. HOWEVER, PERMANENT WETLAND IMPACTS TO WETLAND C ARE AVOIDED IN THE SITE PLAN. AFTER EVALUATING MULTIPLE DESIGN OPTIONS, THE ARCHITECTURAL TEAM DETERMINED THAT COMPLETE AVOIDANCE OF STANDARD 100-FOOT BUFFERS ARE NOT FEASIBLE FOR THIS PROJECT. MINIMIZATION. WETLAND C (CAT III) WAS PRESERVED, IN PART, DUE TO ITS LARGER SIZE AND HIGHER FUNCTIONS COMPARED TO WETLAND B (CAT IV). SEVERAL MINIMIZATION TECHNIQUES WERE UTILIZED DURING THE DESIGN PROCESS TO LIMIT IMPACTS TO WETLAND C AND ITS BUFFER. FIRST, SITE IMPROVEMENTS WERE DESIGNED AROUND THE WETLAND AND BUFFER TO THE EXTENT FEASIBLE. EXISTING TREES IN AND ADJACENT TO THE STANDARD BUFFER ARE DELIBERATELY PRESERVED. THE TEMPORARY WETLAND BUFFER IMPACT AREA IS VEGETATED PRIMARILY WITH INVASIVE OR NON-NATIVE PLANT SPECIES INCLUDING CREEPING BUTTERCUP, REED CANARYGRASS, ENGLISH IVY, AND BLACKBERRY. MITIGATION. MITIGATION FOR UNAVOIDABLE, PERMANENT WETLAND C IMPACTS IS PROVIDED VIA CREDIT WITHDRAWL FROM AN APPROVED MITIGATION BANK (SEE CRITICAL AREAS REPORT AND BANK USE PLAN FOR DETAILS). TEMPORARY WETLAND C BUFFER IMPACTS, BUFFER RESTORATION AND WETLAND AND BUFFER ENHANCEMENT IS PROPOSED ON THIS PLAN. PROPOSED BUFFER MITIGATION EXCEEDS MINIMUM REQUIREMENTS UNDER RMC 4-3-050C.3.19. THE PROPOSED MITIGATION IS BASED ON CITY CODE AND WASHINGTON STATE DEPARTMENT OF ECOLOGY GUIDANCE. PROPOSED IMPACTS AND MITIGATION ARE SUMMARIZED IN TABLE 1 ABOVE. MITIGATION AREA WORK SEQUENCE (SEE MATERIALS FOR ITEMS IN BOLD) 1. MARK THE CLEARING LIMITS WITH HIGH VISIBILITY FENCING OR SIMILAR MEANS. 2. INSTALL EROSION CONTROL MEASURES AS SHOWN ON THE SITE PREPARATION PLAN (SHEET W4.00). 3. WATER IN EACH PLANT THOROUGHLY TO REMOVE AIR POCKETS. 4. INSTALL A TEMPORARY IRRIGATION SYSTEM CAPABLE OF SUPPLYING AT LEAST 1-INCH OF WATER PER WEEK TO THE ENTIRE PLANTED AREA DURING THE DRY SEASON (JUNE 1ST THROUGH SEPTEMBER 30TH). 5. ONE YEAR AFTER INITIAL PLANTING, APPLY A SLOW -RELEASE, PHOSPHOROUS -FREE, GRANULAR FERTILIZER TO EACH INSTALLED PLANT. GOALS 1. ENHANCE DEGRADED WETLAND BUFFER. A. REMOVE NON-NATIVE AND INVASIVE PLANT SPECIES FROM THE ENHANCEMENT AREA. B. CREATE A DENSE, NATIVE, TREE AND SHRUB COMMUNITY IN AREAS NOT CURRENTLY FORESTED. C. ENHANCE UNDERSTORY IN EXISTING FOREST PATCHES. B. INCREASE HABITAT INTERSPERSION BY PLANTING GROUPINGS OF DIFFERENT NATIVE VEGETATION STRATA. C. RE-ESTABLISH NATURAL DECADENCE BY ADDING LARGE WOODY DEBRIS TO THE WETLAND. PERFORMANCE STANDARDS THE FOLLOWING PERFORMANCE STANDARDS WILL BE USED TO GAUGE THE SUCCESS OF THE PROJECT OVER TIME. IF ALL PERFORMANCE STANDARDS HAVE BEEN SATISFIED BY THE END OF YEAR FIVE, THE PROJECT SHALL BE CONSIDERED COMPLETE. 1. SURVIVAL: SURVIVAL STANDARDS MAY BE ACHIEVED THROUGH ESTABLISHMENT OF PLANTED MATERIAL, RECRUITMENT OF NATIVE VOLUNTEERS, AND/OR REPLACEMENT PLANTS AS NECESSARY. A. ACHIEVE 100% SURVIVAL OF ALL INSTALLED TREES AND SHRUBS BY THE END OF YEAR ONE. B. ACHIEVE 80% SURVIVAL OF ALL INSTALLED SHRUBS BY THE END OF YEAR TWO. C. ACHIEVE 80% SURVIVAL OF ALL INSTALLED TREES AND SHRUBS BY THE END OF YEAR FIVE. SURVIVAL STANDARDS MAY BE ACHIEVED THROUGH ESTABLISHMENT OF PLANTED MATERIAL, RECRUITMENT OF NATIVE VOLUNTEERS, OR REPLACEMENT PLANTS AS NECESSARY. 2. SPECIES DIVERSITY: ESTABLISH AT LEAST TWO NATIVE TREE SPECIES, FOUR NATIVE SHRUB SPECIES, AND TWO GROUNDCOVER SPECIES IN THE BUFFER ENHANCEMENT AREAS BY THE END OF YEAR FIVE. ESTABLISHMENT IS DEFINED AS FIVE OR MORE INDIVIDUAL PLANTS OF THE SAME SPECIES ALIVE AND HEALTHY. 3. COVER BUFFER: A. ACHIEVE 25% COVER OF NATIVE TREES AND SHRUBS BY THE END OF YEAR THREE. B. ACHIEVE 60% COVER OF NATIVE TREES AND SHRUBS BY THE END OF YEAR FIVE. 4. INVASIVE SPECIES STANDARD: NO MORE THAN 10% COVER BY INVASIVE SPECIES LISTED AS CLASS A, B, OR C BY THE KING COUNTY NOXIOUS WEED CONTROL BOARD IN ANY MONITORING YEAR. 5. LARGE WOODY DEBRIS STANDARD: MAINTAIN AT LEAST FIVE PIECES OF LARGE WOODY DEBRIS IN THE ENHANCEMENT AREA WITH GOOD GROUND CONTACT DURING ANY MONITORING YEAR MONITORING PRIOR TO THE COMMENCEMENT OF THE MONITORING PHASE, AN AS -BUILT PLAN DOCUMENTING THE SUCCESSFUL INSTALLATION OF THE PROJECT WILL BE SUBMITTED TO THE CITY OF RENTON. IF NECESSARY, THE AS -BUILT REPORT MAY INCLUDE A MARK-UP OF THE ORIGINAL PLAN THAT NOTES ANY SIGNIFICANT CHANGES OR SUBSTITUTIONS THAT OCCURRED. DURING THE AS -BUILT INSPECTION, THE RESTORATION SPECIALIST WILL ESTABLISH AT LEAST FOUR PERMANENT PHOTO -POINTS. THE SITE WILL BE MONITORED TWICE ANNUALLY FOR FIVE YEARS BEGINNING WITH APPROVAL OF THE AS -BUILT REPORT. EACH SPRING THE RESTORATION SPECIALIST WILL CONDUCT A BRIEF MAINTENANCE INSPECTION FOLLOWED BY A MEMO SUMMARIZING MAINTENANCE ITEMS NECESSARY FOR THE UPCOMING GROWING SEASON. THE FORMAL LATE -SEASON MONITORING INSPECTION WILL TAKE PLACE ONCE ANNUALLY DURING LATE SUMMER OR EARLY FALL. DURING EACH LATE -SEASON MONITORING INSPECTION, THE FOLLOWING DATA WILL BE COLLECTED: 1. PLANT COUNTS: COUNTS OF DEAD PLANTS BY SPECIES IN ALL MITIGATION AREAS. A TOTAL PLANT COUNT WILL BE DONE IN YEAR 1. BELT-TRANSECTS WITH BASELINE COUNTS ESTABLISHED DURING THE AS -BUILT INSPECTION MAY BE USED TO ESTIMATE SURVIVAL IN YEARS 2 THROUGH 5 IN LIEU OF A SITE -WIDE COUNT. COUNTS OF DEAD PLANTS WHERE MORTALITY IS SIGNIFICANT IN ANY MONITORING YEAR WILL BE RECORDED. 2. NATIVE WOODY COVER AS DETERMINED USING VISUAL COVER CLASS ESTIMATES OR ESTABLISHED TRANSECTS. 3. NATIVE GROUNDCOVER PLANT COVER AS DETERMINED USING VISUAL COVER CLASS ESTIMATES. 4. ESTIMATES OF INVASIVE HERBACEOUS PLANTS OR GROUNDCOVER USING VISUAL COVER ESTIMATES OR ESTABLISHED TRANSECTS, AS APPLICABLE. 5. THE SPECIES COMPOSITION, NOTING WHETHER A SPECIES IS NATIVE OR EXOTIC AND WHETHER PLANTS WERE INSTALLED OR ARE VOLUNTEERS. 6. THE GENERAL HEALTH AND VIGOR OF THE INSTALLED VEGETATION. 7. PHOTOGRAPHS FROM FIXED PHOTO -POINTS ESTABLISHED DURING THE AS -BUILT INSPECTION. 8. ANY EVIDENCE OF WILDLIFE USAGE IN THE MITIGATION AREA. MONITORING REPORTS SHALL BE SUBMITTED ANNUALLY TO THE CITY. REPORTS SHALL DOCUMENT THE CONDITIONS OF THE SITE, INCLUDING QUANTITATIVE DATA COLLECTED DURING THE MONITORING INSPECTION, AND SHALL PROVIDE MAINTENANCE RECOMMENDATIONS THAT MAY BE NECESSARY TO HELP THE SITE ACHIEVE THE STATED PERFORMANCE STANDARDS. MAINTENANCE THE SITE SHALL BE MAINTAINED FOR FIVE YEARS FOLLOWING SUCCESSFUL INSTALLATION. 1. REPLACE EACH PLANT FOUND DEAD IN THE SUMMER MONITORING VISITS IN THE FOLLOWING DORMANT SEASON (OCTOBER 15 - MARCH 1). REPLACEMENT SHALL BE OF THE SAME SPECIES AND SIZE PER PLAN UNLESS OTHERWISE APPROVED BY THE RESTORATION SPECIALIST. 2. GENERAL WEEDING FOR ALL PLANTED AREAS A. AT LEAST TWICE ANNUALLY, REMOVE COMPETING GRASSES AND WEEDS FROM AROUND THE BASE OF EACH INSTALLED PLANT TO A RADIUS OF 12 INCHES. WEEDING SHOULD OCCUR AT LEAST ONCE IN THE SPRING AND ONCE IN THE SUMMER. THOROUGH WEEDING WILL RESULT IN LOWER PLANT MORTALITY AND ASSOCIATED PLANT REPLACEMENT COSTS. B. MORE FREQUENT WEEDING MAY BE NECESSARY DEPENDING ON WEED CONDITIONS THAT DEVELOP AFTER PLANT INSTALLATION. C. NOXIOUS WEEDS MUST BE REMOVED FROM THE ENTIRE MITIGATION AREA, AT LEAST TWICE ANNUALLY. D. DO NOT USE STRING TRIMMERS IN THE VICINITY OF INSTALLED PLANTS, AS THEY MAY DAMAGE OR KILL THE PLANTS. 3. MAINTAIN A THREE -INCH -THICK LAYER OF WOODCHIP MULCH ACROSS THE PLANTING AREA, EXCEPT FOR THE EMERGENT PLANTING AREA IN THE WETLAND. MULCH SHOULD BE PULLED BACK TWO INCHES FROM THE PLANT STEMS. 4. INSPECT AND REPAIR THE IRRIGATION SYSTEM AS NECESSARY EACH SPRING. DURING AT LEAST THE FIRST TWO GROWING SEASONS, MAKE SURE THAT THE ENTIRE PLANTING AREA RECEIVES A MINIMUM OF ONE INCH OF WATER PER WEEK FROM JUNE 1ST THROUGH SEPTEMBER 30TH. CONTINGENCY PLAN IF ANY MONITORING REPORT REVEALS THAT THE RESTORATION PLAN HAS FAILED IN WHOLE OR IN PART, AND SHOULD THAT FAILURE BE BEYOND THE SCOPE OF ROUTINE MAINTENANCE, THE APPLICANT WILL SUBMIT A CONTINGENCY PLAN TO THE CITY OF RENTON FOR APPROVAL. THIS PLAN MAY INCLUDE REPLANTING, SOIL AMENDMENTS OR TOP DRESSING, SUBSTITUTIONS FOR SPECIES SELECTED IN THE ORIGINAL PLAN, AND ADAPTIVE WEED CONTROL METHODS. SITE PROTECTION THE WETLAND WILL REMAIN ON PROPERTY OWNED BY CITY OF RENTON SCHOOL DISTRICT. THE WETLAND AND BUFFER WILL BE NOTED ON THE PROPERTY TITLE AS A MAINTENANCE COVENANT. MATERIALS 1. WOODCHIP MULCH: ARBORIST CHIPS (CHIPPED WOODY MATERIALS) APPROX. 1 TO 3 INCHES IN MAXIMUM DIMENSION (NOT SAWDUST OR COARSE HOG FUEL). THIS MATERIAL IS COMMONLY AVAILABLE IN LARGE QUANTITIES FROM ARBORISTS OR TREE -PRUNING COMPANIES. MULCH MUST NOT CONTAIN APPRECIABLE QUANTITIES OF GARBAGE, PLASTIC, METAL, SOIL, AND DIMENSIONAL LUMBER OR CONSTRUCTION/DEMOLITION DEBRIS. 2. COMPOST: CEDAR GROVE COMPOST OR EQUIVALENT "COMPOSTED MATERIAL" PER WASHINGTON ADMIN. 3. FERTILIZER: SLOW -RELEASE, PHOSPHOROUS -FREE GRANULAR FERTILIZER. MOST COMMERCIAL NURSERIES CARRY THIS PRODUCT. LABEL MUST INDICATE THAT PRODUCT IS SAFE FOR AQUATIC ENVIRONMENTS. FOLLOW MANUFACTURER'S INSTRUCTIONS FOR USE. KEEP FERTILIZER IN WEATHER -TIGHT CONTAINER WHILE ON -SITE. FERTILIZER IS ONLY TO BE APPLIED IN YEARS TWO AND THREE, NOT IN YEAR ONE. 4. LARGE WOODY DEBRIS: TREES SALVAGED FROM ON -SITE CLEARING, INCLUDING LOGS, ROOTWADS, AND LIMBS WHICH ARE TO BE PLACED ON THE GROUND AT THE DIRECTION OF THE RESTORATION SPECIALIST. MATERIAL FROM CONIFEROUS TREES IS PREFERRED. WOOD SHOULD HAVE A DIAMETER OF 16 INCHES OR MORE AND A MINIMUM LENGTH OF 10 FEET. 5. RESTORATION SPECIALIST: QUALIFIED PROFESSIONAL ABLE TO EVALUATE AND MONITOR THE CONSTRUCTION OF ENVIRONMENTAL RESTORATION PROJECTS. 6. IMPORT TOPSOIL: SOIL AND COMPOST MIXTURE. THIS MATERIAL IS SOLD AS "2-WAY TOPSOIL" AT CEDAR GROVE COMPOST [425-408-85581. PLEASE USE THIS MATERIAL OR EQUIVALENT. ,,,,,, ,,,,,,,,,,,,,,,,,,,,, I"'ITPI. ..".....,.... ... .,..T.0 g- 1....... EDWIN J. GREEN JR wmcr: xao, AS SHOWN 0160NT''1 N1°' Vim' GM AMC HM/AMGM ^, �� DATUM CIF NU CIIE NO. REVISION BY DATE APPR ^°_^ " `=Ro"" THE WATERSHED COMPANY CITY OF RENTON Planning/Building/Public Works Dept. R-4192146 IN COMPLIANCE WITH CITY OF RENTON STANDARDS 04/13/2022 NEW ELEMENTARY SCHOOL NO.16 DUVALL AVENUE NE, RENTON, WA 98059 MITIGATION NOTES m O O O N Q D 0) 00 N V O O N 04 MAR 2022 V Q E` W7 LU exm: 147 M147 (L