1001 N BROADWAY LEARNING RESOURCE CENTER 2026-01-15

Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) Recommended Frequency Maintenance Com- a Condition when Maintenance is Needed (Stand- Action Needed (Procedures) ponent Routine Main- ards) Inspection tenance preceding seed dis- appropriate persal) • Follow IPM protocols forweed management(see"Additional Maintenance Resources"section for more information on IPM protocols) Once in early to Low-lying vegetation growing beyond facility edge • Edge or trim groundcovers and shrubs at facility edge mid-May and once • y onto sidewalks, paths, or street edge poses ped- Avoid mechanical blade-type edger and do not use edger or trimmer within 2 feet of tree trunks in early-to mid- estrian safety hazard or may clog adjacent permeable September pavement surfaces due to associated leaf litter, • While some clippings can be left in the facility to replenish organic material in the soil, excessive leaf litter can cause mulch, and soil surface soil clogging • Determine whether pruning or other routine maintenance is adequate to maintain proper plant density and aesthetics Excessive vegetation • Determine if planting type should be replaced to avoid ongoing maintenance issues (an aggressive grower under per- Excessive vegetation density inhibits stormwater fect growing conditions should be transplanted to a location where it will not impact flow) As needed flow beyond design ponding or becomes a hazard for . Remove plants that are weak, broken or not true to form; replace in-kind pedestrian and vehicular circulation and safety • Thin grass or plants impacting facility function without leaving visual holes or bare soil areas • Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants As needed Vegetation blocking curb cuts, causing excessive Remove vegetation and sediment buildup sediment buildup and flow bypass Mulch • Supplement mulch with hand tools to a depth of 2 to 3 inches Bare spots (without mulch cover)are present or • Replenish mulch per O&M manual. Often coarse compost is used in the bottom of the facility and arborist wood chips Mulch Following weeding mulch depth less than 2 inches are used on side slopes and rim (above typical water levels) • Keep all mulch away from woody stems Watering Based on man- ufacturer's instruc- Irrigation system present Follow manufacturer's instructions for O&M Irrigation system(if tions any) A Sprinklers or drip irrigation not directed/located to Redirect sprinklers or move drip irrigation to desired areas properly water plants • 10 to 15 gallons per tree Once every 1-2 • 3 to 5 gallons per shrub Summer watering(first weeks or as needed Trees, shrubs and groundcovers in first year of estab- • 2 gallons water per square foot for groundcover areas year) during prolonged lishment period • Water deeply, but infrequently, so that the top 6 to 12 inches of the root zone is moist dry periods • Use soaker hoses or spot water with a shower type wand when irrigation system is not present o Pulse water to enhance soil absorption, when feasible - 2019 Stormwater Management Manual for Western Washington Volume V-Appendix A -Page 1023