1001 N BROADWAY LEARNING RESOURCE CENTER 2026-01-15

Table V-A.21: Maintenance Standards - Bioretention Facilities (continued) Recommended Frequency a Maintenance Com- Condition when Maintenance is Needed (Stand- Action Needed (Procedures) ponent Routine Main- ards) Inspection tenance • If specific plants have a high mortality rate, assess the cause and replace with appropriate species. Consultation with a landscape architect is recommended. • When working around and below mature trees, follow the most current ANSI A300 standards and ISA BMPs to the extent practicable(e.g., take care to minimize any damage to tree roots and avoid compaction of soil). Fall and Spring Planting beneath mature trees • Planting of small shrubs or groundcovers beneath mature trees may be desirable in some cases; such plantings should use mainly plants that come as bulbs, bare root or in flinch pots; plants should be in no larger than 1-gallon con- tainers. Verify location of facility liners and underdrain(if any)prior to stake installation in order to prevent liner puncture or pipe damage Fall and Spring Presence of or need for stakes and guys (tree growth, . Monitor tree support systems: Repair and adjust as needed to provide support and prevent damage to tree. maturation, and support needs) • Remove tree supports (stakes, guys, etc.)after one growing season or maximum of 1 year. • Backfill stake holes after removal. Trees and shrubs adja- Maintain appropriate height for sight clearance cent to vehicle travel • When continued, regular pruning(more than one time/growing season)is required to maintain visual sight lines for areas (or areas where A Vegetation causes some visibility(line of sight)or safety or clearance along a walk or drive, consider relocating the plant to a more appropriate location. visibilityneeds to be driver safety issues • Remove or transplant if continual safety hazard maintained) • Consultation with a landscape architect is recommended for removal, transplant, or substitution of plants Flowering plants A Dead or spent flowers present Remove spent flowers (deadhead) Perennials Fall Spent plants Cut back dying or dead and fallen foliage and stems Hand rake sedges and rushes with a small rake or fingers to remove dead foliage before new growth emerges in spring or Emergent vegetation Spring Vegetation compromises conveyance earlier only if the foliage is blocking waterflow (sedges and rushes do not respond well to pruning) - Leave dry foliage for winter interest Ornamental grasses Dead material from previous years growing cycle or (perennial) Winter and Spring dead collapsed foliage • Hand rake with a small rake orfingers to remove dead foliage back to within several inches from the soil before new growth emerges in spring or earlier if the foliage collapses and is blocking waterflow • Hand rake with a small rake or fingers to remove dead growth before new growth emerges in spring Ornamental grasses Fall and Spring Dead growth present in spring g y (evergreen) Clean, rake, and comb grasses when the become too tall • Cut back to ground or thin every 2-3 years as needed • By law, class A&B noxious weeds must be removed, bagged and disposed as garbage immediately M (March-October, • Reasonable attempts must be made to remove and dispose of class C noxious weeds Listed noxious vegetation is present(refer to current Noxious weeds preceding seed dis- county noxious weed list) • It is strongly encouraged that herbicides and pesticides not be used in orderto protect waterquality; use of herbicides persal) and pesticides may be prohibited in some jurisdictions • Apply mulch after weed removal (see"Mulch") Weeds M(March-October, Weeds are present • Remove weeds with their roots manually with pincer-type weeding tools, flame weeders, or hot water weeders as -- 2019 Stormwater Management Manual for Western Washington Volume V-Appendix A -Page 1022