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an • • No.21(continued)-Maintenance Standards and Procedures for Bioretention Facilities. Maintenance Recommended Frequency. Condition when Maintenance Is Needed Action Needed Component Inspection Routine Maintenance (Standards) (Procedures) /nbts/Outtets/Pipes(conl'd) Trash rack S Trash or other debris present on trash rack Remove/dispose A Bar screen damaged or missing Repaldreplace Overflow A,S Capacity reduced by sediment or debris Remove sediment or debris/dispose Underdrain pipe Clean pipe as Clean orifice at least •Plant roots,sediment or debris reducing capacity of •Jet clean or rotary cut debris/roots from underdraln(s) needed biannually(may underdrain •If underdrains am equipped with a flow restrictor(e.g.,orifice)to attenuate flows,the orifice must be cleaned regularly. need more frequent •Prolonged surface ponding(see"Ponded water") cleaning during wet season) Vegetation Facility bottom area Fall and Vegetation survival rate falls below 75%within first two •Determine cause of poor vegetation growth and correct condition and upland slope Spring years of establishment(unless project O&M manual or •Replant as necessary to obtain 75%survival rate or greater.Refer to original planting plan,or approved jurisdictional vegetation record drawing stipulates more or less than 75%survival species list for appropriate plant replacements(See Appendix 3-Bioretention Plant List,in the LID Technical Guidance rate). Manuel for Puget Sound). •Confirm that plant selection is appropriate for site growing conditions •Consultation with a landscape architect is recommended for removal,transplant,or substitution of plants Vegetation(general) As needed Presence of diseased plants and plant material •Remove any diseased plants or plant parts and dispose of in an approved location(e.g.,commercial landfill)to avoid risk of spreading the disease to other plants •Disinfect gardening tools after pruning to prevent the spread of disease •See Pacific Northwest Plant Disease Management Handbook for Information on disease recognition and for additional SOLIMBS •eReplant as necessary according to recommendations provided for"tadily bottom area and upland slope vegetation Trees and shrubs All pruning seasons Pruning as needed •Prune trees and shrubs in a manner appropriate for each species.Pruning should be pertomted by landscape professionals (timing varies by familiar with proper pruning techniques species) •All pruning of mature trees should be performed by or under the direct guidance of an ISA certified arborist A Large trees and shrubs Interfere with operation of the •Prune trees and shrubs using most current ANSI A300 standards and ISA BMPs. facility or access for maintenance •Remove trees and shrubs,if necessary. Fall and Standing dead vegetation is present •Remove standing dead vegetation Spring •Replace dead vegetation within 30 days of reported dead and dying plants(as practical depending on weather/planting season) •If vegetation replacement is not feasible within 30 days,and absence of vegetation may result in erosion problems, temporary erosion control measures should be pm In place immediately. •Determine cause of dead vegetation and address issue,if possible •If specific plants have a high modality rate,assess the cause and replace with appropriate species.Consultation with a landscape architect is recommended. Fall and Planting beneath mature trees •When working around and below mature trees,follow the most current ANSI A300 standards and ISA BMPs to the extent Spring practicable(e.g.,take cam to minimize any damage to tree roots and avoid compaction of soil). •Planting of small shrubs orgroundcovers beneath mature trees maybe desirable in some cases;such plantings should use mainly plants that come as bulbs,bare root or in 4-inch pots;plants should be In no larger than tyallon containers. Volume V—Runoff Treatment BMPs—December 2014 4.5d