220 OLYMPIC BLVD VA OUTPATIENT CLINIC 2023-02-09

S450 BMPs for Irrigation Description of Pollutant Sources: Irrigation consists of discharges from irrigation water lines, landscape irrigation,and lawn or garden watering. Excessive watering can lead to discharges of chlorinated potable water runoff into drainage systems; it can also cause erosion; and negatively affect plant health. Improper irrigation can encourage pest problems, leach nutrients, and make a lawn completely dependent on artificial watering. Mosquito breeding habitats may form through excessive watering. Pollutant Control Approach: Limit the amount and location of watering to prevent runoff and dis- charges to drainage systems. Applicable Operational BMPs: . Irrigate with the minimum amount of water needed. Never water at rates that exceed the infilt- ration rate of the soil. . Maintain all irrigation systems so that irrigation water is applied evenly and where it is needed. . Ensure sprinkler systems do not overspray vegetated areas resulting in excess water dis- charging into the drainage system. . Inspect irrigated areas for excess watering.Adjust watering times and schedules to ensure that the appropriate amount of water is being used to minimize runoff. Consider factors such as soil structure,grade,time of year, and type of plant material in determining the proper amounts of water for a specific area. . Inspect irrigated areas regularly for signs of erosion and/or discharge. . Place sprinkler systems appropriately so that water is not being sprayed on impervious sur- faces instead of vegetation. . Repair broken or leaking sprinkler nozzles as soon as possible. . Appropriately irrigate lawns based on the species planted,the available water holding capa- city of the soil,and the efficiency of the irrigation system. The depth from which a plant normally extracts water depends on the rooting depth of the plant.Appropriately irrigated lawn grasses normally root in the top 6 to 12 inches of soil; lawns irrigated on a daily basis often root only in the top 1 inch of soil. . Do not irrigate plants during or immediately after fertilizer application.The longer the period between fertilizer application and irrigation,the less fertilizer runoff occurs. . Do not irrigate plants during or immediately after pesticide application(unless the pesticide label directs such timing). . Reduce frequency and/or intensity of watering as appropriate for the wet season (October 1 to April 30). 2019 Stormwater Management Manual for Western Washington Volume IV-Chapter 4-Page 535