1815 13TH ST SEATTLE CHILDRENS NORTH CLINIC 2019-07-08

MAGNUSSON KLEMENCIC ASSOCIATES ■ • The City may require pond designs that provide additional or different stormwater flow control if necessary to address local conditions or to protect properties and waterways downstream from erosion due to increases in the volume, velocity, and peak flow rate of stormwater runoff from the project site. • Applicable BMPs: — BMP C235: Straw Wattles — BMP C241: Temporary Sediment Pond ELEMENT#5: STABILIZE SOILS The selected contractor shall update this section as required. • All exposed and unworked soils shall be stabilized by application of effective BMPs that protect the soil from the erosive forces of raindrop impact,flowing water, and wind. • Full stabilization means all soil disturbing activities at the site have been completed and areas where the soil or natural vegetative cover has been disturbed have been properly covered and accepted to meet permanent erosion control. Permanent erosion control can include concrete or asphalt paving; quarry spalls used as ditch lining; application of thick layers of gravel or mulch; or vegetative cover in a manner that will fully prevent soil erosion. Where the term "fully established" is used to describe vegetative cover or plantings, it shall be understood to mean that healthy vegetation covers 90 percent of exposed bare soil. The application of hydroseeding, even in conjunction with a bonded fiber matrix (BFM) or rolled erosion product will not be accepted as fully established permanent erosion control before the necessary development and ground cover requirements of the plantings are met. The strong root structures of well-established vegetation are an essential mechanism in controlling soil erosion. The City will inspect and must approve all areas as fully stabilized before the release of financial guarantees. • Temporary erosion control measures shall remain in place until permanent measures are established. • From October 1 through April 30, no soils shall remain exposed and unworked for more than 2 days. From May 1 to September 30, no soils shall remain exposed and unworked for more than 7 days. This condition applies to all soils on site, whether at final grade or not. • Soils shall be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. • Applicable practices include, but are not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, the early application of gravel base on areas to be paved, and dust control. • Soil stabilization measures should be appropriate for the time of year, site conditions, estimated duration of use, and potential water quality impacts that stabilization agents may have on downstream waters or groundwater. • Soil stockpiles must be stabilized from erosion, protected with sediment trapping measures, and when possible, be located away from storm drain inlets, waterways and drainage channels. • Linear construction activities, including trenching for utilities, shall be conducted to meet the soil stabilization requirement. Contractors shall install the bedding materials, structures, pipelines, or utilities and restabilize the disturbed soils so that: — From October 1 through April 30 no soils shall remain exposed and unworked for more than 2 days, and — From May 1 to September 30, no soils shall re remain exposed and unworked for more than 7 days. Construction Stormwater Pollution Prevention Plan 7 Providence Regional Medical Center Everett, North Site, Everett, Washington