3800 RIVERFRONT BLVD 2025-07-23 - Laserfiche WebLink

1 Maintenance Standards Subsurface drains shall be checked periodically to ensure that they are free -flowing and not clogged with sediment or roots. • The outlet shall be kept clean and free of debris. • Surface inlets shall be kept open and free of sediment and other debris. • Trees located too close to a subsurface drain often clog the system with their roots. If a drain becomes clogged, relocate the drain or remove the trees as a last resort. Drain placement should be planned to minimize this problem. • Where drains are crossed by heavy vehicles, the line shall be checked to ensure that it is not crushed. BMP C206: Level Spreader Purpose To provide a temporary outlet for dikes and diversions consisting of an excavated depres- sion constructed at zero grade across a slope. To convert concentrated runoff to sheet flow and release it onto areas stabilized by existing vegetation or an engineered filter stri p. Conditions of Use Used when a concentrated flow of water needs to be dispersed over a large area with existing stable vegetation. . Items to consider are: 1. What is the damage if the flow become risk of erosion or may concentrated? 2. Is an easement required if discharged to adjoining property? 3. Most of the flow should be as ground water and not as surface flow. 4. Is there an unstable area downstream that cannot accept additional ground water? • Use only where the slopes are gentle, the water volume is relatively low, and the soil will adsorb most of the low flow events. Design and Installation Specifications Use that by above undisturbed areas are stabilized existing vegetation. If the level spreader has any low points, flow will concentrate, create channels and may cause erosion. 1 2014 Stormwater Management Manual for Westem Washington Volume 11 - Chapter - Page 348