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Stormwater- See Section 3.4 in Volume III of this manual for more specific guidance related Design regarding required field testing, assignment of infiltration rate correction Procedures factors, project submission requirements, and modeling. Runoff Model See Appendix III-C for runoff modeling guidance under WWHM3 and Representation under WWHM 2012. Maintenance Please see table 22 within Table 4.5.2 in Chapter 4 of this Volume. Maintenance recommendations for all facilities: • Erosion and introduction of sediment from surrounding land uses should be strictly controlled after construction by amending exposed soil with compost and mulch, planting exposed areas as soon as possible, and armoring outfall areas. • Surrounding landscaped areas should be inspected regularly and possible sediment sources controlled immediately. • Installations can be monitored for adequate or designed minimum infiltration rates by observing drainage immediately after heavier rainstorms for standing water or infiltration tests using ASTM C1701. • Clean permeable pavement surfaces to maintain infiltration capacity at least once or twice annually following recommendations below. • Utility cuts should be backfilled with the same aggregate base used under the permeable paving to allow continued conveyance of stormwater through the base, and to prevent migration of fines from the standard base aggregate to the more open graded permeable base material (Diniz, 1980). • Ice build up on penneable pavement is reduced and the surface becomes free and clear more rapidly compared to conventional pavement. For western Washington, deicing and sand application may be reduced or eliminated and the permeable pavement installation should be assessed during winter months and the winter traction program developed from those observations. Vacuum and sweeping frequency will likely be required more often if sand is applied. Porous asphalt and pervious concrete • Clean surfaces using suction, sweeping with suction or high-pressure wash and suction (sweeping alone is minimally effective). Hand held pressure washers are effective for cleaning void spaces and appropriate for smaller areas such as sidewalks. • Small utility cuts can be repaired with conventional asphalt or concrete if small batches of permeable material are not available or are too expensive. Volume V — Runoff Treatment BMPs — December 2014 5-25