V4 12 Stormwater Maintenance Manual

• At the time of initial establishment of the permanent grass mixture specified for the detention basin, bi-weekly inspections of vegetation health shall be performed during the first growing season or until the grass vegetation is established. The New Jersey recommended grass seed mixture is No. 14 Turf-Type Tall Fescue (Blend of 3 cultivars) at planting rate of 3.5 lbs/1000 square feet (Appendix, Exhibit 1). Once established, inspections of vegetation (grass) health, density, and diversity shall be performed at least twice annually during both the growing and non-growing seasons. • The vegetative cover (grass mixture) should be maintained at 85 percent. If vegetation has greater than 50 percent damage, the area should be re-established by overseeding with the above-specified grass seed mixture in accordance with the original specifications contained in the project Landscape Plan and Soil Erosion and Sediment Control Plan. • All use of fertilizers, mechanical treatments, pesticides, and other means to assure optimum vegetation health must be minimized as to not compromise the intended purpose of the detention basin. All vegetation deficiencies should be addressed without the use of fertilizers and pesticides whenever possible. C. STRUCTURAL COMPONENTS • All structural components must be inspected for cracking, subsidence, spalling, erosion, and deterioration at least annually (See Appendix, Figure 1 – Stormwater Location Plan) D. OTHER MAINTENANCE PROCEDURES • The detention basins have been designed to drain in less than 72 hours as the approximate time it would normally take to completely drain the maximum design storm runoff volume (100 yr storm) from each basin. If significant increases or decreases in the normal drain time are observed, the basin’s outlet structure, underdrain system, and both groundwater and tailwater levels must be evaluated and appropriate measures taken to comply with the maximum drain time requirements and maintain the proper functioning of the basin. Below is a table relating the approximate times to drain versus inches of rainfall: Storm Event (yr.) Inches of Rainfall Time to Drain Time to

functioning of the basin. Below is a table relating the approximate times to drain versus inches of rainfall: Storm Event (yr.) Inches of Rainfall Time to Drain Time to Drain (hrs.) (hrs.) Basin #2 Basin #3 100 8.66 27 27 6