07/25/2001 Env Bd Packet - Laserfiche WebLink

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Excavation of Materials in Infiltration Basins/Ponds • Initial grading and excavation of materials in the infiltration basins /ponds must not exceed 2 -3 feet above the final grade. • During the construction process, stormwater infiltration basins /ponds may not be backfilled with any material unless authorized by the engineer in writing. • Final grading of the infiltration basins /ponds requires excavation of the remaining 2- 3 feet of overlying material down to the naturally occurring permeable subsurface material. This shall be done with a low ground pressure D4 dozer (LPG), low ground pressure D5 dozer or 864 traxcavator (rubber Tracks). Soil compaction • Minimize compaction of underlying soils by not traveling over the infiltration basins /ponds and surrounding buffer areas with heavy equipment except to the minimal extent necessary to grade and construct the infiltration basins /ponds. • Grading of the final 2 -3 feet of overlaying material should be done with light earth - moving equipment to minimize compaction to the soils. See above for the recommended equipment. • Once the final grade has been established, the infiltration areas shall be treated as a septic area. No other heavy earth moving equipment shall be allowed to traverse these areas. If the silt fence has been disturbed, the silt fence around the ponds and infiltration areas will be replaced. Using Infiltration Areas for Sediment Removal during Construction • Each infiltration basins inlet shall have a temporary sediment forebay. The main purpose of this is to offer some sediment deposition areas for the larger particle sizes. This is an attempt to reduce the deterioration, plugging and surface clogging of the basins infiltration capacity. These proposed forebays are approved for this project. Landscaping of Infiltration Areas • The establishment of native vegetation that can withstand wet/dry cycling and fluctuations in water levels, are salt tolerant and have a deep root systems promotes the infiltration capacity of the underlying soils. The basins, pond benches and mitigation areas shall be seeded with the City of Lino Lake seed specification. It shall be seeded per the City of Lino Lake planting specification. The developer shall allow any specialty seeding contractors to bid on the city seed and planting specification. See the City of Lino Lake's specification - Appendix B. Pretreatment • The inlet forebays shall serve as minor pretreatment areas prior to the water fling the infiltration basins. Other best management practices noted on the final grading plan shall be implemented and maintained. Inspections and recommended actions may be made by the project engineer, City engineer and the Rice Creek Watershed District inspector. Page 2