1910 MERRILL CREEK PKY 2018-11-15

Mr. Darren Peugh January 19, 2004 Water Quality Pond Exterior pond berm slopes can be graded to a finish inclination of 2:1. Interior pond sidewalls should be graded to an inclination not exceeding 3:1. The fuushed slope faces should be thoroughly compacted and vegetated where not covered with quarry rock to guard against erosion. Fill placed to create the perimeter pond berm should be constructed as structural fill. For containment of stored water, fill used to construct the pond berrn should consist of soils containing at least 20 percent soil fines (material passing No. 200 sieve). Our field exploration indicates that soils in the pond area consist of dense silty sand with gravel fll. Laboratory testing indicates that the soils contain about 40 percent soil fines. These soils, when compacted, will exhibit relatively low pertneability. In our opinion, if soils of this nature are exposed by the pond excavation and are used to construct the perimeter containment berm, lining of the pond to reduce seepage loss would not be necessary. Soil conditions at the pond location should be examined at the time of construction to verify this condition. Surface Drainage Final exterior grades must provide free and positive drainage away from the site at all times. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building area. We recommend providing a minimum drainage gradient of three percent for a minimum distance of ten feet from the building perimeter, except in paved locations. In paved locations, a minimum gradient of one percent should be provided, unless provisions are included for collection and disposal of surface water adjacent the structure. Surface water must not be allowed to flow uncontrolled over the crest of the site slopes and embankments. Surface water should be directed away from the slope crests to a point of collection and controlled discharge. If site grades do not allow for directing surface water away from the slopes, the water should l�e collected and tightlined down the slope face in a controlled manner. Subsurface Drainage In our opinion, with positive site drainage provided and pavement or other hard surfaces extending up to the building perimeter, installation for perimeter foundation drains would not be necessary. Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) specifications. As a minimum, trench backfill should be placed and compacied as structural fill, as described in the Site Preparation and Grading section of this report. As noted, soils excavated on-site should be suitable for use as backfill material. However, because of the soils fines content, if utility construction will take place during wet weather, it may be necessary to import suitable wet weather fill for utility trench backfilling. Project No. T-5471 Page No. 8