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<br />1 <br />j <br /> <br />" <br />I <br />I <br />~ <br /> <br />n <br />'J <br /> <br />'.. <br />'1 <br />ji <br />:.J <br /> <br />1"'1 <br />j: <br />J 1 <br />~ <br /> <br />r <br />~ <br /> <br />Jl <br />:.J <br /> <br />r <br />I ! <br /> <br />]1 <br />:.J <br /> <br />II <br /> <br />-..; <br /> <br /> <br />r <br />J <br />r <br />~ <br /> <br />- <br /> <br />07/16/03 J6:13 FAX <br /> <br />@004 <br /> <br />_ <br /> <br /> <br />DESIGN ANALYSIS <br /> <br />Infonnation made avaUable to this office indicates that a detention basin is planned for CODStruction <br />at the site. <br /> <br />DETENTION BASIN . <br /> <br />A stoIm water dete~tion basin is planned at the site. The soils generally consist of moderate to <br />highly plastic sandy clays and clays. Groundwater was only encountered in Boring B-4 at a depth <br />of fifteen (IS) feet. The clay (CH) soil~ at the site are highly plastic and do not meet the <br />requirements of Texas Department of Transportation Item 132, Type A material for embankment <br />construction. However, sandy clays encounter~ in Borings B-3, :8-4, B-7, B-I0 and B-ll, <br />generally between four (4) and twelve (12) feet appear to meet the requirements of Type A <br />material. <br /> <br />B~ed on local experience, 1 (V) to 3 (H) side slopes of the basin in cohesive soils such as sandy <br />clays and clays should be stable for slope heights of approximately ten (10) feet. Maximum depth <br />of excavation should be limited to eight (8) feet in the vicinity of Boring B-4 to provide sufficient <br />cover above the water bearing sands at twelve (12) feet. Apart from sliding stability consideration, <br />a 1 (V) to 3 (H) slope is easier to maintain and will sustain vegetation much better than steeper <br />slopes. <br /> <br />Based on this preliminary study, the site is suitable for construction of a detention basin. <br />However, a deta!led investigation program should be undertaken, especially in the vicinity of <br />Boring B-4 to delineate any sballow waterbearlng sand layers that may adversely affect the <br />proposed detention basin. <br /> <br />SITE PREPARATION <br /> <br />. In order to remedy construction problems, which may develop, if attempts are made to work.the <br />surface materials following pr~longed periods of rainfall, which are common to this area, it is <br />recommended that. prior to starting any work at the site, that proper construction drainage be <br />provided to maintain a relatively 'dry construction site. <br /> <br />3 <br />