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' PN: 50663GE <br />November 20, 2006 <br />' We encountered formational material in our test borings. We suspect that it may be difficult to <br />excavate this material using conventional techniques. If blasting is planned it must be conducted <br />' strategically to reduce the affect of the blasting on the support chazacteristics of the site materials <br />and the stability of adjacent slopes. <br />1 8.2.1 Excavation Cut Slopes <br />We anticipate that some permanent excavation cut slopes may be included in the site <br />development. Temporary cut slopes should not exceed five (5) feet in height and should not be <br />steeper than about one to one (1:1, horizontal to vertical) for most soils. Permanent cut slopes of <br />greater than five (5) feet or steeper than two and one-half to one (2%z:l, h:v) must be analyzed on <br />' a site specific basis. We have provided analysis of excavation cut slopes in Section 5.0 of this <br />report. <br />We observed evidence of existing unstable slope azeas influencing the site, but due to the <br />steepness and extent of the slopes in the azea we suggest that the magnitude of the proposed <br />excavation slopes be minimized and/or supported by retaining structures. <br />8.3 Utility Considerations <br />We understand that a gas line may be constructed along the roadway. Subsurface utility <br />trenches will be constructed as part of the site development. Utility line backfill often becomes a <br />conduit for post construction water migration and can negatively influence the lateral migration <br />of water through the sloped soils. We recommend that a subsurface drain system be included in <br />the pipeline trench if water is encountered during construction, or if it is apparent that the trench <br />may negatively influence natural water migration during the spring snow melt. The subsurface <br />trench drain may be constructed similar to that discussed above in Section 7.0. The drain system <br />may include placement of afree-draining aggregate material as the pipe bedding. Placement of a <br />collection pipe within the free-draining aggregate is optional and may be determined as the <br />pipeline excavation commences. The free draining material should be graded through lateral <br />trenches to surface outlets about every 200 feet, or less. An impervious soil bulkhead should be <br />placed down gradient of each daylight trench. The periodic daylight trench and bulkhead are <br />intended to reduce the distance of water migration and to reduce the development of significant <br />head and velocity of the water. The lateral trenches may need to more closely spaced in steep <br />sloped azeas. <br />22 TRAUTNER ~ -~ <br />A DIVISION OF TRIGONif~ <br />