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HomeMy WebLinkAboutBAUMER S-3430t i - h r" r Lynn P. Wallace P.E. 4839 Tampa Circle 1th.:i1VEU Anchorage, Alaska 99.�U4 June 11, 1974 JUN ? 11974 Ahl Mr. Rolf Strickland Chief Sanitarian GARB OA1fttc+av°an40"nuou�i�ii" 3»u C Street OLPT. Anchorage, Alaska 99503 Dear Mr. Strickland; Re: S-3430 Baumer Subdivision The soils test holes for this subdivision were made to the depth of the hardpan layer that supports the surficial soil deposits. This depth ranged from 10-1/2 feet to 12-1/2 feet in the three test holes that were excavated, as shown on the drawings and test logs which were submitted. The hardpan layer is a densly packed layer of non uniformly graded gravel sand and rockflour, genera* classified as a CP soil. This hardpan layer generally extends downward fur an additional ten to twenty feet in the subject subdivision, before bedrock is encountered. There is no evidence of a static water table on this hillside and all water seeps observed or reported, occur above the hardpan layer. Wells In the area are cased to bedrock and extend down approximately 75 to 80 feet or greater from the ground surface. The wells are supplied rrom water seeping through the fractured bedrock from spurces on the mountains above. Utilizing this information, I have determined that deeper excavations would not provide significantly different data and had the excavator stop after successfully penetrating the hardpan layer. I therefor submit that the _hardpan soil continues to a depth exceeding 17 feet and that no static is cc Don Lucas ct P. Wallace P.E. 9=1STIREd (OON n Greater Anchorage Area Borough Planning Department 3500 Tudor Road Anchorage, Alaska 99507 Attention: Mr. Wayne Mabry Subject: Soils Evaluation Resubdivision of Addition $2 Dear Mr. Mabry: 4839 Tampa Circle Anchorage, Alaska 99504 June 2, 1974 and Related Items - Baumer Subdivision, TR 10, Donald C. Schroeder Subdivision, The following information concerning the soils conditions for the proposed Baumer Subdivision located on the Eagle River Road in Eagle River, is submitted to satisfy the requirements of GAAB Ordinance No. 112-72A, Chapter 21; and Title 18, Environmental Conservation, 18 AAC 72.060 of the State of Alaska. Test Hole logs and project location maps follow the text. SITE LOCATION AND DESCRIPTION. The approximately 4.5 acre parcel to be subdivided is located five miles east of the Glenn Highway on the Eagle River Road. The property is overgrown with Alders and small Birch as a second growth after having been cleared for home- steading. "The topography is generally sloping to the south becoming steeper near Hammond Road to the north of the property. EXISTING YELLS AND SUBSURFACE DRAIN FIELDS. The location of existing wells on or near the parcel to be subdivided are shown on the project location map. Water has-been located in this area approximately 85' to 110' below the surface. Neighboring sub- divisions (not shown on map) have wells of sufficient capacity to supply domestic needs. The existance of reliable water sources in this geological area has been proven sufficiently to Borough, Officials in the immediate past. Previous chemical and bacterio- logical testing of existing water sources has indicated that drinking water quality standards are satisfied. FIELD EXPLORATION. On May 27, 1974, three(3) testholes were excavated on siEe to depths of 12-1/21,12' and 10-1/2' respect- ively. The hole locations are shown on the location map. All holes were excavated by Hamann Construction Company of Eagle River, Alaska, using aCase Backhoe with a 1/2 CY bucket. Direct observations were made on soil strata and grab samples were taken both during and after excavation. Testhole placement was made on each of the smaller three tracts to insure that soil conditions were as expected. There is more than sufficient room on the tracts to locate water and wastewater facilities. 5343 0 JUL 2 1974: Creater Anchorage n ^ r'^ orough "� Page 2 June 2, 1974 GEOLOGY. The Eagle River drainage area is located within the Chugach Mountains that border Cook Inlet. These mountains are a complex mixture of deformed and metamorphosed sedimentary and igneous rocks deposited during the late Paleozoic and Mesozoic Eras. Five major Pleistocine glacial advances along the consequent or subsequent lacustrine and alluvial deposits greatly influenced the present topography of the area. The surficial geologic unit of the site appears to be part of the Eagle River cut as it worked through the late Pleistocene lateral moraine deposits. The till of this deposit is commonly sandy and stoney with cobbles common. Broken rock and sand pre- dominate but silt and rock dust are ever present. Cobbles and rocks are rounded rather than angular. SUBSURFACE CONDITIONS. The ground cover over the site generally consists o a few inches of organic cover underlain with silty sandy gravel with a trace of organics for another three feet. The surficial deposits of silty gravels or sandy silty gravels are inter-spersed with cobbles. The upper layer of material is of medium density and the lower level of harder density as evidenced by the effort of the backhoe during excavation. A consolidated layer was encountered at three feet but was broken through at four and 1/2 feet. Below this layer was 5-1/2 feet of well graded .'gravel. The soils in general can be classified as CW/GM by the Unified Soil Classification System. The hardpan appears to be a GP soil. The gravelly soils contain about 608 by weight gravel or cobbles a4ith the remainder sand and/or silt. Groundwater'was encountered only as a seeping flow just above the hardpan layer and not as a saturated level. Since the water was flowing through the soil and not ponding, it is felt that the ground water level is much lower than the depth of the test holes. There was no visible evidence of ponded water,rather the soil appeared to be well drained, but compact. CONCLUSION. Sufficient exploration has been accomplished on this sma subdivision for the intended use with individual on-site water and sewer facilities. Each tract has sufficient acreage to allow for replacement soil absorption systems should the initial system fail. The soils are suitable with respect to foundation bearing capacity within the range of conventionally applied bearing pressures for Greater Anchorage A�4a Borough Page 3 June 2, 1974 residential continuous concrete footings. If other than convent- ional loads are anticipated, professional help may be required to design the foundation. The steep'slopes must be considered in any foundation system. Please contact the undersigned if any expansion or clarification of these data is necessary. P_,%Z-jk]•ace, P.E. L LYNN ►. VL1t61Cf `'%I