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HomeMy WebLinkAboutWHALEY Soil Evaluation(f_.,U ALU AT, o N 4839 Tampa Circle Anchorage, Alaska June 14, 1974 99504 Greater Anchorage Area Borough Planning Department 3500 Tudor Road Anchorage, Alaska 99507 Attention: Mr. Wayne Mabry Subject: Soils Evaluation and Related Items , Whaley Park Subdivision Addition 5. Dear Mr. Mabry: The following information concerning the soils conditions for the proposed 5th addition to the Whaley Park Subdivision located near · Peter's Creek in Chugiak, is submitted to satisfy the requirements of GAAB Ordinance No. 112-72A, Chapter 21; and Title 18, Envinron- mental Conservation, 18 AAC 72.060 of the State of laska. Test Hole logs and project location maps follow the text. SITE LOCATION AND DESCRIPTION. The approximately 4.1 acre parcel and the approximately 6.3 acre parcel to be subdivided are located three-fourths of a mile east of the Glenn Highway near Peter's Creek in Chugiak. The property is overgrown with alders and small birch as a second growth after having been cleared for homesteading. The topography is generally sloping to the northeast on tract lB and to the northwest on tract 5B while tract 5A is generally level. All slopes are gentle with no adverse greades. EXISTING WELLS AND SUBSURFACE DRAIN FIELDS. The location of existing wells on or near the parcels to be subdivided are shown on the project location map. Ample water has been located in this area approximately 170' to 220' below the surface. Neighboring subdivisions (not shown on the map) have wells of sufficient capacity to supply a small community. The existance of a reliable water source in this geological area has been proven sufficiently to Borough Officials in the immediate past. Previous chemical and bacteriological testing of existing water sources has indicated that drinking water quality standards are satisfied. FIELD EXPLORATION. On June 14, 1974, two (2) testholes were excavated on-site to depths of 15-1/2' each. The hole locations are shown on the location map. Both holes were excavated by Wallace Construction Company (no relation to the engineer) of Chugiak, Ak., using a Drott Backhoe with a 3/4 yard bucket. Testholes were observed during excava'tion and s~ples were taken directly from the strata or from the excavated material. The testholes were located to provide sufficient information to augment previous soils investigations conducted by the engineer in this immediate area. There is more than sufficient room on the subject tracts to locate water and wastewater facilities. Greater Anchorage ~ea Borough Page 2 June 14, 1974 GEOLOGY. The Chugiak area is located within the Lower Matanuska Lowland, a part of the Cook Inlet Lowland physiographic subprovince that borders Cook Inlet. Five major Pleistocine glacial advances along the consequent or subsequent lacustrine and alluvial deposits greatly influenced thepresent topography of the area. The surficial geologic unit of the site appears to part of the Peter's Creek Fan as'it worked through the late Pleistocene lateral moraine deposits. The till of this deposit is commonly sandy and stoney with cobbles and boulders common. Pebbles and sand predom- inate but silt and rock dust are ever present. Cobbles and pebbles are rounded rather than angular. SUBSURFACE CONDITIONS. The ground cover over the site generally consists of a foot of organic cover or peat underlain with organic silty sand for another foot and a half to two feet. The surficial deposits of silty sandy gravels or sand gravels are interspaced with cobbles and some boulders. One thin frozen layer was encountered in hole ~2 while the main portion of the excavation was not hard digging. A solid hardpan was not reached and well graded gravel seemed to predominate. Hole %1 had a three foot layer of gravely sand that seeped water. This layer was underlain with a dense layer about a foot thick which seemed to channel the water seepage. Under the dense layer was well graded gravel and neit~hole showed evidence of a static water level. The soils in general can be classified as SW/GW with a little SM/GM by the Unified Soil Classification System. The soils appear to be excelent for drainage. CONCLUSION. Because of knowledge of the surrounding area, it is felt that sufficient exploration has been accomplished on these two parcels for the intended use of single family dwellings equipped with individual on-site water and wastewater facilities. Each lot or tract has adequate acreage to allow for replacemtn 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 residential continous concrete footings. If other than conventional loads are anticipated, professional help may be required to design the foundation. Please contact of these data the undersigned if any expansion or clarification is necessary. RespeCt fully /--~Ly. nn/ P. Wallace, P.E. Wayne Mabry DEQ Comments October 4, 1973 Page Four developed until the area is served by public sewer and a more suit- able method of waste disposal can be provided to those residents that will be building on the lots in question~ 25) S 3185 Suetawn Estates Subdivision, Addition # 1 Soils information was run and a sewer system has already been installed on this lot. Individual wells on the adjoining lot show that adequate volumes of water can be obtained. 26) S 3203 Valley View Estates, Addition # 1 The engineer has provided soils data that shows the land can adequately support on-site seuage disposal at the present lot size. We would ask, however, prior to final approval of this plat, certain items be supplied to this Department: 1. Water availability data from wells drilled within the subdivision. 2. Soils data ( two (2) additional soils tests) from Block 2 of the proposed subdivision. At tbe present time we have sufficient information that we feel this plat meets our standards for preliminary approval. 27) S 3204 Whaley Park Subdivision The information supplied and field review indicates only one (l) prob- lem at the present time. Due to the exceedingly steep slope on Lot l, we would recommend that Lot 1 and Lot 2 be combined into one (1) lot. The topography of Lot 1 is such that it would be impossible to install individual utilities on this lot and very questionable if a residence could be built on this lot. Lot 2 is a more or less flat bench which would adequately support a home with individual sewer and water utilities. mld CC: Dennis Gardner Public Works Department Customer Services Supervisor 4839 Tampa Circle Anchorage, Alaska 99504 ~?ovember 19, 1973 Greater 7u~cborage Area Borough PlanninR Department 3500 Tudor Road Anchorage, Alaska 99507 Attention: Mr. Wayne Maybray Subject: Soils ~Valuation and Related Items - ~aley Subdivision, 4th Addition Dear Sirs: t~e followin~ information concerning the soi].s conditions for the oroposed dth addition to the Whaley Suhdivision located near Peter's Creek in Chugiak is submitted to satisfy tile requirements of GAAB Ordinance No. 112-72A, Chapter 21; and Title 18, Enviror~mental Conservation, 18 AAC 72.060 of the State of Alaska. Test Hole logs and a project location map follow the text. SITE LOCATION AND DESCRIPTION, The approximately 26.8 acre ]~arcel to be · subdivided is located one-half mile east of the Glenn Highway near Peter's Creek in Cbugiak. The property is overgrown with Alders and Small Birch as a second growth after having been cleared for homesteading. The topography is generally sloping to tile northwest becoming steeper near the ski road to the north of the property. EXISTING WELLS AND SUBSURFACE DRAIN FI~LDS. The location of existin~ wells on or near the parcel to be subdivided are shown on the project location map. Ample water has been located in this area approximately 170' to 220' below the surface. 5[eighboring subdivisions (not sbo~.rn on map) have wells of sufficient capacity to supply a sn~all co.unity. The water level of the one well located on tract 1-C is reported to have dropped approximately 25~ after the 1964 earthquake, but has remained stable since tbat ti~e. ' The existence of a reliable water sonrce in this geological ar~a has b~en proven sufficiently to Borough O~ficials in the immediate p?st, Previoqs~ch~aical and bacteriological testing of existing water sources has indicated that drinking water quality' standards are satisfied. FIELD EXPI~P~TION. On November 15, 1973, two (2) testholes were excavated on site to depths o[- 15-1/2~, and 14-1/2' respectively. The hole locations are sho~,m on the location map. Both holes were excavated by Wallace Construc- tion Company (No relation to the engineer) of Chugiak, Alaska, using a Drott Backhoe with a 1 CY bucket. Testholes were entered by use of a ladder and direct observations were made on soil strata. Grab s~nples were taken both during and after excavation. Testhole placement was made on t~e smaller two tracts to insure that soil conditions were as expected. 2]~ere is more than suf~czent room on the larger two tracts to locate water and wastewater facilities. 'Creater Anchorage Area Borough Page 2 November 19, 1973 GEOLOGY. The Chugiak area is located within the Lower Matanuska Lowland, a part of the Cook Inlet Lowland physiographic subprovince that borders Cook Inlet. Five major Pleistocine glacial advances along the consequent or subsequent lacustrine and allt~ial deposits greatly influenced the present topography of the area. The surfibial zeologic unit of the site appears to be part of the Peter's Creek alluvial fan as It worked through the late Pleistocene lateral moraine deposits. The till of this deposit is co~onIy sandy and stoney with cobbles common. Pebbles and sand predominate, but silt and rock dust are present. Cobbles and pebbles are rounded rather than angular. SUBSURFACE CONDITIONS. The ground cover over the site generally consists of a foot of organic cover underlain with organic sand for another foot. The surficial deposits of sandy 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 bac~]oe during excavation. The soils in general can be classified as GP/~ by the Unified Soil Classi- fication System. There is some indication of ML soils. The gravelly soils contain about 60% by weight gravel with the remainder sand and/or silt. Because of the silt-sand composition the soils were classified as borderline GP/~4. Groundwater was encountered only as a seeping flow and not as a saturated table. About four inches of water acctnnulated in the bottom of test hole ~1 after sitting overnight. Since the water was flowin~ 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 visual evidence of ponded water, rather the soil appeared to be well drained, but compact. · CONCLUSION. Because of knowledge of the surrounding area, 'it is f~lt that sufficient exploration has been accomplished on this~ small subdiv~ision for the intended use with individual on-site water and sewer facilities. Each tract has suffigient acreage to allow for replacement soil absorotion systems should th~ initial system fail. The soils are suitable with respect to foundation bearing capacity within the range of conventionally applied bearing pressures for residential continuous concrete footings. If other than conventional loads are antici- pated, professional help may be required to design the foundation. Please contact the data is necessary. undersigned if any expansion or clarification of these bt, J