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HomeMy WebLinkAboutSLEEPY HOLLOW #1 Soils Logs CONSULTING ENGINEERS 1940 POST ROAD-ANCHORAGE, ALASKA-99501 TELEPNONE; 907-279-2581 PARTNERS ~ -~ AFFILIATED '" '""wl/ill~ F. '¢/.WI~CE RE., RET ALASKA TESTLAB-- .ASSOCIATES K W BLEDSOE P G HANSEN R W. HUNT ~. L $CHEFFEL RE. July 24, 1972 W.O. 11722 Gross Construction Company 841 West 74th Avenue Anchorage, Alaska 99502 SUBJECT: Soils, Sleepy Hollow Subdivision, Addition #1, Peters Creek, GAAB, Alaska Gentlemen: In accordance with your request, we are currently making a sub- surface investigation of the subject project; included herein is our preliminary report. Following the text are: Test-pit logs Sheets 1 to 5 Standard explanatory information Sheets 6 and 7 Test-pit location sketch Attached The proposed subdivision is located within West 1/2 of Sec. 15, T. 1S N, R.1 W., S.M., Alaska, and totals approximately 100 acres. The bulk of development will be confined to 27 parcels totaling about 80 acres; two tracts comprise the rema~nlng 20 acres. In order to adequately evaluate the subsurface conditions within this subdivision, we have recommended that a minimum of ten test holes or test pits be made within the 100 acres. However, because of access problems due to steep grades at the present time, you were able to excavate by backhoe only four test pits to the recommended depth. Efforts were made to complete the remaining test pits by blasting, but these were not successful. As soon as access becomes satisfactory for Arilling or backhoe equipment to reach the remaining localities, the subsurface investigation should be completed. All test pits were logged by Mr. Ozias Hatch, nician, on July 19, 1972. The writer visited 22, 1972. our senior tech- the site on July The five test pits, including one 5-ft. test pit, indicate that the site soils consist of a thin ground cover of organic materials about six inches thick, and frost-susceptible sandy silt and silty sand, 1 to 2-1/2 feet in thickness, all overlying extensive glacial deposits of nonfrost-susceptible (NFS) sandy gravel and gravelly sand to the depths of exploration. Gross Construction Co. 2 W.O. 11722 With regard to subsurface conditions for the proposed development, the only precaution item should be slope stability only in those areas with significant grades (not road grades) where residences are planned, as the subdivision has a prominent bluff area below the higher ground (plateau). If construction in these steep areas is the case, routine slope-stability analyses should be performed. In all other aspects, the granular soils (sandy grave], and gravelly sand) within the subdivision appear to be consistent, well-drained, and sufficiently dense to provide a more-than-adequate performance for foundation and development purposes. The sandy gravel and gravelly sand deposits are sufficiently permeable, and thus are very suitable for percolation of individual seepage pits. Cor- relation between and consistency of the test pits is excellent, and we anticipate that the remaining test pits will indicate similar subsurface conditions. In our opinion, no foundation conditions have been found to date which are unsatisfactory or prohibitive~ and which would warrant impedence to this project. As soon as site access is improved, the remaining exploration can be completed. Very truly yours, ACLW Consulting Engineers / Paul G. Hans'~n, E'.I.T. Approved: Herr? R. Lee:.E. PGH:ld PROJECq.~.SL_~.EPY H_ OLLO~W DATE JULY ]9, 1972 W.O. NO.. 11722 -TEST PIT ~. ...... EXISTING GROUND CLIENT GROSS CONSTRUCTION SIIEET ~. OF 7 JULY ]9~ 1972 :.,.; W. O. NO..__I. 1722 ' ~z Z ) C'LIENT GPOqS cn~'S'~'t~Uf"PTOx [~'07i'x;~,I DATE ,JULY ]9, 1972 PROJEC~Y ItOLLOI.~~ SUBD~N W.O.NO. 11722 · TEST PIT ~ __ELEv.~XISTING GROUND ~ CL. ENF GROSb CO, IS.RUCTION [~O25.~ DA~E ,IIII,Y ]9, ].97~ ~ ., m PROJEC~ SLEEPY HOLLOIV SUBD~N XV O NO 11722 · TEST PIT ZI.EV EXISTING GROUND CLIENT GROSS CONSTRUCTION PROJECZ ~'P7 }~-L-~fi SUBD~N TEST PIT ~ ELEv. EXISTING GROUND DATE JULY ]9, 1972 W.O~.N0._11722 __7 ALASKA TESTLAB CONSULTATION ~, TESTING ~ EXPLORATION © CHEMICAl_ Q MATERIALS ¢~ INSPECTION SOIL CLASSIFICATION CHART / ~0% GRAVEL \ 0 I0 20 30 40 50 60 70 80 90 100 G.~R AV EL (-F~SCREEN) % B~Y WEIGFLT=T NONFROST SUSCEPTIBLE SOILS ARE INORGANIC SOILS CONTAINING LESS THAN 5% FINER THAN O,02mm. GROUPS OF FROST-SUSCEPTIBLE SOILS: FI GRAVELLY SOILS CONTAINING BETWEEN 3 AND ~0% FINER THAN O.02mm, F~> SANDY SOILS CONTAINING BETWEEN 3 AND 15% FINER THAN O.02mm, F3 o. GRAVELLY SOILS CONTAINING MORE THAN 20% FINER THAN O.02mm. AND SANDY SOILS (EXCEPT [=INF~ SILTY, SANDS)CONTAINING MORE THAN 15% FINER THAN O,O2. mm. b, CLAYS WiTH PLASTICITY INDEXES OF MORE THAN 12. EXCEPT VARVED CLAYS. F4 o, ALL SILTS INCLUDING SANDY SILTS, b. FINE SILTY SANDS CONTAINING MORE THAN 15% FINER THAN O,02mm, ¢. LEAN CLAYS WITH PLASTICI'['Y INDEXES OF LESS THAN 12. d, VARVED CLAYS. TEST HOLE LOGS SOILS DESCRIPTIONS The soil descriptions shown on the logs are the best estimate of the soil charac- teristics at the time of field examination. Such examinations do not achieve the precision of laboratory tests for the various properties. 1. The relative type of soil and the frost classification is shown on the sheet "Soil Classification Chart." 2. Other criteria: Boulder - greater than 8" Cobble - approximately 3" to 8" Blow Count - blows/6" of 140 lb. weight falling 30"; 2" split spoon. (The standard penetration is blows/12".) Density - estimated by the rate of drilling, type of soil, blow count and moisture range PL - Plastic Limit, moisture content being approximated as; above (+) or below (-) plastic limit (PL) or liquid limit (Lw) as appropriate Lw - Liquid Limit, see PL Dilatency - is the ability of water to migrate to the surface upon vibration or jolting of a sample, an aid in determining whether a soil is pre- dominately a clay or silt Well graded - uniformity coefficient greater than 7 Poorly graded - uniformity coefficient less than 7 (Uniform particles, gap graded) Organic Content - estimated by volume, not particularly precise Clayey Soils - a field method now being used as an aid to identification of these soils as a combination ball drop, and rolled thread test in which a 2" diameter ball of the Sand-Silt-Clay fraction is dropped 2' until a 1" thick pat develops. The diameter of a Ihread at crumbling rolled from the resultant pat determines whether clay. or silt predominates. Dry Strength - a small sample of the soil is formed into a cube and air dried, and crushed between the fingers. High dry strength indi- cates clays and low indicates silts. Water Table ~ the apparent water table at the time of observation. Often the actual water table may be higher unless the hole is allowed to remain open or is converted to an observation well. Capillary Fringe - change from moist to very damp, or saturated soil, usually indicates that water table is close. Peat - Fibrous material of macroscopic and microscopic fragments of de- cayed vegetable matter; very compressible, unsuitable for founda- tion or embankment. Color light brown to black. Ao - The upper layer, surface soil or topsoil, containing humus and/or organic debris, not satisfactory for foundation. ALASKA TESTLAB >,