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HomeMy WebLinkAboutSILVER CREST Block 2 Lots 11, 12 & 16 Soil InvestigationIL q'l OkJ LoT' JlI IZl I (P 4040 "B" STREET ANCHORAGE, ALASKA 99503 (907) 278-1551 April 28, 1978 W.O. #D10914 Grid #2439 Mr. Mike Stephens Stephens Construction P.O. Box 3-3772 ECB Anchorage, AK 99501 Subject: Subsurface Investigation for Feasibility for On-Site S~wage Disposal Systems Lots 11, 12 and 16, Block 2, Silvercrest Subdivision and Lot 1, Block 1, SST Subdivision Dear Mr. Stephens: As requested we performed a subsurface investigation on the four above referenced lots to determine their suitability for placement for on-s~te sewage disposal systems. Three test holes were placed on April 12 and 13, 1978. The holes were drilled by Denali Drilling, Inc. The test holes were logged and the drilling supervised by Mr. O.M. Hatch, senior technician/geologist with Alaska Testtab. The holes are located on the adjacent figures #1 and #2. The test hole logs are included as Table A. It may prove helpful in interpreting the data on the test holes logs to review the standard explanatory information contained on Sheets 1-3. Once the test holes were drilled, they were cased with slotted plastic pipe. About a week later the test holes were checked for ground water intrusion into the holes. None had occurred. All three of the test holes were dry. Then on April 25, 1978, the test holes were filled with water and left over night to saturated. A percolation test was theh performed the next day, April 26, 1978, by refilling the holes and monitoring the rate at which the water fell in the holes at 10 minute intervals for a period of one hour. The percolation rates based on this testing are as follows: Lots 11 Lot 16, Lot 1, and 12, Block 2, Silvercrest -- 10 minutes/inch. Block 2, Silvercrest Subdivision -- 5.7 minutes/inch° Block 1, SST Subdivision -~ 2 minutes/inch. Mr. Mike Stephens April 28, 1978 Page 2 We would caution the use of a percolation rate as fast as 2 minutes/inch in Lot 1, Block 1, SST Subdivision. It is our experience that due to the clogging action of sewage effluent, that a more conservative design value be used in silty sands and silts. They that have a tendency to clog. We would recommend a design value of 5 minutes/inch. We hope this is sufficient for your present needs. If we can be of further service or offer any clarification of any data presented here, please do not hesitate to contact us. Very sincerely, ALASKA TESTLAB Melvin R. Nichols, P.E. Laboratory Manager MRN:rb : .2 ~ 619 S.C 13 B L K , 12 g ~ ~ 47,045 s.~ 5 ~, 945 ~.~. ,~. 53~622 s.f. 52~ 377 s.f. ~IA;7 A ~4°~'~' 17 43,002 s.f. ~ ,~ 43¢756s.f. ' -~6~¢¢¢ 51~ 510 s.f. / 2 EAST 178 12 ., ~I~S CIR. ~9,449 s.f i 78. 12 I ~ 22 ':'~ ~c',:,2 - ~ , . DIMOND ~, 49,499 s.L 40, 5 I , T't"' ) Fl6, Lots 11 & 12 Block 2 Table A WO #D10914 Logged By: O.M. Hatch Date: April 12. 1978 Depth in Feet From To 0.0' - 0.5' 0.5' - 7.0' 7.0' 11.0' 11.0' 16.0' Soil Description Brown Peat, Pt, damp, soft. F-4, brown Gravelly Sandy Silt, ~, stiff, NP, particles to 2" F-4, brown Sandy Silt, ML, damp, stiff, NP. F-l, brown Silty-Sandy Gravel, GM, damp, particles to 3" Bottom of Test Hole: Frost Line: Free Water Level: 16[0' 0.5' None Observed Lot 16, Block 2 Table A WO #D10914 Logged By: O.M. Hatch Date: April 12, 1978 Depth in Feet From To 0.0' 1.5' '1.5' 6.0' 6.0' 16.0' Soil Description Br6wn Peat, Pg, damp, soft. F-4, brown Sandy Silt, ML, damp, stiff, NP. F-4, brown Gravelly Sandy Silt, ML, damp~ stiff, NP. Bottom of Test Hol~: Frost Line: Free Water Level: 16.0' 0.5' None Observed Lot 1 Block 1 , SST Subd. Table A WO ~D10914 Logged By: O.M. Hatch Date: April 13, 1978 Depth in Feet From To 0.0' - 1.0' 1.0' - 2.0' 2.0' - 16.0' Soil Dpscription Brown Peat? Pt~, damp, soft. F-4, brown Sandy Silt, ML, damp, stiff, NP. F-2, brown Silty Gravelly Sand, SM, damp, particles to 3". Bottom of Test Hole: Frost Line: Free Water Level: 16.0' 0.5' None Observed Test Hole Log - Description Guide precision of a laboratory testing procedure. If thc log includes soils sampJes, to verify the field examinatiom The logs often include the following items: Depth Interval usually shown to 0.1 foot, within that zone no significant change in soil type was observed through drill action, direct observation or sampling. Frost Classification NFS, Fl, F2, F3, F4, see "Soft Classification Chart" Texture of Soil - An engineering classification of the soils by particle size and proportion, see "Soil Classification Chart", note the proportions are approximate and modifications to the soil group due to stratification, inclusions and changes ill properties are included. Moisture Content - this is a qualitative measure: 2, no or tittle apparent surface moisture, daR, moisture forms portion of color, less tban plastic limit, wet, Ilo free water, often soft, if cohesive soil, saturated, free water may be squeezed out, ifa free draining soil; dftatent at natura[ moisture content, ifa non-plastic silt or fine sand. (The moisture content is further defined by reference to PI, LW, NP, M%or dilatency.) Density -- refers to more-or-less non-cohesive soils, such as sand gravel mixtures with or without a fine fraction, derived from drilling action and/or sample data; usually described as: very loose, loose, medium dense, very dense. General intent is to portray earthwork characteristics. Stiffness - refers to more-or-]ess cohesive soils and fine grained silts of the day-silt groups. Derived from drill action and/or sample data. Very soft, soft, stiff, very stiff and hard are commonly used terms. Particle size - The largest particle recovered b1, the split spoon is 1-3/8", Shelby tube 3", auger flights (minute-man) 2", Auger flights {B-SO hollow stem) 6"-8". Larger particles are described indirectly by action of the drftling and are referred to as cobbles, 3" to 8", or boulders 8"+. Therefore when reviewing the gradation sheets, if any, the description on the hole log must be considered for an indication of larger particles. Unified Soil Classification ~ This is a two letter code. See Unified C~assificYation sheet for £urther definition. In some cases AASHO and/or FAA soil classifications may be shown as well as tile unified. Atterberg Limits - useful for fine grained and other plastic softs. P~I; natural moisture content believed to be less than plastic limit PI+; natural moisture content believed to be between plastic and liquid Ii-mits L__.~; natural taoistic content believed to be greater than liquid limit N~P; non-plastic, useful as a modifying description of some silty mad:rials. Dilatenc~ - is the ability of water to migrate to the surface of a saturated or nearly saturated soll sample when vibrated or jolted - used as an aid to determine if a fine grained soil is a slightly or non-plastic silt or a volcanic ash. Rock flour -- finely ground soil that is not plastic but otherwise appears similar to a clayey stir. Organic Content - usually described as Peat, PT, sometimes includes discrete partlclel such as wood. coal, etc. as a modifier to att inorganic soil. ~uantity described as; trace, or an estimate of volume, or, in case of all organic, -. as Peat. This may include tundra, muskeg and bog material. Muck - a modifier used to describe very soft, senti organic deposits usuafly occuring below a peat deposit. Amorphus peat - organic particles n~arly or fully disintegrated. Fibrous Peat - organic particles more-or-less intact. Bottom of Testhole - includes last sample interval. Frost Line - seasonal frost depth as described bs' drilling action and/or samples at the time of drilling. Frozen Ground - other than frost line. described by samples, usually includes description of ice contenl, often wdl include modified Unified Classification for frozen soils - this is a special case related to permafrost studies, Free Water Level - The free water level noted during drilling. This is not necessarily tile static water table at the time of drilling or at other seasons. Static water table determination in other titan very permeable soils requires observation wells or piezometer installations, used only in special eases. Blow/6" - The number of blows of a 140 weight free falling 30" to advance a 2" split spoon 6": the number of blows for a 12" advance is, by definition, the standard penetration: ,,4% - natural moisture content of tile soil sample, usually not p~rformed on clean sands or gravels below the water table. Type of Sample - S__P, refers to 2" split spoon driven into the soil by 140 pound weight, a disturbed sample, ~, thin wall tube, "Shelby" used to obtain undisturbed samples of fine grained soil, ~, "grab" disturbed sample from auger flights or wall of trench. g, cut sample, undisturbed sa~nple from wall of trench. Dry Strength - a useful indicator of a soil's clayey fraction, N=None, L=Low, M=Medium, H=High Groul~ - The samples are placed into apparently similar groups based on color and texture and are arbitrarily assigned a group letter. Further disturbed tests including Atterberg Limits, grain size, moisture density relationship, etc. nlay be performed on the group and are assmned to reflect the general distrubed characteristics of the soils assigned to the group. This is an important phase of tile soil analysis and is used to standardize the various qualitative deterndnations and to reduce the number of quantitative tests necessary to describe the soil mass. SOIL CLASSIFICATION CHART 30% GRAVEL CLAY o CLAYEY OR SILTY CLAYEY CLAYEY CLAYEY SILTY SILTY % SILTY GRAVEL GRAVELLY SAND SANDY GRAVEL SAND SAND GRAVELLY SAND GRAVEL GRAVEL 0 ! 0 20 30 40 50 60 70 80 90 100 GRAV'EL (+#4 SCREEN)'% BY WEIGHT NONFROST SUSCEPTIBLE SOILS ARE INORGANIC SOILS CONTAINING LESS THAN 3% FINER THAN 0.02 mm. GROUPS OF FROST-SUSCEPTIBLE SOILS: F! GRAVELLY SOILS CONTAINING BETWEEN 3 AND 20% FINER THAN 0.02 mm. F2 SANDY SOILS CONTAINING BETWEEN 3 AND 15% FINER THAN 0,02 mm. F3 a. GRAVELLY SOILS CONTAINING MORE THAN 20% FINER THAN 0.02 mm- AND SANDY SOILS (EXCEPT FINE SILTY, SANDS) CONTAINING MORE THAN 15% FINER THAN 0.02 mm. b, CLAYS WITN PLASTICITY INDEXES OF MORE THAN 12. EXCEPT VARVED CLAYS, F4 a. ALL SILTS INCLUDING SANDY SILTS. b. FINE SILTY SANDS CONTAINING MORE TNAN 15% FINER THAN 0.02 mm. c. LEAN CLAYS WITH PLASTICITY INDEXES OF LESS THAN 12. d, VARVED CLAYS.