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Home My WebLink AboutTIMBERLINE S-2989Lo-r' GREATER A~';CIIORAGE AREA BOROUGH Depart~',~nt of Environl]m~}tal Quali NENORANDUH iqarcii 29, 1973 TO: SUBJECT: Ala~l Scheen P1 atoning 9epart~mn~ Roll Strickland, R.S. Ch~f Sanitarian S 2~89 Timberlino Subdivision For :h~ meeting o~ April ll, 1973 On this particular subdivision, the o~ly ~.i~ing that we i]ave r~¢eived as of this date ]s an aerial ':opographic map of tt]e subdivision. have no soils data. :~e i~ave no water awilabJlity d~ta. It is difficult to deter~:ine ti~e size of the lots. We have no data dicatJng that on--site sewage disposa] systems can be plac~d o~] e~ch lot. And, ~n esse~ce, unti~ ~iffs informa~io~ is ~)rovided ~}art~-~m~¥~ by the engi~aer or engi~teers uakno~, ~e can ~ake ~o further recom]~mdation. On this particular cas~, aC this %jme, reco¢¢~end postpone~n~ un%il ~h]s information is available. told Box 1866 Anchorage, Alaska 99510 March l, 1973 Greater Anchorage Area Planning Department 3500 Tudor Road Anchorage, Alaska Borough Attention: Mr. Alan Subject: 99507 G. Scheen, Platting Officer Soils Evaluation and Related Items Timberline Subdivision Dear Mr. Scheen: The following is to be' considered a comprehensive report concern- ing the soils conditions for the proposed Timberline Subdivision. This report 'is submitted per the requirements in GAAB O'~dinance No. 112-72A~ Chapter 21 Following the text are: Project !.o..ation Sheet 1 Boring Location Sheet 2 Boring L~gs Sheets 3 - 6 Standard Explanatory Information Sheets 7 9 Site Location and Descri~otio'n. The approximately 20.5 acre pa.r- cel to be sube, ivided per location sketch sheet is located one-half mile east of Lake Hideaway bordering Trails End Road on ~he east. The property is generally heavily wooded with spruce and birch and slopes downhill from east to west. A detailed topographic map will be supplied upon completion~ This map will show relief, drainage channel!;, roadways, etc. as required. Field Exp~o~r~a_t_io~Z. On February 19, 1973~ four (4) testholes were drilled on the site to depths of 15 feet. The hole locations are as shown on Sheet 2. Gre~ter Anchorage Area ~age 2 March l, 1973 Borough All testholes ~ere drilled by Denali Drilling, Inc., Anchorage, Alaska, using a Mobile B-50 Drill mounted on a Nodwel! tracked vehicle; continuous flight auger drilling was employed with grab sampling as necessary. Testhole placement was on a random basis with the attempt to cover the entire site within the constraints of operating on the hillside in 1½ to 2 feet of snow. Because of the snow, access was continually difficult. Geolgj~_y_. The Anchorage area is located within the Lower Matan- uska Lowland, a part of the Cook Inlet Lowland physiographic subprovince that borders Cook Inlet. Five major Pleistocene glacial advances along the consequent or subconsequent lacustrine and alluvial deposits greatly influenced the present topography of the area. The surficia! geol'ogic unit as the site area appears to be Pre- Wisconsin (late Pleistocene) lateral moraine deposits. The lateral moraine is a s~stem of hummocky composite linear ridges tending south-southwesterly. Two parallel ridges form the major features of the moraine. The higher of the two rises conspicuously about one-half mile east of Lake Hideaway. Tile till of this la- teral moraine is commonly san. dy and stoney with cobbles common. Pebbles and sand predominate although angular boulders 10 feet long are scattered throughout the moraine. The lateral moraine was derived from talus and avalanche debris that accumulated on and along the margin of the ice as the glaci~r moved down the Turnagain Arm from the north. As tile glacier thinned, this debris accumulated on the slope as conspicuous ridges. Subsurface Conditions. Generally the ground'cover over the site consists of 2 to 3 feet of organic cover with underlying surficiai deposits of silty gravels or sandy silty gravels with random cobbles. The deposits, on the basis of drilling effort, can be classed as medi~lm dense. The soils in general can be classified as GP/GH per the Unified Soil Classific~.tion System, with isolated instances of ML soils. The gravelly soils contain about 50 to 70% by weight gravel with remainder sand and/or silt. For this reason, most soils were classified as borderline GP/GM. Greater Anchorage P age 3 ~,~arch l, 1973 Area Borough is not i~dicacive of the general area a~d represeq~s a local condition, possibly temporary during ,,.~inter. Conclusion. It is felt that sufficient exploration has been per-T~to classify this site as acceptable for the intended use under the current R-6 zoning classification with indiv'~dual on-site waten and sewer facilities. The soils are~.also suitable, with respect to foundation bearing capacity within the range of conventionally applied bearing values, for residential continuous concrete footings. As with any site, professional help may be necessary during the building phase if exotic designs with concentrated loads are planned or unexpected conditions are encountered. It is hoped this report provides a clear indication of the con- ditions. Please contact the undersigned if any expansion or clari- fication of this data is necessary. .~Sincerel~, ~. ,. James L. Scheffel, P.E. JLS:jss :l 8 Z d 15 -- T.H. vi 'rEST HOLE LOGS .SOIL DESCRIPTIONS ' The soil d¢'Scripttons shown on the logs are the best estimate of the soil characteristics at the time of field e×amlnatlon. 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 Glasslflcat~on Chart." 2. Othe~qrlterla Boulder --- greater than 8" Gobble - 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 ;nols~ure range. PL - Plastic Limit, moisture content being approximated as; above (+) or below (-) plastic limit (PL) or liquid limit (Lw) as appropriate. Lv~ - Liquid Limit, see PL Dilatency - Is the ability of water to migrate to the kurface upon vibration or jolting of a sample, an aid in deterrainlng whether a soil is predomi- nately'a clay or silt. Well ...... ~rc~ueu - 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 meLhod now being used as an aid to identification of these soils as a co?nbinaUon ball drop, and rolled thread tes~ ia which a 2" diameter ball of the 5and-S~h-GJay fraction is &opped "until a 1" thick pat develops. The diameter of a thread at crumbling rolled from the resultant pat determines 'whether cia,/ or slit predominates. Dr? Strength ~ a small sample of the soil is formed into a cube and air dried, and crushed between the fingers. High dry strength mol~ates clays and low silts. .Water Table - the apparent water, table at the time ofobse~w'ation. Often the a.¢tuaI Water table may be higher unless the hole ls allowed to remain open or is converzed to an observatiqn ',*,'ell. C~plllary Fringe - change from moist to very damp, or saturated sot!, usually Indicates that water table is close. Peat - ¥ibrous material of macroscopic and microscopic fragments of decayed vegetable matter; very compressible, unsuitable for foundation or embankment. Color light brown to black. Ac - ti'he upper layer, surface soil or topsoil, containing humus and/or organic' debris, not satisfactory for foundations, 30% GRAVEL SOIL CLASSI?IOATION CHART NONFROST GROUPS OF FI F2 F3 F4 b. I0 20 30 40 50 60 70 80 90 I00 GRAVEl_ (4-~,~4SCREEN) % BY WEIGHT SUSCEPTIBLE SOILS ARE INORGANIC SOILS CONTAINING LESS THAN 3% FINER THAN O.02mrn. FROST-SUSCEPTIBLE SOILS: GRAVELLY SOILS CONTAINING BETWEEN 3 AND 2:0% FINER THAN O.02mm. SANDY SOILS CONTAINING BETWEEN .5 AND 15% FINER THAN 0.02 mm. GRAVELLY SOILS CONTAINING MORE THAN 20% FINER THAN O.02mm, AND SANDY SOILS (EXCEPT ~_1~_.~ SILTY~ SANDS) CONTAINING i~ORE THAN t5°/o FINER THAN 0.02 CLAYS WI'i'It Pt_ASTICIT'f INDEXES OF MORE THAN !2, EXCEPT VARVED CLAYS. ALL SILl'S INCt-UDI,~'G SANDY SILTS. F_-LC~_E.. SILTY SANDS CONTAINING MORE THAN t5% FhNER THAN O.02mm, LEAN CLAYS WITH PLASTICITY INDEXES OF LESS THAN 12, VARVED CLAYS, i{ECEI'¥ED Alpine Development Company Box 1866 Anchorage, Alaska 99510 April 12, 1973 Greater Anchorage Area Borough Department of Environmental Quality 3330 "C" Street Anchorage, Alaska 99503 Attention: Mr. Roll Strickland, Chief Sanitarian Subject : Timberline Subdivision/S-2989/ ~Terence ~-~quirement-Potable Water Gentlemen: In order to substantiate the availability of potable water subdivision, we submit the following information as being of the quantity of water obtained in the area. for this indicative As you know though, the wells of this area bedrock, and while I think adequate water tions, some residents have had difficulty. does not often occur. are drilled into fractured is available in most loca- This situation, I believe, My water well is 55 feet deep, and produced 5 to 6 gal/min originally in 1968, and I have no reason to believe that capacity was diminished. The following list reflects other well capacities in the immediate area: Property Well Capacity Owner Depth (ft) (gal/min.) L. P. Glenn 65 5+ W. Boedecker 85 5+ J. Stone 100 3+ D. E. Matthews 80 5+ The enclosed map shows the location of these wells. As an item of interest, a substantial number of people have filed water rights applications in this area, and I am continuing my observation of the quality of my well water through periodic analysis by State Health Department facilities. If further information is required, please call me at 279-25181 days, or Mr. D. E. Matthews at 272-9548. GAAB 2 April 12, 1973 We would appreciate hearing from you at your earliest as we are anxious to proceed with the final stages of division process. Sincerely, ALPINE DEVELOPMENT COMPANY oames L. Sch f~:e~l,~ .E. JLS:das convenience, the sub- Box 1866 Anchorage, Alaska 99510 March 1, 1973 Greater Anchorage Area Borough Planning Department 3500 Tudor Road Anchorage, Alaska 99507 Attention: Mr. Alan G. Scheen, Platting Officer Subject: Soils Evaluation S u b di w~j~s_i_on ..... Dear Mr. Scheen: and Related Items - Timberline The following is to be considered a comprehensive report concern- ing the soils conditions for the proposed Timberline Subdivision. This report is submitted per the requirements'in GAAB Ordinance No. 112-72A, Chapter 21. Following the text are: Project Location Sheet 1 Boring Location Sheet 2 Boring Logs Sheets 3 - 6 Standard Explanatory Information Sheets 7 - 9 Site 'Location and Description. The approximately 20.5 acre par- cel to be subdivided per location sketch sheet is located one-half mile east of Lake Hideaway bordering Trails End Road on the east. The property is generally heavily wooded with spruce and birch and slopes downhill from east to west. A detailed topographic map will be supplied upon completion. This map will show relief, drainage channels, roadways, etc. as required. Field Exploration. On February 19, 1973, four (4) testholes were drilled on the site to depths of 15 feet. The hole locations are as shown on Sheet 2. Greater Anchorage Area Page 2 March 1, 1973 Borough All testholes ~ere drilled by Denali Drilling, Inc., Anchorage, Alaska, using a Mobile B-50 Drill ~oonted on a Nodwell tracked vehicle; continuous flight auger drilling was employed with grabsampling as necessary. Testhole placement was on a random basis with the attempt to cover the entire site within the constraints of operating on the hillside in 1½ to 2 feet of snow. Because of the snow, access was continually difficult. Geolo~yo The Anchorage area is located within the Lower Matan- uska Lowland, a part of the Cook Inlet Lowland physiographic subprovince that borders Cook Inlet. Five major Pleistocene glacial advances along the consequent or subconsequent lacustrine and alluvial deposits greatly influenced the present topography of the area. The surficial geologic unit as the site area appears to be Pre- Wisconsin (late Pleistocene) lateral moraine deposits. The lateral moraine is a system of hummocky composite linear ridges tending south-southwesterly. Two parallel ridges form the major features of the moraine. The higher of the two rises conspicuously about one-half mile east of Lake Hideaway. The till of this la- teral moraine is commonly sandy and stoney with cobbles common. Pebbles and sand predominate although angular boulders l0 feet long are scattered throughout the moraine. The lateral moraine was that accumulated on and moved down the Turnagain this debris accumulated derived from talus and avalanche debris along the margin of the ice as the glacier Arm from the north. As the glacier thinned, on the slope as conspicuous ridges. Subsurface Conditions. Generally the ground cover over the site consists of 2 to 3 feet of organic cover with underlying surficial deposits of silty gravels or sandy silty gravels with random cobbles. The deposits, on the basis of drilling effort, can be classed as medium dense. The soils in general can be classified as GP/GM per the Unified Soil Classification System, with isolatnd instances of ML soils. The gravelly soils contain about 50 to 70% by weight gravel with remainder sand and/or silt. For this reason, most soils were classified as borderline GP/GM. fl 1973 Greater Anchorage Area Borough Page 3 March 1, 1973 Ground water was encountered in testhole #1 at a depth of four feet. This was the only indicatio~ o'f ground water. Other test- holes were left open to check for water after drilling. It is significant to note that no water was encountered in testhole #4 adjacent to testhole #1. It is felt that water encountered is not indicative of the general area and represents a local condition, possibly temporary during winter. Conclusion. It is felt that sufficient exploration has~been performed to classify this site as acceptable for the intended use under the current R-6 zoning classification with individual on-site water and sewer facilities. The soils are also suitable, with respect to foundation bearing capacity within the range of conventionally applied bearing values, for residential continuous concrete footings. As with any site, professional help may be necessary during the building phase if exotic designs with concentrated loads are planned or unexpected conditions are encountered. It is hoped this report provides a clear ditions. Please contact the undersigned fication of this data is necessary. indication of the con- if any expansion o~' clari- ~Sincerely, James L. Scheffel, P.E. JLS:jss O~? , ~e .Fy. Oe, a~rd, t, lp ' The 'soil des~riptions shown on the logs are the best estimate of the soil characteristics at the time of field examination. Such examinations do not achieve the :lsion of laboratory tests for the various properties. 1 T~e relative tyPe of soil and the frost classification Is shown on the Sheet "Sgil ~lassiflcatic n 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 (PO 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 predomi- nately a clay or silt. Well graded - uniformity coefficient greater than 7 Poorly graded - uniformity coefflc!ent less than 7 (Uniform particles, gap graded) Organic Content - estimated by volume, not particularly precise. Clayey Soils - a field met,hod 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 thread at crumbling rolled from the resultant pet determines whether clay or slit 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 indicates clays and low silts. .Water Table - the apparent wotectable at the time of observation. Often the ~.ctual weter 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 seturated Soil, usually Indicates that water table is close. Peat - Fibrous material of macroscopic and microscopic fragmentS of decayed vegetable matter; very comprensible, unsuitable for foundat[0n or embankment. Color light brown to black. .,.,,. . Ao -The upper layer, surface soil or topsoil, containing humus and/or organi debris, not satisfactory.for foundations. SOIL CLASSIFICATION CHART GRAVEL 0 I0 20 :50 40 50 60 70 80 90 I00 G R A V E L (+ ~4 SCR E E N) % BY W E IG H T NONFROST SUSCEPTIBLE SOILS ARE INORGANIC SOILS CONTAINING LESS THAN :50/0 FINER THAN O.02mm. GROUPS OF FROST-SUSCEPTIBLE SOILS: .. FI GRAVELLY SOILS CONTAINING BETWEEN :5 AND 20°/o FINER THAN O.02mm. F2 SANDY SOILS CONTAINING BETWEEN :5 AND 15°/o FINER THAN O.02mm. '" F:5 o. GRAVELLY SOILS CONTAINING MORE THAN 20% FINER THAN O.02mm. AND SANDY SOILS (EXCEPT FINE SILTY, SANDS)CONTAINING MORE THAN 15% FINER THAN O.02mm. b. CLAYS WITH PLASTICITY INDEXES OF MORE THAN 12. EXCEPT VARVED CLAYS. F4 a. ALL SILTS INCLUDING SANDY SILTS. b. FINE SILTY SANDS CONTAINING MORE THAN 15% FINER THAN O.02mm.' ¢. LEAN CLAYS WITH PLASTICITY INDEXES OF LESS THAN 12. d. VARVED CLAYS. Og NOl$1Al(lgfl~ ~Nlla~g~l.L