The URL can be used to link to this page

Home My WebLink AboutROBIN HILL #1 S-4191 CASE NUHBER S-4191 · ' Rezoning '. Special Exception PETITION FOR OFRobin Hi'lls \ XVACAT l ON' :'.. !.: of Cases ~ PUBLIC SEWER_NOT AVAILABLE TO SERVICE PETITION AREA. ENVIRONMENTAL ENGINEERING U n- O 0 IL' 0 z LLI Lll Z 0 Z UJ UJ LL 0 " UJ (..9 :3:: U 0 09 0 UJ 03 r~ ILl 0 ~ uJ _l 0 0 ~ U I-- 0 z z 00 - '~0 ~- 0 ~ -J 0 uJ ~ 0 ~ 0 0 u. Oq z I-- J ~ uJ < 0 " 0 ~ I-- 0 z CD UJ ~- o ~- z co o o -J ~ }-- z z ~ ~' ~' tw,-~ uJ 0 }-- z~ o o o "' ~-. n-' Ltl :%D LU 0 Z :32 LL~ "r' ~:~ Z U. n~' 0 0 0 ._J 0 --I ~3 ~Q ~z~ :E 0 0 0 0 0 MUNICIPALITY OF ANCHORAGE PLATING BOARD AUTHORITY AGENDA ADDEDUM City Council Chambers, Loussac L~brary 427 F Street, Anchorage, Alaska October 7, 1976 7:30 PoM. Special Order of Business 1. S'4191 - ROBIN HILLS, BLOCK 4, LOTS 2A & 2B--The MUnicipality of Anchorage has received a petition from Walter Jacobi to resubdivide approximately 2.5 acres from one lot into two lots. The petition area is located on the northeast corner of F.~er-a4~.ane and Mountain Place, approximately ¼ mile sout~illside Drive. ~ Old Business A. Public Hearings I. ~,202 ' I LIAMNA ACRES, LoT5 10A' 'i0B,"'&' 1'0C:.~ The Municipality df Anchora§e has ;irei;.eived a petition from Kenneth M. & Pe~/Ann Don and jack D. & Mary D. Alexander to ;vacate (eliminate) a portion of E. 132nd Avenue :20 feet wide and 285 feet long and to 'tesubd vide approximately 4.407 acres from one,lot ;into three lots. The petition area is ~t'0~ated on the south side of E. 132nd Avenue,'north of E. 134th Avenue, approximately 1~ ] ] ] ] i ! I l' GEOLOGIC AND SOILS INVESTIGATION OF ROBIN HILL SUBI~IVISION Report to JOHN F. KNAPP, OWNER Prepared by ALASKA GEOLOGICAL CONSULTANTS, INC. 3944 Spenard Road Anchorage, Alaska 99503 September 1973 applied esr h sciences Engineering Geology · Mining · Geophysics · Groundwater · Petroleum 25 September 1973 John F. I<napp P. O. Box 3697 E. C. B. Anchorage, Alaska Re: Geologic and Soils Investigation of Robin Hill Subdivision Dear Mr. I<napp: Transmitted herewith is our report presenting the results of a geologic and soils report of Robin Hill Subdivision. We trust that the soils and geologic data presented will permit o. rderly develop- ment of the property within acceptable environmental standards. Please call if you have questions or comments about the report. l--IJM:d Respectfully submitted, ALASKA GEOLOGICAL CONSULTANTS Engineering Geologist ~k ~ 3944 Spenard Road ,, Anchorage, Alaska 99503 · Telephones: 277-7601 277-7602 · Telex: 090-25268 INTRODUCTION This report presents the r 'suks of a geologic and soils irtvestigation conducted on Robin Hill Subdivision, a propose~t residential development. The property is located outside of the area served by public water and sewer utilities .and therefore is planned for on-site water supply and sewage disposal facilities. The purpose of this investigation was, therefore, to define the geologic and soil factors which affect on-site sewage disposal and water supply. Containing approximately 70 acres, the property is located on the lower slopes of the Chugach Mountains between Huffman and DeArmoun Roads It lies within the E½, NW~, Section 26, T. 12N, R3W southeast of Anchorage. S.M. Alaska. FIELD INVESTIGATION Geologic and soils idata at the site wer~ obtained through a geologic reconnaissance of the property followed by a drilling program designed to provide data on subsurface soils and drainage conditions. Nine test borings were drilled utilizing track-mounted auger equipment. In addition to the drilling program, soil exposures in areas of up-rooted trees and power lines clearings were examined and visually classified. ENGINEERING GEOLOGY The surficial geology and topography of the site area are products of recurrent and multiple glaciation- of the region during Pleistocene geologic time. The entire site and the surrounding area is mapped as lateral moraine but also includes end moraine material deposited by smaller tributary glaciers emanating from the Chugach Range. The topography is generally typical of lateral moraines ] l 1 l 1' 3 3 wtith linear ridges parallel to.the direction of ice movement. Side glacial streams and streams issuing from the termini of the tributary glaciers were responsible for a considerable amount of sorting, resulting in deposits of sand and gravel. The resultant morainal topography is therefore somewhat modified. Generally it can be described as hummocky with linear ice-margin channels forming subtle valleys. Kettles occur throughout the site; three contain ponds, whereas others are filled with swampy debris resulting from accumulation of decaying aquatic vegetation. Because of this complex depositional environment, with ice contact and fluvial deposition evident, the surficial soils down to the underlying bedrock are grossly heterogeneous. The heterogeneity is as evident areally as vertically which is' clearly reflected in the logs of the test borings. The material changes abruptly from a clean, washed, highly pervious gravel to a dense cobble till in a matter of a few feet of lateral distance as well as vertical distance. SUBSURFACE MATERIALS AND CONDITIONS Specific types .and depths of materials encountered in the subsurface investigation are tabulated below t~)gether with the specific seepage area require- ment for each soil type: Boring 1 - NW corner Lot 2, Block 1 0 - 2. 5' Brown silty organics - Pt 2. 5' - 4' Silty sand to sandy sik - 250 square feet per bedroom 4' - 6' Gray silty sand with gravel - 225 square feet per bedroom 6' - 13' Interstratified silty sand, sand, gravel, and silty gravel with boulders - 225 square feet per bedroom 13' - 17' Gray silty fine to coarse sand with gravel - 225 square feet per bedroom No water Boring 2 - NW corner of LOt 1, Block 3 0 - 2' 2' - 7' 7' - 13' 13' - 17' 17' - 19' Brown silty organics * Tan silty gravel - 2~square feet per bedroom B~rown gravelly sand with some Occasional boulders. square feet per bedroom silt. Interstratified clean sand and silty sand - SW-SM ¢20~ square feet per bedroom Gray sand and gravel with some silt (09) square feet per bedroom No water Boring 3 - NE corner of Lot 1, Block 3 0 -2' 2' - 10' 10' - i5' 15' - 20' Topsoil - brown silty organics · Gray ,silty sandy gravel With boulders below 7 feet square feet per bedroom ~Xyl silty sand with laye~:s of clean water sorted - Tquare feet per bedroom gravel Gray silty sandy gravel ~190 s~uare feet per bedroom No water · Boring 4 - SE Side of Lot 4, Block 3 0 - 2' Topsoil - silty organics 2' - 8. 5' Gravelly silt to silty gravel interstratified with layers and pods of clean gravel - 250 square feet./)er bedroom 8.5' - 12' Bt'own silty gravel with boulders - 250 square feet per bedroom No water Boring 5 - N Lot line, Lot 6, Block 3 0 - 2' Topsoil Silty sandy gravel with boulders below 7 feet. 240 square feet per bedroom i] 9' -17' Interstratified gravel and silt - glaciofluvial deposition 250 square feet per bedroom & No water Bor~n~ 6 - W. Lot Line, Lot 3, Block 5 0 -1.5' 1.$' - 14' Topsoil - brown silt with organics - pauly eolian, Clean gravel - 125 square feet per bedroom No water Boring 7 - N. Lot Line, Lot 8, Blcok 4 O- 2' TopSoil - eOlian Silt with organics 2' - 6.' Slightly silty gravel - 225 square feet per bedroom 6' - 8' Clean water-sorted gravel - 85 square feet per bedroom 8' - 14' Silty sandy gravel - 225 square feet pe~ bedroom. No water Boring.8 - S. properLy line near center of property. 0 - 1' Silty topsoil 1' - 15' Interstratffied well-graded and poorly graded gravel - 100 square feet per bedroom. No water Boring 9 - Lot 2, Block 5 0 - 1.8' Silty topsoil 1.8' - 14' Silty, sandy gravel - 250 square feet per bedroom. No water As shown in th'e above boring logs, the material changes dramatically throughout the site. Generally, however, the permeability is good and well suited to on-site sewage disposal. The foundation materials have excellent density and ] 1 ] will provide excellent foundation support. We caution, however, that normal precautions must be taken to prevent frost heave in these moderately'frost-sus- ceptible materials. CONCLUSIONS AND RECOMMENDATIONS On the basis of geological and soils data compiled and analysed in this investigation, we conclude that the site is well-suited to the proposed develop- ment, The generous lot sizes are adequate for on~site sewage disposal utilizing septic tanks and seepage pits or drain fields. We further conclude that seepage An average figure would range area requirements will vary from place to place. from 220 to 230 square feet per bedroom. Respectfully submitted, ALP/SKA GEOLOGICAL CONSULTANTS Harold J. Moening Engineering Geologist RONALD L. THIEL, P.E. CONSULTING ENGINEER 519 WEST EIGHTH AVENUE ANCHORAGE, ALASKA 9950t (907} 279,6508 August 24, 1972 ~r. Roll Strickland Dept. of Environmental Quality 3500 Tudor Road Anchorage, Alaska Re: ROBIN HILL SUBDIVISION SOILS CLASSIFICATION Dear Roll: The owner, .~Ir. John Knapp, requested my services in conducting a field investigation on locating test pits and writing a cursory report con- cerning the feasibility of "on site" sewage facilities for the Proposed Robin Hill Subdivision. This proposed subdivision is heavily timbered with large spruce and birch trees throughout plus many windfalls from ages past which offered ~ somewhat of a problem in providing easy access for a tracked backhoe. ConsequeB~ly,~the test pits were confined to the cleared centerline and natural paths which were no2;too preval~nt~ The results of the four test pits show a varied subsoil which is indica- tive of glacial activity and deposition. In general, the northeastern corner as depicted by test pit #1 shows a glacial till with several gravel pockets and lenses of 3 to 4 feet in thickness which allow adequate drainage. The southeastern corner as depicted by test pit #2 shows glacial till and water table without the gravel presents. The southwestern corner as depicted by test pit #3 and cut bank #4 showscan excellant gravel pit and ridge extending essentiall~ throughout lots 3 &.4, block 4 and lot 3, bl~ck S. The northwestern corner as depicted by test pit #5 shows glacial till with rare gravel deposits occurring. Since the~e lots are extremely large in size and far exceeds any zoning or other sizing regulations it is not felt that water and sewer location restrictions should be recommended at this time. It is highly improbable that the location of ones facilities w~ll preclude the neighboring lots practical development. The reco~nendation of the development of this subdivision is two-fold in nature. Firstly, each lot should be extensively investigated by the owner in order to locate the natural occuring gravel deposits for obtRining the highest perculation rate. Secondly, in the areas where the soils clsssification exceeds 250 s.f. a specially engineered absorption system is feasible for on site facilities. The absorption systems as mentioned hy the ~'Manual of Septic-tank Practice" by the U.S. Dept. of Health, Education, and Welfare are recommended for soils ranging between 250 s.f. to 330 s.f. and 30 min. for one inch to 60 min. for one inch perculation rate respectively, In summary, this subdivision will support ~'JOn site" sewage facilities (2) in the form of seepage pits where the 250 s.f. soils classification is not exceeded and absorption systems specially engineered where the soils exceed 250 s.f. but less than 300 s.f. In no instance did the test pits exhibit materials with a 300 s.f. classification. Thank you. Sincerely, R~nal~d L. Thiel, P.E. c, John Knapp ~.~--~GREATER ANCHORAGE AREA BOROUGh HEALTH DEPARTME}tT '?:'_~J 327 EAGLE STREET ANCHORAGE~ ALASKA 99501 Performed For Date Performed This Fo~m Depth -- · .Fee~ Soil Cha~acte~s~c~ ' Location Sketch' :° Was Ground Wa~e~ Encoun~e~od? If Ya$~ At. What d' Rea Net Time Proposed Instsl~Seepage !,. J,,; D;pth T H20' o Net Drop' Drain Field Dep%h Of Inlet Depth To Bottom. b~ CO,qMENTS .~ ............. ~--~REAt~R A~CHORaGE AR~A BORO.UG~ HEALTH DEPARTHENT ~_~.~ 327 EAGLE STREET ANCHORAGE~ ALASKA 99501 Performed For Legal DescriptOr This Fo~m Repo~s · Depth Feet Soil Characteristics' Date Performed Location Sketch''' Was Gx, ound Water Encountered? ~o' tf Yes~ At What Depth Readlng Date Gross Time ~ t T{ ' _- , ,, ',~. . { . e_ -_me Depth To Net Drop Proposed ~nstall~ion: Seepage Pit Drain Field Dep%h Of In!at ' Depth To Bottom Of Pit Or T~enc~ : ............ ~.,,~.~..._ - . . ... ...:: .. .... . ..... ,..... . .. . . . ~9~zlIled By,__ _ _ · "~ "'" ' .... "<" '" ..... ~' "' ...... ' .~-~GRE^TER ANCHORAGE AREA BOROUghs-N HEALTH DEPART}lENT '~\_.) 32? EAGLE STREET ANCHORAGE~ ALASKA 99501 .Depth Feet Performed For Leg~l Descrip~ion':"L0'~ "'BlOck This Fo~m Reports a: So~--~Log .~ Soil Characteris~ic'~' Readlng Date Date Performed Subdlv~slon - ' ' ' -:~lo~iio~ '~s~- .... '" Location Sketch''' Was G~ound Wa~em Encoun-~emed? ~ ~ ~f Ye$~ A~ Wha~ Depth '. ,' ~ Proposed '? ~nstall~t~on: Seepage PiZ - L D~p ' O' th To H2 Net Drop' Dra'in Field ~--~ GREATER A~tCHORAGE AREA BOROU~,~' HEALIH DEPAF. TME~T 'f~_.) CASE ~) 327 EAGLE STREET A~CHORAGE, ALASKA 99501 Pepform~d For Date P~fo~med ~', ~, ~ '~ Legal De~e~ptxon: Lo~ Block~ St~dkv~s~on - "' This Fo~ Reoo~ts a~ S~Log ~e~colation 'f~st .Feet Sox_ Cha~acterxst~c~ ': Location Sketch' ~' '~..' Was Ground WatEr Encountered? ...... ~o J. if Yes~ At What Depths___ Reading Date Cross Tims Net Time Proposed Insta~l~Seepage Pit DP~in Field D~p%h Of Inl~t~ ~--~6~t~a'r~R ANCHORAGE AREA BOROU~G~ HEALTH DEPARTHENT 327 EAGLE STREET ANCHORAGE~ ALASKA 99501 CASE Performed For Legal Descmip~tion: Lo? This Form R~porrs a: Soz~Log ..... . Depth Feet Soil Characteristics ' L. '- -' . : ' : '''h~' Date Performed 'VP~ol~'tioh Tes~ '' Location Sketch''' Was Ground WaTe~ Encountered? If Yes~ At Wha~ Depth__ Reading Date Gross Time Net Time Proposed 'Instal~Seepage Pit Deplh Of Inlet ........ ~ ..... ' Dep~ To B~ttom. COMMENTS~ DePth To H20' D~ain Ffeld 'Of Pf~ Or 1 /TC,'~.?;; v i