HomeMy WebLinkAboutDAWN VILLAGE S-4053S10
DEPARTI'~ ,,~T OF HEALTH AND ENVIRONMENTAL P~,JTECTION
PLATTING OR PLANNING AND ZONING CASE REVIEW
PETITION FOR Rezoning
Special Exception
Date Received
Comment to Planning by
for meeting of
of Cases
HARDING--LAWSON ASSOCIATES
127 West Flreweerl Lane, Anchorage, Alaska 99503 · (907} 279-7011
En. gineers, Geologists and Geophysicists
JaY M. ENGLAND
Proresslonal Engineer
Assoclate4n-Charge
DUANE' g MILLER
Profosslonel Engineer
Chief Engineer
March 1, 1976
5552,001.08
Unwin, Scheben & Korynta
Civil Engineers
103 E. 26th Avenue
Anchorage, Alaska 99503
Attention: Mr. Earl Korynta, P.E.
Gentlemen:
Soils Engineering Services
Pederson Subdivision
INTRODUCTION
This .report presents the results of the soils engineering
services we provided for Pederson Subdivision, Anchorage, Alaska.
The subdivision consists of a five-acre, undeveloped tract located
on the north side of east 68th Avenue about one-quarter mile east
of Lake Otis Parkway. The proposed development will consist of
about 17 single-family, residential lots served by a cul-de-sac
street down the center of the tract. The scope of our work was to
log and sample test borings, to perfor~ laboratory tests and to
describe and classify the soil conditions encountered in the borings.
INVESTIGATION
To investigate the site, five test borings were drilled at the
locations sheen on Plate 1. The borings were drilled to depths rang-
ing from 15 to 30 feet use a track-mounted, hydraulic-rotary drill rig.
The number and depths of the test holes and the locations were determ-
ined and staked by ~nwin, Scheben and Korynta.
Our field engineer was present during drilling to direct the work
and to log and sample the borings. Undisturbed samples of representa-
tive materials were obtained ~qith ai~3-inch (outside diameter), split
spoon sampler driven with a 140-pound hammer falling 30 inches. Blows
required to drive ~he sampler were converted to "equivalent standard
penetration blow counts" for correlation with emperical test data.
The Logs of the Borings are presented on Plates 2 through 4 and include
a description of the soil and ground water conditions, sample depths
and converted bl~,~ counts. The soils are classified in accordance with
the Unified Soil Classification System explained on Plate 5.
S 4 0 5 .'5 I,,,1AY 1 8 1976
Unwin, Scheben & Korynta
March 1, 1976
Page 2
HARDIHO--LAWSON A~SOCIATE~ '
In our laboratory, the soil samples were tested to determine
their moisture content, dry density and grain size. The moisture
Content and dry density test results are presented on the logs in
the manner described by the Key to Test Data on Plate 5. Detailed
results of the particle size analysis are presented on Plate 6.
SITE AND SOIL CONDITIONS
The proposed subdivision is a rectangular shaped parcel about
626-feet-long in a north-south direction and about 330-feet-wide.
The property slopes do%~n to the north at about three percent gradient
and has little relief, except at the north end where the surface is
somewhat hummocky. About half the site contains a growth of spruce
and birch trees. The remainder of the site has been cleared and is
generally, free of vegetation, except for grass and shrubs. The brush
and trees from the previous clearing have been piled in mounds up
to ten-feat-high in the center of the site.
The test borings indicate that the site is underlain by silty,
sandy and gravelly soils to the depths explored. The surface is
blanketed by a layer of silt which range from four to seven-feet-
deep. In Boring 5, the Silt is overlain by a two-foot-thick layer of
peat. The silt and'peat are weak and compressible and are highly frost
susceptible.(*) Beneath ~ese surface soils, sands and gravels were
encountered to the bottom of the borings. These soils are medium dense
to dense and will provide satisfactory support for streets, utilities
and building foundations where unfrozen. However, these granular soils
contain a relatively high percentage of fines (,No. 200 sieve size
materials) and are also frost susceptible.
In Boring 5, the soils were frozen belo~ adept]{ of 15 feet.
The undisturbed sample driven at the 15 feet depth contained clear ice
nodules and lenses up to 1/4-inch-thick in the sample. The soils appear-
ed to be marginally frozen do~ to at least 24-feet below the surface
with possibly some interbedding of dry unfrozen soil. Thes~ deeper,
frozen soils are probably a remnant of the past when the climate was
colder and do not thaw on an annual cycle. Since these soils are
'very likely close to thawing temperatures, they should be considered
highly unstable. The extent of this frozen layer should be determined
by additional test borings.
At the time of our investigation, the ground surface was covered
by about one-foot of snow and the annual frost had penetrated to depths
ranging from three to six feet. Ground water was encountered in Boring
5 at a depth of nine feet.
Frost susceptibl-~means that the soils will support the capillary
rise of water and may develop ice-lansing and subsequent ground
heaving if free water is present and the soils are subjected to
freezing temperatures.
Unwin, Scheben & Korynta.
March 1, 1976
Page 8
HARDING --LAWSON ASSOCIATES
ILLUSTRATIONS
The following plates are attached and complete this report2
Boring 'Location Plan
Plate 1
Plates 2
through 4
Plate 5
Plate 6
Logs of Borings
Soil Classification Chart ~nd Key to Test Date.
Particle Size Analysis
Yours very truly,
I{ARDI~';G-LAWSON ASSOCIATES
/'Jay M. England ~
Civil Engineer 1943E
~4E: cs
Attachments
Test Hole.
by others
SCALE: 1"=100'
Contour
Interval = 2'
160
Brush S.
Stockpiles
170
68th Avenue
Reference: Topographic Survey by Unwin, Scheben & ]',o'ryn'ta,
Civil Engineers '
c'2~%~.'~i~J<~-L~%V/~O~'~%~.~OO{~7~ BORING LOCATION PLAI,I PLATe
G Co~uI~(n~7 ~.;{~eer# ~d Geo~o~Ti~ PEDERSON SUBDIVIS ION
Anchorage, Alaska
JobNo. 5552.nn'1_..98 appr Date 2/.76
-- ~'~ o c Equipment Six-inch Flight Auger
n~ n ~ Elevation 170 feet* Date 2-18-76
0.-
LIGHT BROWN SANDY SILT (ML)
slightly organic, (frozqn)
.... wet at 5'
6'3.5% passing 29.7 - 5
i~200 sieve
BROWN SILTY SAND (SD4)
'' with a few gravel sizes, medium
dense, moist
9.2 - ]
BROWN SILTY GRAVELLY SAND '(S.'4)
m~dium dense, moist,gravel sizes
to ' " 2,
6.3 - 15' color change to gray at 15'
~'; No free water encountered
' ' *Interpolated from topographic
surveY.LoG OF BORING 2
Equipmen't 3-3/8"I .D. Ilollow St6m
~uqor
Elevc~tlon~ Date 2-I 9-7 6
O-
BROWN SANDY SILT (ML)
with organic material, (frozen
with ice lansing)
GF~AY-BROWN SILTY SAMDY GRAVEL(G~4.)
SIEVE ANALYSIS 10 8.4) 1322 medium dense, moist, gravel size
41.4% passing to 1".
#200 sieve
(easier drilling at 7')
]0 dense at 10'
35 8.0 -
(harder drilling at 14')
~5
30 7.8 133
No free water observed
:~ARDING-LAV/soN ASSOCIATES LO0 OF BORINGS 1 & 2 PLAT,."'
PEDERSON SUBDIVISION
Anchorage, Alaska
Job No._5.5_52-_091_..0_8 Appr:_.~,.'~ Date__2_/76 ,
Laborolon/.Tests
61.8% passing
~200 sieve
,0.
5.
28
10-
14 7.1 144
15-
15 5.6 145
S I l']Vi". A[IALYS IS
32.6% passing
~200 sieve
5
40 ' 7.3 125
10
50 6.0'.131
44 7.3 122 ]5
· [-:;~,-~.DING- I-^%~/SON ASSOCIATES
Co~sMting A'ngln'cers a*~d Geologists
i:Jab N0._5._5_5..2__-_0__0..-!_;_0_.8. Appr:_.~L'~_..Oate 2-76
L~G OF BO!:1!;:; .~
Equipment 3 3/8" I.D. llollow Stem
AuJ~ar_
EleVation 154 feet Date2-19-76
LIGIIT BROWN PEATY SILT (ML)
(frozen) :
less organic material' and a f:ew
gravel.sizes at 3'
GRAY-BROWN'GRAVELLY SILTY SAND
' (s,'i)'. ' ' ·
medium dense, moist
"color change to qray at 10' '
gravel sizes 'to 3"
easier drilling at 15'
]:,to free water observed
LOG OF BORI.~iG 4
· Equipmanf3 3/8"I.D. Hollow .~tem
,~calfcn:
ElevaHon 166 feat Date 2-1'9-'16
LIGHT BROW~I SA~;DY SILT (ML)
(frozen)
BROWN GRAVELLY SILTY
dense, moist
color change to gray at 10'
increasing qravel content ak 13'/
Mo free water observed ,'~
LOG. OF no~z~.:G 3 & 4 PLATE
P~Rso>~ sU~D~v~q zo:~ ~h
Anchorage, Alaska (5* ,
Laboratory Tests
· ~ ILVE A:iALYSIS
118.9% passing
'~!200 .~ieve
23 5.3
.F 75
' C
8.8 133
18.3 15.
7~7
40
6.0 141.
48 7.2
75 7.7
4C
! J '.L~ J":O ..?.r.-'.?_-2_-0 ~_]:_'08 .... Appr:~4;~(." Date ,. 2/76
BROWN PEAT (Pt)
(frozen) " :
13R~WN SANDY SILT (.,'.'%~,)'
with organic material and
occasional ,gravel sizes
GRAY-BROWN GRAVELLY SILTY SAND
(st4)
medi~un dense,. damp with occa-
sionai pockets of clean,
coarse sand.
V Water.level .2-19-76
.e.asier 'drilling. at 14
frozen at 15' ,.qith segro?ated
clear ice vibible.to 1/~%"
·
diameter
ice crystals vi.,~ible' in auqer
cuttings from 15 to 24'
ha~d drilling at 24'
GP~Y SA[ID (SP~
dense, wet ~ith occasional
gravel sizes
Note:
?he frozen soils belo'.¢
15' are relatively :.;arm
(31.5 to 32°) :~ith a.
high percentage of the
pore water unfro::en.
LOG' OF BORING.5 r~,~ ~,,,:..,,,, .... :
PEDEqSO"I ~U3D!VI,q I,q:I
Anchorage, ,Alaska
LIAd03 DiVI=~0;',I3
GRAVELS
· ~'~: FO~LY G~A~D G~AV~LS, G~VEL - SAND
WI~ LITTLE ~ ....
~AND~ NO FINES ~P " ?O0~LY GRADED SANDS~ G~V~LLY ~NO$
~C C~Y[Y SANDS, POLLY G~D:D ~AND - ~y
' c~v S~LTS
S I LTg AN D C LA Y ~ IN~GANIC C~ OF L~ 10 ~:DIUM F~CI~
~ L~ ~S/l~
SILTS AND CLAY~
HIGHLY OROANIC SOILS
UNIFIED S01L C!,.A$$1FICATION SYST,E'.[',I '
eta 320 (2600)
TxC:u 320 (2600)
os 27~0 (;ooo)
FVS 470
*UC 2000
LV$ 700
Sheer S reno h, p~f
Conlel~ Conlolldetlon
LL -- Liquid Limit (in %)
PL -- Flottle Limit (In %)
SA --' Sieve Anelylll
[] "Undllturbed' Sample
{2) ' Indlallel 1.4' dlemetce Bempla.
KF.Y TO
Co~ls,ltbl~ E,#i,cers a~zd Geolo#ists
~Jnb~o. 5552-001.0B ^p~r: . Da~e 2/76
TEST DATA
SOIL CLASSIFICATION CF. AP, T
AND
KEY TO TES:T DATA
U.$.Stondord S;eve Opening Size
U.S. Sfondord Sieve Numbors I H)ldromolef
810 16,2030~;05050 I00 200Z70
I0
5 I 0.5
GRAIN SIZE IN MILLIMETERS
I GRAVEL I SANO
CODDLES COARSE I FINE COA RSE~ MEDIUM I FINE
QOI QO05
SILT OR CLAY
S:/mbol Sample Source ' Classification
BORING 2;
BORING 4 ,
BORI:{G 5 ,
Co~s~,lti~ E,~i~¢ers aud G¢olo~ists
Jot) Ho. 5_5 5 2 - 0 01.0 8
__ Appr:~/.."- 'Date 2/7_6
SANDY, SILTY GRAVEL (G;~)
GRAVELLY, SILTY SAND (S:4)
GRAVELLY, SILTY SAND
PARTICLE SIZE A~:ALYSIS
PEDERSON SUBDIVISION
Anchora .qe, Alaska
PLAT=2