HomeMy WebLinkAboutDEBORA General Information►,J �CsCG
\.,UTdI nfNa JA cc n
DATE,
TO3
FROM
Municipality
November 20, 1975
of Anchorage
MEMORANDUM
Rolf Strickland, R.S., Chief Sanitarian
Environmental Control Officer
File No.: 4-1
SUBJECT, Deborah Subdivision (Original and 1st Addition)
Epidemiological Study
The survey area is located in Eagle River between the Old and New Glenn Highways.
After giving the results a preliminary review, it was apparent that a detailed report
on the findings was not needed.
As in the other studies, a door-to-door survey was conducted. If the home owner
could not be contacted, he was provided with a survey to mail back to the Department.
Unlike the previous studies, a revised survey was utilized which was designed to
provide more accurate information on the type of on-site system in use and the history
of system upgrades (see attached survey).
The survey statistics are as follows:
Number Delivered:
34
Number Returned:
20
Percentage Returned:
59
The operational data and survival curve calculations drawn from the survey findings,
Tables I and II, respectively, are not indicative of an area having serious on-site
sewage problems. While admitting the sample was small, the data suggests that over
80% of the on-site systems installed in the survey area should operate satisfactorily
(survive) into their tenth year of operation. A rough survival curve was con-
structed from the available data (see Figure I). however, the validity of the curve
is questionable because of the scattering of data points (i.e. , the result shown for
the 10 - 12 year time interval) .
Premature failure is not suggested by the age data for those systems which did fail.
Only one of the six failures occurred within the 0-3 year time interval.
The location and present operating status of each system covered by survey is given
In Figure 2. Development in the area is such that many of the systems are situated
on a lot adjacent to the lot on which the actual residence is located. This multiple
lot ownership has reduced the overall density of development in the subdivision.
The system shown in Figure 1, which is presently failing, serves the two trailers
owned by Mrs. Strain (lots 15 and 16, Original) . There was evidence of failure
the day the survey was taken. Failures have occurred on adjacent lots, but they
have operated satisfactorily after upgrading.
r-' n
Rolf Strickland, R.S.
Deborah Subdivision
Page Two
November 20, 1975
It appears from the results of the survey that the Strain case is an isolated problem.
Continual system failure can generally be attributed to either the design of the septic
tank system itself or to natural conditions. Soil conditions are the most critical
natural factor affecting the operation of septic tank systems. Subsurface soils in
the survey area contain large amounts of clean sand and gravel, which display good
drainage and percolation characteristics. This leaves only the question of system
design and capacity, and it is difficult to determine from the records what is actually
in the ground. According to Mr. Herman (elder) , the system consists of a single
septic tank and crib.
In closing, the on-site sewage disposal systems serving this portion of Deborah
Subdivision are, by and large, working satisfactorily. The major reason for this
being the presence of good soils. In four instances (see Figure 2) the comments
made by respondents suggested that the system in use was either a cesspool or
holding tank.
—4,
Lawrence A. Jones
V
Environmental Control Officer
LAJ/lw
Attachment
TABLE I !^ n
t"� ?-�
OPERATIONAL DATA FOR DEBORAH SURVEY AREA
to- la
a
3
13-15
O
1
OVER 15
O
O
S
S 1 O
LU
J
m
Q
F-
n r�
FIGURE 1
loo
5o
to
10
6o
SURVIVAL CURVE FOR DEBORAH SURVEY AREA
i
5�
o -a �1-ti �-y 10-1a
Tim — Ap Intvvol (Veers)
13-15
OVER IS
y
C1
y r
cn -n RIS iD
ti o
o
cf
to
JI
O
p . f. f ;O o! 1..
_I•
10:
_I q
r
C)
C-)
22;
0
z
-1
0
m
..
0
c
N
O
-f1
N
•N -I
3
N
z
0
m
00
0
N
c
{
m
ri
.I
V
0
_
�
_ I W
I
� IIC11 rz.
'
O 3
two
Ln
00 I
t !
O I orb
w �;
_(D
,n
� , I
u)
-
�_�
_
� !R/S rv.a✓
W I
y
C1
y r
cn -n RIS iD
ti o
o
cf
to
JI
O
p . f. f ;O o! 1..
_I•
10:
_I q
r
C)
C-)
22;
0
z
-1
0
m
..
0
c
N
O
-f1
N
•N -I
3
N
z
0
m
00
0
N
c
{
m
ri
r-(, P-)
u
MUNICIPALITY OF ANCHORAGE
POUCH 6-650 ANCHORAGE. ALASKA 99502
ON-SITE SEWAGE DISPOSAL OPERATIONAL SURVEY
This survey attempts to measure the operating success of septic -tank sewage
disposal systems in the surveyed area.
A septic tank is considered to have failed if sewage daylights (appears) on the
surface of the ground. This indicates that the drain field is not absorbing the
sewage properly. A failure can either be complete, meaning the sewage continues
to accumulate on the surface for a long period of time, or periodic, meaning failure
occurs periodically followed by reabsorbtion. In addtion, having to pump a system
more than once a year also constitutes a failure.
1. Location of home (legal description, if known).
2. Number of bedrooms.
3. Type if system in use:
a Septic tank with trench or seepage pit.
b Septic tank with drain field.
(c) Cesspool or seepage pit without septic tank.
4. Is the existing system the original unmodified system (i.e. there has been no new
septic tank or seepage area installed)? •
Yes No Doesn't Know
5. When was the original system installed? Year
6. If the system has been modified, in what year(s) was it done (a) and what was
done (b)?
(a) Year(s) (b) 1. New septic tank installed
2. New trench or drain field instaT-ed
I
November 20. 1015
Rolf Strickland. R.S.. Chief Sanitarian
Environmental Control OMaer
rile No.: 4-1
Deborah Subdivision (Original and lat . Addition)
EpidEsaiological Study
The survey area in located In Eagle River between the Old and liew Clens highways.
After giving the results a preliminary "view. it was apparent that a detailed report
on the Finding was not needed.
As in the other studies. a door-to-door survey was eoodueted. tf the home owner
could not be contacted he was provided with a survey to mail book to the Departm"U.
UnUkc the previous studies, a revised surrey was utilised which was designed to
provide more ooeurate isAwmotion on the type of on -mita srsten• in use and the history.
of system upgrades (see attached survey).
The survey statistics are as follows:
Number Delivered: 34
Number Returned: 20
Pereentage Retuirneds St
The operational data and survival curve calculations drawn from the survey findings.
Tables I and li, rospectieety, are riot bndieative of sn area having serious on-site
sewage problems. While admitting the sample was small, the data suggests that over '
80% of the on-site systema installed in the survey area should operate satisfactorily
(survive) Into their tenth year of operation. A rough survival curve was ean-
strueted from the available data (aa Figure I). however, the validity of the curve
Is questionable because of the scattering of data pob to (i.e., the result shown for
the 10 - li year time Interval).
Premature failure is not suggested by the ago data for these systems whirls did fail.
Only one of the six failures occurred within the 0-2 year time interval.
The location end present operating states of saeb system covered by survey to gives
in Figure 2. Development in the urea Is such that many of the systems are situated
on a lot sdjaee d to the lot on which the actual residence is located. This multiple
let ownership has reduced the overall density of development in the subdivision. ;
The system shown In Figure 1 a which Is presently failing, serves the two trailers
owned by Mrs. Strata (lots 19 and li. Original). There was evidence of failure
the day the survey was talon. • Failures have occurred an adjoeout lots, but they .
have operated satis4ctotily after npgradtng.
Rolf Strickland. R. S.
Dotorah Subdivision
Page Two
lfovember 20. 1915
It appears from the rasults of the avrvey that the Strain caso is en isolated problem.
Continual system failure can generally be attributed to either the design of the septic
tank system itself or to natural condition. Soil oonditiona are the most critical
natural factor affecting tha operation of septic tank s=ystems. Subsurface Boils In
tho survey area eontnin large amounts of clean sand and gravel, which display good
drainage and percolation eharactertattes. This leavee only the question of system
design and capacity, and it is difficult to determine from the records what is schmIly
In the ground. According to Mr. Herman (elder), the system consists of a single
septic tank and crib.
In closing. the on-site sewage disposal systems serving this portion of Deborwh
Subeivision are, by and large, working satisfactorily. The major reason for this
being the presence of good soils. In four Instances (see Figure 2) the comments
made by respondents suggested that the system in ase was either a cesspool or
holding tank.
Lawrence A. Jones
Environmental Control officer
LAJ/lw
Attachment