HomeMy WebLinkAboutSYLEA S12421Onsite File
�.r
May 8, 2018
Municipality of Anchorage
Building Safety Division
On Site Water and Wastewater Program
4700 Elmore Street
Anchorage, AK 99507
Attention: Deb Wockenfuss
Subject: Sylea Subdivision — 512421
Septic System Feasibility and Water Availability Study
Dear Debbie:
A petition has been submitted to subdivide one parcel and an additional lot into five lots, forming
the new Sylea Subdivision. We our presenting our findings that each new lot will have sufficient
area and potential for on-site wells and septic systems.
The property in general is moderately sloped towards the north, at times towards slight depressions
in the properties, at grades ranging from I% up to around 10%. There are a few small bluffs of 6-
12' high that slope steeper, between 25-60%. Property sizes are all over 40,000 SF each, and the
attached site plan demonstrates that there is enough space available to meet separation
requirements for the future septic systems.
Test holes were dug in early February of 2018. Two test holes were placed on each property in
areas that seemed appropriate for septic locations. Monitoring tubes were placed in the test holes
and groundwater checked on March 6th, over a week after the last hole was excavated. The test
holes were dug down to 15'-18' in most areas. Groundwater was encountered in all of the test
holes, typically between 6'-12. The water levels were measured at the seasonal high and recorded
on the test hole logs. Soils were fairly uniform in the area, consisting mostly of gravelly and silty
sands (SP/SW). Percolation benches were constructed between 4-6' below the ground surface in
each test hole. The percolation cavity in each bench was prepared and presoaked in accordance
with municipal requirements. Again, results were very uniform in the area, with almost all perk
tests results falling under 5 min/in. One test was just over 5 min/in, and another was an outlier at
24 min/in. Individual test results are including in the attached test hole information.
Lot 19A is a special case in terms of the soils on the lot. Our test holes indicted that the soils were
primarily fill down 10'-14'. We were able to identify them as such due to the noticeable difference
from the soils in the rest of the subdivision. Additionally, there were organics mixed into the soils-
not enough to indicate a refuse or disposal pit, but an amount indicating that the area was probably
not completely grubbed from vegetation and small brush when the soils were placed. Finally, there
was a layer of peat underneath that separated it from the underlying layer matching the rest of the
subdivision. Municipal records indicate that this section of the tract was identified as `fill placed
on marsh' in a memo dating to 1984. However, after 35 years, this soil can be considered
consolidated and treated as `in-situ' material. While it may need special engineering to determine
bearing capacity for a foundation, we would like it to be considered acceptable soils for absorption
trenches.
Using the slope and perk test information attached, areas appropriate for septic systems were set
aside for each lot. According to Table 7 of municipal code, perk rates between 1-5 minutes/inch
require 10,000 SF of reserve area. This is appropriate for Lots 16A and 17A. Lot 18A had a test
hole that perked 24 min/in, so 14,000 SF was set aside, and on Lot 19A 12,000 SF was designated.
Nearly all of the septic reserve areas designated are on slopes under 25%. Most of them are greater
than 50' upslope from these steeper slopes, as well. However, there are a few small sections in the
reserve areas where the slopes exceed 25%. Any trench that crosses these small sections will need
to be constructed to meet the "steep slopes" requirements of the code, including vertical separation
distances measured from the up -gradient side of the field; trenches 5' or narrower; natural
vegetation retained or erosion control measures taken; and the distribution pipe placed sufficiently
deep. Under these guidelines, these small sections of steeper slopes are appropriate for
development as septic systems.
All of the existing lots in the area are served by public water, and most of the new lots have access
to water mains. Lots 18A and 19A will not have the possibility of being served by public water,
so potential well locations are indicated on those lots. These locations are 100' away from proposed
septic reserve areas, as well as septic locations on neighboring lots. As all the surrounding lots for
several neighborhoods are on public water, we do not have any good well information to anticipate
well depths and flow rates. However, it is clear that the underlying aquifer is mostly untapped, and
there will be no detrimental effect to drilling two wells for these lots.
Based on our field studies, research, and Nater monitoring completed to date, it is clear that all lots
of the proposed subdivision are capable of supporting new onsite septic systems and wells.
Sincerely,
�"°p,c``�-�
Benjamin Schiller, PE
Benjarrrtchiller
CE 12592
1��'SlF�• 5/1019
4���nd�'ROfESS1fl�� .�
AT DEPTH? 10' L
NITORING: 7' 0
N'ITOI2ING: 5/28/18 P
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
MUNICIPALITY OF ANCHORAGE,9��j��
2/07
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
1:30 - 1:40
DEVELOPMENT SERVICES DEPARTMENT
a�" - �"
116�
co�P4��
' TH
2
4.700
ELMORE ROAD ANCHORAGE, AK 99519-6650
a;�° - s,;�°
;
3
1:52 - 2:02
10
4;�" - �"
116
SOILS
LOG AND PERCOLATION TEST'
10
4,�' - �"
Benla i-
5
2:14 - 2:24
10
4�' - �"
chiller
LEGAL DESCRIPTION: SYLAE SUBDIVISION - LOT
16A
10
�c'pF. °'E °?092 ���2��
��� �PROFESS00
21s
PERFORMED
FOR: TROY DAVIS HOMES
DATE:
02/07/18 PROJECT No.:
Professional Engineers Stamp:
PARCEL ID#: TECHNICIAN:
C. JOHANSEN
DEPTH
TEST HOLE #1
(lixt)
OB
1
.•
SLOPE
SITE PLAN
3
4
5
.,
SEE SITE PLAN
SILTY SAND
6
W/ GRAVEL
7
.
8
9
10
WATER SEEPS WAS GROUND WATER ENCOUNTERED?
IF YES a WH
YES
S
AT I O'
I I
DEPTH OF WA"CER AFTER MO
DATE OF Mo12
13
.
14
15
16
;
14,
17
18
19
20
PERCOLATION
RATE: 5.0 (MIN/INCH) PERC. HOLE DIA. 6 (INCHES)
TEST RUN BETWEEN:
4 FT. and 5
FT.
COMMENTS:
-
AT DEPTH? 10' L
NITORING: 7' 0
N'ITOI2ING: 5/28/18 P
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
2/07
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
1:30 - 1:40
10
a�" - �"
116�
2
1:41 - 1:51
10
a;�° - s,;�°
1 � s"
3
1:52 - 2:02
10
4;�" - �"
116
4
2:03 - 2:13
10
4,�' - �"
216�
5
2:14 - 2:24
10
4�' - �"
216��
6
2:25-2:35
10
ate" -sem"
21s
DEPTH
(feet)
1 -
2
3-
4
5-
6
7
8
9-
10-
11-
12-
13-
14-
15-
16-
17-
18-
19-
20 -
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 ELMORE ROAD ANCHORAGE, AK 99519-6650
SOILS LOG AND PERCOLATION TEST
LEGAL DESCRIPTION: SYLAE SUBDIVISION — LOT 16A
PERFORMED FOR: TROY DAVIS HOMES
DATE: 02/07/18 PROJECT No.:
PARCEL ID#: TECHNICIAN: C. JOHANSEN
TEST HOLE #2
•:
SILTY SAND
W/ GRAVEL
5
COMMENTS: --
WATER SEEPS
AT 8
•'i
SITE PLAN
SEE SITE PLAN p
WAS GROUND WATER ENCOUNTERED?
YES
GROSS TIME
(MINUTES)
IF YES a, WHAT DEPTH?
8'
L
2/07
DEPTH OF WATER AFTER MONITORING:
6'
0
11:10/11:16
DATE OF MONITORING:
5/28/18
P
2
11:17/11:24
E
4,' - 104g"
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
2/07
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
11:10/11:16
6:15
4, - 10-x"
6-01,
2
11:17/11:24
6:23
4,' - 104g"
6,0 "
3
11:25/11:32
6:22
4-,W" - 101-8g"
6-,Og"
4
11:33/11:40
6:47
4�g' - 104g"
*1
5
11:41/11:48
6:47
4 -,W" -104g"
4"
6
11:49/11:56
6:47
4-,W" - 1 Ct,8"
�"
PERCOLATION RATE: 1.1 (MIN/INCH) PERC. HOLE DIA. 6 (INCHES)
TEST RUN BETWEEN: 3 FT. and 4 FT.
DEPTH
(Feet)
1-
2-
3-
4-
5-
6-
7
8
9-
10-
11-
12-
13-
14-
15-
16-
17-
18-
19-
20 -
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 ELMORE ROAD ANCHORAGE, AK 99519-6650
SOILS LOG AND PERCOLATION TEST
LEGAL DESCRIPTION: SYLAE SUBDIVISION — LOT 17A
PERFORMED FOR: TROY DAVIS HOMES
DATE: 02/07/18 PROJECT No.:
PARCEL ID#: TECHNICIAN
TEST HOLE #1
•:
SILTY SAND W/ GRAVEL
f • GETS SILTIER W/ DEPTH
i
C. JOHANSEN
SITE PLAN
SEE SITE PLAN
COMMENTS: --
DATE
READING
WAS GROUND WATER ENCOUN"PERED?
NO
DEPTH TO
WATER
(INCHES)
NET DROP
(INCHES)
2/08
IF YES a, WIIAT DEPTH?
NONE
L
10:11/10:21
•
419 - 10 6"
DEPTH OF WATER AFTER MONITORING:
8'
0
10:22/10:32
10
41°-6
DATE OF MONITORING:
5/28/18
P
10:33/10:43
10
41'-100,,
53^
s
4
10:44/10:54
COMMENTS: --
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH TO
WATER
(INCHES)
NET DROP
(INCHES)
2/08
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
10:11/10:21
10
419 - 10 6"
2
10:22/10:32
10
41°-6
6
3
10:33/10:43
10
41'-100,,
53^
s
4
10:44/10:54
10
416" - 914e,
5r 6
5
10:55/11:05
10
41s" his"
51-4"
s
6
11:06/11:16
10
476„ Q4"
5i4"
1s
PERCOLATION RATE: 1.8 (MIN/INCH) FERC. HOLE DIA. 6 CINCHES)
TEST RUN BETWEEN: 4 FT. and 5 FT.
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700
ELMORE ROAD ANCHORAGE, AK 99519-6650
A <~s 4.
SOILS LOG AND PERCOLATION TEST"
Benlarryn•5chluer
-,q
SYLAE SUBDIVISION — LOT 17A
F CE 12592
LEGAL DESCRIPTION:
"
PROFES5ONp��®'®
PERFORMED
FOR: TROY DAVIS HOMES
DATE:
02/07/18 PROJECT No.:
Professional Engineers s`an'e:
PARCEL ID#: TECHNICIAN:
C. JOHANSEN
DEPTH
TEST HOLE #2
(feet)
OB
1
SLOPE
SITE PLAN
2
4
5
SEE SITE PLAN
SANDY GRAVEL
6
7
8
9
10
WAS GROUND WATER ENCOUNTERED?
NO
IF YES to WHAT DEPTH?
NONE
1 1
DEPTH OF WATER AF'T'ER MONITORING:
8.5' 0
"
DATE OF MONITORING:
5/28/18 P
E
12
13
t ..,
DATE
READING GROSS TIME NET TIME DEPTH To NET DROP
WATER
.
(MINUTES)
(MINUTES) (INCHES) (INCHES)
14
'
2/08
TEST HOLE PRESOAKED PRIOR TO TESTING:
15
1
12:10!12:20
10 5 8 �°�" 3
16
'
2
12:21/12:31
10 5-0g'-7-'��" 2�s"
3
12:32/12:42
10 5-0g' - 7 2
17
4
12:43/12:53
10 5 7-8g" 2�'
18
5
12:54/1:04
10 5 107" - 7 -186" 2 t6"
19
6
1:05/1:15
10 5 �°�" - 7 �' 276-
20
PERCOLATION
RATE: 4.0
(MINANCH)
PERC. HOLE DIA.�INCHES)
TEST RUN BETWEEN:
4
FT. and
5 FT.
COMMENTS:
-
"
MUNICIPALITY OF ANCHORAGEOF•rt„9���`
DEVELOPMENT SERVICES DEPARTMENT
L,700 ELMORE ROAD ANCHORAGE, AK 99519-6650 11N
SOILS LOG AND PERCOLATION TEST Benjarryr)chiller
CE 42092
19
LEGAL DESCRIPTION: SYLAE SUBDIVISION — LOT 18A ����Fa1'ROfESS10Na���®
PERFORMED FOR: TROY DAVIS HOMES
DATE: 02/08/18 PROJECT No.: Professional Engineers Stamp:
PARCEL ID#: TECHNICIAN: C. JOHANSEN
DEPTH TEST HOLE #1
(feet) OB
1 SLOPE SITE PLAN
3
4
5 .j SEE SITE PLAN
SILTY SAND
6 W/ GRAVEL
7 S"
8
9
1• •
1 O WAS GROUND WATER ENCOUNTERED? YES
IF YES a WHAT DEP"I'H? 12'
1 1
DEPTH OF WATER AFTER MONITORING: 15' 0
DATE OF MONITORING: 5/28/18 P
. E
12 •r ..•r"
.
"
15
16
s
18 `
19
20
PERCOLATION RATE: 18.5 (MIN/INCH) FERC. HOLE DIA.�INCHES)
TEST RUN BETWEEN: 5 FT. and 4 FT.
COMMENTS:
GROSS TIME NET TIME DEPTH To NET DROP
DATE READING (MINUTES) (MINUTES) WATER
13 (INCHES)
(INCHES)
14
2/08
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
1:35
4�'
2
2:35
30
5'�0"
1 �'
3
2:36
0'
4 i6
4
3:06
30
5
is�
5
3:07
0 "
4 is
6
3:37
30
5�'
1110"
,s
DEPTH
(leer)
1 -
2
3
4
5-
6
7
8
9
10-
11-
12-
13-
14-
15-
16-
17-
18-
19-
20 -
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 ELMORE ROAD ANCHORAGE, AK 99519-6650
SOILS LOG AND PERCOLATION TEST
LEGAL DESCRIPTION: SYLAE SUBDIVISION - LOT 18A
PERFORMED FOR: TROY DAVIS HOMES
DATE: 02/08/18 PROJECT No.:
PARCEL ID#: TECHNICIAN: C. JOHANSEN
TEST HOLE 92
E:
SILTY SAND
S
COMMENTS: --
SLOPE
Engineers
SITE PLAN
SEE SITE PLAN
WAS GROUND WATER ENCOUNTERED?
YES
GROSS TIME
(MINUTES)
IF YES @ WHAT DEPTH?
12'
NET DROP
(INCHES)
2/08
DEPTH OF WATER AFTER MONITORING:
14'
0
4:05
DATE OF MONITORING:
5/28/18
P
2
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH TO
WATER
(INCHES)
NET DROP
(INCHES)
2/08
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
4:05
416"
2
4:35
30
516"
116"
3
4:36
416"
4
5:06
30
516"
1 4
5
5:07
4 16'1
6
5:37
30
516"
114"
PERCOLATION RATE: 24.0 (MIN/INCH) FERC. HOLE DIA. --f INCHES)
TEST RUN BETWEEN: 4 FT. and 5 FT.
MUNICIPALITY OF ANCHORAGE
•„A,��a�®
DEVELOPMENT SERVICES DEPARTMENT
4700
ELMORE ROAD ANCHORAGE, AK 99519-6650
SOILS
LOG AND PERCOLATION TESTJBenjamq'Schiller
5
11:51/11:58
6:44
a�'-�o;�°
s�'
6
CE
6:44
a�'-�o�'
s�'
o25a92
19
����F�PROFESSIONp����
LEGAL DESCRIPTION:
SYLAE SUBDIVISION - LOT 19A
PERFORMED
FOR: TROY DAVIS HOMES
DATE:
02/08/18 PROJECT No.:
Proeesslonal r•.,,�sn���s s�� nP:
PARCEL ID#: TECHNICIAN:
C. JOHANSEN
DEPTH
EST HOLE #1
(IEE[)
1
SLOPE
SITE PLAN
+++
+++
+++
+++
+++
3
+++
+++
+ + +
4+
5
+++
++++++4
SEE SITE PLAN
++++++”
SILTY SAND
6
+++FILL
MIXED
++++++4
W/ ORGANICS
7
—,,+++++
+ + +
8
+++
9
+++
+++
10
+++
+ + +
++ +
WAS GROUND WATER ENCOUNTERED?
No
+ + +
IF YES WHAT DEPTH?
NONE
L
1 1
+ + +
DEPTH OF WATER AFTER MONITORING:
15.5'
0
DATE OF MONITORING:
ORIGINAL OB
5/28/18
12
13
r
DATE
READING
GROSS TIME
NET TIME DEPTH To NET DROP
WATER
.
(MINUTES)
(MINUTES) (INCHES) (INCHES)
14
3/09
TEST HOLE PRESOAKED PRIOR TO TESTING:
15
SILTY CLAY
1
11:20/11:26
6:22 a�'-�o,�" s�°
16
2
11:27/11:34
6:30 a�°- �o�' s;�°
3
11:35/11:42
6:30 a�'-�o�° s;�°
17
4
11:43/11:50
6:33 4�'-�o�' s
18
s
`
19
20
PERCOLATION RATE:
1.1 (MIN/INCH)
PERC. HOLE DIA. 6 (INCHES)
TEST RUN BETWEEN:
5 FT. and 6
FT.
COMMENTS:
5
11:51/11:58
6:44
a�'-�o;�°
s�'
6
11:59/12:06
6:44
a�'-�o�'
s�'
DEPTH
(feet)
I-
2
3
4
5
6
7
8
9
10-
11-
12-
13-
14-
15-
16-
17-
18-
19-
20 -
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 ELMORE ROAD ANCHORAGE, AK 99519-6650
SOILS LOG AND PERCOLATION TEST
LEGAL DESCRIPTION: SYLAE SUBDIVISION - LOT 19A
PERFORMED FOR: TROY DAVIS HOMES
DATE: 02/08/18 PROJECT No.:
PARCEL ID#: TECHNICIAN
TEST HOLE 92
COMMENTS: --
PEAT
SILTY CLAY
C. JOHANSEN
SLOPE
SITE PLAN
SEE SITE PLAN p
WAS GROUND WATER ENCOUNTERED?
NO
GROSS TIME
(MINUTES)
IF YES @ WHAT DEPTH?
NONE
S
3/09
DEPTH OF WATER Al -TER MONITORING:
15.5'
Q
12:38/12:48
DATE OF MONITORING:
5/28/18
P
2
12:49/12:59
E
4,6°-7 6°
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
3/09
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
12:38/12:48
10
4$"-a,16
3 8
2
12:49/12:59
10
4,6°-7 6°
3,°�'
3
1:00/1:10
10
4 6"-7,6"
3,°�
4
1:11/1:21
10
4 6" - 7 6"
3'
5
1:22/1:32
10
4 6" 7 6"
3"
6
1:33/1:43
10
476° - 7,78
3,0'
PERCOLATION RATE: 3.3 (MIN/INCH) PERC. HOLE DIA.--L-(INCHES)
TEST RUN BETWEEN: 4 FT. and 5 FT.
oF
9 TH
...........
Benja In Schiller
C 12�92
May
j�o pROFE5510NA`��
APPROXIMATE
SEPTIC LOCATIOI
SYLAE SUBDIVISION - S12421
NOTE:
ALL LOTS AND SURROUNDING PROPERTIES SERVED BY PUBLIC WATER. NO CONFLICTS WITH NEIGHBORING
WELLS OR SEPTIC SYSTEMS.
0 100 200
FEET
1"=100'
i FrFmn
EXISTING SEPTIC SYSTEM
APPROX LOCATION
CALL BEFORE YOU DIG
THE COMRACTOR SHALL -IFY ALL AREA UTILITY COMPANIES
PW OR TO COMMENCEMENT OF EXCAVATION. THE FOLLOW RG
IS A PARTIAL LIST:
ALASKA DIG LINE - 811
LOCATE CALL CENTER OF ALASKA 278-3121
QNCLUD-ACS. AW I CEA. ELIC, BUTLER AVIATI-ESORO,
GCI CABLE, MLP, TRAFFIC SIGNALS. MOA STORM'STREETS,
MCA- FIBER STAR)
STATE STORM,STREET LIGHTS 333-2411
MILITARY PETROLEUM LINES 862-4112
SEPTIC RESERVE AREAS
SLOPES EXCEEDING 25%
APPROX AREAS WHERE SOME SLOPES EXCEED 46%
EXISTING SEPTIC SYSTEM
APPROX LOCATION
CALL BEFORE YOU DIG
THE COMRACTOR SHALL -IFY ALL AREA UTILITY COMPANIES
PW OR TO COMMENCEMENT OF EXCAVATION. THE FOLLOW RG
IS A PARTIAL LIST:
ALASKA DIG LINE - 811
LOCATE CALL CENTER OF ALASKA 278-3121
QNCLUD-ACS. AW I CEA. ELIC, BUTLER AVIATI-ESORO,
GCI CABLE, MLP, TRAFFIC SIGNALS. MOA STORM'STREETS,
MCA- FIBER STAR)
STATE STORM,STREET LIGHTS 333-2411
MILITARY PETROLEUM LINES 862-4112