HomeMy WebLinkAboutOZZIES KNOLL S12540Onsite File
Ozzies Knoll
#S12540
PO BOX 240773
ANCHORAGE, AK 99524
522-7773 677-7766 (FAX)
December 9, 2020
MOA Development Services Department
On-Site Water & Wastewater Program
4700 Elmore Rd
Anchorage, AK 99507
Attention: Debbie Wockenfuss
On Site Services Engineer
Subject: Ozzies Knoll Lot 1A – Proposed Lots 1-A1 and 1-A2
Case No. 12540
Septic Feasibility Study
Dear Debbie:
Three test holes were placed on Lot 1A, Ozzie’s Knoll Subdivision in mid-October of 2019. The
purpose of the test holes was to determine if septic systems could be placed on the lot for a potential
lot split and the development of two lots. Test holes were placed on each proposed lot in areas
that seemed appropriate for septic locations. Monitoring tubes were placed in the test holes and
groundwater monitored over time. The test holes were completed to 15’ to 17’. No bedrock or
impervious soil lenses were encountered in any of the holes. In addition, no groundwater was
encountered at any depth.
Soils were fairly uniform in the area, consisting mostly of silty, sandy gravel with varying amounts
of sand. Percolation benches were constructed between 3.5’-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 perk tests results falling
under 10 minutes per inch. The percolation rate in Test Hole 2E was less than 1 minute per inch.
Individual test results are included on the attached test hole logs.
The property in general consists of a small 10’ high knoll near the center of the property which
slopes gradually to the north and south at grades ranging from 15% up to around 25%. Most of
the area is in the 10-20% range, with a few portions steeper than 25%. Proposed lot sizes are both
greater than 40,000 S.F. each. Surface drainage is primarily to the north and south and toward the
boundaries of the lot. No standing water has been observed on the property and no drainage issues
are present. Septic systems will not be affected by storm water runoff.
A house is currently in place with a septic system and well on Lot 1A-1. The house is scheduled
to be demolished in its entirety and a new home will be built on the lot. The well currently in place
on the lot will serve the new home. A septic system construction permit, OSP201046, has been
issued for a system to serve the new three-bedroom home. That permit requires that the existing
septic system be decommissioned in accordance with the Uniform Plumbing Code.
A septic system reserve area was calculated for Lot 1A-2 based on percolation test data and Table
7 of the Municipal Code. A reserve area of 10,000 S.F. is required for the lot. Nearly all of the
septic reserve area designated are is slopes under 25%, but steeper slopes do occur. All absorption
trenches designed for this subdivision in areas where slopes greater than 25% are less than 50’
away will need to be constructed to meet the steep slope provisions of the Municipal 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 of a septic system.
The development of Lot 1A-1 will be governed by the existing Municipal permit. An alternate
site is also shown on the attached drawing. Sufficient area is available for both the primary and
alternate site as delineated in the design and permit of the new system. The existing system on the
lot will be decommissioned to comply with the design and permit for the new system. The existing
well will remain in service to provide water to the new home.
Sincerely,
Michael E. Anderson, P.E.
Attachments
PO BOX 240773
ANCHORAGE, AK 99524
522-7773 677-7766 (FAX)
December 9, 2020
MOA Development Services Department
On-Site Water & Wastewater Program
4700 Elmore Rd
Anchorage, AK 99507
Attention: Debbie Wockenfuss
On Site Services Engineer
Subject: Ozzies Knoll Lot 1A – Proposed Lots 1-A1 and 1-A2
Case No. 12540
Water Availability Study
Dear Debbie:
We have collected information on several wells in the area of the proposed Ozzies Knoll Lot 1A
Subdivision to estimate the possible depths and production rates of the well to be constructed in
the future on Lot 1A-2. A well is currently in place on Lot 1A-1 which will continue to serve the
house on that lot. Only one well will be required as a result of the subdivision. No information is
available on the existing well, but information from the Municipal archives indicate it is 263’ deep
and was placed in 1962. We assume from information obtained from surrounding lots that the
well is cased the entire depth with a static water level at approximately 240’. The production rate
of the well is estimated at 3-4 gallons per minute. The well has served the house on that lot
adequately since that time.
Field investigations indicate all of the wells in the immediate area were constructed without the
presence of bedrock below the surface. All wells are cased to the bottom of the well. In all cases
the wells produce a sufficient amount of water and range from 65’ to 272’ in depth. The majority
of the wells are at an average depth of 200’. Static water levels in the existing wells vary from 45’
to 250’.
The map completed by the Municipality of Anchorage which details Nitrate levels in well water
in the area of this subdivision indicates low levels may be found in the water. We anticipate levels
ranging from 0-5 milligrams per liter based on data found on the map. Nitrate levels of 5.5
milligrams per liter were found in the well on the lot immediately to the south of this subdivision.
A level of 5.09 milligrams per liter was found on the lot to the northwest. Other lots with reported
Nitrate values are between .30 and 2.10 milligrams per liter.
OZZIES KNOLL SUBDIVISION
WATER AVAILABILITY STUDY
LEGAL
DESCRIPTION
WELL
DEPTH
PRODUCTION -
LOG
PRODUCTION -
TEST
T12N R3W SEC15 L 110 65’ 16 GPM 5+ GPM
Spring Hill Estates, B2,
L17A 157’ 5 GPM 3.6 GPM
Spring Hill Estates, B2,
L18 242’ 10 GPM 6.7 GPM
T12N R3W SEC 15 L111 87’ 14 GPM 2.17 GPM
Forest Creek, L1 272’ 10 GPM 4.7 GPM
Forest Creek, L2 101’ 10 GPM
Forest Creek, L3 80’ 20 GPM 5+ GPM
T12N R3W SEC 15 L111 230’+ 6.6 GPM
Spring Hill Estates, B2,
L16A 221’ 20 GPM 5.8+ GPM
It is obvious from our study that any well to be constructed in Ozzies Knoll Subdivision on Lot
1A-2 in the future will be placed to a depth of nearly 260’ based on the depth of the closest well
and will be cased the full depth. The production rates will be sufficient to support a five-bedroom
home and can be expected to be between 3 and 5 gallons per minute. The well will not affect the
operation or output of the existing wells in the area.
Sincerely,
Michael E. Anderson, PE
12/14/20
100500
FEET
1"=50'
NOTE:
NO SLOPES >25% WITHIN 50' OR SURFACE WATER WITHIN 100' OF THE
PROPOSED SEPTIC SYSTEM
ALL WELLS ON SURROUNDING LOTS WITH IMPACTS TO THIS
PROPERTY ARE SHOWN. NO CONFLICTS WITH WELLS OR SEPTIC
SYSTEMS.
CO - CLEANOUT
2CO - DOUBLE CLEANOUT
FCO - FOUNDATION CLEANOUT
FS - FLOW SPLITTER VALVE
MH - MANHOLE
MT - MONITORING TUBE
SV - SEPTIC VENT
TH - TEST HOLE
LEGEND
TH-A
OZZIES KNOLL, LOT 1A
12/14/20
10' T&E EASEMENT
10' T&E EASEMENT OUR ROADTH2E
TH1W
40' LONG X 2.5' WIDE X 7.5'
EFFECTIVE DEPTH
ABSORPTION TRENCHES
EXISTING SEPTIC SYSTEM
TO BE DECOMMISIONED
UNDER PERMIT NO.
OSP201046.
EXISTING HOUSE TO
BE DEMOLISHED.
EXISTING WELL TO
REMAIN IN SERVICE.
PROPOSED WELL
DEPTH
(feet)
I-
2
3
4
5
6
7
0�,
SOILS LOG AND PERCOLATION TEST
EN G IN EE ft I NG
LEGAL DESCRIPTION: OZZIES KNOLL L IA
PERFORMED FOR: DENISE DEAL
DATE: 10/17/19 PROJECT No.:
PARCELID#: 015-483-17 TECHNICIAN: J. MILLETTE
TEST HOLE A
•
•' SANDY GRAVEL 2" MINUS
WITH SOME SILT
r „ GM
SLOPE
10
'
GROSS TIME
(MINUTES)
WAS GROUND WATER ENCOUNTERED? NO
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
10/17
TEST HOLE PRESOAKED PRIOR TO TESTING:
IF YES rr WHAT DEPTH? -
L
9:29
I I
,
DEPTH TO WATER AFTER MONITORING: NONE
0
9:59
30
,• :
4-1
DATE OF MONITORING: 10/24/19
P
10:01
51fi
E
10:31
12
13
14
15 '
16 ;
17
1
I
2
COMMENTS:
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
10/17
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
9:29
512
2
9:59
30
916
4-1
3
10:01
51fi
4
10:31
30
9A
3�s
5
10:32
512
6
11:02
30
916
316
PERCOLATION RATE: 8.7 (MIN/INCH) PERC. HOLE DIA. 6 (INCHES)
TEST RUN BETWEEN: 5 FT. and 6 FT.
SOILS LOG AND PERCOLATION TEST
ENGINEERING
LEGAL DESCRIPTION: OZZIES KNOLL LIA
PERFORMED FOR: DENISE DEAL
DATE: 10/16/19 PROJECT No.:
PARCELID#: 015-483-17 TECHNICIAN: J. MILLETTE
DEPTH TEST HOLE 1-W
(feet)
10
11
12
13
14
15
16
17
18
19
20
SLOPE
READING
1' OB
1
♦
NET DROP
(INCHES)
2
TEST HOLE PRESOAKED PRIOR TO TESTING:
SILTY GRAVEL
1
4:50 / 4:57
DEPTH "CO WATER AFTER MONITORING: NONE
3
6"
r
4
DATE OF MONITORING: 10/24/19
P
5-°-6/11�°—�
�.
5
E
9:55
510x/11-1
♦
4
':��'.•
FINE COMPACT SAND
5�0/11�0
611
5
5:30 / 5:40
SM
8
611
6
5:41/5:51
9:52
9
'.' .. .
10
11
12
13
14
15
16
17
18
19
20
SLOPE
COMMENTS:
DATE
READING
WAS GROUND WATER ENCOUNTERED? NO
NET TIME
(MINUTES)
♦
NET DROP
(INCHES)
IF YES a WHAT DEPTH?LS -
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
4:50 / 4:57
DEPTH "CO WATER AFTER MONITORING: NONE
5 �0 111 10-6
6"
r
2
DATE OF MONITORING: 10/24/19
P
5-°-6/11�°—�
�.
3
E
9:55
COMMENTS:
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH TO
WATER
(INCHES)
NET DROP
(INCHES)
10/16
TEST HOLE PRESOAKED PRIOR TO TESTING:
1
4:50 / 4:57
7:15
5 �0 111 10-6
6"
2
4:58/5:07
8:48
5-°-6/11�°—�
611
3
5:08/5:18
9:55
510x/11-1
6"
4
5:19/5:29
9:48
5�0/11�0
611
5
5:30 / 5:40
9:57
5 —0 / 11 0
611
6
5:41/5:51
9:52
5�0x/11-s
6"
PERCOLATION RATE: 1.64 (MIN/INCH) PERC. HOLE DIA. 6 (INCHES)
TEST RUN BETWEEN: 5 FT. and 6 FT.
LEGAL DESCRIPTION:
PERFORMED FOR:
DATE:
PARCEL ID#:
SOILS LOG AND PERCOLATION TEST
TECHNICIAN:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
DEPTH
(feet)
PROJECT No.:
TEST HOLE 2-E
SLOPE
SLOPE
SITE PLAN
DATE READING GROSS TIME(minutes)NET TIME(minutes)
DEPTH toWATER NET DROP
TEST HOLE PRESOAKED PRIOR TO TESTING:
PERC. HOLE DIA. (INCHES)PERCOLATION RATE: (MIN/INCH)
TEST RUN BETWEEN: FT. and FT.
COMMENTS:
(inches)(inches)
Ozzies Knoll L1A
10/16/19
J. Millette
DATE OF MONITORING:
WAS GROUND WATER ENCOUNTERED?
DEPTH TO WATER AFTER MONITORING:
IF YES @ WHAT DEPTH?-
<1 6
3.5 4.5
015-483-17
Denise Deal
5:55
10/16
1
2
3
4
5
6
5 0
16 / 11 0
165:57
5:59
6:01
6:03
6:05
1' OB
Professional Engineers Stamp:
12/14/20
<1 min
NO
None
10/24/19
FINE TO COARSE SAND
SW/SP
6"
SILTY GRAVEL
GM
5 0
16 / 11 0
16<1 min 6"
5 0
16 / 11 0
16<1 min 6"
5 0
16 / 11 0
16<1 min 6"
5 0
16 / 11 0
16<1 min 6"
5 0
16 / 11 0
16<1 min 6"