HomeMy WebLinkAboutMOUNTAIN PARK ESTATES Lts 9A and 11A S11944Onsite File
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ANDERSON ENGINEERING
P.O. BOX 240773
ANCHORAGE, AK 99524
522-7773 - 677-7766 (FAX)
August 22, 2012
Municipality of Anchorage
Building Safety Division
On Site Water and Wastewater Program
4700 Elmore Street
Anchorage, AK 99507
Attention: Debbie Wockenfuss
Subject: Lots 9A and 10A, Block 2, Mountain Park Estates Subdivision
Septic System Feasibility Study
Dear Debbie:
Lots 9, 10 and 11, Block 2, Mountain Park Estates Subdivsion are being combined into
Lots 9A and 11A. Each lot will gain approximately 22,300 square feet in surface area
which will expand the area available for on site septic systems. The attached plan
shows the location of the existing septic system on Lot 9 and the proposed septic
systems on Lot 11. In addition a letter describing the condition of the existing system on
Lot 9 is attached for your review.
The lots are located immediately south of DeArmoun Road near its intersection with
Ridgeview Road. The ground surface of the lots slopes is fairly flat at the southern third
and then slopes in a southerly direction to the southern boundary of the subdivision at
varying grades. This slope is approximately 5% to 25% for the first 200' and then
becomes much steeper. All septic systems proposed for the lots will be placed in areas
where the surface slope is less than 25%. The cross slope on the property is nearly flat.
The proposed absorption systems and reserve areas are placed parallel with the
contours at locations where the slope is the shallowest.
Test holes were placed on Lot 11 in May of 2011. Water monitoring has been ongoing
and no groundwater has ever been noted. The purpose of the test holes was to assess
the underlying soil conditions and to determine whether a septic system could be placed
on the lot to serve single-family homes. The test holes were placed to depths of up to
18' with no bedrock or impermeable lenses of material encountered. The locations of
the test holes were determined in the field as the best locations for a septic system.
Percolation benches were constructed at various depths in the holes, but primarily 4' to
7' below the original ground surface. A percolation cavity was prepared to determine
the absorptive characteristics of the soils encountered. The cavity was presoaked in
accordance with Municipal requirements and a percolation test performed. The results
Lots 9A and 11A, Block 2, Mountain Park Estates
August 22, 2012
Page 2
of the tests are included in the attached documentation. In every case silty sand with
gravel (SM) with varying degrees of silt was encountered to the bottom of each test
hole. The percolation rate in this material ranged from 2.5 to 8 minutes per inch.
All work was completed under the direction of technicians and engineers at Anderson
Engineering. The results of the percolation tests and test hole logs are included as well
as the water monitoring results. A monitor tube remains in place in each hole to
determine the groundwater elevation over a period of time.
The new absorption trenches were designed for a four (4) bedroom home with an
application rate of 1.2 gallons per day per square foot. They are 50' long by 5' wide with
an effective depth of 4'. The total depth of the trenches can be as deep as 12' which
places the bottom of the trenches 6' above the water table and bedrock.
Based on our field study and water monitoring completed to date it appears Lot 9 is
capable of supporting an onsite septic system and well. The size of the home to be
constructed on the lot must be limited to four.(4) bedrooms.
Copies of the test hole logs, percolation tests, test hole location map and the contour
map showing the surface topography of the property are included for your use. We
hereby request your approval of the creation of Lots 9A and 10A, Block 2, Mountain
Park Estates Subdivision.
Sincerely,
Michael E. Anderson, P.E.
Attachments
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MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 BRAGAW STREET ANCHORAGE, AK 99519-6650
DEPTH
(feet)
1-
2-
3-
4-
5
6
7
8
9
10
SOILS LOG - PERCOLATION TEST
LEGAL DESCRIPTION: MOUNTAIN PARK ESTATES, BLOCK 2, LOT
PERFORMED FOR: KYLER AND KAMMY HOWLETT
DATE: 5/14/2011 PROJECT No.:
PARCEL ID#: TECHNICIAN: A. HARALA
TEST HOLE 1
OB/OG
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° SILTY SAND
e WITH GRAVEL
d SM
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MICHAEL E. ANDERSON (�
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Professional Engineers Stamo:
SITE PLAN
SEE SITE PLAN
z
U
WAS GROUND WATER ENCOUNTERED? NO
°
IF YES @ WHAT DEPTH? S
DEPTH OF WATER AFTER MONITORING: NONE 0 SEE SITE PLAN
DATE OF MONITORING: 5/15/2011 P
E
d
16
17 °
a
18 BOH @ 18'
19
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
TEST HOLE PRESOAKED PRIOR TO TESTING:
5115
1
2:11/2:21
10
.50"/4.75"
4.25'
2
2:22/2:32
10
.75"14.75'
4.00"
3
2:33/2:43
10
.62'14.62"
4.00"
4
2:44/2:54
10
.62'/4.62'
4.00"
5
2:55/3:05
10
.50"/4.50"
4.00"
6
3:06/3:16
10
.62'/4.62'
4.00"
PERCOLATION RATE: 2.5 (MINANCH) PERC. HOLE DIA. lit (INCHES)
TEST RUN BETWEEN: 4.5 FT. and 5.5 FT.
COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST.
TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT
THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES IN EFFECT ON THIS
DATE: 5/5/2012
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 BRAGAW STREET ANCHORAGE, AK 99519-6650
DEPTH
(feet)
1-
2
3
4
5
6
7
8
9
10-
11
12-
13-
14-
15-
16-
17-
18-
19 -
SOILS LOG - PERCOLATION TEST
LEGAL DESCRIPTION: MOUNTAIN PARK ESTATES, BLOCK 2, LOT
PERFORMED FOR: KYLER AND KAMMY HOWLETT
DATE: 5/14/2011 PROJECT No.:
PARCEL ID#: TECHNICIAN: A. HARALA
I TEST HOLE 2
a
a.
a SILTY SAND
a WITH GRAVEL
d SM
SLOPE
2%
SITE PLAN
SEE SITE PLAN `
i
U
WAS GROUND WATER ENCOUNTERED? NO
a IF YES @ WHAT DEPTH? S
DEPTH OF WATER AFTER MONITORING: NONE LLs 5%
a DATE OF MONITORING: 5/15/2011 P
E
MORE DENSE
WITH DEPTH
a
a
d
Q
e
BOH @ 18'
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
TEST HOLE PRESOAKED PRIOR TO TESTING:
5/14
1
3:52
1.13"
2
4:22
30
4.88"
3.75"
3
4:23
1.25"
4
4:53
30
5.00"
3.75"
5
4:54
1.13"
6
5:24
30
4.88"
3.75"
PERCOLATION RATE: 8 (MIN/INCH) PERC. HOLE DIA. §� (INCHES)
TEST RUN BETWEEN: 6.0 FT. and 7.0 FT.
COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST.
TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT
THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES IN EFFECT ON THIS
DATE: 9/10/2007
MUNICIPALITY OF ANCHORAGE
DEVELOPMENT SERVICES DEPARTMENT
4700 BRAGAW STREET ANCHORAGE, AK 99519-6650
DEPTH
(feet)
1-
2-
3-
4-
5-
6-
7-
8-
9-
10-
11
12-
13-
14-
15-
16-
17-
18-
19-
SOILS LOG - PERCOLATION TEST
LEGAL DESCRIPTION: MOUNTAIN PARK ESTATES, BLOCK 2, LOT
PERFORMED FOR: KYLER AND KAMMY HOWLETT
DATE: 5/14/2011 PROJECT No.:
PARCEL ID#: TECHNICIAN: A. HARALA
TEST HOLE 3
OB/OG
a
a
e
o SILTY SAND
a WITH GRAVEL
a SM
0
COBBLES TO 2"
d
a
SLOPE
49th `
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..................... ....
2'; MICHAEL E. ANDERSON b
. 4
f' NO. CE -4381
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SITE PLAN
SEE SITE PLAN
i
WAS GROUND WATER ENCOUNTERED? NO
a
IF YES @ WHAT DEPTH? L
DEPTH OF WATER AFTER MONITORING: NONE SEE SITE PLAN
a DATE OF MONITORING: 5/15/2011 P
E
a
a
a
a
BOH @ 17'
DATE
READING
GROSS TIME
(MINUTES)
NET TIME
(MINUTES)
DEPTH To
WATER
(INCHES)
NET DROP
(INCHES)
TEST HOLE PRESOAKED PRIOR TO TESTING:
5/14
1
6:17
.7511
2
6:47
30
7.25"
6.5011
3
6:48
1.2511
4
7:18
30
7.50"
6.25"
5
7:19
1.00"
6
7:49
30
7.25"
6.25"
1
1
i -T
PERCOLATION RATE: 4.5 (MIN/INCH) PERC. HOLE DIA. 6" (INCHES)
TEST RUN BETWEEN: 5.0 FT. and 6.0 FT.
COMMENTS: TEST HOLE PRE SOAKED PRIOR TO TEST.
TEST PERFORMED BY ANDERSON ENGINEERING. I, MICHAEL E. ANDERSON CERTIFY THAT
THIS WAS PERFORMED IN ACCORDANCE WITH ALL STATE AND MUNICIPLE GUIDELINES IN EFFECT ON THIS
DATE: 5/5/2012
