Final Plat ReviewAUTUMN .HILL II
Vancil Road SE @ Birkland St. SE
Yelm, WA
Preliminary Storm Drainage, Infiltration
and Water Quality Report
February 17, 2004
For:
Lubbesmeyer Construction, Inc.
1151 112th Street East
Tacoma, WA 98445
By•
2M Enterprises, LLC
15345 Sunwood Blvd. Suite .302
Tukwila, WA ,98188
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SITE LOCATION MAP
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Reference: The Thomas Guide, King/Pierce/Snohomish Counties, 2000 Edition
Autumn Hi11 II -Storm Drainage, Infiltration and Water
Quality Report
Proi ect Description
.The proposed development is a 23-lot residential plat including public
streets, storm drainage conveyance and infiltration, water quality
improvement, utilities and landscaping. The site is located along Vancil
Road SE at Birkland Street SE in Yelm, Washington.
Existing Conditions
The total area of the property is 6.0 acres, all of which will be developed as
part of this plat. There is currently four structures located on the site
including one house and a few small barns. The house will remain, but all
other structures will be removed prior to construction. The property is
bounded by developed residential property to the west and north, Vancil
Road SE to the east, and the recently constructed plat of Autumn Hill to the
south.
Most of the site is very flat. A portion of the southwest corner slopes toward
the adjacent residential property to the west. There is a small mound near
the the northeast corner of the site, but no other significant topographical
features. The site is mainly pasture land, grassy containing. small clumps of
small to mid-size brush with some scattered trees. There is no evidence of
existing storm drainage systems or natural concentrated surface conveyance
on the property. There is also no evidence of .any upstream storm drainage
flowing into the site.
Site soils are awell-drained Spanaway series formed in glacial outwash.
Based on our field evaluation it appears most if not all storm drainage
infiltrates into the soils or .flows into the wetland/pond area, and there is no
runoff to adjacent properties and/or public .right-of-way.
Developed Conditions
Development will consist of clearing and grading of the 23-lot residential
plat, street paving and associated storm drainage, utility and landscaping
improvements. The plat will be accessed by two new residential streets; an
extension of Birlcland Street SE on the east side and an extension of
Umptanum Street SE on the south side.
Storm. Drainage runoff from the streets and driveways will be collected in a
series of catch basins and tightlined to a biofiltration Swale located in the
northern portion of the developed area. The bioswale will be designed to
provide water quality improvement prior to release into the proposed
infiltration pond. The bioswale is designed to treat storm drainage for the 6-
month/24 hour design event, .and the infiltration pond is designed for the
100-year/24 hour design event. The area draining to the wetpond and
infiltration pond is approximately 6.0 acres, of which approximately 3.0
acres is impervious. Roof Drainage maybe infiltrated by drywells on
individual sites as houses are constructed.
The biofiltration Swale will need to be lined with an impervious clay layer or
geotextile fabric to prevent infiltration into the highly pervious site soils.
Sideslopes of the wetpond and infiltration pond are 3:1 (H:V) and access
will be provided to the infiltration pond for maintenance and/or inspection
purposes.
STORM DRAINAGE INFILTRATION CALCULATIONS
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2./20/04 4:51:14 pm Shareware Release page 1
Autumn Hill 2
Preliminary Storm Drainage Calculations
2752-001
BASIN SUMMARY
BASIN ID: Dev-100 NAME: 100yr/24hr Developed
SBUH METHODOLOGY
TOTAL AREA.......: .6.00 Acres BASEFLOWS: 0.00 cfs
RAINFALL TYPE....: TYPElA PERV
PRECIPITATION.....: 6..15 inches AREA ..: 3.00 Acres
TIME INTERVAL....: 10.00 min CN.. ..: 77.00
TC.. ... 10.00 min
ABSTRACTION COEFF: 0.2-0
PEAK RATE: 6.18 cfs VOL: 2.38 Ac-ft TIME: 480 min
IMP
3.00 Acres
98.00
6.30 min
2/20/04 4:51:51 pm Shareware Release page 1
Autumn Hill 2
Preliminary Storm Drainage Calculations
2752-001
STAGE STORAGE TABLE
CUSTOM STORAGE ID No. Triall
Description: Infiltration Pond
STAGE <----STORAGE----> STAGE <----STORAGE---->
(ft) ---cf--- --AC-Ft- (ft) ---cf--- --AC-Ft-
100.00 0.0000 0.0000 101.30 8897 0.2043
100.10 670.00 0.0154 101.40 9630 0.2211
100.20 1340 0.0308 101.50 10362 0.2379
100.30 2010 0.0461 101.60 11095 0.2547
100.40 2680 0.0615 101.70 11827 0.2715
100.50 3350 0.0769 101.8-0 12560 0.2883
100.60 4020 0.0923 101.90 13292 0.3052
100.70 4690 0.1077 102.00 14025 0.3220
100.50 5360 0.1230 102.10 14822 0.3403
100.90 6030 0.1384 102.20 15620 0.3586
101.00 6700 0.1538 102.30 16417 0.3769
101.10 7432 0.1706 102.40 17215 0.3952
101.20 8165 0.1874 102.50 18012 0.4135
STAGE <----STORAGE---->
(ft) ---cf--- --Ac-Ft-
102.60 18810. 0.4318
102.70 19607 0.4501
102.80 20405 0.4684
102.90 21202 0.4867
103.00 22000 0.5051
103.10 22865 0.5249
103.20 23730 0.5448
103.30 24595 0.5646
103.40 25460 0.5845
103.50 26325 0.6043
103.60 27190 0.6242
103.70 28055 0.6441
103.80 28920 0.6639.
STAGE <----STORAGE---->
(f t) ---cf--- --AC-Ft-
103.90 29785 0.6838
104.00 30650 0.7036
104.10 31585 0.7251
104.20 32520 0.7466
104.30 33455 0.7680
104.40 34390 0.7895
104.50 35325 0.8110
104.60 36260 0.8324
104.70 37195 0.8539
104.80 38130 0.8753
104.90 39065 0.8968
105.00 40000 0.9183
105.00 40000 0.9183
2/20/04 4:51:42 pm Shareware Release page 1
Autumn Hill 2
Preliminary Storm Drainage Calculations
2752-001
STAGE DISCHARGE TABLE
DISCHARGE LIST ID No. Triall
Description: Infiltration Discharge
STAGE <--DBSCHARGE---> STAGE <--DISCHARGE--->
(f t) ---cfs-- ------- (ft) ,--cfs-- -------
100 .00 0.0000- 101.30 1.4800
100 .70 0.1480 101.40 1.4800
100 .20 0.2960 101.50 1.4800
100 .30 0.4440 101.60 1.4800
100 .40 0.5920 101.70 1.4800
100 .50 0.7400 101.80 1.4800
100 .60 0.8880 101.90 1.4800
100. 70 1.0360 102.00 1.4800
100. 80 1..1840 102,10. 1.4800
100. 90 1.3320 102.20 1.4600
101. 00 1.4800 102.30 1.4800
101. 10 1.4800 102.40 1.4800
101. 20 1.4800 102.50 1.4800
STAGE <--DISCHARGE---> STAGE <--DISCHARGE--->
(ft) ---cfs-- ------- (f t) ---cfs-- -------
102.60 1.4800 103.90 1.4800
102.70 1.4&00 104.00 1.4800
102.80 1.4800 104.10 1.5820
102.90 1.4800 104.20 1.6840
103.00 1.4800 104.30 1.7860
103.10 1.4800 104.40 1.8880
103.20 1.4800 104.50 1.9900
103.30 1.4800 104.60 2.0920
103.40 1.4800 104.70 2.1940
103.50 1.4800 104.80 2.2960
103.60 1.4800 104.90 2.3960
103.70 1.4800 105.00 2.5000
103.80 1.4800 105.00 2.5000
2/20/04 4:51:24 pm Shareware Release page 1
Autumn Hill 2
Preliminary Storm Drainage Calculations
2752.-001
LEVEL POOL TABLE SUMMARY
MATCH INFLOW -STO- -DIS- <-PEAK-> OUTFLOW STORAGE
<--------DESCRIPTION---------> (cfs) (cfs) --id- --id- <-STAGE> id (cfs) VOL (cf)
6mo/24hr rout ................ 0.00 1..14 Triall Triall 100.41 1 0.60 2716.81 cf
100yr/24hr rout .............. 0.00 6.18 Triall Triall 103.17 2 1.48 23508.84 cf
WATER QUALITY CALCULATIONS
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2/20/04 4:51:6 pm Shareware Release page 1
Autumn Hill 2
Preliminary Storm Drainage Calculations
2752-001
BASIN SUMMARY
BASIN ID: 6MoDev
SBUH METHODOLOGY
TOTAL AREA.......:
RAINFALL TYPE....:
PRECIPITATION....:
TIME INTERVAL....:
ABSTRACTION COEFF:
PEAK RATE: 1.14
NAME: 6mo/24hr Developed WQ
6.00 Acres BASEFLOWS: 0.00 cfs
TYPElA PERV
1.79 inches AREA..: 3.00 Acres
10.00 min CN....: 77.00
TC..... 10.00 min
0.20
cfs VOL: 0.48 Ac-ft TIME: 480 min
IMP
3.00 Acres
98.00
6.30 min
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ALTET:NATIVE DESIGNS
Paul Morneau, Designer 360-458-9548
P.O. Box 1962 Yelm, WA 98597
Feb. 27, 2004
LUBBESMEYER CONSTRUCTION, INC.
__ _ 1151 E. __ 112th St.
Tacoma, WA 98445
Re: Soil Logs, next lot.. north of Autumn Hill;
Test hole #1 0-20" Black organic gravelly loamy sand
20-36" Tan cobbley vary gravelly loamy sand
36-60" Tan cobbley extremely gravelly sand
60-144" Tan/gray cobbley extremely gravelly sand
Test hole #2 0-22" . Black organic gravelly loamy sand
22-37" Tan cobbley vary gravelly loamy sand
37-56" Tan cobbley extremely gravelly sand
56-144" Tan/gray cobbley extremely gravelly sand
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If you have any further questions please feel free to give me a call, 458-9548.
Yours truly -- - .. _- --
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Paul Morneau, Septic System Designer
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