HomeMy WebLinkAboutPreliminary_TIR_17.02.21
Western Washington Division Eastern Washington Division
165 NE Juniper St., Ste 201, Issaquah, WA 98027 407 Swiftwater Blvd., Cle Elum, WA 98922
Phone: (425) 392-0250 Fax: (425) 391-3055 Phone: (509) 674-7433 Fax: (509) 674-7419
www.EncompassES.net
PRELIMINARY TECHNICAL INFORMATION REPORT
for the
28Hundred Unit Lot Subdivision
February 20, 2017
Encompass Engineering & Surveying Job No. 16663
Prepared For:
Yves Tang
Greystoke LLC
720 North 10th Street #A282
Renton, WA 98057
28Hundred Preliminary Technical Information Report
February 20, 2017 Page i
TABLE OF CONTENTS
I. PROJECT OVERVIEW ................................................................................................................. 1
II. CONDITIONS AND REQUIREMENTS SUMMARY ....................................................................... 3
III. OFF-SITE ANALYSIS ................................................................................................................... 5
IV. FLOW CONTROL, LOW IMPACT DESIGN (LID) AND WATER QUALITY FACILITY ANALYSIS AND
DESIGN ..................................................................................................................................... 8
VI. SPECIAL REPORTS AND STUDIES ............................................................................................ 20
VII. OTHER PERMITS ..................................................................................................................... 20
VIII. CSWPPP ANALYSIS AND DESIGN ............................................................................................ 20
IX. BOND QUANTITIES, FACILITY SUMMARIES, & DECLARATION OF COVENANT ...................... 20
X. OPERATIONS AND MAINTENANCE MANUAL ......................................................................... 20
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 1
I. PROJECT OVERVIEW
Project: 28Hundred Unit Lot Subdivision
Tax Parcel #: 722780-1690 & 722780-1695
Site Addresses: 2800 NE 12th St & 2801 NE 13th ST
Zoning: R-14
Site Area: The project area is 0.66 Acres
Site Location: The site is on the east side of Harrington Avenue NE between NE 12th Street and NE
13th Street
Project Description: This project involves developing a 0.66-acre parcel into a 12-unit, Unit Lot
Subdivision.
Site Plan
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 2
Existing Adjacent Development:
Existing development adjacent to the subject site includes the following:
North – Single Family Residences and NE 13th Street
East – Single Family Residences
South – Single Family Residences & NE 12th Street
West – McKnight Middle School & Harrington Avenue NE
Pre-developed Site Conditions:
The project site presently consists of two parcels totaling 0.66 acres with existing houses/garages
with sidewalks and driveways—the remaining area is covered with sparse mature trees with lawn.
The site generally slopes down from the north to south at approximately 1%.
Critical Areas: No onsite critical areas.
Soils: Per the SCS soil maps, the site is underlain with Arents, Alderwood, gravelly sandy loam (AmC)
soil. Per Geotech report prepared for this project, “Infiltration Evaluation Proposed Harrington
Glade Townhomes 2800 Northeast 12th Street Renton, Washington”, dated August 1, 2014, and
prepared by Earth Solutions NW, the site is underlain with at least 8’ – 14’ of silty sand, infiltratable
soil.
Post-developed Site Conditions:
The proposal incorporates the construction of frontage improvements along NE 13th Street together
with water/sewer/storm for a 12-unit Unit Lot Subdivision. The existing single family residences will
be removed.
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 3
Vicinity Map
II. CONDITIONS AND REQUIREMENTS SUMMARY
Core Requirement #1: Discharge at the Natural Location
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 4
The proposed on-site drainage patterns emulate those of the existing site conditions. Infiltration
will provide the required flow control for the impervious surfaces. The access/parking lot will
drain to a bioswale prior to infiltrating into the soil. There will be an overflow from the
bioswale/infiltration into the public storm system.
Core Requirement #2: Off-site Analysis
See Section III.
Core Requirement #3: Flow Control
Flow control will be provided for the development with infiltration pipes/tanks. See Section IV for a
conceptual design using KCRTS.
Core Requirement #4: Conveyance System
Conveyance and capacity analysis of the new proposed system will be presented with the final
drainage report.
Core Requirement #5: Erosion & Sediment Control
An erosion and sediment control plan, which will serve to minimize soil erosion/sedimentation
during the proposed site construction, will be prepared for the final engineering plans.
Core Requirement #6: Maintenance & Operations
The on-site storm water system will be maintained by the Unit Lot Subdivision HOA.
Core Requirement #7: Financial Guarantees & Liability
The owner will arrange for any financial guarantees and liabilities required by the pe rmit.
Core Requirement #8: Water Quality
Because there will be greater than 5,000 sq-ft of new PGIS, water quality measures will be
provided with a bioswale.
Core Requirement #9: Flow Control BMPs
Flow control BMPs will be provided with infiltration pipes/tanks. See Section IV for a
conceptual design using KCRTS.
Special Requirement #1: Other Adopted Area-Specific Requirements
None
Special Requirement #2: Floodplain/Floodway Delineation
None
Special Requirement #3: Flood Protection Facilities
None
Special Requirement #4: Source Control
Source control is not required for this project.
Special Requirement #5: Oil Control
Oil control is not required for a residential subdivision, it doesn’t qualify as a high-use site.
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 5
III. OFF-SITE ANALYSIS
Location: Tax Parcel #: 722780-1690 & 722780-1695
Site Addresses: 2800 NE 12th St & 2801 NE 13th ST
Site Location: The site is on the east side of Harrington Avenue NE between NE 12th Street and NE
13th Street
Project Description: This project involves developing a 0.66-acre parcel into a 12-unit, Unit Lot
Subdivision. The project site presently consists of two parcels totaling 0.66 acres with existing
houses/garages with sidewalks and driveways—the remaining area is covered with several mature
trees with lawn. The site generally slopes down from the north to south at approximately 1%.
Soils: Per the SCS soil maps, the site is underlain with Arents, Alderwood, gravelly sandy loam (AmC)
soil. Per Geotech report prepared for this project, “Infiltration Evaluation Proposed Harrington
Glade Townhomes 2800 Northeast 12th Street Renton, Washington”, dated August 1, 2014, and
prepared by Earth Solutions NW, the site is underlain with at least 8’ – 14’ of silty sand, infiltratable
soil.
Existing Upstream Drainage
Little if any upstream areas drain to this site.
Existing Downstream Drainage
Any runoff from the site sheet flows southwest and enters into street gutter which drains into public
storm drainage system—a CB at point (A) which is located in the intersection of NE 12th St and
Harrington Ave NE. From there flow drains southwest through a 6-inch Conc. pipe into a CB type II-
MH per survey field and per city of Renton (GIS) records at point (B). From point (B) flow also drains
southwest through a 24-inch CMP pipe into another CB type II-MH at point (C). From there flow
drains west along the NE 12th St through a 36 -inch pipe to another CB type II-MH at point (D) for a
total of 120-feet downstream from the site. From point (D) flow continues west through a 36-inch
pipe to another CB at point (E) per city of Renton records. Form there flow drains through a 36 -inch
pipe to another CB type II-MH at point (F) for a total of approximately 470-feet down stream. From
there flow drains through a 36-inch pipe to another CB type II-MH at point (G). From there flow
drains through a pipe to another CB type II-MH at point (H) located on intersection of NE 12th St
and Edmonds Ave NE for a total of approximately 800-feet from the site. From point (H) flow
continues south along Edmonds Ave NE through an 18-inch pipe to another CB type II-MH at point
(I). From there flow continues south through an 18 -inch pipe to another CB at point (J). From Point
(J) flow drains through another 18-inch pipe to another CB at point (K) for a total of appro ximately
1100-feet downstream from the site. From there pipe continues south (L) to ¼ mile downstream
from the site and enters into public storm drainage system along the NE Sunset Blvd. Eventually the
runoff discharges into Lake Washington.
There were no obvious downstream drainage problems.
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 6
Photo 1: Looking South from Harrington Ave NE/NE 13th St.—Subject property on the left
Photo 2: Intersection of Harrington Ave NE & NE 12th St.—CB at point (A)
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 7
Photo 3: looking west from NE 12th St. towards intersection of Edmonds Ave NE
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 8
IV. FLOW CONTROL, LOW IMPACT DESIGN (LID) AND WATER QUALITY FACILITY
ANALYSIS AND DESIGN
Performance Standards
For conceptual purposes, the site was analyzed using the KCRTS software. Because the underlying
soil is silty sand and is suitable for providing for infiltration, infiltration pipes/tanks were used to
provide the required flow control. For the concept, the infiltration was designed for the 100 -year
rainfall conditions. During the final design, other approved drainage design software will be used as
outlined in the 2016 City of Renton Surface Water Design Manual. Separate infiltration and water
quality designs were made for roofs and pavement.
Infiltration Design for Runoff from Roofs
Roof Area = 8,510 sq-ft = 0.20 acres.
Design Infiltration Rate = IDesign = 1.0 inch/hr => 60min/inch
Use 24” infiltration tank in 4’ wide trench
Design for 100-year storm
Using KCRTS (see below), 268LF tank required for buildings only
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 9
Existing Conditions Map
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 10
Developed Conditions Map
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 11
KCRTS Input File for Roof Infiltration
KCRTS Program...File Directory:
C:\KC_SWDM\KC_DATA\
[C] CREATE a new Time Series
ST
0.00 0.00 0.000000 Till Forest
0.00 0.00 0.000000 Till Pasture
0.00 0.00 0.000000 Till Grass
0.00 0.00 0.000000 Outwash Forest
0.00 0.00 0.000000 Outwash Pasture
0.00 0.00 0.000000 Outwash Grass
0.00 0.00 0.000000 Wetland
0.20 0.00 0.000000 Impervious
Bldgs.tsf
T
1.00000
T
[T] Enter the Analysis TOOLS Module
[P] Compute PEAKS and Flow Frequencies
Bldgs.tsf
Bldgs.pks
[R] RETURN to Previous Menu
KCRTS Output File for Roof Infiltration
KCRTS 1 hour Time Step Peaks for Flow Control – 0.20-acre Buildings Only
Flow Frequency Analysis
Time Series File:bldgs.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.048 7 2/09/01 2:00 0.095 1 100.00 0.990
100year
0.043 8 1/05/02 16:00 0.073 2 25.00 0.960
0.059 3 12/08/02 18:00 0.059 3 10.00 0.900
0.050 6 8/26/04 2:00 0.059 4 5.00 0.800
0.059 4 10/28/04 16:00 0.052 5 3.00 0.667
0.052 5 1/18/06 16:00 0.050 6 2.00 0.500
0.073 2 10/26/06 0:00 0.048 7 1.30 0.231
0.095 1 1/09/08 6:00 0.043 8 1.10 0.091
Computed Peaks 0.087 50.00 0.980
KCRTS Infiltration Design Output for Roof Infiltration
KCRTS Flow Control Design for Buildings Only – 24” Infiltration Tank
Retention/Detention Facility
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 12
Type of Facility: Infiltration Tank
Tank Diameter: 2.00 ft
Trench Width: 4.00 ft
Tank Length: 268.00 ft
Effective Storage Depth: 2.00 ft
Stage 0 Elevation: 0.00 ft
Storage Volume: 1233. cu. ft
Vertical Permeability: 60.00 min/in
Permeable Surfaces: Bottom
Riser Head: 2.00 ft
Riser Diameter: 8.00 inches
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 0.00 0. 0.000 0.000 0.00
0.10 0.10 43. 0.001 0.000 0.02
0.20 0.20 95. 0.002 0.000 0.02
0.30 0.30 152. 0.003 0.000 0.02
0.40 0.40 213. 0.005 0.000 0.02
0.50 0.50 276. 0.006 0.000 0.02
0.60 0.60 342. 0.008 0.000 0.02
0.70 0.70 409. 0.009 0.000 0.02
0.80 0.80 477. 0.011 0.000 0.02
0.90 0.90 547. 0.013 0.000 0.02
1.00 1.00 616. 0.014 0.000 0.02
1.10 1.10 686. 0.016 0.000 0.02
1.20 1.20 755. 0.017 0.000 0.02
1.30 1.30 824. 0.019 0.000 0.02
1.40 1.40 891. 0.020 0.000 0.02
1.50 1.50 957. 0.022 0.000 0.02
1.60 1.60 1020. 0.023 0.000 0.02
1.70 1.70 1081. 0.025 0.000 0.02
1.80 1.80 1138. 0.026 0.000 0.02
1.90 1.90 1189. 0.027 0.000 0.02
2.00 2.00 1233. 0.028 0.000 0.02
2.10 2.10 1233. 0.028 0.205 0.02
2.20 2.20 1233. 0.028 0.581 0.02
2.30 2.30 1233. 0.028 0.921 0.02
2.40 2.40 1233. 0.028 1.060 0.02
2.50 2.50 1233. 0.028 1.190 0.02
2.60 2.60 1233. 0.028 1.300 0.02
2.70 2.70 1233. 0.028 1.410 0.02
2.80 2.80 1233. 0.028 1.500 0.02
2.90 2.90 1233. 0.028 1.590 0.02
3.00 3.00 1233. 0.028 1.680 0.02
3.10 3.10 1233. 0.028 1.760 0.02
3.20 3.20 1233. 0.028 1.840 0.02
3.30 3.30 1233. 0.028 1.920 0.02
3.40 3.40 1233. 0.028 1.990 0.02
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 13
3.50 3.50 1233. 0.028 2.060 0.02
3.60 3.60 1233. 0.028 2.130 0.02
3.70 3.70 1233. 0.028 2.190 0.02
3.80 3.80 1233. 0.028 2.260 0.02
3.90 3.90 1233. 0.028 2.320 0.02
4.00 4.00 1233. 0.028 2.380 0.02
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 0.09 0.00 0.00 1.95 1.95 1212. 0.028
2 0.05 0.00 0.00 1.03 1.03 641. 0.015
3 0.05 0.00 0.00 0.84 0.84 506. 0.012
4 0.06 0.00 0.00 0.75 0.75 441. 0.010
5 0.05 0.00 0.00 0.73 0.73 431. 0.010
6 0.06 0.00 0.00 0.61 0.61 349. 0.008
7 0.05 0.00 0.00 0.27 0.27 133. 0.003
8 0.04 ******* 0.00 0.22 0.22 109. 0.002
100-year stage is 0.05’ below top of 24” infiltration pipe => No Overflow in
100yr storm
----------------------------------
Route Time Series through Facility
Inflow Time Series File:bldgs.tsf
Outflow Time Series File:rdout
Inflow/Outflow Analysis
Peak Inflow Discharge: 0.095 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.000 CFS at 11:00 on Jan 9 in Year 8
Peak Reservoir Stage: 1.95 Ft
Peak Reservoir Elev: 1.95 Ft
Peak Reservoir Storage: 1212. Cu-Ft
: 0.028 Ac-Ft
Flow Frequency Analysis
Time Series File:rdout.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) (ft) Period
0.000 5 2/09/01 19:00 0.000 1.95 1 100.00 0.990
0.000 8 1/05/02 17:00 0.000 1.03 2 25.00 0.960
0.000 4 2/27/03 10:00 0.000 0.84 3 10.00 0.900
0.000 7 8/26/04 3:00 0.000 0.75 4 5.00 0.800
0.000 6 10/28/04 19:00 0.000 0.73 5 3.00 0.667
0.000 2 1/18/06 22:00 0.000 0.61 6 2.00 0.500
0.000 3 11/24/06 6:00 0.000 0.27 7 1.30 0.231
0.000 1 1/09/08 11:00 0.000 0.22 8 1.10 0.091
Computed Peaks 0.000 1.65 50.00 0.980
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 14
Infiltration Design for Runoff from Paving
Paving Area = 7,200 sq-ft = 0.17 acres.
Design Infiltration Rate = IDesign = 1.0 inch/hr => 60min/inch
Use 3.75’ wide by 6.42’ wide infiltration chamber in 8.42’ wide trench
Design for 100-year storm
Using KCRTS (see below), 56LF tank required for paving only
KCRTS Input File for Paving Infiltration
KCRTS Program...File Directory:
C:\KC_SWDM\KC_DATA\
[C] CREATE a new Time Series
ST
0.00 0.00 0.000000 Till Forest
0.00 0.00 0.000000 Till Pasture
0.00 0.00 0.000000 Till Grass
0.00 0.00 0.000000 Outwash Forest
0.00 0.00 0.000000 Outwash Pasture
0.00 0.00 0.000000 Outwash Grass
0.00 0.00 0.000000 Wetland
0.17 0.00 0.000000 Impervious
P-Lot.tsf
T
1.00000
T
[T] Enter the Analysis TOOLS Module
[P] Compute PEAKS and Flow Frequencies
P-Lot.tsf
P-Lot.pks
[R] RETURN to Previous Menu
KCRTS Output for Paving Infiltration
KCRTS 1 hour Time Step Peaks for Flow Control – 0.17-acre Parking Lot Only
Flow Frequency Analysis
Time Series File:p-lot.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.041 7 2/09/01 2:00 0.080 1 100.00 0.990
100yr
0.036 8 1/05/02 16:00 0.061 2 25.00 0.960
0.050 3 12/08/02 18:00 0.050 3 10.00 0.900
0.043 6 8/26/04 2:00 0.050 4 5.00 0.800
0.050 4 10/28/04 16:00 0.044 5 3.00 0.667
0.044 5 1/18/06 16:00 0.043 6 2.00 0.500
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 15
0.061 2 10/26/06 0:00 0.041 7 1.30 0.231
0.080 1 1/09/08 6:00 0.036 8 1.10 0.091
Computed Peaks 0.074 50.00 0.980
KCRTS Infiltration Design Output for Paving Infiltration
KCRTS Flow Control Design for Parking Lot Only – 3.75”X6.42” Infiltration
Chamber
Retention/Detention Facility
Type of Facility: Infiltration Arch Tank
Tank Rise: 3.75 ft
Tank Span: 6.42 ft
Trench Width: 8.42 ft
Tank Length: 56.00 ft
Effective Storage Depth: 4.25 ft
Stage 0 Elevation: 0.00 ft
Storage Volume: 1345. cu. ft
Vertical Permeability: 60.00 min/in
Permeable Surfaces: Bottom
Riser Head: 4.25 ft
Riser Diameter: 8.00 inches
Top Notch Weir: None
Outflow Rating Curve: None
Stage Elevation Storage Discharge Percolation
(ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs)
0.00 0.00 0. 0.000 0.000 0.00
0.10 0.10 31. 0.001 0.000 0.01
0.20 0.20 61. 0.001 0.000 0.01
0.30 0.30 92. 0.002 0.000 0.01
0.40 0.40 123. 0.003 0.000 0.01
0.50 0.50 159. 0.004 0.000 0.01
0.60 0.60 197. 0.005 0.000 0.01
0.70 0.70 197. 0.005 0.000 0.01
0.80 0.80 274. 0.006 0.000 0.01
0.90 0.90 313. 0.007 0.000 0.01
1.00 1.00 353. 0.008 0.000 0.01
1.10 1.10 392. 0.009 0.000 0.01
1.20 1.20 431. 0.010 0.000 0.01
1.30 1.30 471. 0.011 0.000 0.01
1.40 1.40 509. 0.012 0.000 0.01
1.50 1.50 548. 0.013 0.000 0.01
1.60 1.60 587. 0.013 0.000 0.01
1.70 1.70 625. 0.014 0.000 0.01
1.80 1.80 662. 0.015 0.000 0.01
1.90 1.90 700. 0.016 0.000 0.01
2.00 2.00 738. 0.017 0.000 0.01
2.10 2.10 775. 0.018 0.000 0.01
2.20 2.20 811. 0.019 0.000 0.01
2.30 2.30 847. 0.019 0.000 0.01
2.40 2.40 883. 0.020 0.000 0.01
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 16
2.50 2.50 917. 0.021 0.000 0.01
2.60 2.60 963. 0.022 0.000 0.01
2.70 2.70 986. 0.023 0.000 0.01
2.80 2.80 1019. 0.023 0.000 0.01
2.90 2.90 1051. 0.024 0.000 0.01
3.00 3.00 1082. 0.025 0.000 0.01
3.10 3.10 1112. 0.026 0.000 0.01
3.20 3.20 1142. 0.026 0.000 0.01
3.30 3.30 1170. 0.027 0.000 0.01
3.40 3.40 1197. 0.027 0.000 0.01
3.50 3.50 1222. 0.028 0.000 0.01
3.60 3.60 1245. 0.029 0.000 0.01
3.70 3.70 1266. 0.029 0.000 0.01
3.80 3.80 1281. 0.029 0.000 0.01
3.90 3.90 1295. 0.030 0.000 0.01
4.00 4.00 1310. 0.030 0.000 0.01
4.10 4.10 1324. 0.030 0.000 0.01
4.20 4.20 1338. 0.031 0.000 0.01
4.25 4.25 1345. 0.031 0.000 0.01
4.35 4.35 1345. 0.031 0.205 0.01
4.45 4.45 1345. 0.031 0.581 0.01
4.55 4.55 1345. 0.031 0.921 0.01
4.65 4.65 1345. 0.031 1.060 0.01
4.75 4.75 1345. 0.031 1.190 0.01
4.85 4.85 1345. 0.031 1.300 0.01
4.95 4.95 1345. 0.031 1.410 0.01
5.05 5.05 1345. 0.031 1.500 0.01
5.15 5.15 1345. 0.031 1.590 0.01
5.25 5.25 1345. 0.031 1.680 0.01
5.35 5.35 1345. 0.031 1.760 0.01
5.45 5.45 1345. 0.031 1.840 0.01
5.55 5.55 1345. 0.031 1.920 0.01
5.65 5.65 1345. 0.031 1.990 0.01
5.75 5.75 1345. 0.031 2.060 0.01
5.85 5.85 1345. 0.031 2.130 0.01
5.95 5.95 1345. 0.031 2.190 0.01
6.05 6.05 1345. 0.031 2.260 0.01
6.15 6.15 1345. 0.031 2.320 0.01
6.25 6.25 1345. 0.031 2.380 0.01
Hyd Inflow Outflow Peak Storage
Target Calc Stage Elev (Cu-Ft) (Ac-Ft)
1 0.08 0.00 0.00 4.25 4.25 1345. 0.031
2 0.04 0.00 0.00 3.52 3.52 1226. 0.028
3 0.06 0.00 0.00 3.39 3.39 1194. 0.027
4 0.04 0.00 0.00 2.92 2.92 1056. 0.024
5 0.05 0.00 0.00 2.15 2.15 794. 0.018
6 0.05 0.00 0.00 1.39 1.39 504. 0.012
7 0.04 0.00 0.00 0.91 0.91 318. 0.007
8 0.04 0.00 0.00 0.79 0.79 268. 0.006
100-year stage is at top of 3.75”X6.42” Infiltration Chamber (3.75” Chamber
+ 0.5’ under-gravel = 4.25’) => No Overflow in 100yr storm
----------------------------------
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 17
Route Time Series through Facility
Inflow Time Series File:p-lot.tsf
Outflow Time Series File:rdout
Inflow/Outflow Analysis
Peak Inflow Discharge: 0.080 CFS at 6:00 on Jan 9 in Year 8
Peak Outflow Discharge: 0.005 CFS at 12:00 on Jan 9 in Year 8
Peak Reservoir Stage: 4.25 Ft
Peak Reservoir Elev: 4.25 Ft
Peak Reservoir Storage: 1345. Cu-Ft
: 0.031 Ac-Ft
Flow Frequency Analysis
Time Series File:rdout.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) (ft) Period
0.000 2 2/09/01 20:00 0.005 4.25 1 100.00 0.990
0.000 8 1/05/02 18:00 0.000 3.52 2 25.00 0.960
0.000 5 3/06/03 21:00 0.000 3.39 3 10.00 0.900
0.000 7 8/24/04 0:00 0.000 2.92 4 5.00 0.800
0.000 6 10/28/04 20:00 0.000 2.15 5 3.00 0.667
0.000 4 1/18/06 22:00 0.000 1.39 6 2.00 0.500
0.000 3 11/24/06 7:00 0.000 0.91 7 1.30 0.231
0.005 1 1/09/08 12:00 0.000 0.79 8 1.10 0.091
Computed Peaks 0.003 4.25 50.00 0.980
Flow Duration from Time Series File:rdout.tsf
Cutoff Count Frequency CDF Exceedence_Probability
CFS % % %
0.000 61320 100.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
99999.99 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
99999.99 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
8264.31 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 18
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
99999.99 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
8264.31 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
99999.99 0 0.000 100.000 0.000 0.000E+00
0.000 0 0.000 100.000 0.000 0.000E+00
99999.99 0 0.000 100.000 0.000 0.000E+00
Discharge Volume
Discharge Volume from Time Series
rdout.tsf
between 10/01/00 00:00 and 10/30/00 23:59
0. Cu-Ft or 0.000 Ac-Ft in 30.0 days
Water Quality System
For conceptual purposes, the method in the 2009 KCSWDM will be used for bioswale design, using
KCRTS
During the final design, other approved drainage design software will be used as outlined in the
2016 City of Renton Surface Water Design Manual.
Paving Area = 7,200 sq-ft = 0.17 acres, greater than 5,000 sq-ft of PGIS => Water Quality Control
Required
Water Quality design storm = QWQ = 60% of KCRTS 15 minute timestep—see below, Q15min = 0.081cfs
Bioswale Design
1. Design Flow: QWQ = 60% * 0.081cfs = 0.049cfs
2. Swale Bottom Width: b = (QWQ*nWQ)/(1.49*y1.67*s0.5) with nWQ = 0.20, y=0.17’ & s=0.005 =>b=1.79’
Use min. b=2.0’
With b=2.0’ =>y=0.16’ flow depth
3. Flow Velocity: VWQ = QWQ/AWQ , AWQ =0.16(2+0.16*3)=0.80ft2 => VWQ =0.61ft/sec
4. Swale Length: Required Length = 540* VWQ = 32.9’ => use 50’ length bioswale
KCRTS Output for Paving Infiltration
KCRTS 15 min. Time Step Peaks for Water Quality – 0.17-acre Parking Lot Only
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 19
Flow Frequency Analysis
Time Series File:wq.tsf
Project Location:Sea-Tac
---Annual Peak Flow Rates--- -----Flow Frequency Analysis-------
Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob
(CFS) (CFS) Period
0.081 6 8/27/01 18:00 0.200 1 100.00 0.990
0.056 8 9/17/02 17:45 0.153 2 25.00 0.960
0.153 2 12/08/02 17:15 0.110 3 10.00 0.900
0.065 7 8/23/04 14:30 0.091 4 5.00 0.800
0.086 5 10/28/04 16:00 0.086 5 3.00 0.667
0.091 4 10/27/05 10:45 0.081 6 2.00 0.500 2-
year
0.110 3 10/25/06 22:45 0.065 7 1.30 0.231
0.200 1 1/09/08 6:30 0.056 8 1.10 0.091
Computed Peaks 0.185 50.00 0.980
Water Quality Flow = 60% Q2 = 0.6*.081 = 0.049 cfs
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 20
V. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Conveyance calculations will be provided as part of the final engineering documents.
VI. SPECIAL REPORTS AND STUDIES
“Infiltration Evaluation Proposed Harrington Glade Townhomes 2800 Northeast 12th Street Renton,
Washington”, dated August 1, 2014, and prepared by Earth Solutions NW. See Appendix A.
VII. OTHER PERMITS
N/A
VIII. CSWPPP ANALYSIS AND DESIGN
This Stormwater Pollution Prevention Plan (SWPPP)/TESC will be prepared as part permit requirements for
this project in City of SeaTac, Washington during final engineering.
IX. BOND QUANTITIES, FACILITY SUMMARIES, & DECLARATION OF COVENANT
The documents will be prepared and submitted as part of the final engineering documents.
X. OPERATIONS AND MAINTENANCE MANUAL
Operation and maintenance of the site and all proposed stormwater facilities on this project will be
required after the construction completion and throughout the life of this development. Details
will be provided during final engineering.
28Hundred Preliminary Technical Information Report
February 20, 2017 Page 21
Appendix A
Infiltration Evaluation Proposed Harrington Glade Townhomes 2800 Northeast 12th Street Renton,
Washington