21-100244-SU-Conceptual TIR-01-25-2021-V1Larson & Associates
surveyors, engineers and planners
9027 Pacific Avenue, Suite 4
Tacoma, WA 98444
SOUTH CAMPUS ESTATES
CONCEPTUAL TECHNICAL INFORMATION REPORT
PROPONENT:
JKM HOLDINGS, LLC
PO BOX 188
PUYALLUP, WA. 98371
(253) 840-5660
CONTACT: GEOFF SHERWIN
PREPARED BY:
Larson & Associates
surveyors, engineers and planners
9027 Pacific Avenue, Suite 4
Tacoma, WA 98444
(253) 474-3404
January 22, 2021
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PROJECT ENGINEER'S CERTIFICATION......................................................................................................... I
T.I.R.
SECTIONI - PROJECT OVERVIEW........................................................................................................................ 2-4
EXISTING SITE CONDITIONS SUMMARY.......................................................................................................... 3
PROPOSED DEVELOPED SITE CONDITIONS SUMMARY.................................................................................... 3-4
SECTION II - CONDITIONS AND REQUIREMENTS SUMMARY..................................................................................... 4
SECTIONIII - OFFSITE ANALYSIS............................................................................................................................. 4
SECTION IV - FLOW CONTROL, LOW IMPACT DEVELOPMENT & WATER QUALITY FACILITY ANALYSIS & DESIGN 5-6
SECTION V - CONVEYANCE SYSTEM ANALYSIS AND DESIGN.................................................................................. 6
SECTION VI - SPECIAL REPORTS AND STUDIES........................................................................................................ 6
SECTIONVII - OTHER PERMITS............................................................................................................................... 6
SECTION VIII - CSWPPP ANALYSIS AND DESIGN...................................................................................................... 6
SECTION IX - BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .................................. 6
SECTION X- OPERATIONS AND MAINTENANCE MANUAL.......................................................................................... 6
STORM DRAINAGE CALCULATION SUMMARY........................................................................................7-28
APPENDIX A...............................................................................................MISCELLANEOUS INFORMATION
APPENDIXB.................................................................................................................................................CSWPPP
APPENDIX C................................................................................. OPERATION & MAINTENANCE MANUAL
I hereby state that this Technical Information Report for South Campus Estates has
been prepared by me or under my supervision and meets the standard of care and
expertise which is usual and customary in this conununity for professional engineers. I
understand that the City of Federal Way does not and will not assume liability for the
sufficiency, suitability, or performance of the storm drainage facilities prepared by me.
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SECTION 1- PROJECT OVERVIEW
This CONCEPTUAL TIR will focus its attention on providing information to obtain a
clearing/grading and site development permit for the proposed South Campus Estates
application. The proposed improvements for this project consist division of the existing
parcel into 10 lots. Each lot will access off of SW 3661h St. The project is on Parcel
Number 3021049041 on approximately 4.80 acres. The site address is XXX 6t" Ave SW.
The roofs for lots 1-6 & 8-10 will be fitted with a downspout tightline system that will
convey roof runoff to the properly sized onsite individual lot infiltration trench. A
portion of the roof runoff for Lot 7 will be routed to the pervious driveway reservoir
course section for infiltration and the rest of the roof runoff will be routed to an onsite
infiltration trench. The runoff from the driveways for Lots 1 & 2 will be collected and
conveyed to the reservoir course under the pervious driveway stein on Lot 3. The Lot 3
driveway pad at the house location will be impervious and the stormwater runoff will be
collected and conveyed to the reservoir course under the pervious driveway stem of Lot
3. The runoff from the driveways for Lots 4 & 5 will be collected and conveyed to the
reservoir course under the pervious driveway stem on Lot 6. The Lot 6 driveway pad at
the house location will be impervious and the stormwater runoff will be collected and
conveyed to the reservoir course under the pervious driveway stem of Lot 6. The runoff
from the driveway for Lot 7 will be collected and conveyed to the reservoir course under
the pervious driveway stem on Lot 8. The Lot 8 driveway pad at the house location will
be impervious and the stormwater runoff will be collected and conveyed to an onsite
infiltration trench. The driveways for Lots 9 and 10 will be impervious and the
stormwater runoff will be collected and conveyed to an onsite individual infiltration
trench. Stormwater from the driveways will be treated via the native soil which meets the
CEC and organic content required for treatment. The remaining disturbed soils will be
amended per Reference 11 in the in the King County 2016 Surface Water Design
Manual. Each of these stormwater flow control and treatment BMP's have been designed
per the King County 2016 Surface Water Design Manual.
Offsite frontage improvements along SW 366th St consist of a full road improvement
(I 2'w on the south side and 8'w on the north side) with a 2'w gravel shoulder and
bioretention cell on both sides and a 5'w pervious asphalt pathway (impervious at
driveway locations) on the south side. The runoff from the road and driveway
approaches will be collected, treated utilizing infiltration from both the bioretention cells
and the pervious asphalt pathway reservoir course. The bioretention cell and the pervious
asphalt pathway reservoir course will be hydrologically connected by having the
reservoir course directly adjacent to the bioretention soil. The bioretention cells are
located between the driveway approaches with the infiltration trenches located under the
driveway approaches. Frontage improvements along 6th Ave SW consist of a minimum
2'w gravel shoulder and 5'w impervious asphalt path all on the east side of the road
(project side). Regrading of existing ditch will take place as necessary.
0-1
Pre -Developed Areas
ONSITE
OFFSITE
TOTAL
Total Area
4.800 AC.
1.130 AC.
5.930 AC.
Pervious Area
4.800 AC.
0.838 AC.
5.638 AC.
Impervious Area
0.000 AC.
0.292 AC.
0.292 AC.
Existing Road
-----
0.292 AC.
0.292 AC.
Developed Areas
ONSITE
OFFSITE
TOTAL
Total Area
4.800 AC.
1.130 AC.
5.930 AC.
Pervious Area
3.652 AC.
0.621 AC.
4.273 AC.
Yard/Landscape/Native vegetation
3.499 AC.
0.565 AC.
4.064 AC.
Driveway (Driveway Stem from Lots 3,
6 & 8 @ 2,202 SF/EA
0.153 AC.
-----
0.153 AC.
Asphalt Pathway
-----
0.056 AC.
0.056 AC.
Impervious Area
1.148 AC.
0.509 AC.
1.657 AC.
Roofs (10 Lots @ 4000 SF/EA)
0.918 AC.
-----
0.918 AC.
Driveways 10 Lots 1,000 SF/EA
0.230 AC.
-----
0.230 AC.
Road
-----
0.303 AC.
0.303 AC.
Pathway
-----
0.055 AC.
0.055 AC.
Driveway Approach 10
-----
0.045 AC.
0.045 AC.
Ex. Road
-----
0.106 AC.
0.106 AC.
EXISTING CONDITION SUMMARY
The existing site is currently undeveloped and is heavily forested. The sites topography
contains a high point elevation of approximately 386.00 feet and is located in the north
end of the western half of the site. The site topography slopes down from the high point
to the south and east. There is a topographic low point elevation of approximately 362.00
feet located along the eastern property line.
Per the NRCS soils survey, onsite soils consist of Alderwood gravelly sandy loam (0 to
8% slopes). This soil is nearly level to undulating. Surface runoff is slow and the
erosion hazard is slight. See the NRCS soils survey in Appendix A for additional
information.
PROPOSED DEVELOPED SITE CONDITIONS SUMMARY
The roofs for lots 1-6 & 8-10 will be fitted with a downspout tightline system that will
convey roof runoff to the properly sized onsite individual lot infiltration trench. A
portion of the roof runoff for Lot 7 will be routed to the pervious driveway reservoir
course section for infiltration and the rest of the roof runoff will be routed to an onsite
infiltration trench. The runoff from the driveways for Lots 1 & 2 will be collected and
conveyed to the reservoir course under the pervious driveway stem on Lot 3. The Lot 3
driveway pad at the house location will be impervious and the stormwater runoff will be
collected and conveyed to the reservoir course under the pervious driveway stem of Lot
3. The runoff from the driveways for Lots 4 & 5 will be collected and conveyed to the
reservoir course under the pervious driveway stern on Lot 6. The Lot 6 driveway pad at
9
the house location will be impervious and the stormwater runoff will be collected and
conveyed to the reservoir course under the pervious driveway stem of Lot 6. The runoff
from the driveway for Lot 7 will be collected and conveyed to the reservoir course under
the pervious driveway stein on Lot 8. The Lot 8 driveway pad at the house location will
be impervious and the stormwater runoff will be collected and conveyed to an onsite
infiltration trench. The driveways for Lots 9 and 10 will be impervious and the
stonnwater runoff will be collected and conveyed to an onsite individual infiltration
trench. Stormwater from the driveways will be treated via the native soil which meets the
CEC and organic content required for treatment. The remaining disturbed soils will be
amended per Reference 11 in the in the King County 2016 Surface Water Design
Manual. Each of these stormwater flow control and treatment BMP's have been designed
per the King County 2016 Surface Water Design Manual.
Offsite frontage improvements along SW 366"' St consist of a full road improvement
(12'w on the south side and 8'w on the north side) with a 2'w gravel shoulder and
bioretention cell on both sides and a 5'w pervious asphalt pathway (impervious at
driveway locations) on the south side. The runoff from the road and driveway
approaches will be collected, treated utilizing infiltration from both the bioretention cells
and the pervious asphalt pathway reservoir course. The bioretention cell and the pervious
asphalt pathway reservoir course will be hydrologically connected by having the
reservoir course directly adjacent to the bioretention soil. The bioretention cells are
located between the driveway approaches with the infiltration trenches located under the
driveway approaches. Frontage improvements along 61h Ave SW consist of a minimum
2'w gravel shoulder and 5'w impervious asphalt path all on the east side of the road
(project side). Regrading of existing ditch will take place as necessary.
SECTION II - CONDITIONS AND REQUIREMENTS S SUMMARY
This report satisfies the Technical Information Report requirement to provide a written
document discussion project scope.
SECTION III - OFF -SITE ANALYSIS
All onsite stormwater will be controlled onsite via infiltration binps. Stormwater runoff
from the frontage improvements along SW 366th St. will be infiltrated within the adjacent
bioretention cells & infiltration trenches. Emergency overflow of stormwater from the
frontage improvements along SW 366t" St will be conveyed down its natural drainage
path to the east via a 12" storm pipe connecting to the existing stone system
approximately 112 feet to the east along SW 366th St. From here stormwater will
continue east in series of storm pipes for approximately 1,240 feet where stormwater will
be released into the Hylebos Wetlands. Stormwater from the frontage improvements
along 6th Ave SW will be conveyed down its natural drainage path to the south via a
series of ditches and culverts for approximately 360 feet. From here it appears that
stormwater is conveyed south through a natural drainage swale for approximately 1,035
feet which ends our 1/ mile downstream analysis.
0
SECTION IV - FLOW CONTROL, LOW IMPACT DEVELOPMENT AND
W;A.°TER, (QUALITY FACILITY .ANALYSIS & DESIGN
As previously stated, the roofs for lots 1-6 & 8-10 will be fitted with a downspout
tightline system that will convey roof runoff to the properly sized onsite individual lot
infiltration trench. A portion of the roof runoff for Lot 7 will be routed to the pervious
driveway reservoir course section for infiltration and the rest of the roof runoff will be
routed to an onsite infiltration trench. The runoff from the driveways for Lots 1 & 2 will
be collected and conveyed to the reservoir course under the pervious driveway stem on
Lot 3. The Lot 3 driveway pad at the house location will be impervious and the
stormwater runoff will be collected and conveyed to the reservoir course under the
pervious driveway stein of Lot 3. The runoff from the driveways for Lots 4 & 5 will be
collected and conveyed to the reservoir course under the pervious driveway stem on Lot
6. The Lot 6 driveway pad at the house location will be impervious and the stonnwater
runoff will be collected and conveyed to the reservoir course under the pervious driveway
stem of Lot 6. The runoff from the driveway for Lot 7 will be collected and conveyed to
the reservoir course under the pervious driveway stem on Lot 8. The Lot 8 driveway pad
at the house location will be impervious and the stormwater runoff will be collected and
conveyed to an onsite infiltration trench. The driveways for Lots 9 and 10 will be
impervious and the stormwater runoff will be collected and conveyed to an onsite
individual infiltration trench. Stormwater from the driveways will be treated via the
native soil which meets the CEC and organic content required for treatment. The
remaining disturbed soils will be amended per Reference 11 in the in the King County
2016 Surface Water Design Manual. Each of these stormwater flow control and
treatment BMP's have been designed per the King County 2016 Surface Water Design
Manual.
Offsite frontage improvements along SW 3661h St consist of a full road improvement
(I 2'w on the south side and 8'w on the north side) with a 2'w gravel shoulder and
bioretention cell on both sides and a 5'w pervious asphalt pathway (impervious at
driveway locations) on the south side. The runoff from the road and driveway
approaches will be collected, treated utilizing infiltration from both the bioretention cells
and the pervious asphalt pathway reservoir course. The bioretention cell and the pervious
asphalt pathway reservoir course will be hydrologically connected by having the
reservoir course directly adjacent to the bioretention soil. The bioretention cells are
located between the driveway approaches with the infiltration trenches located under the
driveway approaches. Frontage improvements along 6t" Ave SW consist of a minimum
2'w gravel shoulder and 5'w impervious asphalt path all on the east side of the road
(project side). Regrading of existing ditch will take place as necessary.
A geotechnical report was prepared by Terra Associates, Inc. on November 12, 2020.
They found that the soils were conducive to infiltration and determined that a 0.25 in/hr
infiltration rate be used for LID facilities and a 0.1 in/hr infiltration rate be used for
pervious pavement. See the geotechnical report in Appendix A for additional
information.
9
MGSFlood continuous modeling program was utilized to size the infiltration facilities per
City of Federal Way requirements to utilize the latest addition of the King County
Surface Water Design Manual (2016) for stonmwater design. See section titled "Storm
Drainage Calculation Summary" for additional information.
SECTION V - CONVEYANCE SYSTEM ANALYSIS AND DESIGN
A 12" pipe will be utilized to convey stormwater runoff from frontage improvements. 4"
roof drain tightline systems will be provided at each proposed structure location for roof
runoff. Formal conveyance calculations will be provided during final engineering if
needed.
SECTION VI - SPECIAL REPORTS AND STUDIES
See attached geotechnical report prepared by Terra Associates, Inc. on November 12,
2020 located in Appendix A for additional information regarding onsite soils.
SECTION VII - OTHER PERMITS
Other permits will include Site Development permit from the City of Federal Way.
SECTION VIII - GSWPPP ANALYSIS AND DESIGN
The "Construction Stormwater Pollution Prevention Plan" will be completed during final
engineering.
SECTION IX - BOND QUANTITIES FACILITY SUMMARIES AND
TIECLORA.TION OF COVENANT
In accordance with Core Requirement #7, financial guarantee requirements will be met at
the appropriate time.
SECTION X - OPERATIONS AND MAINTENANCE MANUAL
The "Operations and Maintenance Manual" will be completed during final engineering.
STORM DRAINAGE
CALCULATION SUMMARY
LARSON & ASSOCIATES, INC.
SURVEYORS, ENGINEERS AND PLANNERS
9027 PACIFIC AVENUE, SUITE 4
TACOMA, WA 98444 (253) 474-3404
7
SW st. F Ro-�,\ A L-\ J M �FO�J eA4 ENTs (fALCVLA110tJ
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 01/19/2021 6:04 PM
Report Generation Date: 01/19/2021 6:04 PM
Input File Name:
Project Name:
Analysis Title:
Comments:
LpRUE c-T sI oe - SoorN sr0&�
Bioretention Cell - Frontage Improvements (366th st with pervious sidewalk).fld
South Campus Estates
Frontage Improvements
PRECIPITATION INPUT
Computational Time Step (Minutes): 60
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station 961040 Puget East 40 in MAP
Evaporation Scale Factor 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.346 0.264
Area of Links that Include Precip/Evap (acres) 0.000 0.082
Total (acres) 0.346 0.346
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1----------
------- Area (Acres) --------
Till Forest 0.346
Subbasin Total 0.346
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Impervious 0.264
Subbasin Total 0.264
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
LINK DATA
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 3
------------------------------------------
Link Name: New Bio Lnk1
Link Type: Bioretention Facility
Downstream Link Name: Pervious Asphalt Pathway
Base Elevation (ft)
100.00
Riser Crest Elevation (ft)
: 100.50
Storage Depth (ft)
0.50
Bottom Length (ft)
381.0
Bottom Width (ft)
3.0
Side Slopes (ft/ft) : L1= 3.00 L2= 3.00 W1= 2.00 W2= 3.00
Bottom Area (sq-ft)
1143.
Area at Riser Crest El (sq-ft)
2,112.
(acres) :
0.048
Volume at Riser Crest (cu-ft)
1,156.
(ac-ft)
0.027
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Biosoil Thickness (ft)
1.50
Biosoil Saturated Hydraulic Conductivity (in/hr)
2.00
Biosoil Porosity (Percent)
20.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr)
0.25
Riser Geometry
Riser Structure Type
Riser Diameter (in)
Common Length (ft)
Riser Crest Elevation
Hydraulic Structure Geometry
Number of Devices: 0
Link Name: New Copy Lnk3
Link Type: Copy
Downstream Link: None
Circular
6.00
0.000
100.50 ft
Link Name: Pervious Asphalt Pathway
Link Type: Porous Pavement Structure
Downstream Link Name: New Copy Lnk3
Pavement Length (ft)
: 491.00
Pavement Width (ft)
: 5.00
Pavement Slope (ft/ft)
: 0.073
Pavement Infiltration Rate (in/hr)
: 20.000
Number of Infiltration Cells
: 64
Trench Cell Length (ft)
: 10.00
Trench Cell Width (ft)
: 6.25
Trench Cell Depth (ft)
: 1.17
Trench Gravel Porosity (%)
: 30.00
Trench Bed Slope (ft/ft)
: 0.073
0
Native Soil Infiltration Rate (in/hr) : 0.100
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 3
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 59.992
Total: 59.992
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
Link: New Bio Lnk1 Not Computed
Link: New Copy Lnk3 0.000
Link: Pervious Asphalt Pat Not Computed
Total: 0.000
Total Predevelopment Recharge is Greater than Post Developed
Average Recharge Per Year, (Number of Years=158)
Predeveloped: 0.380 ac-ft/year, Post Developed: 0.000 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 3
********** Link: New Copy Lnk3 **********
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 0.02
Inflow Volume Including PPT-Evap (ac-ft): 0.02
Total Runoff Infiltrated (ac-ft): 0.00, 0.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.02
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 0.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Copy Lnk3 ��
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Postdevelopment Runoff
Tr (Years)
Discharge (cfs)
Tr (Years)
Discharge (cfs)
----------------------------------------------------------------------------------------------------------
2-Year
7.346E-03
2-Year
0.000
5-Year
1.254E-02
5-Year
0.000
10-Year
1.560E-02
10-Year
0.000
25-Year
2.013E-02
25-Year
0.000
50-Year
2.424E-02
50-Year
2.505E-03
100-Year
2.909E-02
100-Year
2.670E-02
200-Year
3.934E-02
200-Year
6.942E-02
** Record too Short to Compute Peak Discharge for These
Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.7% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -0.2% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.9% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
P IMIE, M-" Ulf CELL - NORTH St DE 01- 36b" Si"
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 12/23/202010:47 AM
Report Generation Date: 12/28/2020 4:52 PM
Input File Name: Bioretention Cell - Frontage Improvements (north side of 366th st).fld
Project Name: South Campus Estates
Analysis Title: Bioretention Cell
Comments:
Computational Time Step (Minutes):
PRECIPITATION INPUT
,G u
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station 961040 Puget East 40 in MAP
Evaporation Scale Factor 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.126 0.116
Area of Links that Include Precip/Evap (acres) 0.000 0.010
Total (acres) 0.126 0.126
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Till Forest 0.126
Subbasin Total 0.126
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Impervious 0.116
Subbasin Total 0.116
************************* LINK DATA *******************************
ENARIO: PREDEVELOPED t?-
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Bio Lnk1
Link Type: Bioretention Facility
Downstream Link: None
Base Elevation (ft)
100.00
Riser Crest Elevation (ft)
Storage Depth (ft)
0.50
Bottom Length (ft)
220.0
Bottom Width (ft)
2.0
Side Slopes (ft/ft) :
L1= 3.00
Bottom Area (sq-ft)
440.
Area at Riser Crest El (sq-ft)
1,115.
(acres) :
0.026
Volume at Riser Crest (cu-ft)
520.
(ac-ft)
0.012
100.50
L2= 3.00 W 1= 3.00 W2= 3.00
Infiltration on Bottom and Sideslopes Selected
Soil Properties
Biosoil Thickness (ft) 1.50
Biosoil Saturated Hydraulic Conductivity (in/hr) 2.00
Biosoil Porosity (Percent) 20.00
Maximum Elevation of Bioretention Soil : 101.00
Native Soil Hydraulic Conductivity (in/hr) 0.25
Riser Geometry
Riser Structure Type
: Circular
Riser Diameter (in)
: 6.00
Common Length (ft)
: 0.000
Riser Crest Elevation
: 100.50 ft
Hydraulic Structure Geometry
Number of Devices: 0
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Link: New Bio Lnk1 ********** Link WSEL Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
--------------------------------------
1.05-Year
99.266
1.11-Year
99.342
1.25-Year
99.432
2.00-Year
99.648
13
3.33-Year
99.899
5-Year
100.036
10-Year
100.158
25-Year
100.441
50-Year
100.488
100-Year
100.508
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 21.847
Total: 21.847
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
Link: New Bio Lnk1 55.784
Total
55.784
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years=158)
Predeveloped: 0.138 ac-ft/year, Post Developed: 0.353 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Bio Lnk1
**********
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 51.23
Inflow Volume Including PPT-Evap (ac-ft): 55.78
Total Runoff Infiltrated (ac-ft): 55.78, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.01
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Bio Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Tr (Years) Discharge (cfs)
Postdevelopment Runoff
Tr (Years) Discharge (cfs)
2-Year 2.675E-03 2-Year 0.000 J
5-Year
4.566E-03
5-Year
0.000
10-Year
5.681 E-03
10-Year
0.000
25-Year
7.330E-03
25-Year
0.000
50-Year
8.826E-03
50-Year
3.654E-04
100-Year
1.059E-02
100-Year
5.499E-03
200-Year
1.433E-02
200-Year
2.479E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.7% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -0.2% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.9% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
15
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 01/05/2021
Report Generation Date: 01/19/2021 6:06 PM
Input File Name: Lot infiltration trench.fld
Project Name: South Campus Estates
Analysis Title: Infiltration Trench
Comments:
PRECIPITI
Computational Time Step (Minutes): 60
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 PugE
Evaporation Station 961040 Puget E
Evaporation Scale Factor 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS I
Default HSPF Parameters Used (Not P
WATERSHED DEFINITION
Predevelopment/Post Development Tributi
Predev
Total Subbasin Area (acres)
Area of Links that Include Precip/Evap (acres)
Total (acres)
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin: Subbasin 1
-------Area (Acres)
Till Forest 0.092
Subbasin Total 0.092
----------------------SCENARIO: POSTDEVELOPE
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Impervious 0.092
Subbasin Total 0.092
************************* LINK DATA ***************,
ENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
Link Name: New Infilt Trench Lnk1
Link Type: Infiltration Trench
Downstream Link: None
Trench Type
: Trench on Embankment Sideslope
Trench Length (ft)
60.00
Trench Width (ft)
20.00
Trench Depth (ft)
1.50
Trench Bottom Elev (ft)
100.00
Trench Rockfill Porosity (%)
30.00
Constant Infiltration Option Used
Infiltration Rate (in/hr): 0.25
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 15.952
Total: 15.952
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
-----------------------------------------------------------------------------------------------
Subbasin: Subbasin 1 0.000
Link: New Infilt Trench Ln 40.631
Total: 40.631
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years=158)
Predeveloped: 0.101 ac-ft/year, Post Developed: 0.257 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED 17
Number of Links: 1
********** Link: New Infilt Trench Lnk1 **********
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 40.63
Inflow Volume Including PPT-Evap (ac-ft): 40.63
Total Runoff Infiltrated (ac-ft): 40.63, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.01
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Infilt Trench Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Postdevelopment Runoff
Tr (Years)
----------------------------------------------------------------------------------------------------------
Discharge (cfs)
Tr (Years)
Discharge (cfs)
2-Year
1.953E-03
2-Year
0.000
5-Year
3.334E-03
5-Year
0.000
10-Year
4.148E-03
10-Year
0.000
25-Year
5.352E-03
25-Year
0.000
50-Year
6.444E-03
50-Year
5.861 E-03
100-Year
7.736E-03
100-Year
8.610E-03
200-Year
1.046E-02
200-Year
1.946E-02
** Record too Short to Compute Peak Discharge for These
Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.4% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): 0.0% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.9% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
1N1)1V1Vg L- Lyw� t�� �L,1'R�i toy► -rR��c.►�
MGS FLOOD �-)-tiTs 9-10 RooFs @ 01060 5F
PROJECT REPORT j� pR1%jcwAgS & 11000 sr-)
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 01/05/2021 4:06 PM
Report Generation Date: 01/19/2021 6:05 PM
Input File Name: Lot infiltration trench (5,000sf).fld
Project Name: South Campus Estates
Analysis Title: Infiltration Trench
Comments:
PRECIPITATION INPUT
Computational Time Step (Minutes): 60
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station 961040 Puget East 40 in MAP
Evaporation Scale Factor : 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.115 0.115
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 0.115 0.115
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Till Forest 0.115
Subbasin Total 0.115
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin: Subbasin 1
-------Area (Acres)
Impervious 0.115
Subbasin Total 0.115
************************* LINK DATA ******************************* 69
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
Link Name: New Infilt Trench Lnk1
Link Type: Infiltration Trench
Downstream Link: None
Trench Type
: Trench on Embankment Sideslope
Trench Length (ft)
60.00
Trench Width (ft)
26.00
Trench Depth (ft)
1.50
Trench Bottom Elev (ft)
100.00
Trench Rockfill Porosity (%)
30.00
Constant Infiltration Option Used
Infiltration Rate (in/hr): 0.25
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 19.940
Total: 19.940
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 0.000
Link: New Infilt Trench Ln 50.788
Total: 50.788
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years=158)
Predeveloped: 0.126 ac-ft/year, Post Developed: 0.321 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED "LQ
Number of Links: 1
Link: New Infilt Trench Lnk1
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 50.79
Inflow Volume Including PPT-Evap (ac-ft): 50.79
Total Runoff Infiltrated (ac-ft): 50.79, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.01
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Infilt Trench Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Postdevelopment Runoff
Tr (Years)
----------------------------------------------------------------------------------------------------------
Discharge (cfs)
Tr (Years)
Discharge (cfs)
2-Year
2.442E-03
2-Year
0.000
5-Year
4.167E-03
5-Year
0.000
10-Year
5.185E-03
10-Year
0.000
25-Year
6.690E-03
25-Year
0.000
50-Year
8.055E-03
50-Year
0.000
100-Year
9.669E-03
100-Year
0.000
200-Year
1.308E-02
200-Year
2.056E-02
** Record too Short to Compute Peak Discharge for These Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%):-100.0% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.7% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -49.3% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%):-100.0% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
It
l.y "7 1,0FuTR-A 10M -iRC-W-4 (2,000 sP o-F R®ojz)
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 01/05/2021 4:11 PM
Report Generation Date: 01/19/2021 6:05 PM
Input File Name: Lot infiltration trench (2,000sf).fld
Project Name: South Campus Estates
Analysis Title: Infiltration Trench
Comments:
PRECIPITATION INPUT
Computational Time Step (Minutes):
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station 961040 Puget East 40 in MAP
Evaporation Scale Factor 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
Default HSPF Parameters Used (Not Modified by User) ***************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.046 0.046
Area of Links that Include Precip/Evap (acres) 0.000 0.000
Total (acres) 0.046 0.046
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin: Subbasin 1
-------Area (Acres)
Till Forest 0.046
Subbasin Total 0.046
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Impervious 0.046
Subbasin Total 0.046
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Infilt Trench Lnk1
Link Type: Infiltration Trench
Downstream Link: None
Trench Type
: Trench on Embankment Sideslope
Trench Length (ft)
50.00
Trench Width (ft)
12.00
Trench Depth (ft)
1.50
Trench Bottom Elev (ft)
100.00
Trench Rockfill Porosity (%)
30.00
Constant Infiltration Option Used
Infiltration Rate (in/hr): 0.25
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 7.976
Total: 7.976
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 0.000
Link: New Infilt Trench Ln 20.315
Total: 20.315
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years= 158)
Predeveloped: 0.050 ac-ft/year, Post Developed: 0.129 ac-ft/year
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED 13
Number of Links: 1
********* Link: New Infilt Trench Lnk1 *********
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 20.32
Inflow Volume Including PPT-Evap (ac-ft): 20.32
Total Runoff Infiltrated (ac-ft): 20.32, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.00
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Infilt Trench Lnk1
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Postdevelopment Runoff
Tr (Years)
----------------------------------------------------------------------------------------------------------
Discharge (cfs)
Tr (Years)
Discharge (cfs)
2-Year
9.767E-04
2-Year
0.000
5-Year
1.667E-03
5-Year
0.000
10-Year
2.074E-03
10-Year
0.000
25-Year
2.676E-03
25-Year
0.000
50-Year
3.222E-03
50-Year
2.416E-04
100-Year
3.868E-03
100-Year
3.876E-03
200-Year
5.230E-03
200-Year
9.403E-03
** Record too Short to Compute Peak Discharge for These
Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.7% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): .-39.5% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.9% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
IL4
LO T5 S PRWOUS 0SIV6W,4W S7ZNA
MGS FLOOD
PROJECT REPORT
Program Version: MGSFlood 4.46
Program License Number: 200810005
Project Simulation Performed on: 01/05/2021 10:12 AM
Report Generation Date: 01/19/2021 6:11 PM
Input File Name: Pervious Driveway (stem) (3 lots).fld
Project Name: South Campus Estates
Analysis Title: Pervious Pavement
Comments:
PRECIPITATION INPUT
Computational Time Step (Minutes): 60
Extended Precipitation Time Series Selected
Climatic Region Number: 15
Full Period of Record Available used for Routing
Precipitation Station : 96004005 Puget East 40 in_5min 10/01/1939-10/01/2097
Evaporation Station 961040 Puget East 40 in MAP
Evaporation Scale Factor 0.750
HSPF Parameter Region Number: 1
HSPF Parameter Region Name : USGS Default
********** Default HSPF Parameters Used (Not Modified by User) **************
********************** WATERSHED DEFINITION ***********************
Predevelopment/Post Development Tributary Area Summary
Predeveloped Post Developed
Total Subbasin Area (acres) 0.120 0.069
Area of Links that Include Precip/Evap (acres) 0.000 0.051
Total (acres) 0.120 0.120
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Till Forest 0.120
Subbasin Total 0.120
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
---------- Subbasin : Subbasin 1
-------Area (Acres)
Impervious 0.069
Subbasin Total 0.069
************************* LINK DATA *******************************
----------------------SCENARIO: PREDEVELOPED 15
Number of Links: 0
************************* LINK DATA *******************************
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
------------------------------------------
Link Name: New Por Pavemt Lnk1
Link Type: Porous Pavement Structure
Downstream Link: None
Pavement Length (ft)
: 183.50
Pavement Width (ft)
: 12.00
Pavement Slope (ft/ft)
: 0.010
Pavement Infiltration Rate (in/hr)
: 20.000
Number of Infiltration Cells
: 2
Trench Cell Length (ft)
: 91.75
Trench Cell Width (ft)
: 18.00
Trench Cell Depth (ft)
: 1.50
Trench Gravel Porosity (%)
: 30.00
Trench Bed Slope (ft/ft)
: 0.010
Native Soil Infiltration Rate (in/hr)
: 0.100
**********************FLOOD FREQUENCY AND DURATION STATISTICS*******************
----------------------SCENARIO: PREDEVELOPED
Number of Subbasins: 1
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Subbasins: 1
Number of Links: 1
********** Link: New Por Pavemt Lnk1 ********** Link WSEL Stats
WSEL Frequency Data(ft)
(Recurrence Interval Computed Using Gringorten Plotting Position)
Tr (yrs) WSEL Peak (ft)
--------------------------------------
--------------------------------------
1.05-Year
0.701
1.11-Year
0.729
1.25-Year
0.784
2.00-Year
0.881
3.33-Year
0.975
5-Year
1.053
10-Year
1.180
25-Year
1.420
50-Year
1.497
100-Year
1.500
***********Groundwater Recharge Summary *************
Recharge is computed as input to Perind Groundwater Plus Infiltration in Structures
Total Predeveloped Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 20.806
Total: 20.806
e
Total Post Developed Recharge During Simulation
Model Element Recharge Amount (ac-ft)
Subbasin: Subbasin 1 0.000
Link: New Por Pavemt Lnkl 56.914
Total
56.914
Total Predevelopment Recharge is Less than Post Developed
Average Recharge Per Year, (Number of Years=158)
Predeveloped: 0.132 ac-ft/year, Post Developed: 0.360 ac-ftlyear
***********Water Quality Facility Data *************
----------------------SCENARIO: PREDEVELOPED
Number of Links: 0
----------------------SCENARIO: POSTDEVELOPED
Number of Links: 1
********** Link: New Por Pavemt Lnkl **********
Infiltration/Filtration Statistics --------------------
Inflow Volume (ac-ft): 30.47
Inflow Volume Including PPT-Evap (ac-ft): 56.91
Total Runoff Infiltrated (ac-ft): ,56.91, 100.00%
Total Runoff Filtered (ac-ft): 0.00, 0.00%
Primary Outflow To Downstream System (ac-ft): 0.01
Secondary Outflow To Downstream System (ac-ft): 0.00
Percent Treated (Infiltrated+Filtered)/Total Volume: 100.00%
***********Compliance Point Results *************
Scenario Predeveloped Compliance Subbasin: Subbasin 1
Scenario Postdeveloped Compliance Link: New Por Pavemt Lnkl
*** Point of Compliance Flow Frequency Data ***
Recurrence Interval Computed Using Gringorten Plotting Position
Predevelopment Runoff
Postdevelopment Runoff
Tr (Years)
----------------------------------------------------------------------------------------------------------
Discharge (cfs)
Tr (Years)
Discharge (cfs)
2-Year
2.548E-03
2-Year
0.000
5-Year
4.348E-03
5-Year
0.000
10-Year
5.411 E-03
10-Year
0.000
25-Year
6.981 E-03
25-Year
0.000
50-Year
8.405E-03
50-Year
1.568E-03
100-Year
1.009E-02
100-Year
8.288E-03
200-Year
1.364E-02
200-Year
2.964E-02
** Record too Short to Compute Peak Discharge for These
Recurrence Intervals
**** Flow Duration Performance ****
Excursion at Predeveloped 50%Q2 (Must be Less Than or Equal to 0%): -99.9% PASS
Maximum Excursion from 50%Q2 to Q2 (Must be Less Than or Equal to 0%): -99.6% PASS
Maximum Excursion from Q2 to Q50 (Must be less than 10%): -32.9% PASS
Percent Excursion from Q2 to Q50 (Must be less than 50%): 0.0% PASS
MEETS ALL FLOW DURATION DESIGN CRITERIA: PASS
277
**** LID Duration Performance ****
Excursion at Predeveloped 8%Q2 (Must be Less Than 0%):-100.0% PASS
Maximum Excursion from 8%Q2 to 50%Q2 (Must be Less Than 0%): -99.9% PASS
MEETS ALL LID DURATION DESIGN CRITERIA: PASS
APPENDIX "A"
MISCELLANEOUS
INFORMATION
LARSON & ASSOCIATES, INC.
SURVEYORS, ENGINEERS AND PLANNERS
9027 PACIFIC AVENUE, SUITE 4
TACOMA, WA 98444 (253) 474-3404
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Soil Map —King County Area, Washington
Map Unit Legend
Map Unit Symbol
Map Unit Name
Acres in AOI
Percent of AOI
AgB
Alderwood gravelly sandy
loam, 0 to S percent slopes
5.2
100.0%
Totals for Area of Interest
5.2
100.0%
(USDA Natural Resources Web Soil Survey 12/22/2020
i Conservation Service National Cooperative Soil Survey Page 3 of 3
/ L4
meability is moderately rapid I n the surfac
..go
AT
tibsoil and
ayer _^ very slow in the subst-woff.
n e a th
0 s e 'On�-o�i a-ubs�
Roots pease easily to the consolida **Tu-bstra-
Rootsy
re e
they t 0a the c Some
turi where they to mat on the Wi0fT-Ce. some
M where m e e
y t on t
rents, Alderwood material consists of Alden%,o
the subsm th c a k I
roots enter the subs m th cracks. Water
roots eatercracks.Water
SO' that have been so disturbed through urban-
moves on top of the subs in winter. Available
iza on that they no longer can be classified w*
water capacity is Lummn o w to medium,
slow In
medium,
the derwood series. These soils, however, h
t der
and the bazar erosion is mod
man
11 0
man), milax features. The tipper part f the 11,
IS
This is used for timber, pastu rries,
e
to a th of 20 to 40 inches, is brown o da
f 11 1 t .1. t
a crops, and for urban development. ity
brown velly sandy loam. Below this i,� a ayish-
nit IVe-2; woodland group 5dl,
brown, nsolidated and impervious subst-rat
Alderwoodravensandy loam, 0 to 6 Percent!
Slopes 's
Slopes g erally range from 0 to 15 percen,
9
AgBj--This soil is nearly level and
These ils are used for urban develop t.
-slopes
Undulating. It is similar to Alderwood gravelly
sandy loam, 6 to 15 percent slopes, but in places
derwo
its surface layer is 2 to 3 inches thicker. Areas
al, 0 to east slo
are irregular in shape and range from 10 acres to
(Ain .--inm, y areas t is sail is 1ev as a
slightly more than 600 acres in size.
result of sha hig during construction r urban
Some areas are as much as 15 percent included
facilities. A as are rectangular 1 shape and
Norma, Bellingham, Tukwila, and Shalcar soils, all
range from 5 ac s to about 400 acre in size.
of which are poorly drained; and some areas in the
Representati profile of, Arent!.; Alderwood
vicinity of Enumclaw are as much as 10 percent
material,, 0 to 6 ercent san urban area,
lopes, i
Buckley soils.
1,500 feet west a 350 feeof the northeast
Runoff is slow, and the erosion hazard is
isout
corner of see * 23 25 " . I .:
slight.
This Alderwood soil is used for timber, pasture,
0 to 26 inches, dar brown (10Y 4/3) gravelly
berries, and row crops, and for urban development.
sandy loam, pa brown YR 6/3) dry;
Capability unit IVe-2; woodland group 3d2.
massive; slight hard, ery friable, non -
sticky, nonplast ; max roots; medium acid;
ood 0 awn 30
abrupt, smooth be da 23 to 29
es .--Depth to the §777stTatum I this s
thick.
V ies within short distances, but is commonly
26 to 60 inches, grayish- wn (2.5Y 5/2) weakly
ab t 40 inches. Areas are elongated and ran
consolidated to str gly consolidated glacial
from to about 250 acres in size,
till, light browni ray (2.5Y 6/2) dry;
So s included with this soil in mappin Pake
common, medium, pr I - lit mottles of yellowish
up no e than 30 percent of the total a eage.
brown (10YR 5/6) oi.st massive; no roots;
Some are are up to 25 percent Everett that
medium acid. Pia fee thick.
''ils
have slop. of 15 to 30 percent, and s areas are
.
up to 2 per nt BellingfiWn,. NO rma, Seattle soils,
I
:;ea
The upper, very able par Of the soil extends
e
which are in -pressions. Some are , especially
to a depth of 20 to 0 inches a ranges from dark
s tle Hi s, and north of
on. Squak Mount n, in Newcastle
grayish brown to da yellowish own.
I
Tiger Mountain, re 2S percent B , site and Ovall
Some areas are to 30 percel included soils
soils. Beausite ils are unde ain by sandstone,
that are similar this soil mat ial, but either
and Ovall soils by idesite,
shallower or doe r over the compa substratum;
Runoff is medium, end the rosion hazard is
and some areas e 5 to 10 percent ry gravelly
severe. The slippage ate al is moderate.
Everett soils d sandy Indianola sa ls.
This Alderwood soil s sed mostly for timber.
This Arents, Alderwood soil is mac rately well
Some areas on the lower its of slopes are used
drained. Pei eability in the upper, sturbed so.ii
for pasture. Capabi t Vie-2; woodland group
material is derately rapid to modera ly slow,
3dl.
depending o its compaction during cons tiction.
The substr-lum -is very slowly permeable. Roots
e
el it e 3d
VoI.T mapping d7tes about 50 VNIcent erwood
'c
penetrate o and tend to mat on the surf e of the
�o
c t t
gravelly sandy m and 25 per e•Ki ta silt
K a
consolid ed substratum. Some roots ent the
e
rs
n ' b
Distribution t
e D u t on
loam. Slopes 25 to 70 percen Distribution
substrat through cracks. Water moves a op of
file
t he r dl a
within t t ces.
of the soils ari.es greatly within . ort distances,
s 0 n
Ile SU
sub ratum in winter. Available water pacify
an
About 1.5 ercent of some mapped a s is an
A b 0 u t e p e d
is low, Runoff is slow, and the erosion haz d is
a� s
included, named, very deep, moderate coarse
Ile Jude d 0 e oar,
n moderate
sligh
s so-0 is used for urban development
c a as
r ent of e r,
textured oil; and about 10 percent of e areas
.1
pabi ty unit IVe-2; woodland group 3d2,
d 1
is a v - deep, coarse -textured Indianola oi
n 110
r e y f r P.
_ Runoff
off rapid
g an r api d Dr nage and permeability vary. Runo f
to -y rapid, and the erosion hazard is se e to
jr Is s 11. d v to
v j hazard
east Aide o ate"
v re. It
ve severe. The slippage potential is :,e
s es -This so .. as convex slopes.
These soils are used for timber. Capabilit
e rectangular in shape and range from 10 acres
it VIIe-l; woodland group 2dl.
bout 450 acres in size.
10
GEOTECHNICAL REPORT
South Campus Estates
SW 366th Street,and6th Avenue SW
Federal Way, Washington
Project No. T-8347
Im
ASSOCIATES,LRRA Inc*
Consultants in Geotechnical Engineering, Geology
and
Environmental Earth Sciences
November 12, 2020
Project No. T-8347
Mr. Geoffrey P. Sherwin
Entitle Fund Two, LLC
P.O. Box 188
Puyallup, Washington 98371
Subject: Geotechnical Report
South Campus Estates
SW 366th Street and 6th Avenue SW
Federal Way, Washington
Dear Mr. Sherwin,
As requested, we conducted a geotechnical engineering study for the subject project. The attached report presents
our findings and recommendations for the geotechnical aspects of project design and construction.
In general, the soils at the site consist of six to eight inches of topsoil or forest duff overlying medium dense to
dense becoming very dense weathered and unweathered horizons of glacial till soils. No groundwater seepage was
observed during excavation of the site's test pits.
In our opinion, there are no geotechnical conditions that would preclude the planned residential development.
Buildings can be supported on conventional spread footings bearing on competent native soils or on structural fill
placed on competent native soils. Floor slabs and pavements can be similarly supported.
Detailed recommendations addressing these issues and other geotechnical design considerations are presented in
the attached report. We trust the information presented is sufficient for your current needs. If you have any
questions or require additional information, please call.
Sincerely yours,
TERRA ASSOCIATES, INC.
11-12-2020
12220 113th Avenue NE, Ste, 130, Kirkland, Washington 98034
Phone (425) 821-7777 • Fax (425) 821-4334
P
TABLE OF CONTENTS
Page No.
1.0
Project Description.......................................................................................................... 1
2.0
Scope of Work.................................................................................................................1
3.0
Site Conditions................................................................................................................2
3.1 Surface................................................................................................................ 2
3.2 Soils.................................................................................................................... 2
3.3 Groundwater....................................................................................................... 3
3.4 Geologic Hazards............................................................................................... 3
3.5 Seismic Site Class...............................................................................................4
4.0
Discussion and Recommendations..................................................................................4
4.1 General.........................................................................................................4
4.2 Site Preparation and Grading....................................................................... 4
4.3 Excavations..................................................................................................5
4.4 Foundations................................................................................................. 6
4.5 Slab -on -Grade Floors................................................................................... 6
4.6 Lateral Earth Pressures................................................................................ 7
4.7 Infiltration Feasibility.................................................................................. 7
4.8 Drainage ......................... .-..:.:..................... ,........... ...— ........ ,..................... 7
4.9 Utilities........................................................................................................ 8
4.10 Pavements...................................................................................................8
5.0
Additional Services.......................................................................................................... 9
6.0
Limitations.......................................................................................................................9
Figures
VicinityMap......................................................................................................................... Figure 1
Exploration Location Plan.................................................................................................... Figure 2
Typical Wall Drainage Detail............................................................................................... Figure 3
Appendix
Field Exploration and Laboratory Testing.......................................................................Appendix A
Geotechnical Report
South Campus Estates
SW 366th Street and 6th Avenue SW
Federal Way, Washington
1.0 PROJECT DESCRIPTION
We were provided a preliminary site plan titled "Preliminary Plat, South Campus Estates" dated November 2, 2020,
prepared by Larson and Associates. The site will be developed with ten individual residential building lots along
with associated infrastructure improvements. The site's gently sloping topography indicates minor grading will be
required to achieve finished lot and roadway elevations. An undated preliminary civil plan showing storm facility
sections indicates LID features that include permeable driveways, pervious shared access road, and bio-retention
swales are planned as part of storinwater runoff flow control at the site.
We expect that the residential structures will be two- to three-story, wood -frame structures with their main floors
framed over a crawlspace. Foundation loads should be relatively light, in the range of 1 to 2 kips per foot for bearing
walls and 10 to 20 kips for isolated columns.
The recommendations contained in the following sections of this report are based on our understanding of the above
design features. We should review design drawings as they become available to verify that our recommendations
have been properly interpreted and incorporated into project design and to amend or supplement our
recommendations, if required.
2.0 SCOPE OF WORK
Our work was completed in accordance with our authorized proposal, dated April 24, 2020. We explored subsurface
conditions at the site by observing conditions in five test pits, each excavated to a depth of ten feet below existing
surface grades using an excavator. Based on the results of our field study, laboratory testing, and analyses, we
developed geotechnical recommendations for project design and construction. Specifically, this report addresses
the following:
• Soil and groundwater conditions.
• Geologic hazards per the City of Federal Way Municipal Code.
• Seismic site class per 2018 International Building Code (IBC).
• Site preparation and grading.
• Excavations
• Foundations
November 12, 2020
Project No. T-8347
• Floor slabs.
• Lateral earth pressures for wall design.
• Infiltration feasibility.
• Drainage
• Utilities
• Pavements
It should be noted that recommendations outlined in this report regarding drainage are associated with soil strength,
design earth pressures, erosion, and stability. Design and performance issues with respect to moisture as it relates
to the structure environment are beyond Terra Associates' purview. A building envelope specialist or contractor
should be consulted to address these issues, as needed.
3.0 SITE CONDITIONS
3.1 Surface
The project site consists of a single undeveloped tax parcel totaling approximately 4.7 acres of land located at the
southeast corner of SW 366th Street and 6th Avenue SW in Federal Way, Washington. The site is bounded to the
east and south by rural -residential parcels. The approximate site location is shown on Figure 1.
Vegetation consisting of variably sized deciduous trees, scattered mature conifers, and associated understory
currently covers the entire site. The site's topography is mostly level at its western half. The eastern portion of the
site slopes gently down to the east. No. flowing or ponded water was observed at the site during our visit.
3.2 Soils
Our field investigation indicated the soil conditions generally consist of six to eight inches of topsoil/duff overlying
weathered and unweathered horizons of glacial till soils. Weathered till soils were observed in each test pit to
depths ranging from 2 %2 feet to 4 feet. The weathered till consists of medium dense to dense silty sand and silt
with variable gravel and cobble contents. Each test pit showed unweathered till directly underlying the weathered
till. The unweathered till is composed of very dense, moderately to strongly cemented silty sand with gravel and
scattered cobbles. A two -foot thick layer of dense silt was observed within the till at a depth of seven feet at Test
Pit TP-1.
The Lidar-revised Geologic Map of the Poverty Bay 7.5' Quadrangle, King and Pierce Counties, Washington by
R.W. Tabor et al (2014) shows the soils at the site's western and eastern portions mapped, respectively, as Till,
(Qvt) and Ice -contact deposits (Qvi). The soils observed in the test pits are generally consistent with the published
description of till soils.
The preceding discussion is intended to be a general review of the soil conditions encountered. For more detailed
descriptions, please refer to the Test Pit Logs in Appendix A. The approximate locations of the test pits are shown
on Figure 2.
Page No. 2
November 12, 2020
Project No. T-8347
3.3 Groundwater
No groundwater seepage was observed during excavation of the test pits. Test Pits TP-1 and TP-2 showed mottling
of the upper weathered till soils indicating groundwater is likely perched within this layer on a seasonal basis. We
expect the perched condition develops during and shortly following the wet winter months (November through
April).
3.4 Geologic Hazards
We evaluated site conditions for the presence of geologic hazards as designated in the Federal Way Municipal Code
(FWMC). Chapter 19.05.070 of the FWMC states "Geologically hazardous means areas which because of their
susceptibility to erosion, landsliding, seismic, or other geological events require specific studies to determine
appropriate buffers or property use."
Erosion Hazard Areas
According to Chapter 19.05.070 (1) of the FWMC, "Erosion hazard areas are those areas identified by the U.S.
Department of Agriculture's Natural Resource Conservation Service as having a moderate to severe or severe to
very severe rill and inter -rill erosion hazard due to natural agents such as wind, rain, splash, frost action, or stream
flow; those areas containing the following group of soils when they occur on slopes of 15 percent or greater:
Alderwood-Kitsap ("AkF"), Alderwood gravelly sandy loam ("AgD"), Kitsap silt loam ("KpD"), Everett ("EvD"),
and Indianola ("InD"); and those areas impacted by shore land and/or stream bank erosion."
The NRCS maps the site soils as Alderwood gravelly sandy loam, 0 to 8 percent slopes. The erosion hazard rating
assigned by the NRCS to these soils is "slight." Using the above criteria, no erosion hazard areas exist at the site.
The site soils will, however, be susceptible to erosion when exposed during construction. In our opinion, the erosion
potential of site soils would be adequately mitigated'wth proper implementation and maintenance of City of Federal
Way approved Best Management. Practices (BMPs) for erosion prevention and sedimentation control during
construction.
Landslide Hazard Areas
Chapter 19.05.070 (2) of the FWMC lists several criteria defining "landslide hazard areas." Due to the flat to gently
sloping site topography, absence of groundwater, and high inherent shear strength of the glacial soils, it is our
opinion that FWMC criteria defining landslide hazard areas do not exist at the site.
Seismic Hazard Areas
Chapter 19.05.070 (3) of the FWMC defines seismic hazard areas as "...those areas subject to severe risk of
earthquake damage as a result of seismically induced ground shaking, slope failure, settlement or soil liquefaction,
or surface faulting. These conditions occur in areas underlain by cohesionless soils of low density usually in
association with a shallow groundwater table." Based on the soil and groundwater conditions we observed at the
site, it is our opinion that there is no risk for damage resulting from soil liquefaction or subsidence during a severe
seismic event.
Page No. 3
Ali
November 12, 2020
Project No. T-8347
A review of a map titled "Faults and Earthquakes in Washington State," dated 2014 by Jessica L. Czajkowski and
Jeffrey D. Bowman shows that the nearest fault is part of the Tacoma Fault Zone. This fault is located approximately
four miles north of the site. This fault is designated as "Class B" having indeterminate age and "...shows no
evidence of activity during the Quaternary." Accordingly, during a seismic event, the risk of ground rupture along
a fault line at the site is low.
Based on our review, in our opinion, unusual seismic hazard areas do not exist at the site, and design in accordance
with local building codes for determining seismic forces would adequately mitigate impacts associated with ground
shaking.
3.5 Seismic Site Class
Based on the site soil conditions and our knowledge of the area geology, per the 2018 International Building Code
(IBC), site class "C" should be used in structural design.
4.0 DISCUSSION AND RECOMMENDATIONS
4.1 General
Based on our study, there are no geotechnical conditions that would preclude the planned development. In general,
structures can be supported on conventional spread footings bearing on competent native soils, or on structural fill
placed on the competent native soils. Floor slabs and pavements can be similarly supported.
Most of the soils at the site contain a sufficient percentage of fines (silt- and clay -sized particles) such that they will
be difficult to compact as structural fill when too wet or too dry. If grading activities will take place during the
winter season, the owner should be prepared to import free -draining granular material for use as structural fill and
backfill.
Detailed recommendations regarding these issues and other geotechnical design considerations are provided in the
following sections of this report. These recommendations should be incorporated into the final design drawings
and construction specifications.
4.2 Site PrMaration and Gradin
To prepare the site for construction, all vegetation and organic surface soils should be stripped and removed from
the site. Based on our test pit observations, we expect surface stripping depths of about 6 to 8 inches will be required
to remove topsoil or forest duff. Organic soils will not be suitable for use as structural fill but may be used for
limited depths in nonstructural areas or for landscaping purposes.
A representative of Terra Associates, Inc. should examine all bearing surfaces to verify that conditions encountered
are as anticipated and are suitable for placement of structural fill or direct support of building and pavement
elements. Our representative may request proofrolling exposed surfaces with a heavy rubber -tired vehicle to
determine if any isolated soft and yielding areas are present. If unstable yielding areas are observed, we recommend
that they be cut to firm bearing soil and filled to grade with structural fill. In pavement areas, if the depth of
excavation to remove unstable soils is excessive, use of geotextile fabric such as Mirafi 500X or equivalent in
conjunction with clean granular structural fill can be considered in order to limit the depth of removal.
Page No. 4
ADZ
November 12, 2020
Project No. T-8347
The site soils contain a sufficient percentage of fines (silt and clay size particles) that will make them difficult to
compact as structural fill if they are too wet or too dry. Accordingly, the ability to use these soils from site
excavations as structural fill will depend on their moisture content and the prevailing weather conditions when site
grading activities take place. Soils that are too wet to properly compact could be dried by aeration during dry
weather conditions or mixed with an additive such as cement or lime to stabilize the soil and facilitate compaction.
If an additive is used, additional Best Management Practices (BMPs) for its use will need to be incorporated into
the Temporary Erosion and Sedimentation Control (TESC) plan for the project. Soils that are dry of optimum
should be moisture conditioned by controlled addition of water and blending prior to material placement.
Cobbles up to 12 inches in size can be used in structural fill provided they are dispersed throughout the fill during
placement and the contractor adequately compacts soil immediately adjacent to the large cobbles.
If grading activities are planned during the wet winter months, or if they are initiated during the summer and extend
into fall and winter, the owner should be prepared to import wet weather structural fill. For this purpose, we
recommend importing a granular soil that meets the following grading requirements:
U.S. Sieve Size
Percent Passing
6 inches
100
No. 4
75 maximum
No. 200
5 maximum*
*Based on the 3/4-inch fraction.
Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural
fill.
Structural fill should be placed in uniform loose layers no thicker than 12 inches and compacted to a minimum of
95 percent of the soil's maximum dry density, as determined by American Society for Testing and Materials
(ASTM) Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction
should be within two percent of its optimum, as determined by this ASTM standard. In nonstructural areas, the
degree of compaction can be reduced to 90 percent.
4.3 Excavations
All excavations at the site associated with confined spaces, such as utilities and retaining walls, must be completed
in accordance with local, state, and federal requirements. Based on the Washington Industrial Safety and Health
Act (WISHA) regulations, the upper medium dense soils would be classified as Type C soils. The dense to very
dense, cemented till soils would be classified as Type A soils.
Accordingly, temporary excavations having their side slopes in Type C soils should be laid back at a slope
inclination of 1.5:1 (Horizontal:Vertical) or flatter. For Type A soils, side slopes can be laid back at a slope
inclination of 0.75:1 or flatter.
Excavations that expose seasonal perched seepage can likely be dewatered by conventional sump -pumping
procedures along with a system of collection trenches.
Page No. 5
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November 12, 2020
Project No. T-8347
The above information is provided solely for the benefit of the owner and other design consultants and should not
be construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job
site safety is the sole responsibility of the project contractor.
4.4 Foundations
Residential structures may be supported on conventional spread footing foundations bearing on competent native
soils or on structural fill placed above the native soils. Foundation subgrades should be prepared as recommended
in Section 4.2 of this report.
Perimeter foundations exposed to the weather should bear at a minimum depth of 1.5 feet below final exterior grades
for frost protection. Interior foundations can be constructed at any convenient depth below the floor slab. We
recommend designing foundations bearing on competent soil for a net allowable bearing capacity of 2,500 pounds
per square foot (psf). For short-term loads, such as wind and seismic, a one-third increase in this allowable capacity
can be used in design. With the anticipated loads and this bearing stress applied, building settlements should be
less than one-half inch total and one-fourth inch differential.
For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth
pressure acting on the sides of the footings may also be considered. We recommend calculating this lateral
resistance using an equivalent fluid weight of 350 pounds per cubic foot (pcf). We recommend not including the
upper 12 inches of soil in this computation because they can be affected by weather or disturbed by future grading
activity. This value assumes the foundations will be constructed neat against competent native soil or the
excavations are backfilled with structural fill, as described in Section 4.2 of this report. The recommended passive
and friction values include a safety factor of 1.5.
4.5 Slab -on -Grade Floors
Slab -on -grade floors may be supported on a subgrade prepared as recommended in Section 4.2 of this report.
Immediately below the floor slab, we recommend placing a four -inch thick capillary break layer composed of clean,
coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the
potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor
slab.
The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission.
Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a
durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or
fine gravel to protect it from damage during construction, and aid in uniform curing of the concrete slab. It should
be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will be
ineffective in assisting uniform curing of the slab, and can actually serve as a water supply for moisture transmission
through the slab that can subsequently affect floor coverings. Therefore, in our opinion, covering the membrane
with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and
the layer cannot be effectively drained. We recommend floor designers and contractors refer to the current ACI
Collection of Concrete Codes, Specifications, and Practices for further information regarding vapor barrier
installation below slab -on -grade floors.
Page No. 6
AN
November 12, 2020
Project No. T-8347
4.6 Lateral Earth Pressures
The magnitude of earth pressure development on engineered retaining walls will partly depend on the quality of the
wall backfill. We recommend placing and compacting wall backfill as structural fill as described in Section 4.2 of
this report. To guard against hydrostatic pressure development, wall drainage must also be installed. A typical
recommended wall drainage detail is shown on Figure 3.
With wall backfill placed and compacted as recommended, and drainage properly installed, we recommend
designing unrestrained walls that support level grades for an active earth pressure equivalent to a fluid weighing 35
pounds per cubic foot (pcf). We recommend designing unrestrained walls that support a 2:1 (Horizontal:Vertical)
backslope for an active earth pressure equivalent to a fluid weighing 50 pcf. For restrained walls, an additional
uniform load of 100 psf should be added to the above values. For evaluation of wall performance under seismic
loading, a uniform pressure equivalent to 8H psf, where H is the height of the below -grade portion of the wall should
be applied in addition to the static lateral earth pressure.
Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values
for these parameters are provided in Section 4.4 of this report.
4.7 Infiltration Feasibility
Based on our study, the use of stormwater infiltration trenches or drywells as a means of roof runoff flow control
will not be feasible at the site due to the high fines content of the upper weathered silty sand and silt soils, and the
cemented nature of the underlying till.
Limited application of porous pavements (home driveways and access roads) will be feasible in the upper weathered
till soils. Based on our experience with silt and silty sand subgrades, we recommend designing porous pavements
using an infiltration rate of 0.1 in/br. Note that this rate is based on reduced soil permeability resulting from
compaction of subgrades required for pavement construction. LID facilities such as rain gardens and bio-retention
swales will be feasible in the upper weathered till soils using a design infiltration rate of 0.25 in/hr. This rate for
LID features assumes a minimum 1-foot separation distance between the base of the facility and the cemented till
barrier layer.
4.8 Drainage
Surface
Final exterior grades should promote free and positive drainage away from the building areas. We recommend
providing a positive drainage gradient away from the building perimeter. If a positive gradient cannot be provided,
provisions for collection and disposal of surface water adjacent to the structure should be provided.
Page No. 7
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November 12, 2020
Project No. T-8347
Subsurface
We recommend installing a continuous drain along the outside lower edge of the perimeter building foundations.
The drains can be laid to grade at an invert elevation equivalent to the bottom of footing grade. The drains can
consist of four -inch diameter perforated PVC pipe that is enveloped in washed'/z- to 3/4-inch gravel -sized drainage
aggregate. The aggregate should extend six inches above and to the sides of the pipe. The foundation drains and
roof downspouts should be tightlined separately to an approved point of controlled discharge. All drains should be
provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once each year.
4.9 Utilities
Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or
City of Federal Way requirements. At minimum, trench backfill should be placed and compacted as structural fill
as described in Section 4.2 of this report. Soils excavated on -site should generally be suitable for use as backfill
material. However, the vast majority of the upper site soils are fine grained and moisture sensitive; therefore,
moisture conditioning may be necessary to facilitate proper compaction. If utility construction takes place during
the winter, it may be necessary to import suitable wet weather fill for utility trench backfilling.
4.10 Pavements
Pavement subgrade should be prepared as described in the Section 4.2 of this report. Regardless of the degree of
relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade
should be proof rolled with heavy rubber -tire construction equipment such as a loaded 10-yard dump truck to verify
this condition.
The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic
conditions to which it will be subjected. For residential access, with traffic consisting mainly of light passenger
vehicles with only occasional heavy traffic, and with a stable subgrade prepared as recommended, we recommend
the following options for pavement sections:
• Two inches of hot mix asphalt (I IMA) over four inches of crushed rock base (CRB)
• Full depth HMA — 3 %2 inches
The paving materials used should conform to the Washington State Department of Transportation (WSDOT)
specifications for 1/2-inch class HMA and CRB.
Long-term pavement performance will depend on surface drainage. A poorly -drained pavement section will be
subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their
supporting capability. For optimum pavement performance, we recommend surface drainage gradients of at least
two percent. Some degree of longitudinal and transverse cracking of the pavement surface should be expected over
time. Regular maintenance should be planned to seal cracks when they occur.
Page No. 8
A\ b
November 12, 2020
Project No. T-8347
5.0 ADDITIONAL SERVICES
Terra Associates, Inc. should review the final designs and specifications in order to verify that earthwork and
foundation recommendations have been properly interpreted and implemented in project design. We should also
provide geotechnical services during construction in order to observe compliance with our design concepts,
specifications, and recommendations. This will allow for design changes if subsurface conditions differ from those
anticipated prior to the start of construction.
6.0 LIMITATIONS
We prepared this report in accordance with generally accepted geotechnical engineering practices. This report is
the copyrighted property of Terra Associates, Inc. and is intended for specific application to the South Campus
Estates project in Federal Way, Washington. This report is for the exclusive use of Entitle Fund Two, LLC and its
authorized representatives. No other warranty, expressed or implied, is made.
The analyses and recommendations presented in this report are based on data obtained from our on -site test pits.
Variations in soil conditions can occur, the nature and extent of which may not become evident until construction.
If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the recommendations in this
report prior to proceeding with construction.
Page No. 9
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.•• • • Associates, Inc.
• Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
VICINITY MAP
SOUTH CAMPUS ESTATES
FEDERAL WAY, WASHINGTON
Proj.No. T-8347 I Date: NOV 20201 Figure 1
1�
-1;3 ROAD SF.CTION
. ... . . . . . .
—1 .... . ... . . . .....
_... . . .....
------
------
TP-5'
"pa SF
1 15,18
r
T04
..4AW
.............. -------------
............ --------------
L F PIX'0i0 5Rw
TP-2
V 10 1&126r
R
Till
..........
------- ---- --
3F) 7."'w
TP-1
.. ............. ------------
J."
NOTE: LEGEND:
THIS S E PLAN IS SCHEMATIC, ALL LOCATIONS AND APPROXIMATE TEST PIT LOCATION
DIMENSIONS ARE APPROXIMATE. I IS INTENDED FOR
REFERENCE ONLY AND SHOULD NOT BE USED FOR
DESIGN OR CONSTRUCTION PURPOSES.
REFERENC!i PROVIDED BY LARSON& ASSOCIATES. 0-- w 100
APPROXIMATE SCALE IN FEET
Terra EXPLORATION LOCATION PLAN
SOUTH CAMPUS ESTATES
Associates Inc. FEDERAL WAY, WASHINGTON
C—wlws in Gwhol—dw
ErMm=nwm E,'dftS,1,rm, I Proj.No. T-8347 1Date: NOV �2020 Fiprl, 2
AN
12" MINIMUM 3/4"
MINUS WASHED
GRAVEL
12"
- .,
r°
n
SEE NOTE
6"(MIN.)
=f
SLOPE TO DRAIN
STRUCTURAL FILL
IF
12" OVER PIPE
3" BELOW PIPE
4" DIAMETER PERFORATED PVC PIPE)
NOT TO SCALE
EXCAVATED SLOPE
(SEE REPORT TEXT
FOR APPROPRIATE
INCLINATIONS)
NOTE:
MIRADRAIN G100N PREFABRICATED DRAINAGE PANELS OR SIMILAR
PRODUCT CAN BE SUBSTITUTED FOR THE 12-INCH WIDE GRAVEL
DRAIN BEHIND WALL. DRAINAGE PANELS SHOULD EXTEND A MINIMUM
OF SIX INCHES INTO 12-INCH THICK DRAINAGE GRAVEL LAYER
OVER PERFORATED DRAIN PIPE.
Terra TYPICAL WALL DRAINAGE DETAIL
SOUTH CAMPUS ESTATES
}.•• • • Associates, Inc. FEDERAL WAY, WASHINGTON
• Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences Proj.No. T-8347 Date: NOV 2020 Figure 3
r-To
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
South Campus Estates
Federal Way, Washington
On May 22, 2020, we investigated subsurface conditions at the site by excavating 5 test pits, each to a depth of 10
feet below existing surface grades using a CAT 312D excavator. The approximate test pit locations are shown on
Figure 2. The test pit locations were approximately determined in the field using an excavator -mounted GPS device.
The Test Pit Logs are presented on Figures A-2 through A-6.
A geotechnical engineer from our office maintained a log of each test pit as it was excavated, classified the soil
conditions encountered, and obtained representative soil samples. All soil samples were visually classified in the
field in accordance with the Unified Soil Classification System. A copy of this classification is presented as Figure
A-1.
Representative soil samples obtained from the test pits were placed in sealed plastic bags and taken to our laboratory
for further examination and testing. The moisture content of each sample was measured and is reported on the Test
Pit Logs. Grain size analyses were performed on three of the soil samples. The results are shown on Figure A-7.
Project No. T-8347
A2,
MAJOR DIVISIONS
LETTER
TYPICAL DESCRIPTION
SYMBOL
Clean
GW
Well -graded gravels, gravel -sand mixtures, little or no fines.
Gravels (less
GRAVELS
than 5%
J
More than 50%
fines)
GP
Poorly -graded gravels, gravel -sand mixtures, little or no fines.
p
co N
of coarse fraction
Tu w
is larger than No.
GM
Silty gravels, gravel -sand -silt mixtures, non -plastic fines.
O
a� a)
4 sieve
Gravels with
GC
Clayey gravels, gravel -sand -clay mixtures, plastic fines.
z ( uuj
E
fines
o
o N
Clean Sands
SW
Well -graded sands, sands with gravel, little or no fines.
O LO o
uWj
SANDS
(less than
Q(a
_
More than 50%
5% fines)
SP
Poorly -graded sands, sands with gravel, little or no fines.
O
0 �'
of coarse fraction
SM
Silty sands, sand -silt mixtures, non -plastic fines.
U °
Is smaller than
No. 4 sieve
Sands with
SC
Clayey sands, sand -clay mixtures, plastic fines.
fines
L
ML
Inorganic silts, rock flour, clayey silts with slight plasticity.
is m
U .�
SILTS AND CLAYS
p
Ta a)
Liquid Limit is less than 50%
CL
Inorganic clays of low to medium plasticity. (Lean clay)
0
('U)
OL
Organic silts and organic clays of low plasticity.
Z
Eo0
Co
MH
Inorganic silts, elastic.
O
Z
SILTS AND CLAYS
Z
Liquid Limit i5 greater than 50%
CH
Inorganic clays of high plasticity. (Fat clay)
F
° •r
°
OH
Organic clays of high plasticity.
HIGHLY ORGANIC SOILS
PT
Peat.
DEFINITION OF TERMS AND SYMBOLS
Standard Penetration
I 2" OUTSIDE DIAMETER SPILT SPOON SAMPLER
W
Density Resistance in Blows/Foot
1
Z
2.4" INSIDE DIAMETER RING SAMPLER OR
O
Very Loose 0-4
SHELBY TUBE SAMPLER
c4
Loose 4-10
=
Medium Dense 10-30
= WATER LEVEL (Date)
O
Dense 30-50
U
Very Dense >50
Tr TORVANE READINGS, tsf
Pp PENETROMETER READING, tsf
Standard Penetration
Consistancy Resistance in Blows/Foot
W
DD DRY DENSITY, pounds per cubic foot
co
very Soft 0-2
2
Soft
LL LIQUID LIMIT, percent
O
Medium Stiff 4-8
U
Stiff 8-16
PI PLASTIC INDEX
Very Stiff 16-32
Hard >32
N STANDARD PENETRATION, blows per foot
Terra
UNIFIED SOIL CLASSIFICATION SYSTEM
v �.••
SOUTH CAMPUS ESTATES
•'• Associates, Inc.
FEDERAL WAY, WASHINGTON
• Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
Pro . No. T-8347
�
Date: NOV 2020
g
Figure A-1 _j
j-\1Z
LOG OF TEST PIT NO. TP-'I FIGURE A-2
PROJECT NAME: South Campus Estates PROJ. NO: T-8347 LOGGED BY: KPR
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Brush APPROX. ELEV: 363 Feet
DATE LOGGED: May 22,2020 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A
6
a)
Description
Consistency/
o
.E
a
a
E
Relative Density
a�
o
m
U)
0
Light brown mottled silty SAND with gravel, fine sand, moist. (SM) (Weathered till)
1
Medium Dense
2
11.3
3
----------------------------------------------------------------------
Brown-gray silty SAND with gravel, scattered cobbles, fine to medium sand, moderately
cemented, moist. (SM) (Till)
4
5
Very Dense
12.6
6
7
-------------------------------=--=---------------------
Brown-gray SILT with fine sand, non -plastic, moist. (MIL)
8
Dense
21.7
9
------- ----------------------------------------------------------
Brown-gray silty SAND with gravel, scattered cobbles, fine to medium sand, moderately
Very Dense
cemented, moist. (SM) (Till)
10
Test pit terminated at approximately 10 feet.
11
No groundwater.
No caving.
Two-inch slotted PVC standpipe installed to 10 feet with 2.10 feet stick up.
12
13
14
15
-� Terra
NOTE: This subsurface information pertains only to this test pit location and should not be
interpreted as being indicative of other locations at the site.
\.. _..
Associates,rlc.
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF TEST PIT NO. TP-2 FIGUREA-3
PROJECT NAME: South Campus Estates PROJ. NO: T-8347 LOGGED BY: KPR
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Brush APPROX. ELEV: 365 Feet
DATE LOGGED: May 22,2020 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A
6
�Consistency/
o
a
Description
Relative Density
n
a)
E
W
❑
07
0
(8 inches DUFF)
1
Light brown mottled SILT with fine sand, trace gravel, non -plastic, moist. (ML)
(Weathered till)
Medium Dense
2
3
19.9
4
----------------------------------------------------------------
Gray silty SAND with gravel, scattered cobbles, fine to medium sand, strongly cemented,
moist. (SM) (Till)
5
Very Dense
6
.7
9.5
8
Dense
9
Very Dense
10
Test pit terminated at approximately 10 feet.
No groundwater.
11
No caving.
12
13
14
15
_ .A..._. Terra
NOTE: This subsurface information pertains only to this test pit location and should not be <.rtq Associates, Inc.
interpreted as being indicative of other locations at the site. consultants In Geotechnical Engineering
Geology and
AlLA Environmental Earth Sciences
LOG OF TEST POD- NO. TP-3 FIGURE A-4
PROJECT NAME: South Campus Estates PROJ. NO: T-8347 LOGGED BY: KPR
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Brush APPROX. ELEV: 377 Feet
DATE LOGGED: May 22,2020 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A
6
Z
a)
Description
Consistency/
o
a
E
Relative Density
a)
0
m
U)
0
(7 inches TOPSOIL)
1
Light brown silty SAND with gravel, scattered cobbles, fine to medium sand, moist.
(SM) (Weathered till)
Dense
2
10.7
3
----------------------------------------------------------------------
Gray silty SAND with gravel, scattered cobbles, fine to medium sand, strongly cemented,
moist. (SM) (Till)
4
5-
6—
Very Dense
7
$
9.3
9-
10—
Test pit terminated at approximately 10 feet.
No groundwater.
11
No caving.
Two-inch slotted PVC standpipe installed to 10 feet with 2.17 feet stick-up.
12
13
14
15
,.........._... Terra
C\\
NOTE: This subsurface information pertains only to this test pit location and should not be
11
AssociatesInc.
......
interpreted as being indicative of other locations at the site.
.. ^" �— y
.-' Consultants in Geoteehnlcal Engineering
^�
Geology and
Aj\.
C
Environmental Earth Sciences
LOG OF TEST PIT NO. TP-4 FIGURE A-5
PROJECT NAME: South Campus Estates PROJ. NO: T-8347 LOGGED BY: KPR
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Brush APPROX. ELEV: 383 Feet
DATE LOGGED: May 22,2020 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A
0
Description
Consistency/
o
a
Relative Density
;i
u>
E
cu
o
�
0
(6 inches TOPSOIL)
1
Light brown silty SAND with gravel, scattered cobbles, fine to medium sand, moist.
Dense
(SM) (Weathered till)
2
12.7
3
----------------------------------------------------------------------
Gray silty SAND with gravel, scattered cobbles, fine to medium sand, strongly cemented,
moist. (SM) (Till)
4-
5-
6—
Very Dense
7
8
9
10
9.2
Test pit terminated at approximately 10 feet.
No groundwater.
11
No caving.
12
13
14
15
Terra
NOTE: This subsurface information pertains only to this test pit location and should not be
Associates, Inc.
interpreted as being indicative of other locations at the site.
°...°_........a ' Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF TEST PIT NO. TP-5 FIGUREA-6
PROJECT NAME: South Campus Estates PROJ. NO: T-8347 LOGGED BY: KPR
LOCATION: Federal Way, Washington SURFACE CONDITIONS: Brush APPROX. ELEV: 386 Feet
DATE LOGGED: May 22,2020 DEPTH TO GROUNDWATER: N/A DEPTH TO CAVING: N/A
6
Description
Consistency/
a
Q
0
Relative Density
a)
0
ca
co
0
(7 inches TOPSOIL)
1
Light brown silty SAND with gravel, scattered cobbles, 2-foot boulder, fine sand, moist.
(SM) (Weathered till)
Dense
2
10.7
3
----------------------------------------------------------------------
Gray silty SAND with gravel, scattered cobbles, fine to medium sand, moderately
cemented, moist. (SM) (Till)
4
5
12.6
6
Very Dense
7-
8-
9-
10—
Test pit terminated at approximately 10 feet.
No groundwater.
11
No caving.
Two-inch slotted PVC standpipe installed to 10 feet with 2.60 feet stick-up.
12
13
14
15
,_.._._...- Terra
NOTE: This subsurface information pertains only to this test pit location and should not be
Associates, /�
hC.
interpreted as being indicative of other locations at the site.\
--^- Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
Particle Size Distribution Report
%+3„
Coarse
Fine Coarse
Medium
Fine
Silt Ciay
a
0.0
0.0
28.7 11.2
17.2
21.4
21.5
L_ 0.0
17.9
_29.9 10.5
16.0
14.2
11.5
A
0.0
8.8_
11.2 2.8
8.6
17.0
51.6
LL
PL
D
D1
D..
D
Dig C
C
10.3099
1.9830
0.8030
6.1686
20.9687
9.2633
3.8374
0.6791
0.1346
11.8800
0.2001
Material Description
USCS
AASHTO
o Silty SAND
_ .
SM
Q Silty SAND
SM
o SILT
ML
rP-rqj�e-ON6. T-8347
Client:
Entitle Fund Two, LLC
Remarks:
roject: South Campus Estates
Location: TP-4
Location: TP-5
Location: TP-1
Tested By: ,FQ
Depth: -2 feet
Depth: -2 feet
Depth: -8 feet
Terra
tes, inc.
WA
Figure A-7
/�Z,C6
APPENDIX "B"
STORMWATER POLLUTION
PREVENTION PLAN
(WILL BE COMPLETED DURING FINAL ENGINEERING)
LARSON & ASSOCIATES, INC.
SURVEYORS, ENGINEERS AND PLANNERS
9027 PACIFIC AVENUE, SUITE 4
TACOMA, WA 98444 (253) 474-3404
APPENDIX "C"
OPERATION &MAINTENANCE
MANUAL
(WILL BE COMPLETED DURING FINAL ENGINEERING)
LARSON & ASSOCIATES, INC.
SURVEYORS, ENGINEERS AND PLANNERS
9027 PACIFIC AVENUE, SUITE 4
TACOMA, WA 98444 (253) 474-3404
0