HomeMy WebLinkAboutPreliminary Technical Information Report revised dated August 27, 2019Company, Inc.
Preliminary
Technical Information Report
Village Green of Federal Way
Buildings F-J, Memory Care (Building K), 17 Cottages,
Process 4 Land Use Review
Prepared: November 8, 2018
Revised: August 27, 2019
DCI Project: 98480.6
DUNCANSON
145 SW 155th Street Suite 102 Seattle, Washington 98166
Village Green of Federal Way DCI 98480.6
Table of Contents
Section 1 – Project Overview ........................................................................................................................ 3
Section 2 – Conditions and Requirements Summary ................................................................................. 14
Section 3 – Offsite Analysis ......................................................................................................................... 17
Section 4 – Flow Control, LID, & Water Quality Facility Analysis & Design ................................................ 27
Section 5 – Conveyance System Analysis and Design ................................................................................. 32
Section 6 – Special Reports and Studies ..................................................................................................... 34
Section 7 – Other Permits ........................................................................................................................... 74
Section 8 – CSWPP Plan Analysis and Design.............................................................................................. 76
Section 9 – Bond Quantities, Facility Summaries, and Declaration of Covenant ....................................... 78
Section 10 – Operations and Maintenance Manual ................................................................................... 80
Appendix A ‐ WWHM Report 82
2
Village Green of Federal Way DCI 98480.6
Section 1
Project Overview
3
Village Green of Federal Way DCI 98480.6
Section 1 – Project Overview
This project is development of 5 apartment style, independent/assisted living buildings; a 40-unit
memory care building and 13 new independent living cottages. In total approximately 227 new
senior housing units are proposed. The project is divided into two Threshold Discharge Areas
(TDA), coinciding very closely with the two separate tax parcels. TDA 1 is the eastern portion of
the site, which includes the 5 apartment style buildings (Buildings F – J). TDA 2 is the western
portion of the site containing the cottage units and memory care building (Building K).
TDA 1
TDA 1 is mostly vacant land, much of which is forested. A portion of TDA 1 is a large grassy
area that was previously cleared and graded as part of previous development on the Village Green
campus constructed in the mid to late 1990s. TDA 1 also contains one leg of a paved, looped
driveway and a gravel drive and parking area also constructed under previous approvals from the
late 1990s through 2008. Ground slopes in TDA 1 are on the order of 2 to 10%, and generally
draining to the northeast. Soils are mostly till with some areas of outwash as discussed further in
the geotechnical report. A detention/wet pond was constructed to serve the anticipated
development on TDA 1; however, flow control and water quality standards have evolved over the
last 20 year such that some expansion and retrofitting will be required. Also, implementation of
LID is also now required. Further discussion of additional stormwater improvements are included
in Sections 5. A stormwater colletion and conveyance system is provided through the downstream
property to the stormwater ponds.
TDA 2
TDA 2 is the western portion of the site. Roads, stormwater facilities, utilities and grading within
TDA 2 was constructed around 2008 to create ready to build sites for the cottage units. Only
building sites and areas to remain undisturbed remain forested. TDA 2 is served by a pre-
settling/wetpond followed by a “full” infiltration pond. It is the full infiltration from this subbasin
that separates TDA 2 from TDA 1. Current water quality standard are achieved by the wetpond
followed by soil treatment in the infiltration pond. Current flow control standards are achieved by
fully infiltrating stormwater runoff from the TDA. The memory care building represents an
approximate 9,000 SF increase in impervious area over the original design. To offset this increase,
two of the remaining cottage buildings are designed to include full infiltration drywells. These
improvements were approved by the City in 2018. Refer to Section 5 for additional discussion.
Included are Figures 1.1 – Technical Information Report Worksheet, 1.2 – Vicinity Map, 1.3.1 –
TDA 1 Basin Map, 1.3.2 – TDA 2 Basin Map and 1.4 – Soils Map.
This report is intended as a preliminary stage TIR including the required off-site analysis. It also
contains a preliminary hydrologic analysis used to develop a conceptual drainage plan. This report
does not include the detailed design of all drainage components, however, it does contain sufficient
detail for assessing the existing and proposed drainage characteristics.
4
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 1 PROJECT OWNER AND
PROJECT ENGINEER
Part 2 PROJECT LOCATION AND
DESCRIPTION
Project Owner ___________________________
Phone _________________________________
Address _______________________________
_______________________________________
Project Engineer _________________________
Company ______________________________
Phone _________________________________
Project Name _________________________
DPER Permit # ________________________
Location Township ______________
Range ________________
Section ________________
Site Address __________________________
_____________________________________
Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS
Landuse (e.g.,Subdivision / Short Subd. / UPD)
Building (e.g.,M/F / Commercial / SFR)
Clearing and Grading
Right-of-Way Use
Other _______________________
DFW HPA
COE 404
DOE Dam Safety
FEMA Floodplain
COE Wetlands
Other ________
Shoreline
Management
Structural
Rockery/Vault/_____
ESA Section 7
Part 5 PLAN AND REPORT INFORMATION
Technical Information Report Site Improvement Plan (Engr. Plans)
Type of Drainage Review
(check one):
Date (include revision
dates):
Date of Final:
Full
Targeted
Simplified
Large Project
Directed
__________________
__________________
__________________
Plan Type (check
one):
Date (include revision
dates):
Date of Final:
Full
Modified
Simplified
__________________
__________________
__________________
Part 6 SWDM ADJUSTMENT APPROVALS
Type (circle one): Standard / Experimental / Blanket
Description: (include conditions in TIR Section 2)
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Approved Adjustment No. ______________________ Date of Approval: ______________________
2016 Surface Water Design Manual 4/24/20161
X
5
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 7 MONITORING REQUIREMENTS
Monitoring Required: Yes / No
Start Date: _______________________
Completion Date: _______________________
Describe: _________________________________
_________________________________________
_________________________________________
Re: KCSWDM Adjustment No. ________________
Part 8 SITE COMMUNITY AND DRAINAGE BASIN
Community Plan : ____________________________________________________________________
Special District Overlays: ______________________________________________________________
Drainage Basin: _____________________________________________________________________
Stormwater Requirements: ____________________________________________________________
Part 9 ONSITE AND ADJACENT SENSITIVE AREAS
River/Stream ________________________
Lake ______________________________
Wetlands ____________________________
Closed Depression ____________________
Floodplain ___________________________
Other _______________________________
_______________________________
Steep Slope __________________________
Erosion Hazard _______________________
Landslide Hazard ______________________
Coal Mine Hazard ______________________
Seismic Hazard _______________________
Habitat Protection ______________________
_____________________________________
Part 10 SOILS
Soil Type
_________________
_________________
_________________
_________________
Slopes
_________________
_________________
_________________
_________________
Erosion Potential
_________________
_________________
_________________
_________________
High Groundwater Table (within 5 feet)
Other ________________________________
Sole Source Aquifer
Seeps/Springs
Additional Sheets Attached
2016 Surface Water Design Manual 4/24/201626
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 11 DRAINAGE DESIGN LIMITATIONS
REFERENCE
Core 2 – Offsite Analysis_________________
Sensitive/Critical Areas__________________
SEPA________________________________
LID Infeasibility________________________
Other________________________________
_____________________________________
LIMITATION / SITE CONSTRAINT
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
_______________________________________
Additional Sheets Attached
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area)
Threshold Discharge Area:
(name or description)
Core Requirements (all 8 apply):
Discharge at Natural Location Number of Natural Discharge Locations:
Offsite Analysis Level: 1 / 2 / 3 dated:__________________
Flow Control (include facility
summary sheet)
Level: 1 / 2 / 3 or Exemption Number ____________
Flow Control BMPs _______________________________
Conveyance System Spill containment located at: _________________________
Erosion and Sediment Control /
Construction Stormwater
Pollution Prevention
CSWPP/CESCL/ESC Site Supervisor: _____________________
Contact Phone: _________________________
After Hours Phone: _________________________
Maintenance and Operation Responsibility (circle one): Private / Public
If Private, Maintenance Log Required: Yes / No
Financial Guarantees and
Liability
Provided: Yes / No
Water Quality (include facility
summary sheet)
Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog
or Exemption No. ______________________
Landscape Management Plan: Yes / No
Special Requirements (as applicable):
Area Specific Drainage
Requirements
Type: CDA / SDO / MDP / BP / LMP / Shared Fac. / None
Name: ________________________
Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None
100-year Base Flood Elevation (or range): ______________
Datum:
Flood Protection Facilities Describe:
2016 Surface Water Design Manual 4/24/201637
KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area)
Source Control
(commercial / industrial land use)
Describe land use:
Describe any structural controls:
Oil Control High-use Site: Yes / No
Treatment BMP: ________________________________
Maintenance Agreement: Yes / No
with whom? ____________________________________
Other Drainage Structures
Describe:
Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
Clearing Limits
Cover Measures
Perimeter Protection
Traffic Area Stabilization
Sediment Retention
Surface Water Collection
Dewatering Control
Dust Control
Flow Control
Protection of Flow Control BMP Facilities
(existing and proposed)
Maintain BMPs / Manage Project
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Stabilize exposed surfaces
Remove and restore Temporary ESC Facilities
Clean and remove all silt and debris, ensure
operation of Permanent Facilities, restore
operation of Flow Control BMP Facilities as
necessary
Flag limits of SAO and open space preservation
areas
Other ______________________
Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch)
Flow Control Type/Description Water Quality Type/Description
Detention
Infiltration
Regional Facility
Shared Facility
Flow Control BMPs
Other
________________
________________
________________
________________
________________
________________
Vegetated Flowpath
Wetpool
Filtration
Oil Control
Spill Control
Flow Control BMPs
Other
________________
________________
________________
________________
________________
________________
________________
2016 Surface Water Design Manual 4/24/20164
X
X
X
X
X
X
X
X
X
X
8
9
Figure 1.2 – Vicinity Map
Site @ 1st Avenue South & SW 356th Street
Scale: N/A Drawn: JMK Job No: 98480.2
TDA 1
TDA 2
10
Job No. 98480.6Drawn: HMDScale: 1" = 100'Figure 1.3.1 - Village Green TDA 1 Basin MapCivil Engineering · Surveying · Land PlanningD U N C A N S O N C O M P A N Y, I N C.145 SW 155th Street, Suite 102Seattle, Washington 98166Phone 206.244.4141Fax 206.244.445511
SNS N
S Job No. 98480.6Drawn: HMDScale: 1" = 100'Figure 1.3.2 - TDA 2 Basin MapCivil Engineering · Surveying · Land PlanningD U N C A N S O N C O M P A N Y, I N C.145 SW 155th Street, Suite 102Seattle, Washington 98166Phone 206.244.4141Fax 206.244.445512
Figure 1.4 – Soils Map
EvB = Everett Gravelly Sandy Loam, 0-5% Slopes
Scale: NTS Drawn: HMD Job No: 98480.6
13
Village Green of Federal Way DCI 98480.6
Section 2
Conditions and Requirements Summary
14
Village Green of Federal Way DCI 98480.6
Section 2 – Conditions and Requirements Summary
The City of Federal Way requires compliance with the 2016 King County Surface Water Design
Manual (KCSWDM) and the City of Federal Way Addendum to KCSWDM. This report follows
the format specified in the KCSWDM. This Section describes how the Project will meet the
Manual’s Core and Special Requirements.
Core Requirements:
1. Discharge at the Natural Location
The site runoff is separated into two TDAs. Runoff from TDA 1 drains to the northeast and is
collected by the catch basins and pipe network in the existing Village Green campus. A storm
drain is stubbed into this site for a point of connection for the proposed development to
maintain the point of discharge. Runoff from TDA 2 is collected by the catch basin and pipe
system constructed as part of the Cottages West development. Lot drain stubs are provided to
each of the cottage and memory care building sites, which will be used to maintain the point
of discharge. See Figure 3.1 – Offsite Analysis Map for more information.
2. Offsite Analysis
A Level 1 offsite analysis has been performed for this project. See Section 3 for more
information.
3. Flow Control
The site is located in a Conservation Flow Control area. Flow control will be provided by LID
BMPs, the existing (modified) detention pond and the existing infiltration pond. See Section
4 for more information.
4. Conveyance System
Appropriate conveyance calculations will be included in Section 5 at the final engineering
stage.
5. Erosion and Sediment Control
ESC measures will conform to the 2016 KCSWDM. ESC plans will be provided at the final
engineering/building permit stage for each building.
6. Maintenance and Operations
A maintenance and operations manuals are already in place for the stormwater facilities. These
documents will be amended as needed at the final engineering/building permit stage.
7. Financial Guarantees and Liability
The project owner will provide appropriate financial guarantees and liability insurance prior
to construction.
8. Water Quality
The site is in the Enhanced Basic Water Quality Treatment area. See Section 4 for additional
information.
9. Flow Control BMPs
15
Village Green of Federal Way DCI 98480.6
Flow Control BMPs are required in TDA 1 and are generally depicted on the site plan.
Impervious surfaces in TDA 2 is served by an infiltration facility and are exempt from the
BMP requirement. However, soil amendment is required. See Section 4 for additional
information.
Special Requirements:
1. Other Adopted Area-Specific Requirements
The site is in the Hylebos Creek Basin. The City’s flow control and water quality standards
meet or exceed the recommendations of the basin plan.
2. Flood Hazard Area Delineation
This site does not lie within the 100-year flood plain.
3. Flood Protection Facilities
This requirement does not apply.
4. Source Control
Source Control is required. Applicable structural and non-structural source controls are
discussed in Sections 4 and 8.
5. Oil Control
The site is not a high-use site. This requirement does not apply.
16
Village Green of Federal Way DCI 98480.6
Section 3
Offsite Analysis
17
Village Green of Federal Way DCI 98480.6
Section 3 – Offsite Analysis
Task 1 - Study Area Definition & Maps
The study area was defined by the site topography using City of Federal Way’s GIS maps. The
study area includes the site and downstream flowpaths. See Figure 3.1 – Offsite Analysis Map for
more information.
Task 2 - Resource Review
1. Adopted Basin Plan
BW-2: Basinwide Onsite Detention Standard; which is Level 1 Flow Control (KCRTS) –
Match predeveloped 2- and 10- year peak flow rates. Note that this is a dated standard and
current City Flow and Water Quality standards exceed the Basin Plan requirements.
2. Finalized Drainage Studies
Not applicable.
3. Basin Reconnaissance Summary Reports
This project is in the Hylebos Creek Basin and contributes to Tributary 0014B.
4. Critical Drainage Area Maps
See Figure 3.2 – Critical Areas Map for the offsite wetland location.
5. FEMA Maps
Not applicable.
6. Other Offsite Analyses
The downstream analyses for the Village Green Phase I, Tuscany Woods and Cottages West
projects were consulted. These projects include the subject property and adjoin the site to the
west. These downstream analyses did not reveal any problems or require any special
mitigation.
7. Sensitive Areas Folio
A map detailing Federal Way’s critical areas in the site vicinity is included as Figure 3.2. .
18
Village Green of Federal Way DCI 98480.6
8. Drainage Complaints and Studies
Drainage complaint summaries were obtained from King County. See Figure 3.1 – Offsite
Analysis Map. The drainage complaint parcels are shaded orange and have been assigned a
number (DC-2 for example). Two drainage complaints were found to be in the downstream
flowpath. Below is a description of how each drainage complaint has been addressed.
DC-1: 1987-0727
Parcel #292104-9029. This drainage complaint was regarding an old drainage pipe with
constriction issues. This complaint is more than 10 years old, therefore it is not applicable.
DC-2: 1989-0448
Parcel #292104-9030. This drainage complaint was regarding drainage issues with the Sunrise
Methodist Church construction. This complaint is more than 10 years old, therefore it is not
applicable.
9. USDA Soils Survey
See Figure 1.4 – Soils Map. Soils noted as Everett Gravelly Sandy Loam.
10. Wetlands Inventory
No onsite wetlands. See Figure 3.2 for the locations of offsite wetlands.
11. Migrating River Studies
Not applicable.
12. WSDOE Water Quality Atlas
Ecology’s Water Quality Atlas was consulted to investigate for impaired waters. The tributary
to West Hylebos Creek, located downstream from the Site was listed as having temperature
and dissolved oxygen impairments. See Task 5 below.
19
Village Green of Federal Way DCI 98480.6
Task 3 - Field Reconnaissance
A current field reconnaissance was conducted on August 5, 2019. Weather conditions were sunny
and dry. While not part of this specific investigation, several other site visits were conducted
through 2017 and 2018, including during the wet season and also after precipitation events. The
downstream flow paths were observed for ¼ mile. A description of the various downstream runoff
system components is contained under Task 4 below.
Task 4 - Drainage System Description and Problem Screening
TDA 1
Component 1A ~ Pipe Flow (0’ – 880’)
Runoff exits the site via a storm drain system that was stubbed into the site as part of earlier phases
of the Village Green retirement community (Phase I-1996 and Buildings D and E of the original
Phase II plan-1998). This drainage system consists of catch basins and 8” to 18” pipes with slopes
generally between 1 and 10%. Runoff is routed through this system until it reaches a detention/wet
pond, which was also part of the original Village Green development. Pipes and catch basins were
clean. No evidence of flooding or erosion problems was observed.
Component 1B ~ Detention/Wet Pond & Bioswale (880’ – 1,380’)
Runoff outlets into a stormwater facility located in the northeast corner of the Village Green Phase
I site. The facility is a multi-cell, flow through, combined detention wetpond followed by a
biofiltration swale. The facility appears to be in a fully functional condition and has become well
vegetated. Some trash (shopping carts, cans, bottles, etc.) has accumulated, particularly near 1st
Avenue S. Weeds and brush have grown around some of the inlet and outlet pipes. No other
problems or evidence of flooding or erosion were observed.
Component 1C ~ Pipe Flow (1,380’ – 1,825’)
Runoff from the bioswale is collected into a pipe and catch basin system, which routes runoff east
to 1st Avenue S, then north under the west shoulder of 1st Avenue S. This drainage system consists
of catch basins and 18” CPEP and concrete pipes. Runoff is routed north through this system until
it reaches the sag location along 1st Avenue South. No evidence of flooding or erosion problems
was observed. At this sag location, the pipe system connects with the cross culvert under 1st
Avenue S and combines with the overflow flowpath from TDA 2.
Component E ~ Culvert (1,825’– 1,865’)
TDA 1 runoff is routed east under 1st Avenue South. The culvert is a 48” CMP with a slope of
±2%. Several shopping carts and other debris were present in the channel at the inlet of the
culverts. The pipe appeared to be clean, with only minor sedimentation. A small base flow was
observed. The outlet end (east side of 1st Ave S) was partially submerged as a result of downstream
conditions. Long term, natural sedimentation within the wetland below may explain why the
20
Village Green of Federal Way DCI 98480.6
culvert outlet is partially submerged, or it may have been constructed in that manner, or both.
Velocities through the pipe appear to be sufficient to keep the outlet clear so as not to cause
plugging. No other problems or evidence of flooding or erosion problems were observed.
Component F ~ Sheet Flow (1,865’+)
Runoff outlets east from the culvert and into a city identified wetland. A concentrated flowpath
was observed for a several yards, but then flows disperse into the heavily vegetated wetland.
TDA 2
Component 2A ~ Pipe Flow (0’ – 80’)
Runoff exits the site along the northwestern property line and is collected by the drainage system
of Cottages West and is routed north. This drainage system consists of catch basins and 12” CPEP
with an average slope of 3%. No evidence of flooding or erosion problems was observed.
Component 2B ~ Infiltration Pond (80’ – 490’)
Runoff outlets into a pre-settling wetpond followed by an infiltration pond located in the northern
portion of the Cottages West site. No evidence of flooding or erosion problems was observed.
Directly north of the pond, an apartment complex was constructed in the mid 1980’s under King
County jurisdiction under the name of The Height on West Campus. At the time King County
allowed the developer to build a retaining wall along their southern property line of The Height on
West Campus. This retaining wall blocked the natural discharge point and created a manmade
closed depression. If runoff were to leave the pond, approximately 10 feet of water would need to
be in place for any runoff to discharge from the site. Note: The infiltration pond in TDA 2 is
designed to fully infiltrate runoff up to the 100-year storm event. Therefore, the following
discussion applies only to overflows, which exceed the 100-year event and are beyond the scope
design.
Component 2C ~ Channeled Flow (490’ – 630’)
Runoff from the pond would flow north onto an internal road for The Height on West Campus
apartments. This runoff would be routed north over asphalt and along the flowline of the internal
road, which has an average slope of 2%. No problems were observed.
Component 2D ~ Pipe Flow (630’ – 1,440’)
Runoff is collected by the drainage system of The Height on West Campus and routed east, towards
the 1st Avenue South sag location. This drainage system consists of catch basins and 12” pipes
with an average slope of 5%. No problems were observed.
21
Village Green of Federal Way DCI 98480.6
Component E ~ Culvert (1,440’ – 1,480’)
TDA 2 overflows would recombine with TDA 1 runoff at this drainage component.
Task 5 – Mitigation of Existing or Potential Problems
It is recommended that trash and debris, such as shopping carts, be removed from the existing
Village Green stormwater facilities (Component 1B) and from the inlet of the 1st Avenue S cross
culvert (Component E). This debris could cause problems if washed into the pipes and flow control
devices or could cause plugging or improper operation of the pond. It is also recommended that
vegetation be trimmed and mowed within a 5-foot perimeter of the various pond inlet and outlet
pipes to reduce the chance of plugging and also to allow for periodic inspection and cleaning.
Mitigation for the dissolved oxygen problem identified in the resource review applies only to
wetvaults, which are not included in this project.
Mitigation for the temperature problem identified in the resource review requires shading of
wetpond. The wetpond for this project is an existing facility, which is completely surrounded by
trees and with trees growing in the divider berm. Furthermore, no expansion of the wetpool portion
of the pond is proposed. Any expansion of the detention (live storage) portion of the pond should
include replacement of trees to provide shading.
Note that the dissolved oxygen and temperature problems are not applicable to TDA 2, where
runoff is fully infiltrated.
22
Job No. 98480.6Drawn: HMDScale: 1"=300'
Figure 3.1 - OFFSITE ANALYSIS MAP
Civil Engineering · Surveying · Land Planning
D U N C A N S O N C O M P A N Y, I N C.
145 SW 155th Street, Suite 102
Seattle, Washington 98166
Phone 206.244.4141
Fax 206.244.4455
23
Figure 3.2 – Critical Areas Map
Scale: Shown Above Drawn: HMD Job No: 98480.6
24
OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 Basin: Hylebos Creek Basin Subbasin Name: TDA 1Subbasin Number: Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident See map. Type: sheet flow, swale, stream, channel, pipe, pond. Size: diameter, surface area. Drainage basin, vegetation, cover, depth, type of sensitive area, volume. % ¼ ml = 1,320 ft. Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion.Tributary area, likelihood of problem, overflow pathways, potential impacts. 1A Pipe Flow 8” – 18” Pipe Varies <10%0’ – 880’ None None None 1B Combined Detention/Wetpond & Bioswale ±0% 880’ – 1,380’ Trash None w/maint. No flooding or erosion evidence. Trash & debris removal & brush trimming = normal maint.1C Pipe Flow 18” Pipe Varies 1,380’ – 1,825’ None NoneNone E Culvert 48” CMP ±2% 1,825’ – 1,865’ Trash None w/maint.Shopping carts/debris could cause blockage.F Sheet Flow Heavily vegetated ±2 1,865’+ None None Flows disperse beyond outlet. 25
OFF-SITE ANALYSIS DRAINAGE SYSTEM TABLE SURFACE WATER DESIGN MANUAL, CORE REQUIREMENT #2 Basin: Hylebos Creek Basin Subbasin Name: TDA 2Subbasin Number: Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance from site discharge Existing Problems Potential Problems Observations of field inspector, resource reviewer, or resident See map. Type: sheet flow, swale, stream, channel, pipe, pond. Size: diameter, surface area. Drainage basin, vegetation, cover, depth, type of sensitive area, volume. % ¼ ml = 1,320 ft. Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion.Tributary area, likelihood of problem, overflow pathways, potential impacts. 2A Pipe Flow 12” CPEP tightline±3% 0’ – 80’ None None None 2B Pond Presettling/ Wetpond & Infiltration Pond±0% 80’ – 490’ None None None 2C Channeled Flow Over asphalt ±2% 490’ – 630’ None NoneNone2D Pipe Flow 12” CPEP tightline±5% 630’ – 1,440’ None None Flows east under apartment complex road. See TDA1 for Components E and F 26
Village Green of Federal Way DCI 98480.6
Section 4
Flow Control, Low Impact Development
(LID) and Water Quality Facility Analysis
and Design
27
Village Green of Federal Way DCI 98480.6
Section 4 – Flow Control, LID, & Water Quality Facility Analysis & Design
TDA 1
Part A – Existing Site Hydrology
Stormwater from the TDA 1 site is and will be collected in catch basins and routed through an
existing detention/wet pond located in the northeastern corner of the Village Green site – see
Figure 1.3.1 – TDA 1 Basin Map. While Village Green Phase I is not part of the current proposal,
it was necessary to model the hydrology of that existing development since it also contributes to
the same detention pond that the current project TDA 1 will use. The Village Green Phase I
impervious and pervious areas will remain; are not being redeveloped; are mitigated by an existing
facility; and are not target impervious surfaces.
TDA 1 is 4.37 acres. The small paved loop driveway existed prior to 2001 and is not considered
a target surface; and was therefore modeled as impervious. The remainder of TDA 1 is target
surface and is modeled as C, Forest.
The combined existing site hydrology of the existing Village Green Phase I and the current
project TDA 1 is summarized as follows:
28
Village Green of Federal Way DCI 98480.6
Part B – Developed Site Hydrology
See Figures Figure 1.3.1 – TDA 1 Basin Map.
Site improvements for TDA 1 will include sewer and water utility services, storm drain
conveyance piping, dry utilities, roads, sidewalks and five buildings.
The fully developed site conditions will have approximately 6.39 acres of impervious surface
including the existing Phase I areas. The remainder of the site was modeled as C, Lawn.
The various cover types occur in the following proportions:
TDA 2
Stormwater from the TDA 2 is collected in catch basins and routed through an existing
presettling/wet pond to an infiltration pond located in the northwestern corner of the Cottages West
site – see Figure 1.3.2 – TDA 2 Basin Map. Complete water quality and infiltration analysis and
sizing is contained in the TIR for the Plat of Tuscany (FW 01-103235-00-EN). The existing
infiltration pond was design to fully infiltrate all runoff, thus achieving the Conservation Flow
Control standard. Also, since TDA 2 is served by an infiltration pond, On-Site Stormwater BMPs
are not required in this TDA. Soil treatment, preceded by the presettling pond provide the
Enhanced Basic Water Quality Standard.
Part C – Performance Standards
The site is subject to Conservation Flow Control and Enhanced Basic Water Quality standards.
29
Village Green of Federal Way DCI 98480.6
Part D – TDA 1 Flow Control System
The existing detention pond was designed to meet a peak flow matching standard, dating back to
circa 1990 requirements. The current Conservation Flow Control standard is more restrictive.
Based on as-built information the existing pond provides approximately 90,000 CF of storage
volume. A WWHM analysis was run to determine and approximate pond volume to meet the
current Conservation Flow Control Standard, matching forested conditions for all new target
surfaces and existing conditions for existing development draining to the same pond. It is
estimated that the pond will need to be expanded to approximately 147,000 CF (3.38 ac-ft) to meet
current standards. This can be achieved by expanding the pond to the west and south and
increasing the berm height by approximately 0.8 feet. The flow control structure will also need to
be modified. A conceptual pond configuration is presented below. A WWHM report is included
in Appendix A.
30
Village Green of Federal Way DCI 98480.6
BMP Selection
Full Dispersal is not feasible on this site due to lack of available flow paths. Full Infiltration is
also not likely feasible due to soil type. Limited room is available making Bioretention likely
infeasible. BMP requirements are expected to be achieved with areas of Permeable Pavement in
light traffic areas, with Limited Infiltration where soil conditions are favorable and Basic Dispersal
can be employed around the site where minimum flow paths are available. Potential BMPs are
shown on the preliminary drainage plan. Final selection and location of On-Site Stormwater BMPs
will be done at the building permit stage. No credit has been taken for BMPs in the above detention
sizing, although BMPs will likely reduce the required size of the detention pond.
Part E – TDA 1 Water Quality System
The existing wetpond followed by a biofiltration swale does not meet the current Enhanced Basic
Water Quality Standard. In order to meet this standard for this Phase of the project, Filterra planter
boxes are proposed to treat runoff from new/replaced pollution generating surfaces (PGIS and
PGPS). Filterra have WSDOE GULD approval to provide Enhance treatment. Filterra units can
be located adjacent to the drive aisles and parking bays. Where required due to grade constraints,
runoff may be piped to remote Filterra planters to allow for gravity flow. Final placement and
number of Filterra units will be determined at building permit stage when the final grading plan is
developed. The sizing and number of Filterra units will be based on Ecology’s GULD approved
loading rates. Roof material is planned to be composition, which is excluded from PGIS. A non-
leachable covenant can accompany the future building permits. It is not expected that the wetpool
volume will need to be expanded as the sizing methodology of these facilities has not changed
over the years.
31
Village Green of Federal Way DCI 98480.6
Section 5
Conveyance System Analysis and Design
32
Village Green of Federal Way DCI 98480.6
Section 5 – Conveyance System Analysis and Design
This section will be completed at the final engineering stage.
33
Village Green of Federal Way DCI 98480.6
Section 6
Special Reports and Studies
34
Village Green of Federal Way DCI 98480.6
Section 6 – Special Reports and Studies
A current geotechnical report (ZipperGeo 2018) has been prepared and is included in the following
pages.
35
GEOTECHNICAL ENGINEERING REPORT
VILLAGE GREEN RETIREMENT CAMPUS
35419 1st AVENUE S
FEDERAL WAY, WASHINGTON
Project No. 1969.01
March 19, 2018
Prepared for:
RJ Development
Prepared by:
19019 36th Avenue W., Suite E
Lynnwood, WA 98036
Approximate Current
Phase of Construction
36
Project No. 1969.01
March 19, 2018
RJ Development
401 Central Street SE
Olympia, WA 98501
Attn: Mr. Austin Groves
Subject: Geotechnical Engineering Report
Village Green Retirement Campus
35419 1st Avenue S
Federal Way, Washington
Dear Mr. Groves,
In accordance with your request and written authorization, Zipper Geo Associates, LLC (ZGA) has
completed the subsurface exploration and geotechnical engineering evaluation for the current phase of
the proposed Village Green Retirement Campus. This report presents the results of the subsurface
exploration and document review, as well as our geotechnical engineering recommendations for the
project. Our services were completed in general accordance with our Proposal for Geotechnical
Engineering Services (Proposal No. P18103) dated February 6, 2018. Written authorization to proceed
on our proposed scope of services was also provided by RJ Development on February 6, 2018. We
appreciate the opportunity to be of service to you on this project. If you have any questions concerning this
report, or if we may be of further service, please contact us.
Sincerely,
Zipper Geo Associates, LLC
James P. Georgis, L.E.G. Ryan M. Scheffler, P.E.
Principal Senior Geotechnical Engineer
37
TABLE OF CONTENTS
Page
INTRODUCTION ........................................................................................................................................... 1
SITE AND PROJECT DESCRIPTION .......................................................................................................... 1
SUBSURFACE CONDITIONS...................................................................................................................... 2
Mapped Geology ............................................................................................................................................. 2
Soil Conditions ................................................................................................................................................. 2
Groundwater Conditions ................................................................................................................................. 2
Laboratory Testing .......................................................................................................................................... 3
CONCLUSIONS AND RECOMMENDATIONS ............................................................................................ 3
General Considerations ................................................................................................................................... 3
Site Preparation ............................................................................................................................................... 3
Structural Fill Materials and Preparation ........................................................................................................ 4
Seismic Design Considerations ........................................................................................................................ 7
Shallow Foundation Recommendations .......................................................................................................... 8
On-Grade Concrete Slabs ................................................................................................................................ 8
Lateral Earth Pressures .................................................................................................................................... 8
Stormwater Management ............................................................................................................................... 9
CLOSURE ................................................................................................................................................... 10
Figure 1 – Site and Exploration Plan
APPENDICES
Appendix A – Subsurface Exploration Procedures and Logs
Appendix B – Laboratory Testing Procedures and Results
Appendix C – Excerpts from Earth Consultants, Inc. Reports
Cover Page Photo Credit: Google Earth Pro, 2017 Aerial Photo
38
GEOTECHNICAL ENGINEERING REPORT
VILLAGE GREEN RETIREMENT CAMPUS
FEDERAL WAY, WASHINGTON
Project No. 1969.01
March 19, 2018
INTRODUCTION
This report documents the surface and subsurface conditions encountered at the project site and our
geotechnical engineering recommendations for the current proposed phase of the Village Green
Retirement Campus in Federal Way, Washington. The project description, site conditions, and our
geotechnical conclusions and design recommendations are presented in the text of this report.
Supporting data including detailed exploration logs and field exploration procedures, results of laboratory
testing, and other supporting information are presented as appendices.
Our geotechnical engineering scope of services for the project included a review of published geologic
maps and previously completed geotechnical reports for the site by Earth Consultants, Inc. (ECI), site
reconnaissance, subsurface evaluation, laboratory testing, geotechnical engineering analysis, and
preparation of this report. The subsurface evaluation included advancement of six exploratory borings
(designated B-1 through B-6) extending to depths between approximately 16½ to 26½ feet below the
existing ground surface near the proposed building locations. ECI’s previous reports also include exploration
logs for 2 borings and 23 test pits completed across the larger project site, including three test pits within
the bounds of the current project phase.
SITE AND PROJECT DESCRIPTION
The project is located on a roughly 4.9-acre parcel north of SW 356th Street and west of 2nd Avenue SW
in Federal Way, Washington. In addition to the subject parcel, two additional parcels to the north and
east comprise the Village Green Retirement Campus. Residences and community buildings with
associated infrastructure were previously constructed on the adjacent eastern parcel during an initial
development phase in 2002 or 2003 and an on the northern parcel some time between 2007 and 2009.
Two new residential structures are currently under construction near the northeast corner of the subject
parcel.
We understand the project will consist of constructing four new residential structures, a small community
building, and a larger multi-story memory care facility. The site generally grades down from southeast to
northwest. Based on the site grades and layout of existing buildings, we expect the new buildings will
primarily consist of 1 to 2 stories with daylight basements below. Access roads (4th Place SW, SW 353rd
Place, and 354th Place) and utilities for the current development phase were previously constructed, so
limited paving and minor utility connections are anticipated. We understand the stormwater detention
and infiltration ponds located near the northwest corner of the campus were originally sized for the fully
developed site and resizing or construction of new facilities is not currently anticipated. A groundwater
monitoring program is currently in place within the existing infiltration pond and results will be presented
after the data loggers have been removed upon conclusion of the wet season.
39
SUBSURFACE CONDITIONS
Mapped Geology
According to the U.S. Geological Survey Geologic Map of the poverty bay 7.5’ quadrangle, King and Pierce
Counties, by Booth, D.B., Waldron, H.H., and Troost, K.G. (2004), the surficial geology including the area
of the project site is mapped as recessional outwash deposits (Qvr) with glacial till (Qvt) deposits mapped
nearby to the west. The recessional deposits are described as consisting of stratified sand and gravel with
some areas of silty sand that were deposited by meltwater streams during glacial retreat. The glacial till
deposits were transported, deposited, and overridden by glaciers and commonly consist of compact
mixture of sand, silt, and gravel that is often referred to as “hardpan.” The soil conditions encountered in
our borings generally matched the mapped deposits and we interpreted the upper, relatively coarse-
grained material as recessional outwash with the siltier glacial till below. ECI’s reports did not label the
upper material, but they described the soil below as glacial till.
Soil Conditions
The subsurface evaluation for this project included advancement of six borings (B-1 through B-6)
completed throughout the area of the current phase. The borings were extended to depths ranging from
about 16½ to 30½ feet below the existing ground surface and their approximate locations are shown on
Figure 1, the Site and Exploration Plan.
Soils were visually classified in general accordance with the Unified Soil Classification System. A
descriptive log of the subsurface exploration and the procedures utilized in the subsurface exploration
program are presented in Appendix A. A generalized description of soil conditions encountered in the
borings is presented below. Please refer to the boring logs in Appendix A for a more detailed description
of the conditions encountered at the exploration locations.
Soil conditions observed in the borings generally consisted of about 4 to 6 inches of root mass, forest duff,
and topsoil underlain by medium dense to very dense gravels and sands with a low to moderate silt content,
interpreted as recessional outwash, to depths ranging from about 7 to 19 feet. Below the outwash, very
dense silty sand with gravel, interpreted as glacial till, was encountered to the full exploration depths. The
moisture content of the samples collected from the borings generally ranged from damp to moist.
Three test pits advanced by ECI within the area of the current phase (TP-105 through TP-107) were
excavated to depths of about 8 to 9 feet below the ground surface. The logs of these test pits, as well as
ECI’s Boring & Test Pit Location Plan, are included in Appendix C. Within the test pits, ECI generally
reported similar soil conditions to those noted above, though these test pits did not appear to extend into
the underlying glacial till.
Groundwater Conditions
Groundwater was not encountered within the full depth of our borings during the time of drilling, nor was
it reported by ECI within their explorations. Fluctuations in groundwater levels, and the development of
40
perched groundwater layers, will likely occur due to seasonal variations in the amount of rainfall, runoff
and other factors not evident at the time the exploration was performed. Therefore, groundwater levels
during construction or at other times in the life of the structure may be higher than indicated on the logs.
The possibility of groundwater level fluctuations should be considered when developing the design and
construction plans for the project. A groundwater monitoring program is currently in progress within the
infiltration pond near the northwest corner of the site. Results of the monitoring program will be
presented following conclusion of the wet season.
Laboratory Testing
Laboratory testing for soil moisture content, fines content, and grain-size distribution was completed on
selected samples obtained from our borings. The results of the moisture content tests are presented on the
boring logs in Appendix A while the results of the grain-size distribution tests are presented in Appendix B. In
general, test results indicated the upper recessional outwash soils have a fines content (that portion passing
the U.S. No. 200 sieve) on the order of about 5 to 13 percent, while the deeper glacial till has a fines
content of about 32 to 35 percent.
CONCLUSIONS AND RECOMMENDATIONS
General Considerations
Based on the subsurface conditions encountered and described in previous sections, in our opinion the
proposed buildings can be supported on conventional shallow foundations bearing on at least medium
dense native soil, contingent on proper design and construction practices and implementation of the
recommendations presented in this report.
Geotechnical engineering recommendations for shallow spread footings and other earthwork related
phases of the project are presented below. The recommendations contained in this report are based
upon the results of field and laboratory testing (which are presented in Appendices A and B), review of
previews reports for the larger development by ECI (excerpts of which are presented in Appendix C),
engineering analyses, and our current understanding of the proposed project. ASTM and Washington
State Department of Transportation (WSDOT) specification codes cited herein respectively refer to the
current manual published by the American Society for Testing & Materials and the 2016 edition of the
Standard Specifications for Road, Bridge, and Municipal Construction (M41-10).
Site Preparation
Clearing and Stripping: Based on conditions observed in our borings we expect stripping depths on the
order of about 4 to 8 inches in depth will be required to remove the upper forest duff and organic material
from below areas of future pavements and structures. These materials are not suitable for reuse as
structural fill. Greater depths will likely be required to remove root balls associated with the trees and
brush covering much of the undeveloped portions of the site.
41
Subgrade Preparation: Once site preparation is complete, all areas that do not require over-excavation
and are at design subgrade elevation or areas that will receive new structural fill should be compacted to
a firm and unyielding condition. Depending on conditions encountered at the time of construction, some
moisture conditioning of subgrade soils may be required to achieve a moisture content appropriate for
compaction. The extent of moisture conditioning will likely be a function of when the site earthwork takes
place. A suitable moisture content is generally within ±2 percent of the soils optimum moisture content.
As noted above, laboratory tests indicate the upper recessional outwash sands and gravels encountered
in our explorations have a fines content on the order of about 5 to 13 percent. These soils will be
moderately sensitive to disturbance from construction activity and increased moisture. If exposed in
excavations for daylight basements or deeper footings, the underlying glacial till soils will be highly
moisture sensitive due to their relatively high fines content.
If possible, we recommend that earthwork be completed during drier periods of the year when the soil
moisture content can be controlled by aeration and drying. If earthwork or construction activities take
place during extended periods of wet weather, or if the in situ moisture conditions are elevated above the
optimum moisture content, the soils could become unstable or not be compactable. Construction activity
should be monitored and should be limited to the extent feasible if the activity is causing subgrade
disturbance. In the event the exposed subgrade becomes unstable, yielding, or unable to be compacted
due to high moisture conditions, we recommend that the materials be removed to a sufficient depth in
order to develop stable subgrade soils that can be compacted to the minimum recommended levels. The
severity of construction problems will be dependent, in part, on the precautions that are taken by the
contractor to protect the subgrade soils.
If protecting stable subgrades becomes necessary, either inside or outside the building pads, we
recommend using crushed rock or crushed recycled concrete. The thickness of the protective layer should
be determined by the contractor at the time of construction based on the moisture condition of the soil,
weather conditions, and the amount of anticipated traffic.
Freezing Conditions: If earthwork takes place during freezing conditions, exposed subgrades should be
allowed to thaw and then be compacted prior to placing subsequent lifts of structural fill. Alternatively,
the frozen material could be stripped from the subgrade to expose unfrozen soil prior to placing
subsequent lifts of fill or foundation components. The frozen soil should not be reused as structural fill
until allowed to thaw and adjusted to the proper moisture content, which may not be possible during
winter months.
Structural Fill Materials and Preparation
Structural fill includes any material placed below or adjacent to foundations, below concrete slabs, within
utility trenches, or other areas to support settlement-sensitive site improvements. Prior to the placement
of structural fill, all surfaces to receive fill should be prepared as previously recommended in the Site
Preparation section of this report.
42
Reuse of Site Soils as Structural Fill: Field and laboratory test data indicate that the soils encountered on
site below the topsoil and forest duff are suitable for reuse as general structural fill from a compositional
standpoint provided the soil is placed and compacted in accordance with the compaction
recommendations presented in this report. However, as noted above, the recessional outwash sand and
gravel soil has a fines content on the order of about 5 to 13 percent and will be moderately sensitive to
increases in moisture content. The underlying glacial till has a relatively high portion of fines and will be
highly moisture sensitive. If site soils are planned for reuse, they should be protected from an increase in
moisture content during periods of wet weather. At a minimum, we recommend stockpiles of excavated
material to be used as structural fill on the site be covered with plastic sheeting if rain is in the forecast.
We recommend that site soils used as structural fill have less than 4 percent organics by weight and have
no woody debris greater than ½ inch in diameter. We recommend that all pieces of organic material
greater than ½ inch in diameter be picked out of the fill before it is compacted. Any organic-rich soil
derived from earthwork activities should be utilized in landscape areas or wasted from the site.
Imported Structural Fill: Imported structural fill may be required if the on-site soils cannot be adequately
compacted at the time of construction due to elevated moisture content, or other reasons. The
appropriate type of imported structural fill will depend on weather conditions. During extended periods
of dry weather, we recommend imported fill, at a minimum, meet the requirements of Common Borrow
as specified in Section 9-03.14(3) of the 2016 Washington State Department of Transportation, Standard
Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications). During wet
weather and/or wet site conditions, higher-quality structural fill might be required, as Common Borrow
may contain sufficient fines to be moisture-sensitive. During wet conditions, we recommend that
imported structural fill consist of a “clean”, free-draining pit-run sand and gravel. Such material should
generally contain less than 5 percent fines, based on that soil fraction passing the U.S. No. 4 sieve, and
not contain discrete particles greater than 3 inches in maximum dimension. Alternatively, Crushed
Surfacing Base Course or Gravel Borrow conforming to Sections 9-03.9(3) and 9-03.14(1), respectively, of
the WSDOT Standard Specifications could be used during wet weather. It should be noted that the
placement of structural fill is, in many cases, weather-dependent. Delays due to inclement weather are
common, even when using select granular fill. We recommend that site grading and earthwork be
scheduled for the drier months, if possible.
Moisture Content: The suitability of soil for use as structural fill will depend on the time of year, the
moisture content of the soil, and the fines content of the soil. As the amount of fines increases, the soil
becomes increasingly sensitive to small changes in moisture content. Soils containing more than about 5
percent fines (such as the deeper on-site glacial till soils) cannot be consistently compacted to the
appropriate levels when the moisture content is more than approximately 2 percent above or below the
optimum moisture content (per ASTM D 1557). Optimum moisture content is that moisture content
which results in the greatest compacted dry density with a specified compactive effort.
Fill Placement and Compaction: Structural fill should be placed in horizontal lifts not exceeding 10 inches
in loose thickness. Thinner lifts may be necessary, depending on the size and weight of the compaction
43
equipment. Each lift of fill should be compacted to the minimum levels recommended in the table below
based on the maximum laboratory dry density as determined by the ASTM D 1557 Modified Proctor
Compaction Test. Structural fill placed in municipal rights-of-way should be placed and compacted in
accordance with the jurisdiction codes and standards. We recommend that a geotechnical engineer be
present during grading so that an adequate number of density tests may be conducted as structural fill
placement occurs. In this way, the adequacy of the earthwork may be evaluated as it proceeds.
Recommended Soil Compaction Levels
Location Minimum Percent Compaction*
Stripped native subgrade soils, prior to fill placement (upper 12 inches) 95
All fill below building floor slabs and foundations 95
Upper 2 feet of fill below pavements 95
Pavement fill below two feet 92
Utility trench backfill 95
Landscape Areas 90
* ASTM D 1557 Modified Proctor Maximum Dry Density
Temporary and Permanent Slopes: Temporary excavation slope stability is a function of many factors,
including:
• The presence and abundance of groundwater;
• The type and density of the various soil strata;
• The depth of cut;
• Surcharge loadings adjacent to the excavation; and
• The length of time the excavation remains open.
It is exceedingly difficult under the variable circumstances to pre-establish a safe and “maintenance-free”
temporary cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe
temporary slope configurations since the contractor is continuously at the job site, able to observe the
nature and condition of the cut slopes, and able to monitor the subsurface materials and groundwater
conditions encountered. Unsupported vertical slopes or cuts deeper than 4 feet are not recommended if
worker access is necessary. The cuts should be adequately sloped, shored, or supported to prevent injury
to personnel from local sloughing and spalling. The excavation should conform to applicable Federal,
State, and Local regulations.
We recommend permanent fill placed on slopes steeper than about 5H:1V (Horizontal:Vertical) be keyed
and benched into soils comprising the underlying slope. We recommend that the base downslope key be
cut into undisturbed native soil and be at least 5 feet wide and 2 feet deep. The hillside benches cut into
the native soil should be at least 3 feet in width. The intent of the benches is to provide a level surface
onto which new fill can be placed and compacted. The face of the embankment should be compacted to
44
the same relative compaction as the body of the fill. This may be accomplished by over-building the
embankment and cutting back to the compacted core.
We recommend that all permanent cut or fill slopes constructed in native soils be designed at a 2½H:1V
(Horizontal:Vertical) inclination or flatter. All permanent cut and fill slopes should be adequately
protected from erosion both temporarily and permanently.
Seismic Design Considerations
Seismic Setting: Based on our review of the Washington Interactive Geologic Map available online
(https://fortress.wa.gov/dnr/protectiongis/geology/), the project site lies within the Tacoma Fault Zone.
The nearest mapped fault trace, however, is located approximately 1 mile to the northeast. According
the USGS, the fault age is less than 15,000 years, has been mapped with east striking features, and is in
the slip rate category of between 0.2 and 1.0 mm/year. Based on the information described above, we
estimate that the risk associated with fault surface rupture at the site is low.
IBC Seismic Design Parameters: Values provided below are based upon data from the 2012/2015
International Building Code. The following table summarizes our recommended seismic design criteria.
Our recommendation to use Seismic Site Class D is based on the subsurface conditions encountered, deep
subsurface conditions presented on geologic maps that include the project site, and our familiarity of the
geologic conditions in the area.
IBC Seismic Design Criteria
Parameter Value
2012/2015 International Building Code Site Classification
Site Class D
Site Latitude/Longitude 47.2839/-122.3379
Mean Peak Ground Acceleration, PGAM 0.500g
Spectral Short-Period Acceleration, Ss 1.285g (Site Class B)
Spectral 1-Second Acceleration, S1 0.495g (Site Class B)
Site Coefficient for a Short Period, Fa 1.000
Site Coefficient for a 1-Second Period, Fv 1.505
Spectral Acceleration for a 0.2-Second Period, SMS 1.285g (Site Class D)
Spectral Acceleration for a 1-Second Period, SM1 0.745g (Site Class D)
Design Short-Period Spectral Acceleration, SDS 0.857g (Site Class D)
Design 1-Second Spectral Acceleration, SD1 0.497g (Site Class D)
The site soils are not considered to be prone to liquefaction due to their relative density and the absence
of groundwater observations within the full depth of our explorations. The potential for seismic related
settlement is considered low and foundation bearing capacity failure is considered unlikely during a
design-level earthquake.
45
Shallow Foundation Recommendations
Allowable Bearing Pressure: In order to limit settlement to less than 1 inch total and ¾ inch over 40 feet
differential, we recommend that continuous and column footings bearing on at least medium dense
outwash soil or structural fill placed in accordance with the recommendations in this report and
compacted to at least 95 percent of the modified Proctor maximum dry density per ASTM D 1557 be
designed using a maximum allowable bearing capacity of 3,000 psf. A one-third increase of the bearing
pressure may be used for short-term dynamic loads such as wind and seismic forces.
Shallow Foundation Depth and Width: For frost protection, we recommend the bottom of all exterior
footings bear at least 18 inches below the lowest adjacent outside grade, whereas the bottoms of interior
footings should bear at least 12 inches below the surrounding slab surface level. We recommend that all
continuous wall and isolated column footings be at least 12 and 24 inches wide, respectively.
Lateral Resistance: We recommend using allowable base friction and passive earth resistance values 0.40
and 350 pcf equivalent fluid pressure, respectively. We recommend that passive resistance be neglected
in the upper 18 inches of embedment.
On-Grade Concrete Slabs
Subgrade Preparation: After removal of trees, forest duff, organic material, and other items noted in the
Site Preparation section of this report, we recommend at least the upper 12 inches of material below the
slab base be scarified and recompacted to a firm and unyielding condition and to a minimum of 95 percent
of the modified Proctor maximum dry density per ASTM D 1557.
Slab Base: To provide a uniform slab bearing surface, capillary break, and even working surface, we
recommend the on-grade slabs be underlain by a 6-inch thick layer of compacted crushed rock meeting
the requirements of Crushed Surfacing Top Course as specified in Section 9-03.9(3) of the WSDOT
Standard Specifications with the modification that a maximum of 7.5 percent of the material passes the
U.S. No 200 sieve.
Vapor Barrier: From a geotechnical perspective, a vapor barrier is not considered necessary beneath the
slab on grade floor unless moisture sensitive floor coverings and/or adhesives are used. If a vapor barrier
is used, we recommend using a 15-mil, puncture-resistant proprietary product such as Stego Wrap, or an
approved equivalent that is classified as a Class A vapor retarder in accordance with ASTM E 1745. Overlap
lengths and the appropriate tape used to seal the laps should be in accordance the vapor retarder
manufacturer’s recommendations. To avoid puncturing of the vapor barrier, a thin sand layer placed over
the crushed gravel is recommended. When conditions warrant the use of a vapor retarder, the slab
designer and slab contractor should refer to ACI 302 and ACI 360 for procedures and cautions regarding
the use and placement of a vapor retarder/barrier.
Lateral Earth Pressures
The lateral soil pressures acting on backfilled retaining walls will depend on the nature and density of the
soil behind the wall, and the ability of the wall to yield in response to the earth loads. Yielding walls (i.e.
46
walls that are free to translate or rotate) that are able to displace laterally at least 0.001H, where H is the
height of the wall, may be designed for active earth pressures. Non-yielding walls (i.e. walls that are not
free to translate or rotate) should be designed for at-rest earth pressures. Non-yielding walls include walls
that are braced to another wall or structure, and wall corners.
Assuming that walls are backfilled and drained as described in the following paragraphs, we recommend
that yielding walls supporting horizontal backfill be designed using an equivalent fluid density of 35 pcf
(active earth pressure). Non-yielding walls should be designed using an equivalent fluid density of 50 pcf
(at-rest earth pressure).
Surcharge pressures due to sloping backfill, adjacent footings, vehicles, construction equipment, etc. must
be added to these lateral earth pressure values. For traffic loads, we recommend using an equivalent
two-foot soil surcharge of about 250 psf.
For yielding and non-yielding walls with level backfill conditions, we recommend that a uniformly
distributed seismic pressure of 7H psf for the active case and 12H psf for the at-rest case, where H is the
height of the wall, be applied to the walls.
The above equivalent fluid pressures are based on the assumption of no buildup of hydrostatic pressure
behind the wall. If groundwater is allowed to saturate the backfill soils, hydrostatic pressures will act
against a retaining wall; however, if the recommended drainage system is included with each retaining
wall, we do not expect that hydrostatic pressures will develop.
Stormwater Management
As a part of previous construction phases, a stormwater detention pond and an infiltration pond were
constructed near the northwest corner of the campus. We understand the ponds were sized to
accommodate the full campus buildout and will be used to treat and infiltrate stormwater runoff from the
current proposed phase.
In order to aid in evaluation of the current functionality of the infiltration pond, we excavated a small pit
using hand tools near the center of the pond and installed a groundwater level data logger within a
vertical, slotted PVC pipe. The data logger will be retrieved upon conclusion of the wet season and hourly
water level readings from the date of installation to the date of retrieval will be downloaded and
processed. A letter addendum to this report will be submitted following retrieval of the data logger that
includes a summary of the water levels observed in the infiltration pond, subsurface conditions
encountered in our hand excavation, and results of cation exchange capacity and organic content tests
performed on shallow soils obtained from our hand excavation.
47
CLOSURE
The analysis and recommendations presented in this report are based, in part, on the explorations
completed for this study and review of previously prepared reports described in the text. The number,
location, and depth of the explorations for the current phase of the project were completed within the
constraints of budget and site access so as to yield the information to formulate our recommendations.
Project plans were in the preliminary stage at the time this report was prepared. We therefore
recommend Zipper Geo Associates, LLC be provided an opportunity to review the final plans and
specifications when they become available in order to assess that the recommendations and design
considerations presented in this report have been properly interpreted and implemented into the project
design.
The performance of shallow foundations and slabs on grade depend greatly on proper site preparation
and construction procedures. We recommend that Zipper Geo Associates, LLC be retained to provide
geotechnical engineering services during the site preparation and foundation construction phases of the
project. If variations in subsurface conditions are observed at that time, a qualified geotechnical engineer
could provide additional geotechnical recommendations to the contractor and design team in a timely
manner as the project construction progresses.
This report has been prepared for the exclusive use of RJ Development, and their agents, for specific
application to the project discussed and has been prepared in accordance with generally accepted
geotechnical engineering practices. No warranties, express or implied, are intended or made. Site safety,
excavation support, and dewatering requirements are the responsibility of others. In the event that
changes in the nature, design, or location of the project as outlined in this report are planned, the
conclusions and recommendations contained in this report shall not be considered valid unless Zipper
Geo Associates, LLC reviews the changes and either verifies or modifies the conclusions of this report in
writing.
48
B-2B-1B-4B-3B-5B-6TP-105TP-106TP-107FIGUREJob No.Zipper Geo Associates, LLC19019 36th Ave. W.,Suite ELynnwood, WASHT. of11SITE AND EXPLORATION PLAN1969.01DATE: MARCH 20181VILLAGE GREEN RETIREMENT CAMPUS35419 1ST AVENUE SOUTHFEDERAL WAY, WASHINGTONSCALE IN FEET0 30
LEGENDZGA BORING NUMBER ANDAPPROXIMATE LOCATION (2018)REFERENCE: MARKETING SITE PLAN BY RJ DEVELOPMENT DATED OCTOBER 31, 2017.5050250APPROXIMATE SCALE IN FEETTP-106B-6EARTH CONSULTANTS, INC. TESTPIT NUMBER AND APPROXIMATELOCATION (2000)49
APPENDIX A
SUBSURFACE EXPLORATION PROCEDURES AND LOGS
50
APPENDIX A
SUBSURFACE EXPLORATION PROCEDURES AND LOGS
Field Exploration Description
Our field exploration for this project included advancing six borings across the proposed current phase of
the project on February 18, 2018. The approximate locations of the explorations are presented on Figure
1, the Site and Exploration Plan. Exploration locations were determined in the field based on hand
measurements from existing site features. As such, the exploration locations should be considered
accurate only to the degree implied by the measurement method. Descriptive logs of the borings are
enclosed in this appendix. A current topographic survey of the site was not available at the time of this
report. Therefor, ground surface elevations of the explorations were not determined.
The borings were advanced using a track-mounted drill rig operated by an independent drilling company
(Holocene Drilling, Inc.) working under subcontract to ZGA. The borings were advanced using hollow-
stem auger drilling methods. An engineer from our firm continuously observed the borings, logged the
subsurface conditions encountered, and obtained representative soil samples. All samples were stored
in moisture-tight containers and transported to our laboratory for further evaluation and testing. Samples
were obtained by means of the Standard Penetration Test at 2.5- to 5-foot intervals throughout the drilling
operation.
The Standard Penetration Test (ASTM D 1586) procedure consists of driving a standard 2-inch outside
diameter steel split spoon sampler 18 inches into the soil with a 140-pound hammer free falling 30 inches.
The number of blows required to drive the sampler through each 6-inch interval is recorded, and the total
number of blows struck during the final 12 inches is recorded as the Standard Penetration Resistance, or
“blow count” (N value). If a total of 50 blows is struck within any 6-inch interval, the driving is stopped
and the blow count is recorded as 50 blows for the actual penetration distance. The resulting Standard
Penetration Resistance values indicate the relative density of granular soils and the relative consistency
of cohesive soils.
The enclosed boring logs describe the vertical sequence of soils and materials encountered in the borings,
based primarily upon our field classifications. Where a soil contact was observed to be gradational, our
log indicates the average contact depth. Where a soil type changed between sample intervals, we inferred
the contact depth. Our logs also graphically indicate the blow count, sample type, sample number, and
approximate depth of each soil sample obtained from the borings. If groundwater was encountered, the
approximate groundwater depth, and date of observation, are depicted on the logs.
51
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
B-1
B-1
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 2
BORING
LOG:TestingPlastic Limit
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
0 20 40 60
6"
7"
6"
0"
6"
13"
S-1
S-2
S-3
S-4
S-5
S-6
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1219
31
31
56
50/4
50/6
MC
SNM
6 inches of grass, organics, and forest duff
Medium dense to dense, moist, tan, gravelly SAND, some silt
(Recessional Outwash)
Very dense, moist, gray-brown, silty SAND, with gravel
(Glacial Till)
52
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Federal Way, Washington
1969.01
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
BORING
LOG:B-1
Page 2 of 2
March 2018
35419 1st Avenue South
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Plastic Limit
Natural Water Content
Village Green Retirement Campus
Boring Location:
B-1
Date Drilled:Depth (ft)SOIL DESCRIPTION
Sample Number SAMPLES RecoveryGround WaterPENETRATION RESISTANCE (blows/foot)Blow CountsTesting12"S-7
0 20 40 60
25
30
35
40
45
50
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/3
SNM
Boring terminated at approximately 26 1/2 feet. Groundwater
not observed while drilling.
53
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
B-2
B-2
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 2
BORING
LOG:TestingPlastic Limit
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
0 20 40 60
0"
0"
0"
5"
5"
13"
S-1
S-2
S-3
S-4
S-5
S-6
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/6
22
19
19
19
50
MC
SNM
2 inches crushed gravel surfacing
Medium dense, moist, brown, sandy GRAVEL, some silt
(Recessional Outwash)
Blowcount overstated on rock
Hard, wet, brown, sandy SILT, with gravel
Very dense, moist, gray-brown, silty SAND, with gravel
(Glacial Till)
54
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:
B-2
Date Drilled:Depth (ft)SOIL DESCRIPTION
Sample Number SAMPLES RecoveryGround WaterPENETRATION RESISTANCE (blows/foot)Blow CountsTesting35419 1st Avenue South
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Plastic Limit
Natural Water Content
Village Green Retirement Campus
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Federal Way, Washington
1969.01
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
BORING
LOG:B-2
Page 2 of 2
March 2018
1"S-7
0 20 40 60
25
30
35
40
45
50
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/3
SNM
Boring terminated at approximately 25 1/4 feet. Groundwater
not observed while drilling.
55
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
B-3
B-3
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 2
BORING
LOG:TestingPlastic Limit
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
0 20 40 60
10"
14"
13"
18"
18"
13"
S-1
S-2
S-3
S-4
S-5
S-6
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/6
50/6
50/6
77
50/6
50/6
GSA
MC
SNM
4 to 6 inches of grass, organics, and forest duff
Very dense, moist, tan, sandy GRAVEL, some silt
(Recessional Outwash)
Very dense, moist, gray-brown, silty SAND, with gravel
(Glacial Till)
56
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:
B-3
Date Drilled:Depth (ft)SOIL DESCRIPTION
Sample Number SAMPLES RecoveryGround WaterPENETRATION RESISTANCE (blows/foot)Blow CountsTesting35419 1st Avenue South
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Plastic Limit
Natural Water Content
Village Green Retirement Campus
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Federal Way, Washington
1969.01
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
BORING
LOG:B-3
Page 2 of 2
March 2018
15"S-7
0 20 40 60
25
30
35
40
45
50
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/6
SNM
Boring terminated at approximately 26 feet. Groundwater not
observed while drilling.
57
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
B-4
B-4
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 1
BORING
LOG:TestingPlastic Limit
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
0 20 40 60
0"
13"
18"
2"
18"
S-1
S-2
S-3
S-4
S-5
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/3
40
41
59
65
MC
MC
SNM
4 to 6 inches of moss and forest duff
Dense, moist, tan-brown, SAND, with gravel, some silt
(Recessional Outwash)
Very dense, moist, brown-gray, silty SAND, with gravel
(Glacial Till)
Boring terminated at approximately 16 1/2 feet. Groundwater
not observed while drilling.
Blowcount overstated on rock
58
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
B-5
B-5
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 2
BORING
LOG:TestingPlastic Limit
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
0 20 40 60
8"
7"
8"
0"
8"
1"
S-1
S-2
S-3
S-4
S-5
S-6
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1230
23
58
50/3
50/6
50/2
GSA
MC
SNM
6 to 8 inches of moss and forest duff
Medium dense, moist, brown, sandy GRAVEL, with silt
(Recessional Outwash)
Grades to very dense
Very dense, moist, gray-brown, silty SAND, some gravel
(Glacial Till)
Thin sandy SILT zone at 20 feet
59
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:
B-5
Date Drilled:Depth (ft)SOIL DESCRIPTION
Sample Number SAMPLES RecoveryGround WaterPENETRATION RESISTANCE (blows/foot)Blow CountsTesting35419 1st Avenue South
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Plastic Limit
Natural Water Content
Village Green Retirement Campus
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Federal Way, Washington
1969.01
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
BORING
LOG:B-5
Page 2 of 2
March 2018
10"S-7
0 20 40 60
25
30
35
40
45
50
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/6
SNM
Boring terminated at approximately 26 feet. Groundwater not
observed while drilling.
60
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:Sample Number SAMPLES RecoveryDepth (ft)SOIL DESCRIPTION
Date Drilled:
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.Ground WaterPENETRATION RESISTANCE (blows/foot)
B-6
B-6
1969.01Blow CountsVillage Green Retirement Campus
35419 1st Avenue South
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
Federal Way, Washington
Page 1 of 2
BORING
LOG:TestingPlastic Limit
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Natural Water Content
March 2018
0 20 40 60
4"
6"
18"
15"
18"
12"
S-1
S-2
S-3
S-4
S-5
S-6
0
5
10
15
20
25
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1229
21
45
77
50/6
50/5
GSA
200W
SNM
6 to 8 inches of moss and forest duff
Medium dense, moist, brown, gravelly SAND, some silt
(Recessional Outwash)
Grades to dense, silty SAND, with gravel
Very dense, moist, gray-brown, silty SAND, with to some
gravel (Glacial Till)
61
Drilling Company:Bore Hole Dia.:
Top Elevation:Drilling Method:Hammer Type:
Drill Rig:Logged by:
Standard Penetration Test
Hammer Weight and Drop:
SAMPLE LEGEND GROUNDWATER LEGEND % Fines (<0.075 mm)
2-inch O.D. split spoon sample Clean Sand % Water (Moisture) Content
3-inch I.D. Shelby tube sample Bentonite Liquid Limit
Grout/Concrete
Screened Casing
TESTING KEY Blank Casing
GSA = Grain Size Analysis
200W = 200 Wash Analysis Date:Project No.:
Consol. = Consolidation Test
Att. = Atterberg Limits
Boring Location:
B-6
Date Drilled:Depth (ft)SOIL DESCRIPTION
Sample Number SAMPLES RecoveryGround WaterPENETRATION RESISTANCE (blows/foot)Blow CountsTesting35419 1st Avenue South
The stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Plastic Limit
Natural Water Content
Village Green Retirement Campus
Groundwater level at
time of drilling (ATD) or
on date of
measurement.
Federal Way, Washington
1969.01
Zipper Geo Associates
19019 36th Ave. W, Suite E
Lynnwood, WA
BORING
LOG:B-6
Page 2 of 2
March 2018
0"S-7
0 20 40 60
25
30
35
40
45
50
See Figure 1, Site and Exploration Plan
-
2/18/2018
Holocene Drilling
Hollow Stem Auger
D50
8 inches
Auto
11/2/1250/1
SNM
Boring terminated at approximately 25 1/2 feet. Groundwater
not observed while drilling.
62
APPENDIX B
LABORATORY TESTING PROCEDURES AND RESULTS
63
APPENDIX B
LABORATORY TESTING PROCEDURES AND RESULTS
A series of laboratory tests were performed by ZGA during the course of this study to evaluate the index
and geotechnical engineering properties of the subsurface soils. Descriptions of the types of tests
performed are given below.
Visual Classification
Samples recovered from the exploration locations were visually classified in the field during the
exploration program. Representative portions of the samples were carefully packaged in moisture tight
containers and transported to our laboratory where the field classifications were verified or modified as
required. Visual classification was generally done in accordance with ASTM D 2488. Visual soil
classification includes evaluation of color, relative moisture content, soil type based upon grain size, and
accessory soil types included in the sample. Soil classifications are presented on the exploration logs in
Appendix A.
Moisture Content Determinations
Moisture content determinations were performed on representative samples obtained from the
explorations to aid in identification and correlation of soil types. The determinations were made in
general accordance with the test procedures described in ASTM D 2216. Moisture contents are presented
on the exploration logs in Appendix A.
200 Wash Analysis
A 200 wash analysis indicates the fines content of a sample (percent of sample by weight passing the US
No. 200 sieve). 200 wash analyses were performed on representative samples in general accordance with
ASTM: D-1140. The results of the 200 wash analyses for the samples were used in classification of the
soils, and are presented on the exploration logs in Appendix A.
Grain Size Analysis
A grain size analysis determines the range in diameter of soil particles included in a particular sample.
Grain size analyses were performed on representative samples in general accordance with ASTM D 422.
The results of the grain size determinations for the samples were used in classification of the soils, and
are presented in this appendix.
64
0
10
20
30
40
50
60
70
80
90
100
0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS
GRAIN SIZE ANALYSIS
Comments:
36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200
Coarse Medium Fine Silt ClayFineCoarse
COBBLESBOULDERS GRAVEL SAND FINE GRAINED
SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER
Project No.:PROJECT NAME:
Village Green Retirement
Campus
DATE OF TESTING:
Exploration Sample Depth (feet)Moisture (%)Fines (%)Description
B-3 2 1/2 -4 ft.2.7 Sandy GRAVEL,
some siltS-1 5.5
1969.01
2/16/2018
ASTM D 422Test Results Summary
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants
65
0
10
20
30
40
50
60
70
80
90
100
0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS
GRAIN SIZE ANALYSIS
Comments:
36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200
Coarse Medium Fine Silt ClayFineCoarse
COBBLESBOULDERS GRAVEL SAND FINE GRAINED
SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER
Project No.:PROJECT NAME:
Village Green Retirement
Campus
DATE OF TESTING:
Exploration Sample Depth (feet)Moisture (%)Fines (%)Description
B-5 2 1/2 -4 ft.8.4 Sandy GRAVEL,
with siltS-1 13.1
1969.01
2/16/2018
ASTM D 422Test Results Summary
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants
66
0
10
20
30
40
50
60
70
80
90
100
0.0010.0100.1001.00010.000100.0001000.000PERCENT FINER BY WEIGHTPARTICLE SIZE IN MILLIMETERS
GRAIN SIZE ANALYSIS
Comments:
36"12"6"3"1 1/2"3/4"3/8"4 10 20 40 60 140 200
Coarse Medium Fine Silt ClayFineCoarse
COBBLESBOULDERS GRAVEL SAND FINE GRAINED
SIZE OF OPENING IN INCHES U.S. STANDARD SIEVE SIZE HYDROMETER
Project No.:PROJECT NAME:
Village Green Retirement
Campus
DATE OF TESTING:
Exploration Sample Depth (feet)Moisture (%)Fines (%)Description
B-6 7 1/2 -9 ft.8.4 Silty SAND, with
gravelS-3 31.7
1969.01
2/16/2018
ASTM D 422Test Results Summary
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants
67
APPENDIX C
EXCERPTS FROM EARTH CONSULTANTS, INC. REPORTS
68
69
70
71
72
73
Village Green of Federal Way DCI 98480.6
Section 7
Other Permits
74
Village Green of Federal Way DCI 98480.6
Section 7 – Other Permits
Building, Clearing/Grading and Right-of-Way Use Permits are anticipated after the Process 4 land
use approval.
75
Village Green of Federal Way DCI 98480.6
Section 8
CSWPP Plan Analysis and Design
76
Village Green of Federal Way DCI 98480.6
Section 8 – CSWPP Plan Analysis and Design
This section will be completed at the final engineering/building permit stage.
77
Village Green of Federal Way DCI 98480.6
Section 9
Bond Quantities, Facility Summaries, and
Declaration of Covenant
78
Village Green of Federal Way DCI 98480.6
Section 9 – Bond Quantities, Facility Summaries, and Declaration of
Covenant
This section will be completed at the final engineering/building permit stage.
79
Village Green of Federal Way DCI 98480.6
Section 10
Operations and Maintenance Manual
80
Village Green of Federal Way DCI 98480.6
Section 10 – Operations and Maintenance Manual
This section will be completed at the final engineering/building permit stage.
81
Village Green of Federal Way DCI 98480.6
Appendix A
WWHM Report
82
WWHM2012
PROJECT REPORT
83
Prelim WWHM 11/8/2018 1:04:17 AM Page 2
General Model Information
Project Name: Prelim WWHM
Site Name: Village Green TDA1
Site Address:
City:
Report Date: 11/8/2018
Gage:Seatac
Data Start: 1948/10/01
Data End: 2009/09/30
Timestep: 15 Minute
Precip Scale: 1.00
Version Date: 2015/11/05
Version: 4.2.11
POC Thresholds
Low Flow Threshold for POC1: 50 Percent of the 2 Year
High Flow Threshold for POC1: 50 Year
84
Prelim WWHM 11/8/2018 1:04:17 AM Page 3
Landuse Basin Data
Predeveloped Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Forest, Flat 4.15
C, Lawn, Flat 4.74
Pervious Total 8.89
Impervious Land Use acre
ROOF TOPS FLAT 4.16
Impervious Total 4.16
Basin Total 13.05
Element Flows To:
Surface Interflow Groundwater
Trapezoidal Pond 1 Trapezoidal Pond 1
85
Prelim WWHM 11/8/2018 1:04:17 AM Page 4
Mitigated Land Use
Basin 1
Bypass:No
GroundWater:No
Pervious Land Use acre
C, Lawn, Flat 6.66
Pervious Total 6.66
Impervious Land Use acre
ROOF TOPS FLAT 6.39
Impervious Total 6.39
Basin Total 13.05
Element Flows To:
Surface Interflow Groundwater
Trapezoidal Pond 2 Trapezoidal Pond 2
86
Prelim WWHM 11/8/2018 1:04:17 AM Page 5
Routing Elements
Predeveloped Routing
Trapezoidal Pond 1
Bottom Length:150.00 ft.
Bottom Width:80.00 ft.
Depth:6 ft.
Volume at riser head: 2.0878 acre-feet.
Side slope 1:3 To 1
Side slope 2:3 To 1
Side slope 3:3 To 1
Side slope 4:3 To 1
Discharge Structure
Riser Height:5.54 ft.
Riser Diameter:18 in.
Orifice 1 Diameter: 2.77 in. Elevation:0 ft.
Orifice 2 Diameter: 3.13 in. Elevation:4.6 ft.
Element Flows To:
Outlet 1 Outlet 2
Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)
225.26 0.275 0.000 0.000 0.000
225.33 0.277 0.018 0.053 0.000
225.39 0.279 0.037 0.076 0.000
225.46 0.281 0.055 0.093 0.000
225.53 0.284 0.074 0.107 0.000
225.59 0.286 0.093 0.120 0.000
225.66 0.288 0.112 0.131 0.000
225.73 0.290 0.132 0.142 0.000
225.79 0.292 0.151 0.152 0.000
225.86 0.294 0.171 0.161 0.000
225.93 0.297 0.190 0.170 0.000
225.99 0.299 0.210 0.178 0.000
226.06 0.301 0.230 0.186 0.000
226.13 0.303 0.250 0.193 0.000
226.19 0.305 0.271 0.201 0.000
226.26 0.308 0.291 0.208 0.000
226.33 0.310 0.312 0.215 0.000
226.39 0.312 0.333 0.221 0.000
226.46 0.314 0.353 0.228 0.000
226.53 0.316 0.374 0.234 0.000
226.59 0.319 0.396 0.240 0.000
226.66 0.321 0.417 0.246 0.000
226.73 0.323 0.439 0.252 0.000
226.79 0.326 0.460 0.257 0.000
226.86 0.328 0.482 0.263 0.000
226.93 0.330 0.504 0.268 0.000
226.99 0.332 0.526 0.274 0.000
227.06 0.335 0.548 0.279 0.000
227.13 0.337 0.571 0.284 0.000
227.19 0.339 0.593 0.289 0.000
227.26 0.342 0.616 0.294 0.000
227.33 0.344 0.639 0.299 0.000
87
Prelim WWHM 11/8/2018 1:04:17 AM Page 6
227.39 0.346 0.662 0.304 0.000
227.46 0.349 0.685 0.308 0.000
227.53 0.351 0.709 0.313 0.000
227.59 0.353 0.732 0.318 0.000
227.66 0.356 0.756 0.322 0.000
227.73 0.358 0.780 0.327 0.000
227.79 0.361 0.804 0.331 0.000
227.86 0.363 0.828 0.335 0.000
227.93 0.365 0.852 0.340 0.000
227.99 0.368 0.877 0.344 0.000
228.06 0.370 0.901 0.348 0.000
228.13 0.373 0.926 0.352 0.000
228.19 0.375 0.951 0.356 0.000
228.26 0.378 0.976 0.360 0.000
228.33 0.380 1.001 0.364 0.000
228.39 0.382 1.027 0.368 0.000
228.46 0.385 1.052 0.372 0.000
228.53 0.387 1.078 0.376 0.000
228.59 0.390 1.104 0.380 0.000
228.66 0.392 1.130 0.383 0.000
228.73 0.395 1.156 0.387 0.000
228.79 0.397 1.183 0.391 0.000
228.86 0.400 1.209 0.395 0.000
228.93 0.402 1.236 0.398 0.000
228.99 0.405 1.263 0.402 0.000
229.06 0.407 1.290 0.405 0.000
229.13 0.410 1.318 0.409 0.000
229.19 0.412 1.345 0.413 0.000
229.26 0.415 1.373 0.416 0.000
229.33 0.418 1.400 0.419 0.000
229.39 0.420 1.428 0.423 0.000
229.46 0.423 1.456 0.426 0.000
229.53 0.425 1.485 0.430 0.000
229.59 0.428 1.513 0.433 0.000
229.66 0.430 1.542 0.436 0.000
229.73 0.433 1.571 0.440 0.000
229.79 0.436 1.600 0.443 0.000
229.86 0.438 1.629 0.446 0.000
229.93 0.441 1.658 0.518 0.000
229.99 0.444 1.688 0.550 0.000
230.06 0.446 1.717 0.575 0.000
230.13 0.449 1.747 0.596 0.000
230.19 0.451 1.777 0.616 0.000
230.26 0.454 1.807 0.633 0.000
230.33 0.457 1.838 0.650 0.000
230.39 0.459 1.868 0.665 0.000
230.46 0.462 1.899 0.680 0.000
230.53 0.465 1.930 0.694 0.000
230.59 0.468 1.961 0.708 0.000
230.66 0.470 1.992 0.721 0.000
230.73 0.473 2.024 0.734 0.000
230.79 0.476 2.056 0.746 0.000
230.86 0.478 2.087 0.992 0.000
230.93 0.481 2.119 1.485 0.000
230.99 0.484 2.152 2.118 0.000
231.06 0.487 2.184 2.842 0.000
231.13 0.489 2.217 3.609 0.000
231.19 0.492 2.249 4.373 0.000
88
Prelim WWHM 11/8/2018 1:04:17 AM Page 8
Mitigated Routing
Trapezoidal Pond 2
Bottom Length:240.00 ft.
Bottom Width:90.00 ft.
Depth:6.5 ft.
Volume at riser head: 3.3834 acre-feet.
Side slope 1:0 To 1
Side slope 2:2 To 1
Side slope 3:3 To 1
Side slope 4:3 To 1
Discharge Structure
Riser Height:5.8 ft.
Riser Diameter:18 in.
Orifice 1 Diameter: 2.18 in. Elevation:0 ft.
Orifice 2 Diameter: 1.6 in. Elevation:2.05 ft.
Orifice 3 Diameter: 0.7 in. Elevation:3.8 ft.
Element Flows To:
Outlet 1 Outlet 2
Hydraulic Table
Stage(feet) Area(ac.) Volume(ac-ft.) Discharge(cfs) Infilt(cfs)
0.0000 0.495 0.000 0.000 0.000
0.0722 0.497 0.035 0.034 0.000
0.1444 0.499 0.071 0.049 0.000
0.2167 0.501 0.108 0.060 0.000
0.2889 0.503 0.144 0.069 0.000
0.3611 0.505 0.180 0.077 0.000
0.4333 0.507 0.217 0.084 0.000
0.5056 0.509 0.254 0.091 0.000
0.5778 0.511 0.291 0.098 0.000
0.6500 0.513 0.328 0.104 0.000
0.7222 0.515 0.365 0.109 0.000
0.7944 0.517 0.402 0.114 0.000
0.8667 0.519 0.439 0.120 0.000
0.9389 0.521 0.477 0.125 0.000
1.0111 0.523 0.515 0.129 0.000
1.0833 0.525 0.553 0.134 0.000
1.1556 0.527 0.591 0.138 0.000
1.2278 0.529 0.629 0.142 0.000
1.3000 0.531 0.667 0.147 0.000
1.3722 0.533 0.706 0.151 0.000
1.4444 0.535 0.744 0.155 0.000
1.5167 0.537 0.783 0.158 0.000
1.5889 0.539 0.822 0.162 0.000
1.6611 0.541 0.861 0.166 0.000
1.7333 0.543 0.900 0.169 0.000
1.8056 0.545 0.939 0.173 0.000
1.8778 0.547 0.979 0.176 0.000
1.9500 0.549 1.018 0.180 0.000
2.0222 0.551 1.058 0.183 0.000
2.0944 0.553 1.098 0.201 0.000
2.1667 0.555 1.138 0.213 0.000
2.2389 0.557 1.178 0.223 0.000
2.3111 0.559 1.219 0.231 0.000
89
Prelim WWHM 11/8/2018 1:04:17 AM Page 9
2.3833 0.561 1.259 0.239 0.000
2.4556 0.563 1.300 0.246 0.000
2.5278 0.566 1.341 0.253 0.000
2.6000 0.568 1.382 0.259 0.000
2.6722 0.570 1.423 0.265 0.000
2.7444 0.572 1.464 0.271 0.000
2.8167 0.574 1.505 0.277 0.000
2.8889 0.576 1.547 0.282 0.000
2.9611 0.578 1.589 0.288 0.000
3.0333 0.580 1.630 0.293 0.000
3.1056 0.582 1.672 0.298 0.000
3.1778 0.584 1.715 0.303 0.000
3.2500 0.586 1.757 0.308 0.000
3.3222 0.588 1.799 0.313 0.000
3.3944 0.591 1.842 0.318 0.000
3.4667 0.593 1.885 0.322 0.000
3.5389 0.595 1.928 0.327 0.000
3.6111 0.597 1.971 0.331 0.000
3.6833 0.599 2.014 0.336 0.000
3.7556 0.601 2.057 0.340 0.000
3.8278 0.603 2.101 0.347 0.000
3.9000 0.605 2.145 0.353 0.000
3.9722 0.608 2.188 0.358 0.000
4.0444 0.610 2.232 0.364 0.000
4.1167 0.612 2.276 0.369 0.000
4.1889 0.614 2.321 0.373 0.000
4.2611 0.616 2.365 0.378 0.000
4.3333 0.618 2.410 0.383 0.000
4.4056 0.620 2.455 0.387 0.000
4.4778 0.623 2.500 0.392 0.000
4.5500 0.625 2.545 0.396 0.000
4.6222 0.627 2.590 0.400 0.000
4.6944 0.629 2.635 0.405 0.000
4.7667 0.631 2.681 0.409 0.000
4.8389 0.633 2.726 0.413 0.000
4.9111 0.636 2.772 0.417 0.000
4.9833 0.638 2.818 0.421 0.000
5.0556 0.640 2.865 0.425 0.000
5.1278 0.642 2.911 0.429 0.000
5.2000 0.644 2.957 0.433 0.000
5.2722 0.647 3.004 0.437 0.000
5.3444 0.649 3.051 0.440 0.000
5.4167 0.651 3.098 0.444 0.000
5.4889 0.653 3.145 0.448 0.000
5.5611 0.655 3.192 0.451 0.000
5.6333 0.658 3.240 0.455 0.000
5.7056 0.660 3.287 0.459 0.000
5.7778 0.662 3.335 0.462 0.000
5.8500 0.664 3.383 0.644 0.000
5.9222 0.667 3.431 1.147 0.000
5.9944 0.669 3.479 1.821 0.000
6.0667 0.671 3.528 2.600 0.000
6.1389 0.673 3.576 3.426 0.000
6.2111 0.676 3.625 4.236 0.000
6.2833 0.678 3.674 4.973 0.000
6.3556 0.680 3.723 5.587 0.000
6.4278 0.682 3.772 6.056 0.000
6.5000 0.685 3.822 6.389 0.000
90
Prelim WWHM 11/8/2018 1:04:17 AM Page 11
Analysis Results
POC 1
+ Predeveloped x Mitigated
Predeveloped Landuse Totals for POC #1
Total Pervious Area: 8.89
Total Impervious Area: 4.16
Mitigated Landuse Totals for POC #1
Total Pervious Area: 6.66
Total Impervious Area: 6.39
Flow Frequency Method: Log Pearson Type III 17B
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow(cfs)
2 year 0.320631
5 year 0.415677
10 year 0.482923
25 year 0.572994
50 year 0.643914
100 year 0.718208
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow(cfs)
2 year 0.292033
5 year 0.415896
10 year 0.51407
25 year 0.658327
50 year 0.781715
100 year 0.919858
Annual Peaks
Annual Peaks for Predeveloped and Mitigated. POC #1
Year Predeveloped Mitigated
1949 0.286 0.220
1950 0.355 0.318
1951 0.621 0.461
1952 0.250 0.175
1953 0.244 0.263
1954 0.318 0.292
1955 0.351 0.292
1956 0.367 0.339
1957 0.302 0.285
1958 0.315 0.308
91
Prelim WWHM 11/8/2018 1:05:00 AM Page 12
1959 0.289 0.241
1960 0.435 0.430
1961 0.292 0.302
1962 0.233 0.168
1963 0.308 0.286
1964 0.302 0.270
1965 0.311 0.325
1966 0.269 0.259
1967 0.338 0.305
1968 0.276 0.267
1969 0.287 0.235
1970 0.290 0.254
1971 0.324 0.304
1972 0.414 0.378
1973 0.279 0.309
1974 0.311 0.301
1975 0.336 0.276
1976 0.326 0.297
1977 0.206 0.178
1978 0.283 0.297
1979 0.226 0.168
1980 0.418 0.436
1981 0.264 0.258
1982 0.401 0.385
1983 0.335 0.296
1984 0.244 0.214
1985 0.266 0.232
1986 0.398 0.356
1987 0.409 0.400
1988 0.264 0.215
1989 0.209 0.218
1990 0.435 0.434
1991 0.522 0.417
1992 0.296 0.300
1993 0.288 0.220
1994 0.189 0.164
1995 0.349 0.313
1996 0.622 0.458
1997 0.647 1.474
1998 0.265 0.224
1999 0.400 0.412
2000 0.287 0.312
2001 0.210 0.156
2002 0.384 0.369
2003 0.246 0.256
2004 0.577 0.454
2005 0.337 0.298
2006 0.323 0.316
2007 0.562 1.052
2008 0.670 0.655
2009 0.385 0.362
Ranked Annual Peaks
Ranked Annual Peaks for Predeveloped and Mitigated. POC #1
Rank Predeveloped Mitigated
1 0.6695 1.4736
2 0.6475 1.0524
3 0.6223 0.6546
92
Prelim WWHM 11/8/2018 1:05:00 AM Page 13
4 0.6211 0.4612
5 0.5767 0.4580
6 0.5622 0.4542
7 0.5217 0.4364
8 0.4350 0.4336
9 0.4347 0.4296
10 0.4181 0.4167
11 0.4138 0.4115
12 0.4089 0.4003
13 0.4010 0.3847
14 0.4002 0.3783
15 0.3979 0.3688
16 0.3850 0.3616
17 0.3835 0.3561
18 0.3671 0.3387
19 0.3546 0.3254
20 0.3515 0.3182
21 0.3492 0.3160
22 0.3376 0.3130
23 0.3372 0.3122
24 0.3360 0.3094
25 0.3355 0.3079
26 0.3257 0.3048
27 0.3244 0.3043
28 0.3227 0.3020
29 0.3183 0.3006
30 0.3149 0.2999
31 0.3114 0.2978
32 0.3114 0.2973
33 0.3075 0.2972
34 0.3025 0.2963
35 0.3020 0.2919
36 0.2965 0.2919
37 0.2923 0.2860
38 0.2905 0.2848
39 0.2890 0.2758
40 0.2877 0.2704
41 0.2870 0.2675
42 0.2865 0.2627
43 0.2865 0.2591
44 0.2832 0.2581
45 0.2793 0.2556
46 0.2764 0.2539
47 0.2687 0.2408
48 0.2657 0.2346
49 0.2649 0.2323
50 0.2645 0.2241
51 0.2635 0.2203
52 0.2504 0.2199
53 0.2462 0.2178
54 0.2439 0.2153
55 0.2438 0.2142
56 0.2330 0.1781
57 0.2264 0.1749
58 0.2104 0.1685
59 0.2089 0.1678
60 0.2063 0.1635
61 0.1887 0.1562
93
Prelim WWHM 11/8/2018 1:05:00 AM Page 15
Duration Flows
The Facility PASSED
Flow(cfs) Predev Mit Percentage Pass/Fail
0.1603 92549 91138 98 Pass
0.1652 86175 80721 93 Pass
0.1701 80336 70711 88 Pass
0.1750 75652 62840 83 Pass
0.1799 70433 54092 76 Pass
0.1847 65535 46841 71 Pass
0.1896 60808 45301 74 Pass
0.1945 56338 43933 77 Pass
0.1994 52253 42649 81 Pass
0.2043 48510 41088 84 Pass
0.2092 45195 39398 87 Pass
0.2140 42243 37623 89 Pass
0.2189 39890 35890 89 Pass
0.2238 37067 33880 91 Pass
0.2287 34479 31891 92 Pass
0.2336 32019 30094 93 Pass
0.2385 29902 28148 94 Pass
0.2434 27891 26265 94 Pass
0.2482 25987 24276 93 Pass
0.2531 24105 22415 92 Pass
0.2580 22330 20741 92 Pass
0.2629 20837 19665 94 Pass
0.2678 19190 18236 95 Pass
0.2727 17686 16987 96 Pass
0.2776 16283 15746 96 Pass
0.2824 14946 14215 95 Pass
0.2873 13689 13036 95 Pass
0.2922 12692 11892 93 Pass
0.2971 11967 10866 90 Pass
0.3020 11426 10046 87 Pass
0.3069 10694 9069 84 Pass
0.3117 10021 8421 84 Pass
0.3166 9388 7886 84 Pass
0.3215 8705 7424 85 Pass
0.3264 7961 6953 87 Pass
0.3313 7347 6500 88 Pass
0.3362 6750 6032 89 Pass
0.3411 6406 5630 87 Pass
0.3459 6098 5392 88 Pass
0.3508 5677 5084 89 Pass
0.3557 5307 4849 91 Pass
0.3606 4988 4532 90 Pass
0.3655 4601 4231 91 Pass
0.3704 4325 3953 91 Pass
0.3752 4047 3715 91 Pass
0.3801 3717 3469 93 Pass
0.3850 3356 3178 94 Pass
0.3899 3148 3014 95 Pass
0.3948 2868 2808 97 Pass
0.3997 2588 2599 100 Pass
0.4046 2342 2415 103 Pass
0.4094 2110 2239 106 Pass
0.4143 1901 2035 107 Pass
94
Prelim WWHM 11/8/2018 1:05:00 AM Page 16
0.4192 1671 1810 108 Pass
0.4241 1557 1561 100 Pass
0.4290 1455 1386 95 Pass
0.4339 1288 1183 91 Pass
0.4388 1088 1047 96 Pass
0.4436 939 949 101 Pass
0.4485 818 786 96 Pass
0.4534 806 585 72 Pass
0.4583 795 323 40 Pass
0.4632 785 187 23 Pass
0.4681 776 183 23 Pass
0.4729 767 181 23 Pass
0.4778 752 177 23 Pass
0.4827 741 175 23 Pass
0.4876 732 172 23 Pass
0.4925 718 167 23 Pass
0.4974 707 164 23 Pass
0.5023 691 162 23 Pass
0.5071 682 159 23 Pass
0.5120 670 157 23 Pass
0.5169 656 156 23 Pass
0.5218 628 154 24 Pass
0.5267 607 153 25 Pass
0.5316 577 152 26 Pass
0.5364 545 149 27 Pass
0.5413 509 149 29 Pass
0.5462 483 148 30 Pass
0.5511 458 145 31 Pass
0.5560 434 145 33 Pass
0.5609 403 144 35 Pass
0.5658 368 142 38 Pass
0.5706 340 142 41 Pass
0.5755 300 135 45 Pass
0.5804 273 129 47 Pass
0.5853 253 121 47 Pass
0.5902 240 118 49 Pass
0.5951 227 110 48 Pass
0.6000 215 105 48 Pass
0.6048 198 96 48 Pass
0.6097 180 87 48 Pass
0.6146 163 83 50 Pass
0.6195 138 76 55 Pass
0.6244 105 71 67 Pass
0.6293 94 68 72 Pass
0.6341 86 66 76 Pass
0.6390 79 64 81 Pass
0.6439 73 62 84 Pass
95
Prelim WWHM 11/8/2018 1:05:00 AM Page 17
Water Quality
Water Quality BMP Flow and Volume for POC #1
On-line facility volume: 0 acre-feet
On-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
Off-line facility target flow: 0 cfs.
Adjusted for 15 min: 0 cfs.
96
Prelim WWHM 11/8/2018 1:05:00 AM Page 18
LID Report
97
Prelim WWHM 11/8/2018 1:05:30 AM Page 19
Model Default Modifications
Total of 0 changes have been made.
PERLND Changes
No PERLND changes have been made.
IMPLND Changes
No IMPLND changes have been made.
98
Prelim WWHM 11/8/2018 1:05:30 AM Page 20
Appendix
Predeveloped Schematic
99
Prelim WWHM 11/8/2018 1:05:31 AM Page 21
Mitigated Schematic
100