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Preliminary Technical Information Report
August 26, 2015
Prepared for
Taylor Development
15 Lake Bellevue Drive, Suite 102
Bellevue, WA 98005
(425) 869-1300
Submitted by
ESM Consulting Engineers, LLC
33400 8th Avenue S, Suite 205
Federal Way, WA 98003
253.838.6113 tel
253.838.7104 fax
www.esmcivil.com
PRELIMINARY TECHNICAL INFORMATION REPORT
FOR
KINKADE CROSSING
Prepared for:
Taylor Development
15 Lake Bellevue Drive, Suite 102
Bellevue, WA 98005
Prepared by:
ESM Consulting Engineers, LLC
33400 8th Avenue S, Suite 205
Federal Way, WA 98003
August 26, 2015 Job No. 994-001-015
Approved By:
City of Renton Date
1
TABLE OF CONTENTS
1. PROJECT OVERVIEW ................................................................................................................................................................................ 1-1
2. CONDITIONS AND REQUIREMENTS SUMMARY .................................................................................................... 2-1
3. OFF-SITE ANALYSIS .................................................................................................................................................................................... 3-1
4. FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS AND DESIGN .............................4-1
5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN .............................................................................................. 5-1
6. SPECIAL REPORTS AND STUDIES ........................................................................................................................................... 6-1
7. OTHER PERMITS ............................................................................................................................................................................................. 7-1
8. CSWPPP ANALYSIS AND DESIGN ............................................................................................................................................ 8-1
9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ...9-1
10. OPERATIONS AND MAINTENANCE MANUAL ............................................................................................................ 10-1
LIST OF FIGURES
1.1 Vicinity Map
1.2 Existing Site Conditions
1.3 Proposed Site Conditions
1.4 Soils Map
3.1 KCGIS Parcel Reports/Environmental Hazards
3.2 Drainage Complaint Map
3.3 Site Topography
3.4 Offsite Analysis Downstream Flowpath
3.5 Offsite Analysis Drainage System Table
4.1 Pond Tributary Area
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1. PROJECT OVERVIEW
The proposed Kinkade Crossing Plat is a 17-lot plat located south of the intersection of
116th Ave SE and SE Petrovitsky Road in the City of Renton, WA. The plat incorporates
one parcel numbered 322305-9303, which is zoned R-8. See Figure 1.1 for the Vicinity
Map.
The existing site consists of 1 single-family dwelling with associated driveway and several
detached sheds near the dwelling. The existing site is relatively flat (mean slope of 5.5%,
less than 10% max slopes on site) with a slope from the southwest to the northeast
corners of the project site. The pervious portions of the parcel are generally pasture. See
Figure 1.2 for the Existing Site Conditions.
The proposed 3.63 acre project site consists of 17 residential lots and 1 open space tract.
All 17 residential lots will have new single-family dwelling units. Those lots will be 5,000
square feet minimum and will be served by a new street from 177th PL to 116th Ave SE and
two hammerheads, with one shared access easement off of the south hammerhead to
provide access to lots 4-6. See Figure 1.3 for the Proposed Site Conditions.
The stormwater detention and water quality treatment will be provided with a combined
detention/water quality pond in the storm drainage tract located in the northeast corner of
the site. The combined detention/water quality pond will discharge east to a proposed
stormwater conveyance system in 116th Ave SE in the project’s east frontage and
ultimately flow east along SE Petrovitsky Road and enter Big Soos Creek. See Section 3
for the Level 1 Downstream Analysis.
According to the Geotechnical Engineering Report (GER)by The Riley Group, Inc. (RGI), on
July 08, 2015 and attached in Section 6, the soils onsite include loose to very dense silty
sand with gravel. See Figure 1.4 for the Soils Map.
Based on the City of Renton’s Flow Control Application Map, the project site is in the Flow
Control Duration Standard (Forested Conditions, Level 2) area. The project will be subject
to Full Drainage Review per the City of Renton 2009 Surface Water Design Manual
Amendments and the 2009 King County Surface Water Design Manual (2009 KCSWDM).
The City of Renton 2009 Surface Water Design Manual Amendment and the 2009
KCSWDM will collectively be referred to as the “2009 Surface Water Design Manual”.
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Figure 1.1
Vicinity Map
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Figure 1.2
Existing Site Conditions
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Figure 1.3
Proposed Site Conditions
6
Figure 1.4
Soils Map
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2. CONDITIONS AND REQUIREMENTS SUMMARY
Review of the 8 Core Requirements and 6 Special Requirements
This section describes how the project will meet the 2009 Surface Water Design Manual’s
Core and Special Requirements.
Core Requirement No. 1 Discharge at the Natural Location
In the existing conditions, the site drains to the northeast, however the flows converge
about 200 feet downstream, at the intersection of SE Petrovitsky Road and 116th Ave SE.
In the proposed condition, the combined detention/water quality pond will discharge east
on 116th Ave SE, which is the natural discharge location for the project site.
Core Requirement No. 2 Off-site Analysis
A Level 1 Downstream Analysis was performed by ESM on June 22, 2015. See Section 3
for the offsite analysis.
Core Requirement No. 3 Flow Control
The proposed project generates 1.33 cfs for the 100 year developed peak flow which is
1.018 cfs more than the 0.312 cfs of the 100 year predeveloped peak flow. Since the
difference between the two flows is more than 0.1 cfs, the proposed project will have to
meet the flow control requirements. Based on the City of Renton’s Flow Control
Application Map, the project site is in the Flow Control Duration Standard (Forested
Conditions, Level 2) area. See Section 4 for Flow Control Analysis and Calculations.
Core Requirement No. 4 Conveyance System
The stormwater drainage conveyance system will be sized as part of the final TIR to
convey the 25 year design storm event and to contain the 100 year design storm event.
Core Requirement No. 5 Erosion and Sediment Control
The proposed project will include clearing and grading for the 17 new single-family units,
open space tract, associated roadways, and pond area. Erosion and sediment controls will
be provided to prevent, to the maximum extent possible, the transport of sediment from
the project site to downstream drainage facilities, water resources, and adjacent
properties. The Temporary Erosion and Sedimentation Control (TESC) Plans will be shown
on the final construction plans and described in the final TIR.
Core Requirement No. 6 Maintenance and Operations
The Operations and Maintenance Manual will be provided as part of the final TIR.
Core Requirement No. 7 Financial Guarantees and Liability
All drainage facilities constructed or modified for projects will comply with the financial
guarantee requirements as provided in the City of Renton Bond Quantities Worksheet.
The Bond Quantities Worksheet, Facility Summaries, and Declaration of Covenant will be
provided as part of the final TIR.
Core Requirement No. 8 Water Quality
The proposed project produces more than 5,000 square feet of pollution generating
impervious area and is required to meet the water quality requirements. According to King
County iMap, the project site requires Basic Water Quality. The site does not meet the
requirements for enhanced treatment in the 2009 Surface Water Design manual.
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Treatment for the pollution generating surfaces will be provided by a combined
detention/water quality pond. See Section 4 for more information.
Special Requirement No. 1 Other Adopted Area-Specific Requirements
There are no master drainage plans, basin plans, salmon conservation plans, stormwater
compliance plans, flood hazard reduction plan updates, or shared facility drainage plans
for this project. Special Requirement No. 1 does not apply.
Special Requirement No. 2 Flood Hazard Area Delineation
There is no 100-year flood plain associated with a large body of water (i.e. lake or stream)
on the site or adjacent to the site. Special Requirement No. 2 does not apply.
Special Requirement No. 3 Flood Protection Facilities
The project lies outside any pre-defined flood plain. Special Requirement No. 3 does not
apply.
Special Requirement No. 4 Source Control
The project is a residential subdivision and is not subject to this requirement. Special
Requirement No. 4 does not apply.
Special Requirement No. 5 Oil Control
The project does not have a “high-use site characteristic” and is not a redevelopment of a
high-use site. Special Requirement No. 5 does not apply.
Special Requirement No. 6 Aquifer Protection Area
According to the “Groundwater Protection Areas in the City of Renton” map, the project site
is not in an Aquifer Protection Area. Special Requirement No. 6 does not apply.
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3.OFF-SITE ANALYSIS
Task 1: Study Area Definition and Maps
Figure 1.2 shows the existing site conditions. Figure 3.4 shows the extent of offsite
analysis and the downstream flow path from the site.
Task 2: Resource Review
·Flow Control Map
According to the City of Renton Flow Control Application Map, the site is a Flow
Control Duration Standard (Forested Conditions) area.
·Soil Survey Map
According to the City of Renton Soil Survey prepared by City of Renton Public
Works Department on 01/09/2014, the geologic map of the area indicates that the
soil type on the project site is AgB: ALDERWOOD GRAVELLY SANDY LOAM, 0 TO 6
PERCENT SLOPES. The GER indicates that the soils onsite include loose to very
dense silty sand with gravel. Further details and descriptions can be found in the
GER attached in Section 6.
·King County iMap
According to the King County GIS Viewer (iMap), the project is NOT in any of the
following areas:
o Streams & 100 year floodplains
o Erosion Hazard Areas
o Seismic Hazard Areas
o Landslide Hazard Areas
o Coal Mine Hazard Areas
o Wetlands
·City of Renton 2009 Surface Water Manual Amendments
According to Reference 11-B in the City of Renton 2009 Surface Water Design
Manual Amendments, the project is NOT in any of the following areas:
o Aquifer Protection Areas
o Groundwater Protection Areas
·Road Drainage Problems
None noted
·Wetlands Inventory
There are no recorded wetlands on or near the site according to iMap and the
1990 King County Wetlands Inventory Notebooks.
·Migrating River Study
None noted
·Downstream Drainage Complaints
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According to the information available on iMap, there have been no downstream
drainage complaints in the study area within the last 10 years.
11
Figure 3.1
KCGIS Parcel Report/Environmental Hazards
12
Task 3: Field Inspection (Level 1 Inspection)
A Level 1 Downstream Analysis was completed by ESM Consulting Engineers in the
afternoon on 22 JUN 2015, when it was partly cloudy and 76°F. During the inspection it
was found that the project site slopes from the southwest to the northeast, with no offsite
areas observed to drain to the property. There are approximately 5 residential lots at the
southwest corner of the property that appear to be higher than the project site, that are
bordered by fences and dense landscaping. These lots do not appear to drain to the
project site but to 114th Place SE. Typical culverts were 12” CMP along the east frontage
and constricted from vegetation and litter. The edge of the asphalt pavement of 116th Ave
SE has eroded into the roadside ditch in some places along the east frontage of the
project site.
Task 4: Drainage Description and Problem Descriptions
According to iMap, the project site is in the Soos Creek (King County WRIA number: 9)
basin. Big Soos Creek is located to the north and east of the project site.
The project site’s high point is the south-west corner which causes the existing site to flow
to the north and east boundaries. All flows on the east boundary flow into a roadside ditch
and enter the storm drainage system on 116th Ave SE. All flows on the north boundary
enter the storm drainage system on SE Petrovitsky Road. Some flows at the north-east
corner of the project site sheet flow onto the parcel adjacent to the project at the corner of
116th Ave SE and SE Petrovitsky Road. All of these flows converge in the storm drainage
system on SE Petrovitsky Road and flow along SE Petrovitsky Rd in a piped catch basin
system for about 1300 feet until they are discharged into Big Soos Creek.
Task 5: Mitigation of Existing or Potential Problems
All runoff from the site will be collected in a piped storm system and directed to the
proposed combined detention/water quality pond. From there, runoff will be discharged at
the Flow Control Duration Standard (Forested Conditions) into the existing storm drainage
system in 116th Ave SE.
13
Figure 3.2
Drainage Complaint Map
14
15
Figure 3.3
Site Topography
16
17
Figure 3.4
Offsite Analysis Downstream Flowpath
18
19
Figure 3.5
Offsite Analysis Drainage System Table
20
Figure 3.6
Picture from Point #1 Looking north along 116th Ave SE
21
Figure 3.7
Picture from Point #2 Looking north along 116th Ave SE
The 12” CMP culvert was almost completely covered with vegetation.
22
Figure 3.8
Picture from Point #3 Looking north along 116th Ave SE
The 12” CMP culvert was covered with vegetation under the driveway.
23
Figure 3.9
Picture from Point #4 Looking north along 116th Ave SE
Flows from the ditch enter the culvert and are piped into the storm drain system from this
location. The culvert was covered with litter and vegetation.
24
Figure 3.10
Picture from Point #5 Looking west along SE Petrovitsky Road
25
Figure 3.11
Picture from Point #6 Looking east along SE Petrovitsky Road
The manhole cover shown in the crosswalk is estimated to be the point of convergence
between the 116th Ave SE and SE Petrovitsky Road storm drains. From there it’s piped to
Big Soos Creek.
26
Figure 3.12
Picture from Point #7 Looking east along SE Petrovitsky Road
The estimated discharge location of the project site’s storm water, approximately 1300 feet
downstream of the project site.
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4. FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS AND DESIGN
4.1 Existing Site Hydrology
The existing site consists of 1 single-family dwelling with associated driveway and several
detached sheds near the dwelling. The existing site is relatively flat (mean slope of 5.5%,
less than 10% max slopes on site) with a slope from the southwest to the northeast
corners of the project site. The pervious portions of the parcel are generally pasture.
According to the GER by RGI the soils onsite include loose to very dense silty sand with
gravel. See Figure 1.4 for the Soils Map. This report shows that the site is generally
underlain with Till soils, which are incapable of infiltration. Therefore Till soils are used in
the KCRTS model, with the predeveloped area being modeled as Till Forest.
Due to the existing site slope, the site will flow toward the northeast corner of the property.
These flows converge about 200 feet downstream of the project site at the intersection of
SE Petrovitsky Road and 116th Ave SE.
The predeveloped basin for the project site also includes the frontage improvements. This
area will be improved with a new sidewalk including curb and gutter.
TABLE 4.1
Pre-Developed Tributary Area
SUBBASIN TOTAL AREA
(Ac)
TILL FOREST
(Ac)
IMPERVIOUS
(Ac)
Onsite Basin 3.52 3.52 0.00
Bypass Basin 0.11 0.11 0.00
Offsite Basin 0.11 0.00 0.11
TOTAL 3.74 3.63 0.11
4.2 Developed Site Hydrology
The project will create 17 single family lots with associated roadway, sidewalk, driveways,
roof areas, landscaped yards, and a combined detention/water quality pond adjacent to
an open space tract. All 17 residence lots will have new single-family dwelling units.
A portion of the frontage improvement area will bypass the pond and be treated as
bypass area. For more information, see Table 4.3 below and Figure 4.1.
The maximum impervious surface area allowed by the City of Renton Zoning Code 4-2-
110A for R-8 zoned lots is 65%. However, the site will utilize Flow Control BMP C2.9
Reduced Impervious Surface Credit, and reduce on-site allowable impervious area by
10%. Therefore, building rooftops and impervious areas (driveway, porch, patios) are
modeled as 55% impervious.
The combined detention/water quality pond is located in the north eastern corner of the
site. The combined detention/water quality pond will discharge to the east into the existing
116th Ave SE system, which is the site’s natural discharge location.
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TABLE 4.2
Developed Pond Detained Area
SUBBASIN TOTAL AREA
(Ac)
TILL GRASS
(Ac)
IMPERVIOUS
(Ac)
Onsite Basin 3.52 1.21 2.31
Offsite Basin 0.11 0.00 0.11
TOTAL 3.63 1.21 2.42
TABLE 4.3
Developed Bypass Area
SUBBASIN TOTAL AREA
(Ac)
TILL GRASS
(Ac)
IMPERVIOUS
(Ac)
Bypass Basin 0.11 0.00 0.11
TOTAL 0.11 0.00 0.11
See Figure 4.1 for a visual representation of the Developed Tributary Area.
4.3 Performance Standards
Performance Standards for flow control design use the KCRTS Methodology with hourly
time steps as described in Section 4.4 below. Runoff files for the existing, proposed, and
bypass conditions were created using the historic KCRTS time series data sets for the
SeaTac Rainfall Region with a Correction Factor of 1.0.
The site requires basic water quality treatment. Water quality will be satisfied with a
wetpond, which will be located in the combined detention/water quality pond.
4.4 Flow Control System
The proposed project generates 1.33 cfs for the 100 year developed peak flow which is
1.018 cfs more than the 0.312 cfs of the 100 year predeveloped peak flow. Since the
difference between the two flows is more than 0.1 cfs, the proposed project will have to
meet the flow control requirements. The pond was sized per the requirements in the 2009
Surface Water Design Manual. Per the City of Renton’s Flow Control Application Map, the
project site is in the Flow Control Duration Standard (Forested Conditions, Level 2) area.
This standard requires the site to match the durations of high flows at their
predevelopment levels for all flows from one-half of the 2 year peak flow up to the 50 year
peak flow. The project will also match developed peak discharge rates to predeveloped
peak discharge rates for the 2 and 10 year return periods.
The offsite flows being routed through the pond are not subject to flow control, therefore
the offsite flows will be added to the predeveloped and developed flows.
PreDevFT = PreDev (Onsite + Bypass) + Offsite (Flow Through)
DevFT = Dev (Onsite) + Offsite (Flow Through)
The target flows are calculated as follows:
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50% 2 year: 50% of the 2 year from PreDev (Onsite) + Offsite 2 year
50 year: PreDev 50 year + Offsite 50 year
The pond’s inflow will be modeled using the DevFT time series and the pond’s outflow
will be the RDout time series. This RDout time series plus the Bypass time series will
match the Flow Control Duration Standard (Forested Conditions, Level 2) at the Point of
Compliance 200 feet downstream of the project site.
KCRTS v6.0 was used to design the proposed pond. Procedures and design criteria
specified in the 2009 Surface Water Design Manual were followed for the hydrologic and
hydraulic modeling. The KCRTS pond sizing output is included at the end of this section.
The KCRTS output models the required detention volume as 47,175 cubic feet of storage,
with 8.50 feet of detention. The proposed pond provides 62,109 cubic feet of storage,
which results in a 24% factor of safety.
4.5 Water Quality Facility
The proposed project produces more than 5,000 square feet of pollution generating
impervious area and is required to meet core requirement #8 for water quality. The
proposed water quality pond for Kinkade Crossing will use the 2009 Surface Water Design
Manual guidance for Basic Menu wetpond(s) that would be sized to a VB/VR ratio of 3.0,
which will treat approximately 95 percent of all runoff.
A VB/VR = 3 is calculated by dividing the wetpond volume (VB) by the volume of runoff
(VR) from the mean annual storm. The sizing of wetponds is accomplished by
determining the acreage of pervious and impervious land. Runoff volumes from
pervious and impervious areas were determined by multiplying the acreage of each
category by the mean annual storm (0.47 inches). Runoff factors of 0.25 for till grass
areas, 0.10 for till forest areas and 0.90 for impervious areas were utilized. The sum of
these values is the total runoff volume (VR). The required basin volume or the volume
of the wetpond is determined by multiplying the VR by 3.0.
VR_Till_Grass = 1.21 Ac (Table 4.2) x 0.47 in. x 0.25/12 = 0.0118 Acre - feet
VR_Impervious = 2.31 Ac (Table 4.2) x 0.47 in x 0.90/12 = 0.0814 Acre - feet
Total runoff volume VR = VR_Till_Grass + VR_Impervious = 0.0933 Acre - feet
Total basin volume VB = 0.0933 x 3 = 0.2798 Acre - feet = 12,189 cubic feet
Wetpond Volume provided = 14,549 cubic feet
The bypass area will not be able to be treated due to topography. The bypass area is less
than 5000 square feet and therefore will not require treatment in accordance with Core
Requirement #8 of the 2009 City of Renton Surface Water Design Manual.
Additionally, the wetpond will not have a till liner, as the existing soils are impermeable till.
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Figure 4.1
Pond Tributary Area
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5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN
The stormwater drainage conveyance system will be sized to convey the KCRTS 15
minute time series 25 year design storm event and to contain the 100 year design storm
event. A detailed Conveyance System Analysis and Design will be provided with the final
TIR.
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6. SPECIAL REPORTS AND STUDIES
Following are the reports and studies referenced for the proposed development:
·Geotechnical Engineering Report, by The Riley Group, Inc., dated July 08, 2015
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7. OTHER PERMITS
The National Pollutant Discharge Elimination System (NPDES) permit will be prepared with
the final construction plans.
This project will also require the following permits:
Building Permits
Clearing & Grading Permits
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8. CSWPPP ANALYSIS AND DESIGN
CSWPPP analysis and design will be provided with final engineering.
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9.BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF
COVENANT
Bond Quantities, Facility Summaries, and Declaration of Covenant will be provided in the
final TIR.
36
10.OPERATIONS AND MAINTENANCE MANUAL
The Operations and Maintenance Manual will be provided in the final TIR.