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Technical Information Report
SUNSET TERRACE DEVELOPMENT
BUILDING 1
(AKA COLPITTS SITE 9/10)
Prepared for
Colpitts Development
and City of Renton, WA
Prepared by
Osborn Consulting, Inc.
1800 112th Ave NE, Suite 220E
Bellevue, WA 98004
(425) 451-4009
Final: March 2018
3-26-18
LUA-15000159
PR-16000306
U-16002232
R-4003
FINAL
IN COMPIANCE WITH CITY OF RENTON STANDARDS
DEVELOPMENT ENGINEERING
Ann Fowler 03/30/2018
SURFACE WATER UTILITY
rstraka 04/02/2018
Technical Information Report i
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
T ABLE OF C ONTENTS
Section I Project Overview ........................................................................................................... 1
Project Description ....................................................................................................................... 1
Proposed Improvements .............................................................................................................. 1
Existing Drainage System ............................................................................................................ 6
Proposed Drainage System ......................................................................................................... 6
Soils ............................................................................................................................................. 7
Section II Conditions and Requirements Summary ................................................................... 8
Core Requirements ...................................................................................................................... 8
Core Requirement 1: Discharge at Natural Location ............................................................... 8
Core Requirement 2: Offsite Analysis ...................................................................................... 8
Core Requirement 3: Flow Control .......................................................................................... 8
Core Requirement 4: Conveyance System .............................................................................. 9
Core Requirement 5: Erosion and Sediment Control ............................................................... 9
Core Requirement 6: Maintenance and Operations ................................................................ 9
Core Requirement 7: Financial Guarantees & Liability ............................................................ 9
Core Requirement 8: Water Quality ......................................................................................... 9
Special Requirements .................................................................................................................. 9
Special Requirement 1: Other Adopted Area-Specific Requirements ..................................... 9
Special Requirement 2: Floodplain/Floodway Delineation ....................................................... 9
Special Requirement 3: Flood Protection Facilities ................................................................. 9
Special Requirement 4: Source Control ................................................................................. 10
Special Requirement 5: Oil Control ........................................................................................ 10
Special Requirement 6: Aquifer Protection Area ................................................................... 10
Section III Off-site Analysis ........................................................................................................ 11
Task 1: Study Area Definition and Maps ................................................................................... 11
Task 2: Resource Review .......................................................................................................... 11
Task 3: Field Inspection ............................................................................................................. 12
Task 4: Drainage System Description and Problems Description ............................................. 13
Task 5: Mitigation of Existing or Potential Problems .................................................................. 13
Section IV Flow Control and Water Quality Facility Analysis and Design ............................. 14
Existing Site Hydrology (Part A) ............................................................................................. 14
Developed Site Hydrology (Part B) ........................................................................................ 14
Performance Standards (Part C) ........................................................................................... 15
Flow Control System (Part D) ................................................................................................ 16
Water Quality System (Part E) ............................................................................................... 18
Section V Conveyance System Analysis and Design .............................................................. 19
Section VI Special Reports and Studies ................................................................................... 22
Section VII Other Permits ........................................................................................................... 23
Section VIII CSWPPP Analysis and Design .............................................................................. 24
ESC Plan Analysis and Design (Part A) ................................................................................ 24
Stormwater Pollution Prevention and Spill (SWPPS) Plan Design (Part B) ........................... 26
ESC Site Inspection Forms .................................................................................................... 29
Technical Information Report ii
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
CWSPPP Worksheet Forms / Cleanup Report ...................................................................... 34
Section IX Bond Quantities, Facility Summaries, and Declaration of Covenant ................... 35
Bond Quantities Worksheet ................................................................................................... 35
Flow Control and Water Quality Facility Summary Sheet and Sketch ................................... 35
Declaration of Covenant for Privately Maintained Flow Control and WQ Facilities................ 35
Declaration of Covenant for Privately Maintained Flow Control BMPs .................................. 35
Section X Operations and Maintenance Manual. ..................................................................... 36
References ................................................................................................................................... 39
Appendices
A – Permit Plans
B – WWHM Detention Sizing Results and TESC Sizing Results
C – Geotechnical Report
D – Flow Control BMPs Requirement
Figures
1 – TIR Worksheet………………………………………………………………………………………..2
2 – Site Location…………………………………………………………………………………………..4
3 – Drainage Basins, Subbasins, and Site Characteristics…………………………………………..4
4 – Soils…………………………………………………………………………………………………....5
6 - Map of the proposed conditions…………………....………………………....…………………....15
7 – Section of the Detention Vault showing volume calculation…………………....……………....16
8 – Manning Conveyance Calculation for Existing Downstream Pipe………………………..…....19
9 – Manning Conveyance Calculation for Proposed Vault Outfall Pipe…………………………....19
10 – Manning Conveyance Calculation for Interceptor Ditch …………………....………………....24
Technical Information Report 1
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION I
PROJECT OVERVIEW
Project Description
This Technical Information Report (TIR) summarizes the stormwater requirements
and the proposed stormwater management practices governing the design for the
proposed Sunset Terrace Development Colpitts Site 9/10. The TIR worksheet is
shown in Figure 1.
The proposed improvement is located adjacent to King County’s new Renton
Highlands Library between NE Sunset Blvd, NE 10th St, Sunset Lane NE and
Harrington Ave NE, in the City of Renton, King County, Washington (Figure 2).
The proposed improvement lot is 26,313 square feet and will include a six-story
mixed use residential and commercial building with associated structured parking.
Proposed Improvements
The development provides these elements:
Creation of six-story mixed use building and associated structured
parking
Drainage detention system
Sidewalk improvements to the property line
Technical Information Report 2
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Figure 1, page 1 of 2
King County Department of Development and Environmental Services
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
PART 1 PROJECT OWNER AND
PROJECT ENGINEER
PART 2 PROJECT LOCATION
AND DESCRIPTION
Project Owner Colpitts Development
Project: Sunset Terrace Development Colpitts Site 9/10
Address 1015 37th Ave E, Seattle, WA, 98112 Location
Phone 206-322-1381 Township 23N
Project Engineer Robert Parish, PE Range 5E
Company Osborn Consulting, Inc. Section 9
Address/Phone 1800 112th Ave NE, Suite 220E,
Bellevue, WA 98004 (425) 451-4009
PART 3 TYPE OF PERMIT APPLICATION PART 4 OTHER REVIEWS AND PERMITS
Subdivision DFW HPA Shoreline Management
Short Subdivision COE 404 Rockery
Grading DOE Dam Safety Structural Vaults
Commercial FEMA Floodplain Other - Building
Other Mixed-Use COE Wetlands
PART 5 SITE COMMUNITY AND DRAINAGE BASIN
Community: Renton, King County, WA
Drainage Basin: Johns Creek Drainage Basin
PART 6 SITE CHARACTERISTICS
River Floodplain
Stream Wetlands
Critical Stream Reach Seeps/Springs
Depressions/Swales High Groundwater Table
Lake Groundwater Recharge
Steep Slopes Other (Portion of Property in Aquifer Protection Zone)
PART 7 SOILS
Soil Type Slopes Erosion Potential Erosive Velocities
Fill 0-4% Slight
Silty Sand (USCS SP/SM) - Till 0-4% Slight
Additional Sheets Attached
Technical Information Report 3
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Figure 1, page 2 of 2
King County Department of Development and Environmental Services
TECHNICAL INFORMATION REPORT (TIR) WORKSHEET
PART 8 DEVELOPMENT LIMITATIONS
REFERENCE LIMITATION/SITE CONSTRAINT
Downstream Analysis
Flow Control Standards Level 1 Flow Control plus 100 year peak matching
Wetlands and Stream Report
Additional Sheets Attached
PART 9 ESC REQUIREMENTS
MINIMUM ESC REQUIREMENTS
DURING CONSTRUCTION
MINIMUM ESC REQUIREMENTS
AFTER CONSTRUCTION
Sedimentation Facilities Stabilize Exposed Surface
Stabilized Construction Entrance Remove and Restore Temporary ESC Facilities
Perimeter Runoff Control Clean and Remove All Silt and Debris
Clearing and Grading Restrictions Ensure Operation of Permanent Facilities
Cover Practices Flag Limits of SAO and open space preservation areas
Construction Sequence Other
Other
PART 10 SURFACE WATER SYSTEM
Grass Lined Channel Tank Infiltration Method of Analysis
Pipe System Vault Depression WWHM
Open Channel Energy Dissipater Flow Dispersal Compensation/Mitigation
Dry Pond Wetland Waiver of Eliminated Site Storage
Wet Pond Stream Regional Detention
Brief Description of System Operation Detention, connecting to existing storm drain in ROW
Facility Related Site Limitations
Reference Facility Limitation
PART 11 STRUCTURAL ANALYSIS PART 12 EASEMENTS/TRACTS
Cast in Place Vault Drainage Easement
Retaining Wall Access Easement
Rockery > 4' High Native Growth Protection Easement
Structural on Steep Slope Tract
Other - Building Other
PART 14 SIGNATURE OF PROFESSIONAL ENGINEER
I or a civil engineer under my supervision have visited the site. Actual site conditions as observed were incorporated into this
worksheet and the attachments. To the best of my knowledge the information provided here is accurate.
Signed/Date
KCLSLIBRARYBASINBOUNDARY(0.606 ACRES)BUILDING FOUNDATIONMATCHES LOT PROPERTY LINE(ZERO SETBACK LOT)FIGURE 3. DRAINAGE BASINS, SUBBASINS, AND SITECHARACTERISTICS below.RENTON, WASHINGTON / /31417RENTON, WASHINGTON / /31417
Technical Information Report 4
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Note: There are no geographic features and critical areas adjacent to the site.
Figure 2: Site Location (NTS)
Sunset Terrace
Building 1 Site
Limits of
downstream
study
Technical Information Report 5
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Figure 4: Soils (NTS)
Approx boundary of
aquifer protection zone 2
Ragnar-Indianola
association – Outwash
(Per USDA Soil Map)
Fill Soils over Till (Per
Geotechnical Study)
Note: No Areas
are draining to
the site
Sunset Terrace
Building 1 Site
KCLSLIBRARYBASINBOUNDARY(0.606 ACRES)BUILDING FOUNDATIONMATCHES LOT PROPERTY LINE(ZERO SETBACK LOT)FIGURE 5. EXISTING SITE HYDROLOGY (PART A) below.RENTON, WASHINGTON / /31417RENTON, WASHINGTON / /31417
KCLSLIBRARYBASINBOUNDARY(0.606 ACRES)BUILDING FOUNDATIONMATCHES LOT PROPERTY LINE(ZERO SETBACK LOT)FIGURE 6. DEVELOPED SITE HYDROLOGY (PART B) below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
Technical Information Report 6
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Existing Drainage System
The project site is a former Renton Housing Authority site. The property currently
sits upon fill materials and glacial till, and has recently demolished three two-story
multi-family residential buildings. In addition to the buildings, the project site
contained mainly lawn, with a few trees and sidewalks connecting entranceways to
the sidewalks along Sunset Lane NE and Harrington Ave NE. See Table 1 for a
breakdown of the area. Currently, storm drainage runoff originating from within the
limits of the property is routed via catch basins and storm drains to an existing
Right of Way (ROW) storm drain system in Sunset Lane NE and Harrington
Avenue NE to the Sunset Blvd NE that is routed down Sunset Boulevard NE
toward Lake Washington.
The project site property slopes northeast to southwest. The high point of the
property is on the northeast end of the property at approximately elevation 340
NAVD 88. The low point is at the southwest end of the property at approximately
elevation 336 NAVD 88.
Table 1: Existing Areas
Surface
Onsite
Area
(acres)
Bypass Area
(acres)
Total Area
(acres)
Pervious 0.3695
Landscaping 0.290 0.0795
Impervious 0.3652
Buildings, walkways
and roads
0.316 0.0492
Total Site 0.7347
Proposed Drainage System
The project proposes to remove the existing improvements and construct a new
building and sidewalks. See Table 2 for a breakdown of the proposed areas. As
part of these improvements, a detention vault will provide flow control prior to
flowing in to the existing storm drain system in the Harrington Ave NE ROW that
connects to the existing Sunset Blvd NE storm drain and flows along Sunset Blvd
NE toward Lake Washington.
Technical Information Report 7
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
The City of Renton’s February 2010 Surface Water Design Manual Amendment to
the 2009 King County Surface Water Design Manual was used to determine that
the project requires a Full Drainage Review. The project adds 2,000 SF or more of
new impervious surface, therefore all core requirements and special requirements
must be met, if applicable. To comply with the requirements, a detention vault
located in the underground parking structure is proposed. No water quality
treatment is proposed as the roof and sidewalk are non-pollution generating
surfaces.
See Appendix A for a plan view of the proposed system. See Appendix B for a
summary of the sizing calculations from WWHM.
Table 2: Proposed Areas
Surface
Onsite
Area
(acres)
Bypass Area
(acres)
Total Area
(acres)
Pervious 0.0424
Landscaping 0 0.0424
Impervious 0.6923
Buildings and
walkways
0.606 0.0239
Porous concrete
sidewalk
0.0624
Total Site 0.7347
Refer to the plans in Appendix A for drainage areas and existing/proposed storm
drainage systems.
Soils
The soils within the project site are fill soils on top of glacially compacted very
dense silty sand that has a negligible permeability and the same properties glacial
till. These soils are consistent across the site as summarized in the Geotechnical
Engineering Report included in Appendix C.
Technical Information Report 8
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION II
CONDITIONS AND REQUIREMENTS SUMMARY
The project is a mixed-use project that replaces more than 2,000 SF of impervious
surface. As requested by the City of Renton, a Drainage Report has been
completed, with the documented requirements below. Requirements follow the
Full Drainage Review as specified Table 1.1.2.A in the City of Renton’s February
2010 Amendment to King County’s 2009 Surface Water Design Manual
Core Requirements
Core Requirement 1: Discharge at Natural Location
Runoff from the site will continue to flow to the existing storm drain system in the
ROW that flows into Lake Washington.
Core Requirement 2: Offsite Analysis
See Section III for the findings of the Level 1 offsite analysis.
Core Requirement 3: Flow Control
Per Reference 11-A of the City of Renton’s February 2010 Amendment to King
County’s 2009 Surface Water Design Manual, the site is located in a Peak Rate
Flow Control Standard (existing Site Conditions) area. The project will utilize a
detention vault system to provide flow control to provide peak rate flow control to
match the existing 2, 10 and 100-yr peak runoff rates. See Section IV below.
To meet the Flow Control BMP requirement, the project will install porous
pavement in the Right-of Way. See Section IV below and Appendix D.
Since the Flow Control BMP will be installed in the ROW which bypasses the
detention system, the project will need to demonstrate compliance with Section
1.2.3.2.E of the City of Renton’s February 2010 Amendment to King County’s 2009
Surface Water Design Manual. See Section IV below.
Technical Information Report 9
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Core Requirement 4: Conveyance System
All conveyance systems have been designed for the 25-year peak flow. See
Appendix B for a summary of the calculations.
Core Requirement 5: Erosion and Sediment Control
Temporary and permanent erosion and sediment control plans will be
implemented as described in Section VIII. A Temporary Erosion and Sediment
Control Plan is included within the construction documents and is attached in
Appendix A. The construction documents also require the permanent stabilization
be provided through paving and landscape.
Core Requirement 6: Maintenance and Operations
An Operations and Maintenance Manual is included in Section X.
Core Requirement 7: Financial Guarantees & Liability
To be provided by the owner prior to start of construction.
Core Requirement 8: Water Quality
No pollution generating surfaces are proposed as part of this project, therefore, no
water quality treatment is proposed. See Section IV below.
Special Requirements
Special Requirement 1: Other Adopted Area-Specific Requirements
Apart from the Sunset Terrace Master Site plan, there are no other known Adopted
Area-Specific Requirements for the site.
Special Requirement 2: Floodplain/Floodway Delineation
The proposed project is not within or adjacent to an identified floodplain or
floodway.
Special Requirement 3: Flood Protection Facilities
There is no existing or proposed flood protection facility included on the project.
Technical Information Report 10
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Special Requirement 4: Source Control
No existing or proposed water quality pollutant hazard per the King County
Stormwater Pollution Prevention Manual is currently known to be associated with
the proposed building. The project’s Temporary Erosion and Sediment Control
Plan will address measures to reduce pollutant hazards resulting from construction
activities.
Special Requirement 5: Oil Control
The project does not qualify as a high use site therefore this requirement is not
applicable.
Special Requirement 6: Aquifer Protection Area
The northern half of the project area is in an Aquifer Protection Zone per the City
of Renton Sensitive Areas Map. The project is not planning to infiltrate stormwater
onsite.
Technical Information Report 11
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION III
OFF-SITE ANALYSIS
This project falls within the Johns Creek Drainage Basin, as identified by the City
of Renton. Runoff from the project is directed to an existing storm drain pipe
network that direct discharges to Lake Washington. A Level One Offsite Analysis
was completed. No existing or potential problems were identified during this off-
site analysis.
Task 1: Study Area Definition and Maps
The majority of runoff from the proposed project area is collected and detained.
The property slopes from northeast to southwest. The high point of the property is
on the northeast corner of the property at approximately elevation 340 NAVD 88.
The low point is at the southwest corner of the property at approximately elevation
336 NAVD 88. Any overland runoff originating from the property flows toward the
southwest side of the property and would enter the roadway drainage system
along Sunset Blvd NE. The flow continues southwest. According to the City of
Renton Maps, the flow direct discharges into Lake Washington. These limits fall
within Renton, King County, Washington. The proposed project is located within
Section 9 of Township 23 North, Range 5 East, WM in King County, Washington.
The site is located in the Cedar River/Lake Washington Watershed.
Task 2: Resource Review
The following resources have been reviewed for existing or potential problems in
the study area.
Geotechnical Evaluation
Geotech Consultants Inc performed a geotechnical analysis of the site. Refer to
Appendix C for the report.
Renton Flow Control
Per the City of Renton, the site shall provide Level 1 Flow Control.
Technical Information Report 12
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
FEMA Map Review
The FEMA map for the project area was reviewed and showed no floodplains or
floodways within or near the project limits.
Wetlands
The City of Renton Sensitive Areas Map showed no wetlands at the site.
Streams
The City of Renton Sensitive Areas Map does not list any creeks or streams in the
vicinity of the project.
Erosion Hazard
The project site is not indicated on the City of Renton Critical Erosion Hazard Area
map. There is no Critical Erosion Hazard Area within a quarter mile radius of the
project site.
Landslide Hazard
The project site is not indicated as a Landslide Hazard Area. There is no
Landslide Hazard Area within a quarter mile radius of the project site.
Seismic Hazard Areas
The project site is not indicated as a Seismic Hazard Area.
Task 3: Field Inspection
The resource review identified no previously identified problems.
The field visit was completed on 5/7/2012, the weather was clear, 65-degrees,
there had been no rain for at least 48 hours. The finding of the field visit was
checked again on 7/5/2016 (sunny, 65-degrees, with no rain in the past 24-hours)
confirmed the project’s basin boundary and that the northern portion of the site
drains into the existing piped drainage system in Sunset Lane NE where it flows
55-feet to the south-west to the 18-inch diameter storm drain in Harrington Ave
NE. From here it flows about 170-feet to the 30-inch storm drain in Sunset Blvd
NE. The southern portion of the site drains into the existing piped drainage system
on Sunset Blvd NE, approximately 75 ft upstream of the 30-inch storm drain. The
30-inch storm drain follows Sunset Blvd NE to the west turn to the northwest as is
Technical Information Report 13
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
continues down the hill at approximately 8% slope about 1,320-feet to Edmonds
Avenue through a series of Type 2-drianage structures. Edmonds Avenue was the
limits of the field inspection, see Figure 2. No existing or potential problems were
identified during the field inspection.
Task 4: Drainage System Description and Problems
Description
The drainage system is described above in Task 1 and 3.
No existing or potential problems were identified during this study.
Task 5: Mitigation of Existing or Potential Problems
There are no existing or potential problems identified on or near the proposed
project site. The project site development will not increase storm flow rates to
create or exacerbate any existing drainage problems. Mitigation will be provided
by a detention vault, in compliance with the City Drainage Requirements.
Technical Information Report 14
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION IV
FLOW CONTROL AND WATER QUALITY
FACILITY ANALYSIS AND DESIGN
Existing Site Hydrology (Part A)
The site currently sits upon fill materials and glacial till.
Site has recently demolished three two-story multi-family residential buildings. In
addition to the buildings, the project site contained mainly lawn, with a few trees
and sidewalks connecting entranceways to the sidewalks along Sunset Lane NE
and Harrington Ave NE.
There are no natural streams and natural drainage features, including wetlands on
the site.
See Figure 5 for the map of the existing conditions.
See Table 1: Existing Onsite Areas for summary of the areas.
Developed Site Hydrology (Part B)
The project proposes to construct a new building and sidewalks.
As part of these improvements, a detention vault will provide flow control prior to
flowing in to the existing storm drain system in the Harrington Ave NE right of way.
The Harrington Ave NE storm drain connects to the existing Sunset Blvd NE
storm drain matching the existing flow path from the site.
The City of Renton’s February 2010 Surface Water Design Manual Amendment to
the 2009 King County Surface Water Design Manual (The City’s Manual) was
used to determine that the project requires a Full Drainage Review. The project
adds 2,000 SF or more of new impervious surface, therefore all core requirements
and special requirements must be met, if applicable. To comply with the
requirements, a detention vault located in the underground parking structure is
proposed. No water quality treatment is proposed as the roof and sidewalk are
non-pollution generating surfaces. To meet the Flow Control BMP requirement, the
project will install porous pavement in the Right-of Way.
See Appendix A for a plan view of the proposed system. See Appendix B for a
summary of the sizing calculations from WWHM.
Technical Information Report 15
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Refer to the plans in Appendix A for drainage areas and existing/proposed storm
drainage systems.
See Figure 6 for the map of the proposed conditions.
See Table 2: Proposed Areas for summary of the areas.
Performance Standards (Part C)
Onsite Area
Area-specific flow control facility standard: Per Reference 11-A of the City of
Renton’s February 2010 Amendment to King County’s 2009 Surface Water Design
Manual (The City’s Manual), the site is located in a Peak Rate Flow Control
Standard (existing Site Conditions) area. The project will utilize a detention vault
system to provide flow control to provide peak rate flow control to match the
existing 2, 10 and 100-yr peak runoff rates. See Section IV Part D below.
Conveyance system capacity standards: Per Section 1.2.4 of The City’s
Manual, the piped conveyance system serving the project shall convey the 25-year
event with 6-inches freeboard with the top of the drainage structure, and the 100-
year event with no freeboard. In addition it shall meet the headwater requirements
in Section 4.3.1 of The City’s Manual
Land use-specific water quality requirement: Per Section 1.2.8.1, the project
meet the surface area exception, since ether will be less than 5,000 SF of new
plus replaced PGIS.
The proposed used of the project (mixed using commercial and housing) does not
trigger any special requirements for source control per Section 1.3.4 since all
future operations will occur within the building.
In addition the project does is not an high-use site, therefore oil control per Section
1.3.5 is not required.
ROW Bypass Area
Since the only available space for the Flow Control BMP requirement is in the
ROW (See Appendix D) improvements in the ROW would have to bypass the
detention system and demonstrate compliance with demonstrate compliance with
Section 1.2.3.2.E of the City of Renton’s February 2010 Amendment to King
County’s 2009 Surface Water Design Manual. See Section IV Part D below.
Technical Information Report 16
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Flow Control System (Part D)
Onsite Area
As noted above, peak rate flow control is proposed for the project matching
existing site conditions 2, 10 and 100-yr peak-rate runoff for areas draining to
constructed (man-made) drainage systems.
Flow Control will be mitigated as noted on the Drainage Control Plan (Sheet C3.0
and C3.1)in Appendix A, using an detention vault located in the south-west corner
of the parking level 1 coupled with a flow control device. The vault will be part of
the building structure but will be accessible from outside the building.
The detention volume was designed in accordance with Section 5.3.3 of the 2009
KCSWDM as follows:
• Vault was designed as a flow through system.
• The bottom of the vault has a V with 5% side slopes.
• The invert is elevated to provide at least 6-inches of sediment
storage.
• The outflow constrictor meet the applicable requirements.
• The vault is designed by the structural engineer and it part of the
building structural plans.
• Adequate access is provided to the vault with venting.
• The depth of the vault is less than 20-feet and greater then 7-feet.
• The vault access is about 20-feet from the road
WWHM was used to size the orifice and overflow riser, per Appendix B the
orifices are greater than 0.25 inches,
For the overflow riser, the following equation per 2009 King County Surface Water
Design Manual, figure 5.3.4.H was used to verify overflow capacity
Qweir= 9.739 DH3/2 = 9.739 x (8/12) x (0.5)3/2 = 2.29 cfs
Qorifice= 3.782 D2H1/2 = 3.782 x (8/12)2 x (0.5)1/2 = 1.19 cfs
Both of these values exceed the expected 100-year Post Developed Un-Mitigated
peak flow as listed in Table 3 below.
Technical Information Report 17
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Figure 7 – Section of the Detention Vault showing volume calculation (NTS)
Per 2009 King County Surface Water Design Manual section 3.3.4 the project
includes a volumetric safety factor as follows:
WWHM 100-year stage = 5.4 feet = 853.2 CF
Facility storage depth = 6.25 feet = 966 CF
Volumetric Safety Factor = (966 CF – 853.2 CF) / 853.2 CF = 13% >10%
Below in Table 3 is a summary of the peak flows (15-minute time series) for pre-
developed, post-developed, and mitigated conditions. Additional WWHM results
are located in Appendix B.
Technical Information Report 18
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Table 3: Summary of Peak Flows
Condition 2-Year
(cfs)
10-Year
(cfs)
100-Year
(cfs)
Pre-Developed 0.1397 0.2171 0.3285
Post Developed Un-Mitigated
(for conveyance design)
0.2309 0.3329 0.4694
Post Developed Mitigated 0.1341 0.2007 0.3074
To meet the Flow Control BMP requirement, the project will add at least 2,639 SF
of porous pavement and landscaping in the Right-of Way. See Appendix D.
ROW Bypass Area
Since the area needed to meet the Flow Control BMP will bypass the onsite
detention area Section 1.2.3.2.E of the City of Renton’s February 2010
Amendment to King County’s 2009 Surface Water Design Manual will be
addressed as follows:
Section 1.2.3.2.E.1 – The point of convergence will be about 200-feet which is
within a quarter-mile downstream of the facility's project site discharge point.
Section 1.2.3.2.E.2 – The increase in the existing site conditions 100-year peak
discharge from the area of bypassed target surfaces is 0.014 cfs, less than the 0.4
cfs limit.
Section 1.2.3.2.E.3 – The bypassed runoff will not create a significant adverse
impact to downstream drainage systems.
Section 1.2.3.2.E.4 – The bypassed area added to the onsite area will not exceed
the 5,000 SF of new plus replaced PGIS.
Section 1.2.3.2.E.5 – The existing site conditions 100-year peak discharge from
the area of bypassed target surfaces will increase by about 0.014 cfs less than 0.1
cfs, therefore compensatory mitigation by a flow control facility is not needed.
Water Quality System (Part E)
As noted above, the proposed project does not include any pollution generating
surfaces, so no water quality treatment is proposed.
Technical Information Report 19
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION V
CONVEYANCE SYSTEM ANALYSIS AND
DESIGN
The un-mitigated peak flows for the proposed conveyance pipes were modeled
using the Western Washington Hydrologic Model (WWHM) with a 15-minute time
step (See Table 4). All WWHM findings are shown in Appendix B. Plan views of
the system is shown on sheets C3.0 and C3.1 of the plans found in Appendix A.
Table 4: Conveyance Peak Flows
Condition 25-Year Flow (cfs) 100-Year Flow (cfs)
Post Developed Un-Mitigated
(for conveyance design)
0.3865 0.4694
For the existing system, the full flow capacity flow for existing stormwater
downstream pipes in Harrington Avenue NE (note: these pipe will be installed as
part of the City’s Sunset Lane Project that is currently under construction) was
calculated using Manning's equation, results are shown in Table 5, Figure 8 and
Figure 9. This information was used for the backwater analysis shown in Table 6
to verify that the pipe system will still function with more then 6-inches of freeboard
when the existing pipes in the ROW are flowing full.
Table 5: Summary of Conveyance Calculations
Location
From To Size
(in)
Slope
(%)
Mannings
n
Full flow
capacity
(cfs)
Peak
Vel
(fps)
Existing Harrington
Downstream SD
CB#22 CB#21 18 0.50 0.014 6.90 3.90
Proposed SD from
project to ROW
Vault CB#22 8 1.00 0.013 1.18 3.44
Technical Information Report 20
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Figure 8 – Manning Conveyance Calculation for Existing Downstream Pipe
Figure 9 – Manning Conveyance Calculation for Proposed Vault Outfall Pipe
Technical Information Report 21
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10) Table 6: Backwater Analysis Method for the Proposed pipe systems
Technical Information Report 22
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION VI
SPECIAL REPORTS AND STUDIES
See Appendix C for the Geotechnical report
See Architectural/Structural plans for the vault design
Technical Information Report 23
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION VII
OTHER PERMITS
N/A
Technical Information Report 24
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION VIII
CSWPPP ANALYSIS AND DESIGN
ESC Plan Analysis and Design (Part A)
See proposed ESC plan and Erosion control notes on the Demolition, and Erosion
Sediment Control Plan (Sheet 4) in Appendix A.
As discussed in the project overview of the TIR, the proposed improvement is
located adjacent to King County’s new Renton Highlands Library between NE
Sunset Blvd, NE 10th St, Sunset Lane NE and Harrington Ave NE, in the City of
Renton, King County, Washington.
The contractor shall implement Erosion and Sediment control (ESC) measures
during construction according to the City of Renton and King County Drainage
Requirements. The proposed erosion control plan includes a stabilized
construction entrance, inlet protection, chain link fencing, sediment trap/portable
storage tanks, straw wattles, slope protections, interceptor swales, silt fence and
sump pumps (to be located and sized by the contractor to meet field conditions).
Approximate sizing of the portable storage tanks/baker tank was based upon 2009
King County Surface Water Design Manual , section D.3.5.1 for Sediment Trap as
follows:
2 Year Peak = 0.140 CFS (assuming a fully disturbed site)
Surface Area = 2080 x 2 year peak flow = 2080 x 0.140 CFS = 291 SF
Volume = 291 SF x 5 feet depth = 1456 CF
Dewatering Orifice Diameter = (per section D.3.5.2 for Sediment Pond)
Ao = As(2h)0.5/(0.6 x 3600 x T x g0.5)
= 4.81(10-6) x As x (h)0.5
= 4.81(10-6) x 291 x (3.5)0.5
= 0.0026 SF
D =13.54(Ao0.5)
= 13.54(0.00260.5)
= 0.69 inches = 1 inch minimum per King County.
Technical Information Report 25
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Over flow riser =
100 Year Peak Flow= 0.328 CFS (assuming a fully disturbed site)
Freeboard = 1-ft
Per 2009 King County Surface Water Design Manual, figure 5.3.4.H, the minimum
size for the over flow riser shall be 10-inches
Due to the depth of the excavation, a pump will be required to drain the Sediment
Pond/ portable storage tanks. This pump should be sized to convey the 100-year
peak flow and be equipped with a functioning automated on/off switch.
Interceptor swales per City of Renton Standard Plan 217.10 have a flow capacity
of 21.56 CFS, see Figure 10, which exceeds the expected 100-year peak flow
rate from the project site.
Figure 10 – Manning Conveyance Calculation for Interceptor Ditch
Actual sizing of the portable storage tanks/baker tank and pumps and all other
erosion control facilities will depend on the contractor's approach, construction
sequence and operations. Per the erosion control notes on the plans the control
is required to upgrade the erosion control facilities as needed to keep the site in
compliance.
The 24-hour ESC contact for the project will be identified by the contractor prior to
start of construction at the pre-construction meeting. Per the erosion control notes
Technical Information Report 26
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
on the plans, at the pre-construction meeting the contractor is required to provide
for City approval a SWPPP and erosion control plans detailing the construction
approach and sequence to keep the site compliant.
Stormwater Pollution Prevention and Spill (SWPPS) Plan Design
(Part B)
As part of construction the contractor shall provide a SWPPS plan utilizing BMP’s
from Washington State Department of Ecology’s 2012 Stormwater Management
Manual the that will detail, at a minimum, the following pollution generating
activities typically associated with construction:
Storage and Handling of Liquids
Leaks and spills of pollutant materials during handling and storage are the primary
sources of pollutants. Once the liquids to be stored and handled onsite are
identified and the types and sizes of containers are specified, secondary
containment methods can be sized.
The following BMP’s can be used to safely store and handle liquids onsite:
S427 BMPs for Storage of Liquid, Food Waste, or Dangerous Waste Containers
S412 BMP’s for Loading and Unloading Areas for Liquid and Solid Material
Storage and Stockpiling of Construction Materials and Wastes
Contact between outside bulk materials (i.e. gravel, sand, topsoil, etc) and
stormwater can cause leachate, and erosion of the stored materials. Contaminants
may include TSS, BOD, organics, and dissolved salts (sodium, calcium, and
magnesium chloride, etc.). Once construction materials and wastes that may be
generated or stockpiled onsite are identified, cover measures and containers can
be specified to keep rainwater from contacting construction materials and wastes
that can contribute pollutants to storm, surface and ground water.
The following BMP’s can be utilized to safely store and stockpile construction
materials and wastes:
S429 BMPs for Storage or Transfer (Outside) of Solid Raw Materials, Byproducts,
or Finished Products
BMP C153 Material Delivery, Storage and Containment
Technical Information Report 27
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Fueling
The method of onsite fueling for construction equipment shall be specified, the
type and size of tanks described, containment methods for fuel spills described,
and lighting and signage plan for evening fueling described using the following
BMP’s:
S419 BMPs for Mobile Fueling of Vehicles and Heavy Equipment
Maintenance, Repairs, and Storage of Vehicles and Equipment
Maintenance and repair areas shall be identified by the contractor. Use of drip
pans or plastic beneath vehicles is required. Methods of collection, storage and
disposal of vehicle fluid will be described and signs will be posted in areas
designated for vehicle maintenance stating that no vehicle washing may occur in
the area. The following BMP’s can be utilized for proper maintenance, repair and
storage of vehicles and equipment:
S414 BMPs for Maintenance and Repair of Vehicles and Equipment
S421 BMPs for Parking and Storage of Vehicles and Equipment
S431 BMPs for Washing and Steam Cleaning Vehicles/Equipment/Building
Structures
Concrete Saw Cutting, Slurry, and Washwater Disposal
If possible, truck washout areas shall be located outside the Aquifer Protection
Area. If truck washout areas are located within an Aquifer Protection Area, the
washout area must be lined with an impervious membrane. Once truck washout
areas and areas for rinsing hand tools are identified, the size of pumps necessary
to collect and contain slurry and washwater can be specified and the methods for
collecting, treating, and disposal of wastewater from exposed aggregate
processes, concrete grinding and saw cutting, and new concrete washing and
curing water can be described. The following BMP’s can be implemented for this
work:
BMP C106 Wheel Wash
BMP C151 Concrete Handling
BMP C152 Sawcutting and Surfacing Pollution Prevention
BMP C154 Concrete Washout Area
S431 BMPs for Washing and Steam Cleaning Vehicles/Equipment/Building
Structures
Technical Information Report 28
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
Handling of pH Elevated Water
New concrete vaults/structures may cause collected water to have an elevated pH.
This water cannot be discharged to storm or surface water until neutralized. Water
can be treated, neutralized and disposed of using the following BMP’s:
BMP C252 High pH Neutralization Using CO2
BMP C253 pH Control for High pH Water
Application of Chemicals including Pesticides and Fertilizers
It is not known at this time if the contractor will apply any chemicals on the site. If
chemicals are to be applied, a list of chemicals that may be used on the project
site shall be provided and where and how the chemicals will be applied and stored
will be described. If chemicals are to be applied on site, the following BMP’s
should be implemented:
S411 BMPs for Landscaping and Lawn/Vegetation Management
BMP C153 Material Delivery, Storage and Containment
Technical Information Report 29
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
ESC Site Inspection Forms
The Contractor shall regularly conduct site inspection to verify compliance with
permit requirements. The results of each site inspection shall be summarized in an
inspection report or checklist that is entered into or attached to the site log book. It
is suggested that the inspection report or checklist be included in this appendix to
keep monitoring and inspection information in one document, but this is optional.
However, it is mandatory that this SWPPS and the site inspection forms be kept
on-site at all times during construction, and that inspections be performed and
documented as outlined below.
At a minimum, each site inspection report or checklist shall include:
a) Inspection date/times.
b) Weather information: general conditions during inspection, approximate
amount of precipitation since the last inspection, and approximate amount
of precipitation within the last 24 hours.
c) A summary or list of all BMPs that have been implemented, including
observations of all erosion/sediment control structures or practices.
d) The following shall be noted:
i. locations of BMPs inspected,
ii. locations of BMPs that need maintenance,
iii. the reason maintenance is needed,
iv. locations of BMPs that failed to operate as designed or intended, and
v. locations where additional or different BMPs are needed, and the
reason(s) why
e) A description of stormwater discharged from the site. The presence of
suspended sediment, turbid water, discoloration, and/or oil sheen shall be
noted, as applicable.
f) A description of any water quality monitoring performed during inspection,
and the results of that monitoring.
g) General comments and notes, including a brief description of any BMP
repairs, maintenance or installations made as a result of the inspection.
h) A statement that, in the judgment of the person conducting the site
inspection, the site is either in compliance or out of compliance with the
terms and conditions of the CSCP and the NPDES permit. If the site
Technical Information Report 30
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
inspection indicates that the site is out of compliance, the inspection report
shall include a summary of the remedial actions required to bring the site
back into compliance, as well as a schedule of implementation.
i) Name, title, and signature of person conducting the site inspection or clean
up; and the following statement: “I certify under penalty of law that this
report is true, accurate, and complete, to the best of my knowledge and
belief”.
When the site inspection indicates that the site is not in compliance with any terms
and conditions of the NPDES permit, the Contractor/Permittee shall take
immediate action(s) to: stop, contain, and clean up the unauthorized discharges, or
otherwise stop the noncompliance; correct the problem(s); implement appropriate
BMPs, and/or conduct maintenance of existing BMPs; and achieve compliance
with all applicable standards and permit conditions. In addition, if the
noncompliance causes a threat to human health or the environment, the
Contractor/Permittee shall comply with the Noncompliance Notification
requirements in Special Condition S5.F of the permit.
Technical Information Report 31
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SITE INSPECTION CHECKLIST (Page 1 of 3)
Project ____________________ Permit No. ___________ Inspector _________ Date and Time ____________
Overall Need
Site BMPs Condition Repair? Comments/Observations
Clearing Limits
●Buffer Zones around sensitive areas G F P Y N
● G F P Y N
● G F P Y N
Construction Access/Roads
●Stabilized site entrance G F P Y N
●Stabilized roads/parking area G F P Y N
● G F P Y N
Control Flow Rates
●Swale G F P Y N
●Dike G F P Y N
●Sediment pond G F P Y N
●Sediment trap G F P Y N
● G F P Y N
● G F P Y N
Install Sediment Controls
●Sediment pond/trap G F P Y N
●Silt fence G F P Y N
●Straw bale barriers G F P Y N
● G F P Y N
● G F P Y N
● G F P Y N
Preserve Vegetation/Stabilize Soils
●Nets and blankets G F P Y N
●Mulch G F P Y N
●Seeding G F P Y N
● G F P Y N
● G F P Y N
Protect Slopes
●Terrace G F P Y N
●Pipe slope drains G F P Y N
● G F P Y N
● G F P Y N
Protect Drain Inlets
●Inserts G F P Y N
● G F P Y N
● G F P Y N
Stabilize Channels and Outlets
●Conveyance channels G F P Y N
●Energy dissipators G F P Y N
● G F P Y N
Control Pollutants
●Chemical Storage Area covered G F P Y N
●Concrete handling G F P Y N
●Any spills? G F P Y N
Control De-watering
● G F P Y N
G=Good F=Fair P=Poor Y=Yes N=No
Technical Information Report 32
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SITE INSPECTION CHECKLIST (Page 2 of 3)
Project ____________________ Permit No. ___________ Inspector _________ Date and Time ____________
Will existing BMPs need to be modified or removed, or other BMPs installed? YES NO
IF YES, list the action items to be completed on the following table:
Actions to be Completed Date Completed/
Initials
1.
2.
3.
4.
5.
Describe current weather conditions
Approximate amount of precipitation since last inspection: __________ inches
and precipitation in the past 24 hours*: __________inches
*based on an on-site rain gauge or local weather data.
Describe discharging stormwater, if present. Note the presence of suspended sediment,
“cloudiness”, discoloration, or oil sheen.
Was water quality sampling part of this inspection? YES NO
If yes, record results in the Water Quality Monitoring Form
Sampling
Location
Turbidity
(NTU)
pH
(Standard Units)
Meets Standards?
(Y/N) Notes
Technical Information Report 33
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SITE INSPECTION CHECKLIST (Page 3 of 3)
Project ____________________ Permit No. ___________ Inspector _________ Date and Time ___________
Date and time of the last calibration of sampling equipment: ________________________________
Is the site in compliance with the SWPPP and the permit requirements? YES NO
If no, indicate tasks necessary to bring site into compliance on the “Actions to be Completed”
table above, and include dates each job WILL BE COMPLETED.
If no, has the non-compliance been reported to Dept. of Ecology? YES NO
If no, should the SWPPP be modified: YES NO
Is Dept. of Ecology was notified, indicate the date, time, contact name and phone number below:
Date: ____________________________________
Time: ____________________________________
Contact Name: ____________________________________
Phone #: ___________________________________
Sign the following certification:
“I certify that this report is true, accurate, and complete, to the best of my knowledge and
belief.”
Inspection completed on:____________ by: (print+signature)___________________
Title/Qualification of Inspector:______________________
Technical Information Report 34
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
CWSPPP Worksheet Forms / Cleanup Report
The Contractor shall provide specifics on spill prevention and cleanup and must include the
following information in addition to any activity-specific information in Subsection A above
related to spill prevention:
1. List the possible sources of a spill and identify the BMPs to be used for each source to
prevent a spill.
2. Identify personnel responsible for spill prevention and cleanup and clearly list the
responsibilities of each person identified. Contact information for these personnel must be
clearly identified in the report and on the SWPPS site plan.
3. Describe the procedures to be used for monitoring spill prevention BMPs and for
responding to a spill incident, including keeping records/reports of all inspections and
spills (see attached worksheets that may be used).
4. Identify where spill response materials will be stored. Make reference to the SWPPS site
plan for location information.
5. Identify disposal methods for contaminated water and soil after a spill.
2009 Surface Water Design Manual (CSWPP Forms) 1/9/2009
Page 1
BMP Implementation
Completed by:
Title:
Date:
Develop a plan for implementing each BMP. Describe the steps necessary to implement the BMP
(i.e., any construction or design), the schedule for completing those steps (list dates), and the person(s) responsible for implementation.
BMPs Description of Action(s) Required for Implementation
Scheduled Milestone and
Completion Date(s)
Person
Responsible for Action
Good Housekeeping 1.
2.
3
1.
2.
3.
Preventive
Maintenance
4.
1.SpillPrevention andEmergency Cleanup
2.
3.
Inspections 1.
2.
3.
2009 Surface Water Design Manual (CSWPP Forms) 1/9/2009
Page 2
BMPs Description of Action(s) Required for Implementation
Schedule Milestone and Completion Date(s)
Person Responsible for Action
Source Control BMPs 1.
2.
3
4.
5.
6.
7.
8.
Treatment BMPs 1.
2.
3.
4.
Emerging
technologies
1.
2.
Flow Control BMPs 3.
4.
2009 Surface Water Design Manual (CSWPP Forms) Page 1 1/9/2009 Material Inventory Completed by: Title:Date: List materials handled, treated, stored, or disposed of at the project site that may potentially be exposed to precipitation or runoff.Quantity (Units) Likelihood of contact with stormwater Past Spill or Used Produced Stored If Yes, describe reason Leak MaterialPurpose/Location (indicate per/wk. or yr.) Yes No
2009 Surface Water Design Manual (CSWPP Forms) Page 1Potential Pollutant Source Identification Completed by: Title:Date:List all potential stormwater pollutants from materials handled, treated, or stored on-site. Potential Stormwater Pollutant Stormwater Pollutant Source Likelihood of pollutant being present in your stormwater discharge. If yes, explain
2009 Surface Water Design Manual (CSWPP Forms) Page 1List of Significant Spills and Leaks Completed by: Title:Date:List all spills and leaks of toxic or hazardous pollutants that were significant but are not limited to, release of oil or hazardous substances in excess of reportable quantities. Although not required, we suggest you list spills and leaks of non-hazardous materials. Description Response Procedure Date(month/day/year) Location (asindicated on site map) Type of Material Quantity Source, If Known Reason for Spill/Leak Amount of Material Recovered Material No longerexposed to Stormwater (Yes/No)Preventive Measure Taken
2009 Surface Water Design Manual (CSWPP Forms) Page 1 1/9/2009 Employee Training Completed by:Title:Date:Describe the annual training of employees on the SWPPP, addressing spill response, good housekeeping, and material management practices. Training Topics 1.) LINE WORKERS Brief Description of Training Program/Materials (e.g., film, newsletter course) Schedule for Training (list dates) Attendees Spill Prevention and Response Good Housekeeping Material Management Practices 2.) P2 TEAM: SWPPP Implementation Monitoring Procedures
2009 Surface Water Design Manual (CSWPP Forms) 1/9/2009
Page 1
Pollution Prevention Team
Completed by: ______________________
Title: ______________________________
Date: ______________________________
Responsible Official: Title:
Team Leader: Office Phone:
Cell Phone #:
Pager #:
Responsibilities:
(1) Title:
Office Phone:
Pager #:
Cell Phone:
Responsibilities:
(2) Title:
Office Phone:
Pager #:
Cell Phone #:
Responsibilities:
Technical Information Report 35
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION IX
BOND QUANTITIES, FACILITY SUMMARIES,
AND DECLARATION OF COVENANT
Bond Quantities Worksheet
See attached.
Flow Control and Water Quality Facility Summary Sheet and
Sketch
To be provided after approval of the plans
Declaration of Covenant for Privately Maintained Flow Control
and WQ Facilities
To be provided after approval of the plans
Declaration of Covenant for Privately Maintained Flow Control
BMPs
To be provided after approval of the plans
Technical Information Report 36
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
SECTION X
OPERATIONS AND MAINTENANCE MANUAL.
Project: Sunset Terrace Development Building 1 – (AKA Colpitts Site 9/10)
Prepared for: Colpitts Development
The attached Operation and Maintenance checklist is intended to provide
guidance to the owner(s) for the operation and maintenance of the drainage and
the stormwater detention system at the Sunset Terrace Development.
The owner is responsible for maintenance of storm drainage facilities within the
property. The owner is not responsible for maintenance within the public right-of-
way. This manual cannot anticipate every problem, but provide a checklist for the
most anticipated maintenance items.
The stormwater system should be regularly maintained on an annual basis during
the summer prior to the start of the "rainy season" at the end of September.
When operating normally, the system should not have any surface ponding of
stormwater and the detention system should fully drain (except for the 4-foot
sump) within 24-hours after a storm event. If either of these are not true then the
system should be reviewed using the maintenance checklist to determine the
problem.
For additional and updated maintenance information visit the King County Storm
resources at:
http://www.kingcounty.gov/environment/waterandland/stormwater.aspx
or the Washington State Department of Ecology's web-site at:
http://www.ecy.wa.gov/programs/wq/wqhome.html
Below is a summary of each component of the storm drainage system:
Detention Vault
The vault in located in the south-west corner of the level 1 parking lot (see
attached plan) at the corner of Harrington Ave NE and Sunset Lane NE. The vault
is only accessible through a maintenance hole located outside the building in the
sidewalk. The purpose of the vault is to use the flow control device (see below) to
temporarily store stormwater runoff from the building roof to reduce the peak
stormwater runoff flows. See the attached “NO. 3 – DETENTION TANKS AND
VAULTS” checklist for items to be reviewed during the inspection.
Technical Information Report 37
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
If any maintenance is required inside the vault, then the owner shall used only
personnel with current confined space entry certification to enter the vault. Prior to
personnel entering the vault, the maintenance hole and three vents shall be
opened and used for forced air venting.
Flow control structure
The flow control structure is located in the vault and is visible from the
maintenance hole. The flow control structure consists of a 12-inch diameter
vertical riser pipe with two orifices sized to only let through a limited flow of
stormwater runoff. The lowest orifice is submerged in the sump located under the
bottom of the riser, the second is located under the elbow that is attached to the
riser pipe near the top of the riser pipe. If the orifices are blocked, the Stormwater
Vault can be drained to allow cleaning by opening a shear gate. This is done by
pulling on the handle attached to the top rung underneath the lid. The shear gate
shall be closed after cleaning. See attached “NO. 4 – CONTROL
STRUCTURE/FLOW RESTRICTOR” checklist for items to be reviewed during the
inspection.
Connection to the City System
The detention system is connected via a storm water drain to the City’s storm
water system in the intersection of Harrington Ave NE and Sunset Lane NE. The
owner is not responsible to maintain the maintenance hole in the public right-of-
way that the project’s storm drain connects to. See attached “NO. 6 –
CONVEYANCE PIPES” checklist for items to be reviewed during the inspection.
Right of Way Porous Pavement and Landscaping
The project includes approximately 3,000 SF of pervious concrete sidewalk and
adjacent landscape strip in the Right of Way along Sunset Boulevard. See
attached “NO. 11 – GROUNDS (LANDSCAPING)” and “NO. 30 – PERMEABLE
PAVEMENT BMP” checklist for items to be reviewed during the inspection.
Below is a stormwater inspection form and checklists to be completed each year at
the time of the inspection and when any maintenance is performed on the storm
drain system. A copy of all the completed forms and checklists shall be kept on
site in a log book for review by the City.
Technical Information Report 38
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
STORMWATER INSPECTION FORM
O.K. Not O.K. Condition, Corrective Action, General Notes
Detention Vault
Flow control structure
Conveyance pipes
Porous Pavement and
Landscape Strip
Comments:
Was any waste disposed? If so where?
Inspection completed by: ____________________ (Signature) ___________________ (Job Title) ________
(Date)
Notes:
• Attached completed checklists.
• Keep a copy of all the completed forms and checklists on site in a log book for review by the City.
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
2009 Surface Water Design Manual – Appendix A 1/9/2009 A-5
NO. 3 – DETENTION TANKS AND VAULTS
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Trash and debris Any trash and debris which exceed 1 cubic foot
per 1,000 square feet (this is about equal to the
amount of trash it would take to fill up one
standard size office garbage can). In general,
there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may
constitute a hazard to County personnel or the
public.
Noxious and nuisance vegetation
removed according to applicable
regulations. No danger of noxious
vegetation where County personnel or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations.Source control BMPs implemented if
appropriate. No contaminants
present other than a surface oil film.
Site
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Trash and debris Any trash and debris accumulated in vault or tank
(includes floatables and non-floatables).
No trash or debris in vault. Tank or Vault
Storage Area
Sediment
accumulation
Accumulated sediment depth exceeds 10% of the
diameter of the storage area for ½ length of
storage vault or any point depth exceeds 15% of
diameter. Example: 72-inch storage tank would
require cleaning when sediment reaches depth of
7 inches for more than ½ length of tank.
All sediment removed from storage
area.
Plugged air vent Any blockage of the vent. Tank or vault freely vents.
Tank bent out of
shape
Any part of tank/pipe is bent out of shape more
than 10% of its design shape.
Tank repaired or replaced to design.
Tank Structure
Gaps between
sections, damaged
joints or cracks or
tears in wall
A gap wider than ½-inch at the joint of any tank
sections or any evidence of soil particles entering
the tank at a joint or through a wall.
No water or soil entering tank
through joints or walls.
Vault Structure Damage to wall,
frame, bottom, and/or
top slab
Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified
inspection personnel determines that the vault is
not structurally sound.
Vault is sealed and structurally sound.
Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet
pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Inlet/Outlet Pipes
Damaged Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering
at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at
the joint of the inlet/outlet pipe.
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
1/9/2009 2009 Surface Water Design Manual – Appendix A A-6
NO. 3 – DETENTION TANKS AND VAULTS
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Cover/lid not in place Cover/lid is missing or only partially in place.
Any open manhole requires immediate
maintenance.
Manhole access covered.
Locking mechanism
not working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts
cannot be seated. Self-locking cover/lid does not
work.
Mechanism opens with proper tools.
Cover/lid difficult to
remove
One maintenance person cannot remove
cover/lid after applying 80 lbs of lift.
Cover/lid can be removed and
reinstalled by one maintenance person.
Access Manhole
Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards.
Allows maintenance person safe
access.
Damaged or difficult
to open
Large access doors or plates cannot be
opened/removed using normal equipment.
Replace or repair access door so it
can opened as designed.
Gaps, doesn't cover
completely
Large access doors not flat and/or access
opening not completely covered.
Doors close flat and covers access
opening completely.
Large access
doors/plate
Lifting Rings missing,
rusted
Lifting rings not capable of lifting weight of door
or plate.
Lifting rings sufficient to lift or
remove door or plate.
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
2009 Surface Water Design Manual – Appendix A 1/9/2009 A-7
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
Maintenance
Component
Defect or Problem Condition When Maintenance is Needed Results Expected When
Maintenance is Performed
Trash or debris of more than ½ cubic foot which
is located immediately in front of the structure
opening or is blocking capacity of the structure by
more than 10%.
No Trash or debris blocking or potentially blocking entrance to
structure.
Trash or debris in the structure that exceeds 1/3the depth from the bottom of basin to invert the
lowest pipe into or out of the basin.
No trash or debris in the structure.
Trash and debris
Deposits of garbage exceeding 1 cubic foot in
volume.
No condition present which would
attract or support the breeding of
insects or rodents.
Sediment Sediment exceeds 60% of the depth from the
bottom of the structure to the invert of the lowest
pipe into or out of the structure or the bottom of
the FROP-T section or is within 6 inches of the
invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section.
Sump of structure contains no
sediment.
Corner of frame extends more than ¾ inch past
curb face into the street (If applicable).
Frame is even with curb.
Top slab has holes larger than 2 square inches or
cracks wider than ¼ inch.
Top slab is free of holes and cracks.
Damage to frame
and/or top slab
Frame not sitting flush on top slab, i.e.,
separation of more than ¾ inch of the frame from
the top slab.
Frame is sitting flush on top slab.
Cracks wider than ½ inch and longer than 3 feet,
any evidence of soil particles entering structure
through cracks, or maintenance person judges
that structure is unsound.
Structure is sealed and structurally
sound.
Cracks in walls or
bottom
Cracks wider than ½ inch and longer than 1 foot
at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks.
No cracks more than 1/4 inch wide at
the joint of inlet/outlet pipe.
Settlement/
misalignment
Structure has settled more than 1 inch or has
rotated more than 2 inches out of alignment.
Basin replaced or repaired to design
standards.
Damaged pipe joints Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering
the structure at the joint of the inlet/outlet pipes.
No cracks more than ¼-inch wide at
the joint of inlet/outlet pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations.
Source control BMPs implemented if appropriate. No contaminants
present other than a surface oil film.
Structure
Ladder rungs missing
or unsafe
Ladder is unsafe due to missing rungs,
misalignment, rust, cracks, or sharp edges.
Ladder meets design standards and
allows maintenance person safe
access.
T section is not securely attached to structure
wall and outlet pipe structure should support at
least 1,000 lbs of up or down pressure.
T section securely attached to wall
and outlet pipe.
Structure is not in upright position (allow up to
10% from plumb).
Structure in correct position.
Connections to outlet pipe are not watertight or
show signs of deteriorated grout.
Connections to outlet pipe are water
tight; structure repaired or replaced
and works as designed.
FROP-T Section Damage
Any holes—other than designed holes—in the
structure.
Structure has no holes other than
designed holes.
Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate.
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
1/9/2009 2009 Surface Water Design Manual – Appendix A A-8
NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR
Maintenance
Component
Defect or Problem Condition When Maintenance is Needed Results Expected When
Maintenance is Performed
Cleanout gate is not watertight. Gate is watertight and works as
designed.
Gate cannot be moved up and down by one
maintenance person.
Gate moves up and down easily and
is watertight.
Chain/rod leading to gate is missing or damaged. Chain is in place and works as
designed.
Damaged or missing Control device is not working properly due to
missing, out of place, or bent orifice plate.
Plate is in place and works as
designed.
Orifice Plate
Obstructions Any trash, debris, sediment, or vegetation
blocking the plate.
Plate is free of all obstructions and
works as designed.
Obstructions Any trash or debris blocking (or having the
potential of blocking) the overflow pipe.
Pipe is free of all obstructions and
works as designed.
Overflow Pipe
Deformed or damaged
lip
Lip of overflow pipe is bent or deformed. Overflow pipe does not allow
overflow at an elevation lower than
design
Sediment
accumulation
Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment.
Trash and debris Trash and debris accumulated in inlet/outlet
pipes (includes floatables and non-floatables).
No trash or debris in pipes.
Inlet/Outlet Pipe
Damaged Cracks wider than ½-inch at the joint of the
inlet/outlet pipes or any evidence of soil entering at the joints of the inlet/outlet pipes.
No cracks more than ¼-inch wide at
the joint of the inlet/outlet pipe.
Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design
standards.
Trash and debris Trash and debris that is blocking more than 20%
of grate surface.
Grate free of trash and debris.
footnote to guidelines for disposal
Metal Grates
(If Applicable)
Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design
standards.
Cover/lid not in place Cover/lid is missing or only partially in place.
Any open structure requires urgent
maintenance.
Cover/lid protects opening to
structure.
Locking mechanism
Not Working
Mechanism cannot be opened by one
maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not
work.
Mechanism opens with proper tools.
Manhole Cover/Lid
Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenance
person.
APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
2009 Surface Water Design Manual – Appendix A 1/9/2009 A-11
NO. 6 – CONVEYANCE PIPES AND DITCHES
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Sediment & debris
accumulation
Accumulated sediment or debris that exceeds
20% of the diameter of the pipe.
Water flows freely through pipes.
Vegetation/roots Vegetation/roots that reduce free movement of
water through pipes.
Water flows freely through pipes.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations.
Source control BMPs implemented if
appropriate. No contaminants
present other than a surface oil film.
Damage to protective
coating or corrosion
Protective coating is damaged; rust or corrosion
is weakening the structural integrity of any part of
pipe.
Pipe repaired or replaced.
Pipes
Damaged Any dent that decreases the cross section area of
pipe by more than 20% or is determined to have
weakened structural integrity of the pipe.
Pipe repaired or replaced.
Trash and debris Trash and debris exceeds 1 cubic foot per 1,000
square feet of ditch and slopes.
Trash and debris cleared from
ditches.
Sediment
accumulation
Accumulated sediment that exceeds 20% of the
design depth.
Ditch cleaned/flushed of all sediment
and debris so that it matches design.
Noxious weeds Any noxious or nuisance vegetation which may
constitute a hazard to County personnel or the public.
Noxious and nuisance vegetation
removed according to applicable regulations. No danger of noxious
vegetation where County personnel
or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations.
Source control BMPs implemented if
appropriate. No contaminants
present other than a surface oil film.
Vegetation Vegetation that reduces free movement of water
through ditches.
Water flows freely through ditches.
Erosion damage to
slopes
Any erosion observed on a ditch slope. Slopes are not eroding.
Ditches
Rock lining out of
place or missing (If
Applicable)
One layer or less of rock exists above native soil
area 5 square feet or more, any exposed native
soil.
Replace rocks to design standards.
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 11 – GROUNDS (LANDSCAPING)
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Site Trash or litter Any trash and debris which exceed 1 cubic foot
per 1,000 square feet (this is about equal to the
amount of trash it would take to fill up one
standard size office garbage can). In general,
there should be no visual evidence of dumping.
Trash and debris cleared from site.
Noxious weeds Any noxious or nuisance vegetation which may
constitute a hazard to County personnel or the
public.
Noxious and nuisance vegetation
removed according to applicable
regulations. No danger of noxious
vegetation where County personnel
or the public might normally be.
Contaminants and
pollution
Any evidence of contaminants or pollution such
as oil, gasoline, concrete slurries or paint.
Materials removed and disposed of
according to applicable regulations.
Source control BMPs implemented if
appropriate. No contaminants
present other than a surface oil film.
Grass/groundcover Grass or groundcover exceeds 18 inches in
height.
Grass or groundcover mowed to a
height no greater than 6 inches.
Trees and Shrubs Hazard Any tree or limb of a tree identified as having a
potential to fall and cause property damage or
threaten human life. A hazard tree identified by
a qualified arborist must be removed as soon
as possible.
No hazard trees in facility.
Damaged Limbs or parts of trees or shrubs that are split or
broken which affect more than 25% of the total
foliage of the tree or shrub.
Trees and shrubs with less than 5%
of total foliage with split or broken
limbs.
Trees or shrubs that have been blown down or
knocked over.
No blown down vegetation or
knocked over vegetation. Trees or shrubs free of injury.
Trees or shrubs which are not adequately
supported or are leaning over, causing exposure
of the roots.
Tree or shrub in place and
adequately supported; dead or
diseased trees removed.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-16
APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES
NO. 30 – PERMEABLE PAVEMENT BMP
Maintenance
Component
Defect or Problem Conditions When Maintenance is Needed Results Expected When
Maintenance is Performed
Preventative Surface cleaning/
vegetation control
Media surface vacuumed or pressure washed
annually, vegetation controlled to design
maximum. Weed growth suggesting sediment
accumulation.
No dirt, sediment, or debris clogging
porous media, or vegetation limiting
infiltration.
Porous Concrete,
Porous Asphaltic
Concrete, and
Permeable Pavers
Trash and debris Trash and debris on the pavement interfering
with infiltration; leaf drop in fall season.
No trash or debris interfering with
infiltration.
Sediment
accumulation
Sediment accumulation on the pavement
interfering with infiltration; runoff from adjacent
areas depositing sediment/debris on pavement.
Pavement infiltrates as designed;
adjacent areas stabilized.
Infiltration rate Pavement does not infiltrate at a rate of 10
inches per hour.
Pavement infiltrates at a rate greater
than 10 inches per hour.
Ponding Standing water for a long period of time on the
surface of the pavement.
Standing water infiltrates at the
desired rate.
Broken or cracked
pavement
Pavement is broken or cracked. No broken pavement or cracks on
the surface of the pavement.
Settlement Uneven pavement surface indicating settlement
of the subsurface layer.
Pavement surface is uniformly level.
Moss growth Moss growing on pavement interfering with
infiltration.
No moss interferes with infiltration.
Inflow Inflow to the pavement is diverted, restricted, or
depositing sediment and debris on the
pavement.
Inflow to pavement is unobstructed
and not bringing sediment or debris
to the pavement.
Underdrain Underdrain is not flowing when pavement has
been infiltrating water.
Underdrain flows freely when water
is present.
Overflow Overflow not controlling excess water to desired
location; native soil is exposed or other signs of
erosion damage are present.
Overflow permits excess water to
leave the site at the desired location;
Overflow is stabilized and
appropriately armored.
Permeable Pavers Broken or missing
pavers
Broken or missing paving blocks on surface of
pavement.
No missing or broken paving blocks
interfering with infiltration.
Level surface Uneven surface due to settlement or scour of fill
in the interstices of the paving blocks.
Pavement surface is uniformly level.
Compaction Poor infiltration due to soil compaction between
paving blocks.
No soil compaction in the interstices
of the paver blocks limiting
infiltration.
Dead grass Grass in the interstices of the paving blocks is
dead.
Healthy grass is growing in the
interstices of the paver blocks.
Inspection Frequency Annually and after large storms, and as needed
seasonally to control leaf drop, evergreen
needles etc.
Permeable pavement is functioning
normally.
4/24/2016 2016 Surface Water Design Manual – Appendix A A-38
Technical Information Report 39
Sunset Terrace Development – Building 1 (aka Colpitts Site 9/10)
REFERENCES
King County
2009 King County Surface Water Design Manual
City of Renton
2010 City of Renton Amendments to the King County Surface
Water Design Manual
http://rentonwa.gov/uploadedFiles/Government/PW/UTILITIES/Surface_W
ater/City%20Amendments%20to%20the%20King%20County%20Surface%
20Water%20Design%20Manual.pdf
Department of Ecology
2012 Stormwater Management Manual for Western Washington
APPENDIX A
PERMIT PLANS
COVER SHEET below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017SUNSET TERRACE DEVELOPMENT - BUILDING 1CONSTRUCTION SETSHEET INDEXSHEET # SHEET TITLEB15001398, B16002230, B16002234, U16002232, LUA 15-000159,LUA 13-001114, LUA 10-052, LUA 14-001475, 5A-A, 5A-M, CUP
GENERAL NOTES below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017CITY OF RENTON - SURFACE WATER DRAINAGE NOTES AND SPECIFICATIONS’’“”CITY OF RENTON - SANITARY SEWER NOTES AND SPECIFICATIONS’’ CITY OF RENTON - WATER UTILITY NOTES AND SPECIFICATIONS’“” “” “” “” ’’
KCLSLIBRARYEROSION AND SEDIMENT CONTROL PLAN below.EROSION CONTROL NOTESRENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017RECOMMENDED CONSTRUCTION SEQUENCE
KCLSLIBRARYDEMOLITION PLAN below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
EROSION CONTROL DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /510171
EROSION CONTROL DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
EROSION CONTROL DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /510171
9/10 COLPITTSFFE=336.50LOWER GARAGE FFE=317.25KCLSLIBRARYGRADING PLAN below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017 / /42716
9/10 COLPITTSFFE=336.50GARAGE FFE=317.25KCLSLIBRARYDRAINAGE CONTROL PLAN below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
BUILDINGDRAINAGE DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
****************DRAINAGE DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
UTILITIES PLAN below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
UTILITY DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
UTILITY DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
UTILITY DETAILS below.RENTON, WASHINGTON / /51017RENTON, WASHINGTON / /51017
S000 SHORING PLANS100 STRUCTURAL GENERAL NOTESS101 STRUCTURAL GENERAL NOTESS200 FOUNDATION / PARKING LEVEL 3 PLAN S201F PARKING LEVEL 2 CONCRETE FRAMING PLANS202F PARKING LEVEL 1 CONCRETE FRAMING PLANS202R PARKING LEVEL 1 CONCRETE REINFORCING PLANS201R PARKING LEVEL 2 CONCRETE REINFORCING PLANS203F LOFT LEVEL FRAMING PLANS203R LOFT LEVEL CONCRETE REINFORCING PLANS204F RESIDENTIAL LEVEL 1 CONCRETE FRAMING PLANS204R RESIDENTIAL LEVEL 1 CONCRETE REINFORCING PLANS204W RESIDENTIAL LEVEL 1 WOOD FRAMING PLANS205 RESIDENTIAL LEVEL 2 WOOD FRAMING PLANS206 RESIDENTIAL LEVEL 3 WOOD FRAMING PLANS207 RESIDENTIAL LEVEL 4 WOOD FRAMING PLANS208 RESIDENTIAL LEVEL 5 WOOD FRAMING PLANS209 ROOF FRAMING PLANS300 TYPICAL FOUNDATION and CONCRETE FRAMING DETAILSS301 TEMPORARY EXCAVATION SHORING DETAILS and SECTIONSS302 BASEMENT WALL SECTIONSS303 BASEMENT WALL SECTIONSS304 BASEMENT WALL SECTIONSS305 BASEMENT WALL SECTIONSS400 TYPICAL P.T. and CONCRETE REINFORCING DETAILSS401 CONCRETE COLUMN SCHEDULES and REINFORCING DETAILSS402 TYPICAL CMU AND CONCRETE DETAILSS403 CONCRETE BEAM SCHEDULES404 TYPICAL VENEER DETAILSS405 TYPICAL CANOPY DETAILSS406 TYPICAL LIGHT GA. FRAMING DETAILSS407 CONCRETE BEAM SCHEDULES408 CONCRETE SHEARWALL DETAILS & SCHEDULES5.1 TYPICAL WOOD FRAMING DETAILSS5.2 WOOD SHEARWALLS SCHEDULE and DETAILSS5.3 TYPICAL WOOD FRAMING SECTIONSS5.4 TYPICAL STEEL & WOOD FRAMING SECTIONSS5.5 TYPICAL DECK FRAMING SECTIONS & DETAILS
APPENDIX B
WWHM DETENTION SIZING RESULTS
AND TESC SIZING RESULTS
Below are the peak flows for the following scenarios:
• 501 POC 1 Pre developed Flow (the existing condition)
• 701 Inflow to POC 1 Mitigated (The pre-mitigated condition – aka the flow into the vault)
• 801 POC 1 Mitigated Flow (the mitigated condition)
APPENDIX C
GEOTECHNICAL REPORT
APPENDIX D
FLOW CONTROL BMPS REQUIREMENT
SUNSET TERRACE MF PROJECT (SUNSET TERRACE - 9/10 SITE) - B16002230
FLOW CONTROL BMP VARIANCE REQUEST 1
Dear Ms. Fowler:
The Sunset Terrace MF Project (Sunset Terrace - 9/10 Site) - B16002230 requests a variance to the Flow
Control BMP requirement as described in Section 1.2.3.3 and 5.2.1.3 of the City of Renton Amendments
to the King County Surface Water Design Manual.
In summary, the project is a “zero setback” building which occupies the entire parcel. As a result, there
are no opportunities on the project parcel for rainwater infiltration into the native soils. Below are the
results of our analysis.
Per section 5.2.1.3-Large Lot High Impervious BMP Requirements, the project falls under section 5.2.1.3
by occupying an area greater than 22,000 SF and is greater than 45% impervious. Section 5.2.1.3 has
three items to evaluate for this project, they are:
1. Full Dispersion: is not feasible, there is no native vegetated surface on the developed site.
2. Flow Control BMPs: Since the site is 100% impervious, flow control BMPs must be applied to
10% of the site (2,639 SF). The Flow Control BMPs are evaluated as follows.
• Full Infiltration per Section 5.4,
Due to building occupying the entire site, this is not feasible due to the following:
o Access requirements (5.3.2.1)
The maximum depth of the facility would exceed 20-feet.
o Setbacks (5.4.3.1)
The facility would be located under the building, hence not meeting 20-feet
setback requirements
• Limited Infiltration per Appendix C, Section C.2.3,
Due to building occupying the entire site, this is not feasible due to the following:
o Setbacks (C.2.2.2)
The facility would be located under the building, hence not meeting 5-feet
setback requirements
• Basic Dispersion per Appendix C, Section C.2.4,
Per section C.2.4.1, the project does not have any landscape to create a vegetated flowpath
segment, hence this is not feasible.
DATE MARCH 17, 2017
TO ANN FOWLER, CITY OF RENTON
CC KENT SMUTNY, VEER ARCHITECTS
FROM ROBERT PARISH, PE, OSBORN CONSULTING, INC.
SUBJECT SUNSET TERRACE MF PROJECT (SUNSET TERRACE - 9/10 SITE) - B16002230
FLOW CONTROL BMP VARIANCE REQUEST
SUNSET TERRACE MF PROJECT (SUNSET TERRACE - 9/10 SITE) - B16002230
FLOW CONTROL BMP VARIANCE REQUEST 2
• Rain Garden per Appendix C, Section C.2.5,
o Per section C.2.5.1:
Due to building occupying the entire site, this is not feasible as the project does
not have any landscape to create a raingarden.
o Per section C.2.4.1
The facility would not be able to meet 5-feet building or property line setback
requirements
• Permeable Pavement per Appendix C, Section C.2.6,
Due to building occupying the entire site, this is not feasible.
• Rainwater Harvesting per Appendix C, Section C.2.7,
o Per section C.2.7.2:
the system would need to be 6,600 CF or 10ft x 10ft x 66ft, there is no room on
the site for a tank, hence this is not feasible.
There is also not enough landscaping on the project to benefit from the stored
water.
o This BMP has been removed from the 2016 KCSWDM list of flow control BMPs.
• Vegetated Roof
o This BMP has been removed from the 2016 KCSWDM list of flow control BMPs.
• Reduced Impervious Surface Credit per Appendix C, Section C.2.9,
Due to building occupying the entire site, this option is not feasible.
• Native Growth Retention Credit per Appendix C, Section C.2.10.
There is no native vegetated surface to be protected.
3. Roof downspouts infiltration: Not possible as all downspouts would infiltrate under the building.
Since there are no feasible onsite flow control BMP’s, in order to comply with the Flow Control BMP
requirement, the project requests to construct at least 2,639 SF of pervious concrete sidewalk with an
adjacent 7.5-ft to 9.5-ft wide landscape strip in the public right of way along Sunset Boulevard. This area
is currently within the project limits of the future Sunset Boulevard project where the City is planning to
replace the existing condition with new sidewalk and landscaping. The proposed area is shown in the
attached plan.
Please contact me with any questions in regards to this request.
Sincerely,
Robert Parish, PE
Osborn Consulting, Inc.
9/10 COLPITTSFFE=336.50GARAGE FFE=317.25KCLSLIBRARYDRAINAGE CONTROL PLAN below.RENTON, WASHINGTON / /3 14 17RENTON, WASHINGTON / /3 14 17Proposed Flow Control BMP: 1,640 SF LandscapingProposed Flow Control BMP: 3,058 SF Pervious Concrete Sidewalk