HomeMy WebLinkAboutRS_Drainage_Report_190711_v1Chateau Tower Expansion
Table of Contents
1 PROJECT OVERVIEW.............................................................................................................1
Figure 1-1: Vicinity Map..........................................................................................................2
2 CONDITIONS AND REQUIREMENTS SUMMARY...................................................................3
2.1 Core Requirements...........................................................................................................3
2.1.1 Core Requirement #1: Discharge at the Natural Location ............................................3
2.1.2 Core Requirement #2: Offsite Analysis ..........................................................................3
2.1.3 Core Requirement #3: Flow Control ..............................................................................3
2.1.4 Core Requirement #4: Conveyance System...................................................................3
2.1.5 Core Requirements #5: Erosion and Sediment Control .................................................3
2.1.6 Core Requirement #6: Maintenance and Operations....................................................3
2.1.7 Core Requirement #7: Financial Guarantees and Liability .............................................3
2.1.8 Core Requirement #8: Water Quality ............................................................................3
2.1.9 Core Requirement #9: On-site BMPs .............................................................................3
2.2 Special Requirement #1: Other Adopted Area-Specific Requirements..............................4
2.2.1 Critical Drainage Areas....................................................................................................4
2.2.2 Master Drainage Plan......................................................................................................5
2.2.3 Basin Plans ......................................................................................................................5
2.2.4 Salmon Conservation Plans (SCPs) .................................................................................5
2.2.5 Stormwater Compliance Plans (SWCPs)..........................................................................5
2.2.6 Lake Management Plans (LMPs) .....................................................................................5
2.2.7 Flood Hazard Reduction Plan Updates (FHRPs) ..............................................................5
2.2.8 Shared Facility Drainage Plans (SFDPs) ...........................................................................5
2.3 Special Requirement #2: Flood Hazard Area Delineation ..................................................5
2.4 Special Requirement #3: Flood Protection Facilities ..........................................................5
2.5 Special Requirement #4: Source Controls ..........................................................................5
2.6 Special Requirement #5: Oil Control ..................................................................................5
2.7 Special Requirement #6: Aquifer Protection Area..............................................................5
3 OFFSITE ANALYSIS..................................................................................................................6
TASK 1 Study Area Definition and Maps...................................................................................6
Development Management Engineers Chateau Valley Tower i
TASK 2 Resource Review ............................................................................................................6
TASK 3 Field Investigation ..........................................................................................................7
Figure 3-1: Downstream Drainage Exhibit .................................................................................8
TASK 4 Drainage System Description and Problem Description.................................................9
TASK 5 Mitigation of Existing and Potential Problems ...............................................................9
4 FLOW CONTROL AND WATER QUALITY DESIGN.....................................................................11
4.1 Pre-developed Site Hydrology ............................................................................................11
4.2 Developed Site Hydrology ..................................................................................................11
Figure 4-1: Sketch of Tributary Areas Lot A...............................................................................12
4.3 Performance Standards.......................................................................................................13
4.4 Flow Control System............................................................................................................14
4.5 Water Quality Calculations..................................................................................................14
5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN .....................................................................15
6 SPECIAL REPORTS AND STUDIES ............................................................................................16
7 OTHER PERMITS.....................................................................................................................17
8 ESC ANALYSIS AND DESIGN....................................................................................................18
9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT ..................19
9.1 Bond Quantities...................................................................................................................19
9.2 Facility Summaries...............................................................................................................19
9.3 Declaration of Covenant......................................................................................................19
10 OPERATIONS AND MAINTENANCE .......................................................................................20
Development Management Engineers Chateau Valley Tower ii
Appendix A – Basin Information
King County Parcel Report
Flow Control Application Map
Appendix B – Resource Review & Off-site Analysis Documentation
FIRM Map
Aquifer Protection Zone
Erosion Hazard Map
Flood Hazard Map
Groundwater Protection Map
Landslide Hazard Map
Steep Slopes Map
Coal Mine Hazard Map
Appendix C – Conveyance Calculations
WWHM model Results
Appendix D – Bond Quantities
Worksheet
Development Management Engineers Chateau Valley Tower iii
1 PROJECT OVERVIEW
The project site is located at the northeast corner of Davis Avenue South and South 45th Street and was
the subject of a first phase of construction in the 2003 time frame originally titled Chateau at Valley
Center. It is south of the area where the Valley Medical Center is situated in the City of Renton, King
County in the northeast quarter of Section 31, Township 23 North, Range 5 East, W.M. It lies in the
Black River sub-basin of the Green River drainage basin. The roadway frontages have all been improved
with curb, gutter, sidewalks, landscaping and street lighting. The entire site drains generally to the north
and eventually to a City 12-inch storm drain in the Davis Avenue conveyance system.
The bulk of the 2.77 acre 2-lot site is occupied by the Chateau Valley Center assisted living facility
constructed in the first phase about 15 years prior. The current project proposes to construct a tower
expansion structure on Lot A of the RENTON Boundary Line Adjustment (BLA) LUA-11-025 Recording
#20120814900003, an area of 0.57-acre. The site is bordered by commercial properties on the east,
which mostly front Talbot Road. Across Davis Avenue is a parking lot associated with the Valley Medical
center.
The King County tax parcel ID number for Lot A is shown in Table 1 below (refer to the King County
Parcel Report included in Appendix A).
Table 1: Parcel Information
KC Parcel # Site Address Site Area (SF)
6391800125 4320 Davis Avenue S 25,104
The current project site, Lot A is 0.57 acres in size and contains some existing surface parking, storm
drainage facilities and other utilities constructed as part of Phase 1. There is also an informal gravel
parking lot at the northerly portion of the site. There is minimal upstream flow from the improved areas
to the east of the site. Those flows were previously analyzed in the Phase 1, (2003) TIR.
As noted above, a portion of the 2003-05 Phase 1 improvements were constructed within Lot A
including surface parking and a portion of the Phase 1 storm drains and stormwater wet vault. The
proposed development of the property, Phase 2, Chateau Valley Tower will include a 2-level parking
garage with a below-grade level and entrance grade level parking. Additional assisted living units are to
be located on the upper floors, in addition to driveways and utilities including a storm drain system.
Frontage improvements include a pair of driveways to serve as access ramps to the parking garage and
exits for the existing surface parking and drop-off area. Most of the Phase 1 improvements located in Lot
A will remain in place. The Phase 2, Chateau Valley Tower construction will be limited to about 0.41
acres of Lot A.
The project will be designed using the guidelines and requirements established in the 2017 City of
Renton Surface Water Design Manual (2017 RSWDM). The project is exempt from flow control since the
100-year flow increase from predeveloped to post developed is less than 0.15 cfs. The project is also
exempt from Basic Water Quality treatment since the Pollution Generating Impervious Surfaces (PGIS) is
less than 5000 SF. The drainage analysis for the site was completed using WWHM.
See Figure 1-1 Vicinity Map for project location.
Development Management Engineers Chateau Tower Expansion Page 1
Figure 1-1: Vicinity Map
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map may or may not be accurate, current, or otherwise reliable.
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Development Management Engineers Chateau Valley Tower Page 2
PROJECT SITE
2 CONDITIONS AND REQUIREMENTS SUMMARY
The proposed project is classified as requiring “Full Drainage Review” per the 2017 RSWDM. Therefore,
all eight core requirements and five special requirements will be addressed per Section 1.1 of the 2017
RSWDM.
2.1 Core Requirements
2.1.1 Core Requirement #1: Discharge at the Natural Location
The project will maintain the natural discharge location on the west side of the parcel to the storm drain
system in Davis Avenue S.
2.1.2 Core Requirement #2: Offsite Analysis
This core requirement is addressed in Section 3 of this report.
2.1.3 Core Requirement #3: Flow Control
The development is exempt from installing a flow control facility per RSWDM Chapter 1.2.3.1 (B) Flow
Control Duration Standard Areas. The difference between pre-developed and developed 100-year flow
is less than 0.15cfs. Refer to Section 4 for the analysis and results.
2.1.4 Core Requirement #4: Conveyance System
A backwater analysis using King County Backwater (KCBW) will be provided in Section 5 to show that the
proposed conveyance system provides sufficient capacity for the 25-year storm as calculated by the
Rational Method.
2.1.5 Core Requirements #5: Erosion and Sediment Control
Erosion and sediment control will be provided through catch basin protection, interceptor swales, rock
check dams, silt fencing and a construction access entrance. Since the construction will involve
excavating below grade for the lower garage level, dewatering may be required at early stages of
construction. Portable construction stormwater tanks, (Baker Tanks) may be specified, if required.
2.1.6 Core Requirement #6: Maintenance and Operations
The owner will be responsible for the maintenance and operations of the stormwater facilities located
on the site. An Operations and Maintenance Manual will be provided in Section 10.
2.1.7 Core Requirement #7: Financial Guarantees and Liability
A bond quantities worksheet will be provided in Section 9.
2.1.8 Core Requirement #8: Water Quality
The project does not add more than 5,000 square feet of new or replaced pollution generating
impervious surface. Therefore, Water quality treatment will not be provided.
2.1.9 Core Requirement #9: On-Site BMPs
On-Site BMPs have been evaluated for the project per section 1.2.9 of the 2017 Renton SWDM .
If the proposed project is on a site/lot larger than 22,000 square feet, then on-site BMPs must be
applied as specified in the requirements below or the project must demonstrate compliance with the
LID Performance Standard (described in Section 1.2.9.1.B) using an approved continuous runoff model.
Development Management Engineers Chateau Valley Tower Page 3
This project is not in compliance with the LID performance standard and has been evaluated for the
following BMPs in order of precedence:
1. Full Dispersion must be evaluated for all target impervious surfaces.
Site constraints cannot accommodate the required flow path of 100 feet of native vegetation for full
dispersion.
2. Where Full Dispersion is not feasible for target impervious roof areas, full infiltration of roof runoff
must be implemented if feasible.
Full infiltration is not feasible on the project site. Per the geotechnical report prepared by Associated
Earth Sciences, see reference Section 6, the soil type is comprised of variable glacial till. In addition,
groundwater seepage was found in depths ranging from 2 feet to 7 feet below surface. This soil type is
typically not recommended for use as an infiltration receptor.
3. All target surfaces not mitigated by requirements 1 and 2 above, must be mitigated to the
maximum extent feasible using one or more of the BMPs from the following list:
Full Infiltration, Limited Infiltration, and Bioretention are infeasible. Per the geotechnical report by
Associated Earth Sciences, the soil type is comprised of variable glacial till and there is groundwater
seepage present. In general, variable till soils have limited capacity for infiltration as a means of
handling stormwater.
• Bioretention is not feasible due to space and site constraints.
• Permeable Pavement is also infeasible. Variable glacial till soils and the presence of
groundwater indicate a limited capacity for infiltration.
4. All target surfaces not mitigated by requirements 1, 2 and 3 above, must be mitigated to the
maximum extent feasible using basic dispersion.
Basic dispersion is not proposed since site and grading constraints cannot accommodate the required
25-foot vegetated flow path.
5. Implementation BMP’s for impervious areas of the site coverage greater than 65% on the buildable
portion of the site must be applied to 20% of the target surface or at least 10% of the site, whichever
is less.
Use of Reduced Impervious Surface Credit, Native Growth Protection Credit, or Tree Retention Credit is
not feasible on this site because of site constraints.
6. The soil moisture holding capacity of new pervious surfaces (target pervious surfaces) must be
protected in accordance with the soil amendment BMP as detailed in Appendix C, Section C.2.13.
The areas proposed for site landscaping will call for use of amended soils BMP.
7. Installation of perforated pipe connection is not considered feasible at this location due to the glacial
till nature of the site native soils.
2.2 Special Requirement #1: Other Adopted Area-Specific Requirements
2.2.1 Critical Drainage Areas
Per the City’s Aquifer Protection Zone map, the project is not in an aquifer protection zone. A copy of
the COR aquifer protection and wellhead protection zone map is included in Appendix B.
Development Management Engineers Chateau Valley Tower Page 4
2.2.2 Master Drainage Plan
Not applicable.
2.2.3 Basin Plans
There are no basin plans for this project.
2.2.4 Salmon Conservation Plans (SCPs)
There is no salmon conservation plan for this project.
2.2.5 Stormwater Compliance Plans (SWCPs)
Not applicable.
2.2.6 Lake Management Plans (LMPs)
Not applicable.
2.2.7 Flood Hazard Reduction Plan Updates (FHRPs)
This project is not within a floodplain (see FEMA map included in Appendix B) and is not within an area
with an applicable Flood Hazard Reduction Plan. Therefore, additional requirements from a Flood
Hazard Reduction Plan do not apply.
2.2.8 Shared Facility Drainage Plans (SFDPs)
Not applicable.
2.3 Special Requirement #2: Flood Hazard Area Delineation
This project is not located within the 100-year floodplain (see FEMA Map included in Appendix B).
2.4 Special Requirement #3: Flood Protection Facilities
As this project is not located within a 100-year floodplain there are no levees, revetments or berms
within the project.
2.5 Special Requirement #4: Source Control
These requirements are only applicable as the project is to the extent that there will be food
preparation on the site. A list of typical controls are included as a part of the M&O plan for the site. A
grease trap will be provided and the lower level parking structure will have floor drains routed to the
sanitary sewer.
2.6 Special Requirement #5: Oil Control
This requirement does not apply because the project is not expected to have more than 15,000 vehicles
per day.
2.7 Special Requirement #6: Aquifer Protection Area
Aquifer Protection Area(s) (APA) are identified in the RMC 4-3-050. If a proposed project is located
within the APA, this special requirement requires the project to determine those components that are
applicable and delineate them on the project’s site improvements plans. Reference Section 15-B
includes a map of the City’s Aquifer Protection Area, Zones 1 and 2.
The proposed project is not located in either APA Zone, therefore no special measures are applicable,
see Appendix B for the Aquifer Zone Protection Map.
Development Management Engineers Chateau Valley Tower Page 5
3 OFFSITE ANALYSIS
TASK 1 Study Area Definition and Maps
The proposed project contains parcel number 6391800125. A map of the downstream drainage systems
can be found in Figure 3-1 Downstream Drainage Exhibit.
TASK 2 Resource Review
Basin Reconnaissance Summary Reports:
No Basin Reconnaissance Summary Reports appear to be available for the area that is within one mile of
this project site.
FEMA Maps:
Per the City’s Effective FEMA Flood Insurance Rate Map, the project site is not in the 100-year
floodplain. The FEMA Map is included in Appendix B.
Sensitive Areas Folio:
Per the City of Renton Sensitive Areas Maps, this project has some steeper slopes peripherally located
along the east property lines; however these have been negated by construction of retaining walls in
Phase 1 or with this project.
Soils
The Geotechnical Report was completed by Earth Consultants, Inc. in January, 2002. The site soils were
found to include varying depths of medium dense, silty, fine to medium grained sand with gravel (SM) or
silty-sand to sandy silt (ML) up to the ten feet depth of the test pits. Groundwater seepage typically
occurred between 2 to 7 feet deep.
Downstream Drainage Complaints
Drainage complaints were researched within the study area. King County lists no complaints within a
quarter mile of the downstream discharge point. See the Figure 3-1 Downstream Drainage Map in the
next section.
Restrictive Well Covenant
There is no existing well onsite.
Development Management Engineers Chateau Valley Tower Page 6
TASK 3 Field Investigation
Upstream Tributary Area
There is minimal upstream drainage area from fully developed parcels to the east.
Downstream Analysis
The site drains northwest to existing catch basins located in the curbed street section of Davis Avenue S
just south of SW 43rd Street. A 12-inch storm pipe heads north and turns west to a 24-inch storm
culvert under SW 43rd Street where it enters the private system in the Valley Medical Center which
continues north in a 27-inch pipe for several hundred feet before daylighting to the northwest through
an undeveloped parcel in a drainage course adjacent to SR-167. The state highway system then conveys
these flows before eventually discharging into Springbrook Creek.
Development Management Engineers Chateau Valley Tower Page 7
9,028
752
City of Renton Print map Template
This map is a user generated static output from an Internet mapping site and
is for reference only. Data layers that appear on this map may or may not be
accurate, current, or otherwise reliable.
Storm water system
7/3/2019
Legend
5120 256
THIS MAP IS NOT TO BE USED FOR NAVIGATION
Feet
Notes
512
WGS_1984_Web_Mercator_Auxiliary_Sphere
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
City and County Labels
City and County Boundary
Parcels
Pump Stations
Discharge Points
Stormwater Mains
Culverts
Open Drains
Facility Outlines
Private Pump Stations
Private Discharge Points
Private Pipes
Private Culverts
Private Open Drains
Private Facility Outlines
Drainage Complaints
Known Drainage Issues
Renton
King County
Streets
Parks
Waterbodies
Map
Extent2010
FIGURE 3.1 DOWNSTREAM DRAINAGE
TASK 4 Drainage System Description and Problem Description
The Drainage Complaints Map in the COR GIS did not reveal any drainage complaint requests. See the
Figure 3.1 above.
TASK 5 Mitigation of Existing and Potential Problems
Downstream Drainage Problems Requiring Special Attention
Type 1 – Conveyance System Nuisance Problems
There are no known, reported or observed current downstream conveyance nuisance problems.
Type 2 – Severe Erosion Problems
There are no known, reported or observed current downstream severe erosion problems.
Type 3-Severe Flooding Problems
There are no known, reported or observed current downstream severe flooding problems.
Downstream Water Quality Problems Requiring Special Attention
Type 1 – Bacteria Problems
There are no known or reported downstream bacteria problems.
Type 2 – Dissolved Oxygen (DO) Problems
There are no known or reported downstream dissolved oxygen problems.
Type 3 – Temperature Problems
Springbrook Creek has a seasonal temperature problem. Due to the distance from the project site and
the highly developed urban nature of this drainage area, there are no special provisions that can address
this issue for this project. See listing information on the next page.
Type 4 – Metals Problems
There are no known or reported downstream metals problems.
Type 5 – Phosphorous Problems
There are no known or reported downstream phosphorous problems.
Type 6 – Turbidity Problems
There are no known or reported downstream turbidity problems.
Type 7 – High pH Problems
There are no known or reported downstream high pH problems.
Bioassessment
Springbrook Creek is a Category 2 for bioassessment.
Drainage Adjustments
There are no proposed drainage adjustments.
Development Management Engineers Chateau Valley Tower Page 9
Receiving Water characteristics
• WTR_NAME
Springbrook Creek
• WRIA_NO
9
• WRIA_NAME
Duwamish-Green
• WTRSHD_ID
902
• WTRSHD_NAME
Duwamish - Green River
• BASIN_ID
90201
• BASIN_NAME
Black River
• RTE_ID
090201010100000000
• STR_LVL
2
• SOURCE_NAME
2012 Aerial Photo
• Water Feature Type
Stream
• Type Classification
S – Shoreline
Parameter: Temperature
Medium: Water
Listing ID: 72608(view listing)
Assessment Unit ID: 17110013008361
Waterbody Name: Springbrook (Mill) Creek
Development Management Engineers Chateau Valley Tower Page 10
4 FLOW CONTROL AND WATER QUALITY DESIGN
4.1 Pre-developed Site Hydrology
The proposed disturbed area of Lot A is approximately 0.433 acres with 0.137 acres of the site
previously developed as part of the Phase 1 development for a total project area of 0.57 acres. The
existing site has asphalt surface parking and informal gravel parking lots occupying the majority of the
site fronting Davis Ave. There are some trees on the east side of the property with an existing slope
running in the north-south direction close to the lot line. The site drains to the northwest at slopes
ranging between 3 and 7 percent and locally steeper at the east property line.
Included with the Phase 2 improvements are two driveway aprons constructed off-site in the Davis
Avenue S right-of-way that will amount to approximately 0.012 acre. The combined on-site and off-site
Phase 2 total disturbed area is 0.445 acres. There is minimal upstream drainage area from fully
developed parcel to the east. Historic site conditions are assumed for the targeted new impervious
onsite areas per Section 1.2.3.1 B. Exceptions of the 2017 RSWDM (page 1-42) and are modeled as Till
Forest and Outwash-Forest.
Pre-developed Conditions Areas
GROUND COVER AREA (acres)
Till-Forest 0.445
TOTAL = 0.445
Pre-developed Peak Flows
Pre-developed Scenario from WWHM model and peak flow rates:
___________________________________________________________________
Flow Frequency Return Periods for Pre-developed conditions.
Return Period Flow (cfs)
2 year 0.0112
5 year 0.017354
10 year 0.02069
25 year 0.024079
50 year 0.026092
100 year 0.027746
4.2 Developed Site Hydrology
In the developed condition, the site will continue to drain to the northwest. The roof of the new tower
expansion is the main area that can reasonably be captured for conveyance.
The developed condition areas are summarized as follows:
The existing pavement on the surface parking lot which will remain and drain to the Phase 1 wet vault
will be excluded from the calculation for new construction areas. The proposed developed area is
primarily the area for the roof of the tower expansion. The remaining areas either slope to Davis
Avenue or back to the lower level parking garage and are therefore unable to be captured, however the
flows were computed and routed to a point of compliance. The remainder of the site will be landscaped
using amended soils as a planting medium which can be modeled as “pasture” because of that BMP.
There is a small area for the proposed drop-off area that will be computed and routed to a point of
compliance for comparison to the pre-developed flows. See Figure 4.1 for sketch of tributary areas on
the following page.
Development Management Engineers Chateau Valley Tower Page 11
GROUND LEVEL
PARKING FF=105.8'
10
2
10
3
10
4
10
5
99
98
112
FIGURE 4.1
SKETCH OF TRIBUTARY AREAS LOT A
The pervious area to be routed to the point of compliance consists of the landscaped area which will be
installed using amended soils. This use of the BMP for amended soils allows the post developed area to
be modeled as “Pasture” rather than “lawn areas”.
Developed Conditions Areas
___________________________________________________________________
Pervious Land Use Acres
C, Pasture, Mod 0.092
Impervious Land Use Acres
ROOF TOPS FLAT 0.281
DRIVEWAYS FLAT 0.045
DRIVEWAYS MOD 0.012
DRIVEWAYS STEEP 0.013
SIDEWALKS FLAT 0.002
TOTAL 0.445
Developed Peak Flows
The Developed scenario from WWHM is shown below:
___________________________________________________________________
Flow Frequency Return Periods for Developed. POC #1
Return Period Flow (cfs)
2 year 0.090686
5 year 0.110571
10 year 0.123451
25 year 0.139547
50 year 0.151471
100 year 0.163374
4.3 Performance Standards
All stormwater facilities will be designed in accordance with the 2017 RSWDM with Conservation Flow
Control Standards. A water quality treatment system will not be required as the runoff from roof areas is
considered clean water and that is the majority of the anticipated flows.
Flow Control: Conservation Flow Control Standard
The Conservation Flow Control Standard requires maintaining the durations of high flows at their pre-
development levels for all flows greater than one-half of the 2-year peak flow through the 50-year peak
flow. The pre-development peak flow rates for the 2-year and 10-year runoff events must also be
maintained under this requirement.
• Per Chapter 1.2.3.1 (B) Flow Control Duration Standard Areas, if the flow (cfs) difference
between pre-developed and developed 100-year flow is less than 0.15cfs the project is
“exempt” from installing a flow control facility.
NET INCREASE IN 100-YEAR FLOW RATE: 0.163-0.028=0.135 CFS, <0.15 cfs therefore the project site is
exempt from flow control.
Development Management Engineers Chateau Valley Tower Page 13
Conveyance Capacity:
The proposed conveyance system will be designed with sufficient capacity to convey and contain the 25-
year peak flow as determined by the Rational Method. It will also be verified that the 100-year peak flow
will not create or aggravate a severe flooding or erosion problem per Section 1.2.2.
Water Quality: Basic Water Quality Menu
This project will add less than 5,000 square feet of pollution generating Impervious surface (PGIS) so no
water quality treatment is required.
4.4 Flow Control System
Calculation of Effective Impervious Area
The impervious area for the site applied to the developed basin time series file was determined using
the criteria in the 2017 RSWDM page 3-24 for commercial zones. The proposed development is urban
assisted residential. The site is zoned Commercial Office (CO) (see parcel information in Appendix A).
For Commercial zones there is no minimum or maximum impervious area per site per the 2017 RSWDM;
rather the impervious surfaces are to be “estimated from layouts of the proposal”.
Small Lot BMP Requirements
If the proposed project is on a site/lot smaller than 22,000 square feet, then flow control BMPs must be
applied as specified in the requirements below or the project must demonstrate compliance with the
LID Performance Standard (described in Section 1.2.9.1.B, p. 1-83) using an approved continuous runoff
model. This project is not in subject to this LID performance standard as it is larger than the threshold.
Small Road Improvement and Urban Road Improvement Projects BMP Requirements
If the proposed project is a road improvement project that is within the UGA or is on a site/parcel less
than five acres in size, then flow control BMPs must be applied as specified in the requirements below:
This project is not subject to this LID performance standard as it is not a road improvement project.
Flow Control
No flow control facility is proposed due to being exempt. The full WWHM report has been included in
Appendix C.
The collected roof area flows will discharge to a catch basin on the existing vault outfall pipe at the back
of sidewalk on Davis Avenue S.
4.5 Water Quality Calculations
The project is adding approximately 3,000 square feet of pollution generating impervious area (PGIS)
which is less than 5,000 square feet so water quality treatment is not required.
Table 4-3 PGIS Area
GROUND COVER AREA (SF)
Driveway Approaches 520
Driveways (estimated) 2,480
TOTAL 3,000
Development Management Engineers Chateau Valley Tower Page 14
5 CONVEYANCE SYSTEM ANALYSIS AND DESIGN
Analysis of the onsite conveyance system will be provided during the construction permit application
phase of the project.
Development Management Engineers Chateau Valley Tower Page 15
6 SPECIAL REPORTS AND STUDIES
Geotechnical Report
Earth Consultants, Inc.
1805 136th Place Northeast, suite 102
Bellevue, WA 98005
Prepared by: Raymond Coglas, P.E.
Dated: January 16, 2002
Plus Supplement Letter dated June 20, 2019
Development Management Engineers Chateau Valley Tower Page 16
7 OTHER PERMITS
➢ Construction Permit
➢ Building Permits
➢ ROW Use Permit
➢ NPDES Permit
Development Management Engineers Chateau Valley Tower Page 17
8 ESC ANALYSIS AND DESIGN
The site will utilize Appendix D of the 2017 RSWDM for the erosion and sedimentation control design to
reduce the discharge of sediment-laden runoff from the site. Clearing limits will be established prior to
any earthwork on the project site. Perimeter protection will be provided by silt fencing to limit the
downstream transport of sediment to neighboring properties. A temporary construction entrance or
wheel wash will be used to reduce the amount of sediment transported onto paved roads by
construction vehicles and, if required dust control will be provided by a water truck.
Development Management Engineers Chateau Valley Tower Page 18
9 BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF
COVENANT
9.1 Bond Quantities
A Site Improvement Bond Quantity Worksheet to be provided with the construction Permit Application.
9.2 Facility Summaries
A facility summary sheet will be provided with the submittal of the final plans.
9.3 Declaration of Covenant
Not applicable.
Development Management Engineers Chateau Valley Tower Page 19
10 OPERATIONS AND MAINTENANCE
The operations and maintenance information follows this Section. The document includes a selection of
portions from Appendix A of the 2017 RSWDM and Construction Permit plan set.
Development Management Engineers Chateau Valley Tower Page 20
#5 – MAINTENANCE CHECKLIST FOR CATCH BASINS:
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE IS
NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS
PERFORMED
Structure Sediment
accumulation
Sediment exceeds 60% of the depth from the
bottom of the catch basin to the invert of the
lowest pipe into or out of the catch basin or is
within 6 inches of the invert of the lowest pipe
into or out of the catch basin.
Sump of catch basin contains no
sediment .
Trash and
Debris
Trash or debris of more than ½ cubic foot which
is located immediately in front of the catch basin
opening or is blocking capacity of the catch
basin by more than 10%.
No Trash or debris blocking or
potentially blocking entrance to catch
basin.
Trash or debris in the catch basin that exceeds
1/3 the depth from the bottom of basin to invert
the lowest pipe into or out of the basin.
No trash or debris in the catch basin.
Dead animals or vegetation that could generate
odors that could cause complaints or dangerous
gases (e.g., methane).
No dead animals or vegetation present
within the catch basin.
Deposits of garbage exceeding 1 cubic foot in
volume.
Inlet and outlet pipes free of trash or
debris.
Damage to
Frame and/or
Top Slab
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 one-fourth inch.
Top slab is free of holes and cracks.
Frame not sitting flush on top slab, i.e.,
separation of more than three-fourth inch of the
frame from the top slab. Frame not securely
attached.
Frame is sitting flush on the top slab.
Cracks in Basin
Walls or
Bottom
Cracks wider than ½ inch and longer than 3 feet,
any evidence of soil particles entering catch
basin through cracks, or maintenance person
judges that structure is unsound.
Catch basin is sealed and is
structurally sound.
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 catch basin
through cracks.
No cracks more than 1/4 inch wide at
the joint of inlet/outlet pipe.
Settlement/
Misalignment
Catch basin 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 catch basin 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.
Inlet/Outlet Pipe 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 and debris in pipes
Development Management Engineers Chateau Valley Tower Page 21
#5 – MAINTENANCE CHECKLIST FOR CATCH BASINS: (cont.)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN MAINTENANCE IS
NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Inlet/outlet pipe
(cont.)
Damaged inlet/outlet
pipe
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.
Metal Grates
(Catch Basins)
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
percent of grate surface inletting capacity.
Cover is missing or only partially in place. Any
open catch basin requires maintenance.
Grate free of trash and debris. footnote
to guidelines for disposal
Damaged or Missing
grate
Grate missing or broken member(s) of the
grate.
Grate is in place and meets design
standards.
Manhole
Cover/Lid
Cover 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.
Cover Difficult to
Remove
One maintenance person cannot remove lid
after applying 80 lbs. of lift.
Cover can be removed and reinstalled
by one maintenance person.
If you are unsure whether a problem exists, contact a professional engineer.
Development Management Engineers Chateau Valley Tower Page 22
NO. 6 – CONVEYANCE PIPES AND DITCHES
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Pipes Sediment &
debris
accumulation
Accumulated sediment or debris that
exceeds 20% of the diameter of the
pipe.
Water flows freely through pipes.
Vegetation/root
growth in pipe
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.
Damaged pipes 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.
Ditches 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 City
personnel or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
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.
Excessive
vegetation growth
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.
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.
Development Management Engineers Chateau Valley Tower Page 23
NO. 11 – GROUNDS (LANDSCAPING)
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Site Trash & 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 City
personnel or the public.
Noxious and nuisance vegetation removed
according to applicable regulations. No
danger of noxious vegetation where City
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.
Excessive growth
of
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 tree
identified
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 tree or
shrub identified
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.
Development Management Engineers Chateau Valley Tower Page 24
NO. 38 – SOIL AMENDMENT BMP
MAINTENANCE
COMPONENT
DEFECT OR
PROBLEM
CONDITION WHEN
MAINTENANCE IS NEEDED
RESULTS EXPECTED WHEN
MAINTENANCE IS PERFORMED
Soil Media Unhealthy
vegetation
Vegetation not fully covering ground
surface or vegetation health is poor.
Yellowing: possible Nitrogen (N)
deficiency. Poor growth: possible
Phosphorous (P) deficiency. Poor
flowering, spotting or curled leaves, or
weak roots or stems: possible
Potassium (K) deficiency.
Plants are healthy and appropriate for site
conditions
Inadequate soil
nutrients and
structure
In the fall, return leaf fall and
shredded woody materials from the
landscape to the site when possible
Soil providing plant nutrients and structure
Excessive
vegetation
growth
Grass becomes excessively tall
(greater than 10 inches); nuisance
weeds and other vegetation start to
take over.
Healthy turf- “grasscycle” (mulch-mow or
leave the clippings) to build turf health
Weeds Preventive maintenance
Avoid use of pesticides (bug and weed
killers), like “weed & feed,” which damage
the soil
Fertilizer
needed
Where fertilization is needed (mainly
turf and annual flower beds), a
moderate fertilization program should
be used which relies on compost,
natural fertilizers or slow-release
synthetic balanced fertilizers
Integrated Pest Management (IPM)
protocols for fertilization followed
Bare spots Bare spots on soil No bare spots, area covered with vegetation
or mulch mixed into the underlying soil.
Compaction Poor infiltration due to soil compaction
• To remediate compaction, aerate
soil, till to at least 8-inch depth, or
further amend soil with compost
and re-till
• If areas are turf, aerate
compacted areas and top dress
them with 1/4 to 1/2 inch of
compost to renovate them
• If drainage is still slow, consider
investigating alternative causes
(e.g., high wet season
groundwater levels, low
permeability soils)
• Also consider site use and
protection from compacting
activities
No soil compaction
Poor infiltration Soils become waterlogged, do not
appear to be infiltrating.
Facility infiltrating properly
Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow
entering area, channelization of runoff)
identified and damaged area stabilized
(regrade, rock, vegetation, erosion control
matting).For deep channels or cuts (over 3
inches in ponding depth), temporary erosion
control measures in place until permanent
repairs can be made
Grass/Vegetation Unhealthy
vegetation
Less than 75% of planted vegetation
is healthy with a generally good
appearance.
Healthy vegetation. Unhealthy plants
removed/replaced. Appropriate vegetation
planted in terms of exposure, soil and soil
moisture.
Noxious Weeds Noxious weeds Listed noxious vegetation is present
(refer to current County noxious weed
list).
No noxious weeds present.
6/30/2019 King County Department of Assessments: eReal Property
https://blue.kingcounty.com/Assessor/eRealProperty/Detail.aspx?ParcelNbr=6391800125 1/3
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New Search Property Tax Bill Map This Property Glossary of Terms Area Report Print Property Detail
PARCEL DATA
Parcel 639180-0125
Name PUBLIC HOSP DISTR#1
KING CO
Site Address 4320 DAVIS AVE S 98055
Geo Area 75-65
Spec Area 153-320
Property Name Chateau at Valley Center
Jurisdiction RENTON
Levy Code 2100
Property Type C
Plat Block / Building Number
Plat Lot / Unit Number 10-12
Quarter-Section-Township-
Range NE-31-23-5
Legal Description
ONE VALLEY PLACE LOT A RENTON BLA LUA-11-025-LLA REC #20120814900003 SD BLA LOTS 10-12 OF SD
PLAT
PLat Block:
Plat Lot: 10-12
LAND DATA
Highest & Best Use As If Vacant COMMERCIAL
SERVICE
Highest & Best Use As
Improved PRESENT USE
Present Use Retirement Facility
Land SqFt 25,104
Acres 0.58
Percentage Unusable
Unbuildable NO
Restrictive Size Shape NO
Zoning CO
Water WATER DISTRICT
Sewer/Septic PUBLIC
Road Access PUBLIC
Parking ADEQUATE
Street Surface PAVED
Views Waterfront
Rainier
Territorial
Olympics
Cascades
Seattle Skyline
Puget Sound
Lake Washington
Lake Sammamish
Lake/River/Creek
Other View
Waterfront Location
Waterfront Footage 0
Lot Depth Factor 0
Waterfront Bank
Tide/Shore
Waterfront Restricted Access
Waterfront Access Rights YES
Poor Quality NO
Proximity Influence NO
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Reference Links
King County Tax
Links
Property Tax Advis
Washington State
Department of
Revenue (External
link)
Washington State
Board of Tax
Appeals (External
link)
Board of
Appeals/Equalizatio
Districts Report
iMap
Recorder's Office
Scanned images of
surveys and other
map documents
Scanned images of
plats
Additional fees apply. Rate
excludes taxes. Speed may not
be available in your area.
Rate requires paperless billing. Maximum
download/upload speed of up to 940 Mbps via a wired
connection.Details
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4 OF
JULYSALE
th
APPENDIX A
6/30/2019 King County Department of Assessments: eReal Property
https://blue.kingcounty.com/Assessor/eRealProperty/Detail.aspx?ParcelNbr=6391800125 2/3
Designations Nuisances
Historic Site
Current Use (none)
Nbr Bldg Sites
Adjacent to Golf Fairway NO
Adjacent to Greenbelt NO
Other Designation NO
Deed Restrictions NO
Development Rights Purchased NO
Easements NO
Native Growth Protection
Easement NO
DNR Lease NO
Topography
Traffic Noise
Airport Noise
Power Lines NO
Other Nuisances NO
Problems
Water Problems NO
Transportation Concurrency NO
Other Problems NO
Environmental
Environmental NO
BUILDING
TAX ROLL HISTORY
This is a government owned parcel.
Change to state law (RCW 84. 40.045 and 84.40.175) by the 2013 Legislature eliminated revaluation of government
owned parcels.
SALES HISTORY
REVIEW HISTORY
PERMIT HISTORY
HOME IMPROVEMENT EXEMPTION
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Appendix B
Effective FEMA Flood
Insurance Rate Map
Appendix C
—————————————————————————————————
Full WWHM report.
Western Washington Hydrology Model
PROJECT REPORT
___________________________________________________________________
Project Name: NoVault
Site Address: DAVIS AVE S
City : RENTON
Report Date : 6/30/2019
Gage : Seatac
Data Start : 1948/10/01
Data End : 1998/09/30
Precip Scale: 1.00
WWHM3 Version:
___________________________________________________________________
PRE-DEVELOPED LAND USE
___________________________________________________________________
Name : Basin 1
Bypass: No
Ground Water: No
Pervious Land Use Acres
C, Forest, Flat 0.445
Impervious Land Use Acres
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
MITIGATED (DEVELOPED) LAND USE
___________________________________________________________________
Name : Basin 1
Bypass: No
Ground Water: No
Pervious Land Use Acres
C, Pasture, Mod 0.092
Impervious Land Use Acres
ROOF TOPS FLAT 0.281
DRIVEWAYS FLAT 0.045
DRIVEWAYS MOD 0.012
DRIVEWAYS STEEP 0.013
SIDEWALKS FLAT 0.002
Element Flows To:
Surface Interflow Groundwater
___________________________________________________________________
ANALYSIS RESULTS
___________________________________________________________________
Flow Frequency Return Periods for Pre-developed. POC #1
Return Period Flow(cfs)
2 year 0.0112
5 year 0.017354
10 year 0.02069
25 year 0.024079
50 year 0.026092
100 year 0.027746
Flow Frequency Return Periods for Developed. POC #1
Return Period Flow(cfs)
2 year 0.090686
5 year 0.110571
10 year 0.123451
25 year 0.139547
50 year 0.151471
100 year 0.163374
NET INCREASE IN 100-YEAR FLOW RATE = 0.135 CFS
___________________________________________________________________
Yearly Peaks for Pre-developed and Mitigated. POC #1
Year Pre-developed Mitigated
1950 0.013 0.093
1951 0.022 0.137
1952 0.028 0.092
1953 0.009 0.079
1954 0.007 0.072
1955 0.010 0.087
1956 0.017 0.092
1957 0.014 0.089
1958 0.011 0.102
1959 0.012 0.092
1960 0.010 0.070
1961 0.017 0.088
1962 0.010 0.077
1963 0.006 0.078
1964 0.008 0.076
1965 0.010 0.089
1966 0.007 0.080
1967 0.008 0.080
1968 0.017 0.117
1969 0.010 0.133
1970 0.010 0.073
1971 0.008 0.080
1972 0.007 0.077
1973 0.020 0.111
1974 0.009 0.072
1975 0.010 0.080
1976 0.014 0.106
1977 0.009 0.072
1978 0.001 0.091
1979 0.008 0.119
1980 0.005 0.118
1981 0.014 0.099
1982 0.007 0.108
1983 0.013 0.147
1984 0.012 0.108
1985 0.008 0.083
1986 0.004 0.077
1987 0.022 0.098
1988 0.018 0.135
1989 0.007 0.065
1990 0.004 0.083
1991 0.029 0.152
1992 0.025 0.142
1993 0.008 0.082
1994 0.010 0.056
1995 0.002 0.067
1996 0.014 0.084
1997 0.026 0.101
1998 0.024 0.097
1999 0.005 0.102
___________________________________________________________________
Ranked Yearly Peaks for Pre-developed and Mitigated. POC #1
Rank Pre-developed Mitigated
1 0.0287 0.1519
2 0.0280 0.1471
3 0.0263 0.1420
4 0.0253 0.1371
5 0.0243 0.1350
6 0.0220 0.1325
7 0.0216 0.1188
8 0.0203 0.1176
9 0.0181 0.1172
10 0.0173 0.1111
11 0.0172 0.1083
12 0.0165 0.1077
13 0.0141 0.1063
14 0.0139 0.1024
15 0.0136 0.1019
16 0.0135 0.1013
17 0.0128 0.0989
18 0.0126 0.0978
19 0.0123 0.0967
20 0.0121 0.0934
21 0.0108 0.0919
22 0.0101 0.0919
23 0.0101 0.0916
24 0.0101 0.0906
25 0.0100 0.0890
26 0.0100 0.0888
27 0.0098 0.0881
28 0.0097 0.0866
29 0.0095 0.0839
30 0.0092 0.0833
31 0.0091 0.0831
32 0.0086 0.0822
33 0.0082 0.0804
34 0.0080 0.0797
35 0.0079 0.0796
36 0.0078 0.0796
37 0.0077 0.0790
38 0.0076 0.0782
39 0.0075 0.0773
40 0.0073 0.0769
41 0.0072 0.0767
42 0.0066 0.0763
43 0.0066 0.0728
44 0.0059 0.0725
45 0.0050 0.0724
46 0.0047 0.0723
47 0.0043 0.0703
48 0.0042 0.0667
49 0.0024 0.0646
50 0.0009 0.0557
___________________________________________________________________
APPENDIX D
Bond Quantities
A Site Improvement Bond Quantity Worksheet to be provided with the Construction Permit Application.