HomeMy WebLinkAboutFYCD Drainage Report 101119 with attachments.pdfTechnical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Storm Water Drainage Assessment Report
Project Name: FYCD Cultural & Education Associates
Project Address: 711 Monroe Ave N.E.
Renton, Washington
Parcel Numbers: 7809200075
Developer:
Engineer: Ali Amirzehni P.E.
Company: Consultant Engineer
Address: 3952 112th Ave N.E., Bellevue, WA 98004
Phone Number: (206) 288-3122
Revised Report Date: October 11, 2019
10/11/2019
_______________________________
Engineer Stamp:
Ali Amirzehni P.E., Consultant Engineer
Zce.engineering@gmail.com, 206-288-3122
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Table of Contents
Section 1: Project Overview
Section 2: Conditions and Requirements Summary
Section 3: Offsite Analysis
Section 4: Flow Control, Low Impact Development (LID) and Water Quality Facility Analysis and Design
Section 5: Conveyance System Analysis and Design
Section 6: Special Reports and Studies
Section 7: Other Permits
Section 8: CSWPP Plan Analysis and Design
SECTION 9 – BOND QUANTITIES, FACILITIES SUMMARIES, AND DECLARATION OF COVENANT
SECTION 10 – OPERATIONS AND MAINTENANCE
Appendix
Soil Report
Drainage Site Plan
Erosion & Sediment Control Plan
Maintenance Requirements
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Section 1: Project Overview
The site is located at 711 Monroe Avenue NE in Renton Washington. The site consists of a single lot with
total area of about 13,532 square feet (0.31 acres). The western portion of the site is currently
developed with a single-family residence. A driveway extends through the north portion of the property
from the east and Monroe Ave NE. The reminder of the property is vegetated with grasses, shrubs,
bushes, and trees. This project is proposing to demolish the existing single family residence and
construct a new structure within the existing structure foot-print. The new structure will be converted
to I Kuan Tao Cultural Center. Surface parking spaces will be provided within the front yard. Access to
the site would be maintained off of Monroe Avenue NE.
The site gently slopes downward toward the southwest and west with topographic relief of less than 8
feet. There is a moderate steep slope extending downward to the west in the area just west of the
property. This area is well vegetated with low lying brushes and trees. The slope is up to 15’ height and
has magnitudes of 30 percent.
The site underlain by glacial till soil which typically has a very low permeability. The factored infiltration
rate is 0.28 inches /hour according to the attached soil report prepared by COBALT Geoscience.
This project proposes 4,674 sf of new plus replaced impervious surface, and Table 1 & 2 summarizes the
impervious area calculation.
Table 1. Summary of existing site conditions
Table 2. Summary of proposed site conditions
Surface Type Area Units Notes
Roof (with eaves) 1,938 s.f.
New Driveway 2,736 s.f.
Existing Parking Area 1,962 s.f. To remain
Total New & Replaced
Imp Area *
4,674 s.f.
Landscaped Area 8,878 s.f.
Total Lot 13,552 s.f.
Surface Type Area Units Notes
Roof (with eaves) 1,720 s.f.
Driveway & walkway 5,020 s.f.
s
Total Imp Area 6,740 sf
Landscaped area 6,812 s.f.
Total Lot 13,552 S.f.
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Aerial Map
Vicinity Map
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Section 2: Conditions and Requirements Summary
This project proposes to construct a cultural center with a 4,674 sf of new plus replaced impervious
surface. As described in City of Renton Surface Water Design Manual, full drainage review is required.
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Core Requirements 1-9 per 2017 City of Renton Surface Water Design Manual will apply.
Core Requirements #1- Discharge at the Natural Location: The project will discharge to the natural
downstream location. Downstream drainage patterns will not be altered.
Core Requirement # 2-Offsite Analysis: Offsite Analysis is provided in Section 3.
Core Requirement # 3 – Flow Control Facility: This project is proposing less than 5,000 sf of new
impervious area and exempt from flow control facility. Refer to Section 4 of this report for a detailed
discussion.
Core Requirement # 4 – Conveyance system is discussed in section 5.
Core Requirement # 5 – Erosion and Sediment Control: All erosion and sediment control measures shall
be governed by the requirements of the City of Renton Surface Water Manual. The project provides the
minimum ESC measures and discussed in Section 8.
Core Requirement # 6 – Maintenance & Operation: Will be provided. Maintenance and operations of all
drainage facilities located within the private residential property is the responsibility of the applicant or
property owner. Maintenance guidelines are discussed in Section 10 of this report.
Core Requirement # 7 – Financial Guarantees & Liability: A financial guarantee will be provided by the
owner upon requested.
Core Requirement #8- Water Quality: The project proposes less than 5,000 sf of new plus replaced PGIS
and exempt from these requirements.
Core Requirement #9- On Site BMP: The requirement for mitigation of target impervious surface is
discussed in Section 4.
Special Requirement #1: Other Adopted Requirements
Based on available data at the time this report was prepared, there are no one Special Adopted
Requirements for this project.
Special Requirement #2: Flood hazard Area
Based on the City of Renton COP map, This site is not located within a flood hazard area.
Special Requirement #3: Flood Protection Facility
N/A
Special Requirement #4: Source Control
N/A
Special Requirement #5: Oil Control
N/A
Special Requirement #6: Aquifer protection Area
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Based on the City of Renton COP map, This site is not located within an aquifer area.
Section 3: Offsite Analysis
Level 1 Downstream Analysis
A field investigation was conducted on April 14, 2019. The weather was cloudy and dry. Stormwater
from the site sheet flows from the property towards the Monroe Ave and discharges into the Monroe
closed conveyance system via a catch basin located on Monroe Ave NE. The Closed conveyance system
consists of series of catch basin and pipe conveyance system that runs east to west along the Monroe
Ave NE
Task 2 – Resource Review
The City of Renton COP GIS map was utilized to review the City closed drainage system. No drainage
complains was documented within one mile of the down-stream of flow path.
•Wetlands Inventory: The project site is not located in or near a mapped wetland per the City of
Renton COP map.
•Landslide Area Maps: The project site is not located in or near a landside area per the City of
Renton COP map.
Task 3 – Field Inspection
The Monroe Ave closed conveyance system consists of series of catch basin and pipe conveyance
system. The system runs east to west and all the structures appears to be in fair condition. No sign of
over-toping or flooding was observed.
Task 4 – Drainage System Description and Problems Descriptions
Based on this field inspection and resources review there appears to be no current significant erosion or
capacity problems.
Task 5 – Mitigation of Existing or Potential Problems
There are no apparent erosion or capacity problems downstream of this project.
4,514752
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.
THIS MAP IS NOT TO BE USED FOR NAVIGATIONWGS_1984_Web_Mercator_Auxiliary_Sphere
Notes
None
04/14/2019
Legend
512 0 256 512 Feet
Information Technology - GIS
RentonMapSupport@Rentonwa.gov
City and County Boundary
Addresses
Parcels
Wellhead Protection Area Zones
Zone 1
Zone 1 Modified
Zone 2
Coalmines
High
Moderate
Unclassified
Erosion Hazard - High
Floodway
Special Flood Hazard Areas (100 year flood)
Other Flood Areas (Zone X - 500 year flood)
Channel Migration Zones (CMZ) as mapped by
King County
Moderate Hazard Area
Potential Hazard Area
Severe Hazard Area
Landslide
Very High
High
Moderate
Unclassified
Environment Designations
Natural
Shoreline High Intensity
Shoreline Isolated High Intensity
Shoreline Residential
Urban Conservancy
Jurisdictions
Streams (Classified)
<all other values>
Type S Shoreline
Type F Fish
Type Np Non-Fish
Type Ns Non-Fish Seasonal
Unclassified
Not Visited
Wetlands
Seismic Hazard Areas
Faults
Water Service Areas
Wastewater Service Areas
Network Structures
Inlet
Manhole
Utility Vault
Unknown Structure
Control Structures
Pump Stations
Discharge Points
Water Quality
Detention Facilities
Pond
Tank
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
Section 4: Flow Control, Low Impact Development (LID) and Water Quality Analysis
Flow Control
Roof runoff
This project is proposing less than 5,000 sf of new impervious area and exempt from flow control facility.
Stormwater on-site BMPs elements are designed in-accordance to the 2017 City of Renton Surface
Water Management Design Manual.
To address the on-site BMPs requirements, implementing of full and basic dispersion trench BMP’s were
considered first and determined to not feasible due to lack of native vegetation and required flow path
and set required setbacks.
Implementation of full and limited infiltration is not feasible due to soil type and shallow ground water
table as described in the soil report prepared by Cobalt Geo dated May 14, 2018. The site is underlain by
glacial till and infiltration is not recommended and/or potentially infeasible (see the attached drainage
report).
Rain garden BMP was also considered. Implementation of Rain garden is also not feasible due to soil
type, land availability, conflict with utilities, and set back requirements.
Perforated pipe connection BMP was selected for the roof runoff. All the downspouts will be tight lined
and connected to the perforated pipe connection structure. The total new roof area is 1,938 sg, and 10’
of trench with perforated pipe will be provided with a connection to the City drainage system on
Monroe Ave NE.
Other hard surfaces:
Implementation of dispersion, full and limited infiltration, permeable pavement is not feasible due to
soil type and shallow ground water table as described in the soil report prepared by Cobalt Geo dated
May 14, 2018. The site is underlain by glacial till soil and molting was also observed at depth of about 2
to 5 ft. Permeable pavement is not recommended and/or potentially infeasible (see the attached
drainage soil report)
A conveyance system will be provided to collect runoff from the parking lot area and connect to the
Monroe Ave N. existing catch basin. The existing driveway drainage will not be altered and will
continue to sheet flow and dissipate into the surrounding landscaped area.
All new pervious area will receive soil amendment per the City Of Renton standard plan.
Water Quality
The project proposes less than 5,000 sf of new plus replaced PGIS and exempt from these requirements.
Section 5: Conveyance System Analysis and Design
Conveyance pipe connection to the Monroe Ave N catch basin
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
12” CPE (corrugated polyethylene pipe) @ min 1% slope will be ued.
Pipe capacity and flow calculation:
Roof = 1,938 sf
New Driveway = 2,736 sf
Existing Parking Area =1,962 sf
Total impervious area= 6,636 sf (0.15 acre)
12” CPE (corrugated polyethylene pipe) capacity @ 1% slope:
Q = 1.486/n * A * R2/3 * S ½
n = roughness coefficient =0.012
A = cross section of pipe = 3.14 (d/2)^2 = 3.14 (1 / 2)^2 = 0.78
R = wetted perimeter of pipe
R^2/3 = (D/4)^2/3 = (1/4)^2/3 =0.39
S = slope 1%
S^1/2 = 0.1
Q = ((1.486/0.012) * 0.78 * 0.39 * 0.1) = 3.76 cfs 12” pipe capacity @ 1%
Site Flow calculation:
C = Runoff Coefficient (weighted average)
C=0.9
A= 6,636 ( 0.15 acres)
IR = Peak Rainfall Intensity
Pr = 3.4 inches (25-year, 24-hour runoff)
ir = ar x Tc-br
aR =2.66
bR = 0.65
Tc = Time of concentration (6.3 minutes minimum)
ir = (3.4) x 1/(6.4)^.65 = 1.01
I= Pr x ir
I25 = 3.4 x 1.01 = 3.43
A = Area in Acres = 0.1 acres
Rational Method Flows:
Q = CIRA = (0.9)(3.43 )(0.15 acres) = 0.46cfs < 3.76 cfs O.k. to use 12” pipe
SECTION 6 – SPECIAL REPORTS
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
N/A
SECTION 7 – OTHER PERMITS
N/A
SECTION 8 – CSWPP ANALYSIS AND DESIGN
ESC Plan Analysis and Design (Part A)
All erosion and sediment control measures shall be governed by the requirements of the City of Renton
Surface Water Manual. An Erosion and Sedimentation Control plan has been prepared to assist the
contractor in complying with these requirements and designed to prevent sediment-laden run-off from
leaving the site during construction.
The Erosion and Sedimentation Control Design meets the 13 minimum requirements:
1. Clearing Limits – Areas to remain undisturbed shall be delineated with a high visibility plastic fence
prior to any site clearing or grading.
2. Cover Measures – Disturbed Site areas shall be covered with mulch and seeded, as appropriate, for
temporary or permanent measures.
3. Perimeter protection – Perimeter protection shall consist of a silt fence down slope of any disturbed
areas or stockpiles.
4. Traffic Area Stabilization – A stabilized construction entrance will be located at the point of
ingress/egress.
5. Sediment Retention – Due to the size of the project and the nature of the proposed improvements,
no sedimentation retention facility is proposed.
6. Surface Water Control – If necessary, surface water control will be provided by interceptor swales.
7. Dewatering Control – Will be provided as needed.
8. Dust Control – Dust control shall be provided by spraying exposed soils with water until wet. This is
required when exposed soils are dry to the point that wind transport is possible which would impact
roadways, drainage ways, surface waters, or neighboring residences.
9. Flow Control – Due to the size of the project, no flow control is proposed.
10. Control Pollutants – Demolition of existing structures and disposition of the demolished material and
other waste will be in accordance to the 2016 KCSWDM Section D.2.2.
11. Protect Existing and Proposed Flow Control BMPs – N/A. No flow control is proposed for this project.
12. Maintain BMPs – BMP’s shall be maintained throughout the project.
13. Manage the Project – ESC Lead will manage site development activities relative to ESC concerns to
assure the success of protective ESC and SWPPS design and implementation.
CSWPP Plans Design (Part B)
Project does not require a CSWPPP since it proposes to disturb less than 1 acre of land.
SECTION 9 – BOND QUANTITIES, FACILITIES SUMMARIES, AND DECLARATION OF COVENANT
STORMWATER FACILITY SUMMARY SHEET
Will be provided by the owner as needed.
DECLARATION OF COVENANT
Will be provided by the owner as needed.
BOND QUANTITY WORKSHEET
Bond worksheets will be provided by the applicant.
Technical Information Report
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I-Kuan Tao Cultural Center 711 Monroe Ave NE Renton, Washington
SECTION 10 – OPERATIONS AND MAINTENANCE
This project will install an on-site perforated pipe connection BMP, and a conveyance system with a
connection to the Monroe Ave conveyance system. The catch basin within the properties is the
responsibility of the applicant or property owner.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
12/12/2016 2017 City of Renton Surface Water Design Manual
A-10
NO. 5 – CATCH BASINS AND MANHOLES
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 catch basin.
Deposits of garbage exceeding 1 cubic
foot in volume.
No condition present which would attract or
support the breeding of insects or rodents.
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 ¼ inch.
Top slab is free of holes and cracks.
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 in 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 catch
basin 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 Sedimentaccumulation 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.
APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS
2017 City of Renton Surface Water Design Manual 12/12/2016
A-11
NO. 5 – CATCH BASINS AND MANHOLES
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% of grate surface.
Grate free of trash and debris. footnote to
guidelines for disposal
Damaged or missing
grate
Grate missing or broken member(s) of the
grate. Any open structure requires
urgent maintenance.
Grate is in place and meets design
standards.
Manhole Cover/Lid 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.
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.
TOPOGRAPHIC & BOUNDARY SURVEY TOPOGRAPHIC & BOUNDARY SURVEYBASIS OF BEARINGSLEGAL DESCRIPTIONVERTICAL DATUMSURVEYOR'S NOTESLEGENDVICINITY MAPN.T.S.REFERENCESI-KUAN TAO FYCD CULTURAL & EDU. ASSO.N.T.S.CONTROL MAP
Cobalt Geosciences, LLC
P.O. Box 82243
Kenmore, Washington 98028
www.cobaltgeo.com (206) 331-1097
May 14, 2018
Ms. Julie Chen
greenhousetex@comcast.net
RE: Stormwater Feasibility Evaluation
Proposed Development Expansion
711 Monroe Avenue NE
Renton, Washington
Dear Ms. Chen,
In accordance with your authorization, Cobalt Geosciences, LLC has prepared this letter to
discuss the results of our stormwater feasibility evaluation at the referenced site. The purpose of
our evaluation was to evaluate the shallow subsurface soil conditions and provide options for
stormwater management.
Site and Project Description
The site is located at 711 Monroe Avenue NE in Renton, Washington. The site consists of one
rectangular shaped parcel with a total area of about 13.552 square feet.
The western portion of the site is currently developed with a single-family residence used as a
business. A driveway extends through the north portion of the property from the east and
Monroe Avenue NE. The remainder of the property is vegetated with grasses, bushes, shrubs, and
sparse deciduous and evergreen trees. The site slopes gently downward toward the southwest and
west with topographic relief of less than 8 feet. There is a moderately steep slope extending
downward to the west in the area just west of the property. This area is well vegetated with low-
lying brush and variable diameter trees. The slope is up to 15 feet in height and has magnitudes of
30 percent.
The property is bordered to the north and west by single-family residences, to the south by a
commercial development, and to the east by Monroe Avenue NE.
The project includes construction of a second story to the existing residence as well as expanded
parking areas in the area between the building and Monroe Avenue NE. Stormwater
management may include permeable pavements, infiltration systems, rain gardens, or other
shallow best management practices (BMPs) from the King County Surface Water Design Manual.
Area Geology
The Geologic Map of King County indicates that the site is underlain by Vashon Glacial Till.
Vashon Glacial Till is typically characterized by an unsorted, non-stratified mixture of clay, silt,
sand, gravel, cobbles and boulders in variable quantities. These materials are typically dense and
relatively impermeable. The poor sorting reflects the mixing of the materials as these sediments
were overridden and incorporated by the glacial ice.
May 14, 2018 Page 2 of 3 Stormwater Feasibility Evaluation
www.cobaltgeo.com (206) 331-1097
Soil & Groundwater Conditions
As part of our evaluation, we excavated two hand borings up to 6 feet below grade. Both hand
borings encountered approximately 5 to 8 inches of topsoil and grass underlain by approximately
2 to 2.5 feet of loose to medium dense, silty-fine to fine grained sand with gravel (Weathered
Glacial Till). This layer was underlain by medium dense to dense, silty-fine to medium grained
sand with gravel (Glacial Till), which continued to the termination depths of the hand borings.
Soil mottling was observed in both hand borings from about 2 to 5 feet below existing grades. Soil
mottling (iron oxide staining) typically indicates the fluctuation level of seasonally perched
groundwater.
We also reviewed available exploration logs from nearby site locations, including across the street
to the east. The soils described in these boring and test pit logs were consistent with those
encountered in the hand borings.
Stormwater Management Feasibility
The site is underlain by glacial till which typically has a very low permeability. We conducted an
EPA Falling Head infiltration test in HB-1 at a depth of 3 feet below grade. The factored
infiltration rate was 0.28 inches/hour. The Washington State Department of Ecology (DOE)
states that infiltration in soils with permeability of less than 0.3 inches/hour is not recommended
and/or potentially infeasible.
It is our opinion that infiltration of stormwater runoff is not feasible due to the underlying soil
and groundwater conditions. The measured infiltration rates were less than 0.3 inches/hour in
the upper 4 feet. Infiltration rates in underlying unweathered glacial till are typically less than 0.1
inches/hour. Groundwater and infiltrating surface waters are likely to migrate laterally to the
southwest, potentially daylighting along the moderately steep slope west of the site.
Depending on the volume of runoff from the new parking areas and roof area, the following
stormwater management BMPs may be feasible:
x Dispersion trenches with limited flowpaths (roof area)
x Sheet flow (parking lots)
x Rain gardens
x Detention systems (R tanks or vaults)
x Permeable pavements for flow control
x Direct connection to City stormwater infrastructure
We recommend that all systems be located east of the existing building to reduce the potential for
impacts to the slope area west of the property. Based on our observations, a combination of
permeable pavements, rain gardens, and detention with overflow to City infrastructure appear
feasible.
It may be necessary to utilize one or more of the above BMPs for stormwater management. Once
the Civil designer has calculated volumes of runoff and has developed preliminary BMPs options,
we can provide additional input. We should review the final plans as they become available.
May 14, 2018 Page 3 of 3 Stormwater Feasibility Evaluation
www.cobaltgeo.com (206) 331-1097
Erosion and Sediment Control
Erosion and sediment control (ESC) is used to reduce the transportation of eroded sediment to
wetlands, streams, lakes, drainage systems, and adjacent properties. Erosion and sediment
control measures should be implemented, and these measures should be in general accordance
with local regulations. At a minimum, the following basic recommendations should be
incorporated into the design of the erosion and sediment control features for the site:
x Schedule the soil, foundation, utility, and other work requiring excavation or the disturbance
of the site soils, to take place during the dry season (generally May through September).
However, provided precautions are taken using Best Management Practices (BMP’s), grading
activities can be completed during the wet season (generally October through April).
x All site work should be completed and stabilized as quickly as possible.
x Additional perimeter erosion and sediment control features may be required to reduce the
possibility of sediment entering the surface water. This may include additional silt fences, silt
fences with a higher Apparent Opening Size (AOS), construction of a berm, or other filtration
systems.
x Any runoff generated by dewatering discharge should be treated through construction of a
sediment trap if there is sufficient space. If space is limited other filtration methods will need
to be incorporated.
Closure
The information presented herein is based upon professional interpretation utilizing standard
practices and a degree of conservatism deemed proper for this project. We emphasize that this
report is valid for this project as outlined above and for the current site conditions, and should not
be used for any other site
Sincerely,
Cobalt Geosciences, LLC
Phil Haberman, PE, LG, LEG
Principal
PH/sc
Proposed Parking Expansion
711 Monroe Avenue NE
Renton, Washington
SITE PLAN
FIGURE 1
Cobalt Geosciences, LLCP.O. Box 82243Kenmore, WA 98028
(206) 331-1097
www.cobaltgeo.com
cobaltgeo@gmail.com
N
HB-1
HB-1
HB-2
Log of Hand Boring HB-1
Date: May 2, 2018
Contractor:
Method: Hand Auger
Depth: 6’
Elevation: N/A
Logged By: PH Checked By: SC
Initial Groundwater: None
Sample Type: Grab
Final Groundwater: N/A
Material Description SPT N-Value
Moisture Content (%)PlasticLimit LiquidLimit
10 20 30 400 50
1
2
3
4
5
6
7
8
9
10
End of Hand Boring 6’
Vegetation/Topsoil
Loose to medium dense, silty-fine to medium grained sandwith gravel and cobbles, dark yellowish brown to yellowish brown,
moist. (Weathered Glacial Till)
SM
Medium dense to dense, silty-fine to medium grained sand,
mottledyellowishbrowntograyishbrown,moist.(GlacialTill)SM
Cobalt Geosciences, LLC
P.O. Box 82243Kenmore, WA 98028(206) 331-1097www.cobaltgeo.com
cobaltgeo@gmail.com
Proposed Parking Expansion
711 Monroe Avenue NE
Renton, Washington
Hand Boring
Log
Log of Hand Boring HB-2
Date: May 2, 2018
Contractor:
Method: Hand Auger
Depth: 6’
Elevation: N/A
Logged By: PH Checked By: SC
Initial Groundwater: None
Sample Type: Grab
Final Groundwater: N/A
Material Description SPT N-Value
Moisture Content (%)PlasticLimit LiquidLimit
10 20 30 400 50
1
2
3
4
5
6
7
8
9
10
End of Hand Boring 6’
Vegetation/Topsoil
Loose to medium dense, silty-fine to medium grained sandwith gravel and cobbles, dark yellowish brown to yellowish brown,
moist. (Weathered Glacial Till)
SM
Medium dense to dense, silty-fine to medium grained sand,mottledyellowishbrowntograyishbrown,moist.(GlacialTill)
SM
Cobalt Geosciences, LLC
P.O. Box 82243Kenmore, WA 98028(206) 331-1097www.cobaltgeo.com
cobaltgeo@gmail.com
Proposed Parking Expansion
711 Monroe Avenue NE
Renton, Washington
Hand Boring
Log
N.T.S.
CONTROL MAP
LANDSCAPING
LANDSCAPING
EXIST. CONC. PAVING TO BE REMAINED
EXIST. CONC. PAVING TO BE REMAINED
REGISTE R E D31169PROF
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ONALI A M I RZ
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LANDSCAPING
LANDSCAPING
EXIST. CONC. PAVING TO BE REMAINED
EXIST. CONC. PAVING TO BE REMAINED
REGISTE R E D31169PROF
E
SSIONAL E N G INEERSTAT E O F WASHIN
GT
ONALI A M I RZ
E
H
NI
REGISTE R E D31169PROF
E
SSIONAL E N G INEERSTATE O F WASHIN
GT
ONALI A M I RZ
E
H
NI