MAPLEWOOD DR STORM DRAINAGE REPORT.pdfMaplewood Drive Short Plat
2moLot Short Subdivission
20226 Maplewood Drive
Edmonds, WA 98026
By: Select Homes
Final Storm Drainage Report
Date: April 1, 2016
-4/1/2016
Prepared by: Rob Long, PE
SAM Engineering, Inc.
16531 13th Ave W, Suite A108, Lynnwood WA 98037
(425) 678-6960 RAMengineeringinc.com
RECEIVED
APR 05 2016
DEVELOPMENSERVICES
COON ER
Job No. 15-028
Maplewood Drive Short Plat
2 -Lot Short Subdivision
Introduction: This summary report provides site design information for a two lot single family
short subdivision. This report includes storm drainage analysis to support permit review and
approval. The property is located along the west side pf Maplewood Drive north of Sierra St, in the
northwest 1/4 of Section 19, T 27 N, R 4 E, W.M.
Site Address: 20226 Maplewood Drive Applicant: Select Homes
Edmonds, WA 98026 16513 13th Ave W, Suite A108,
Lynnwood WA 98037
Tax Parcel Number: 005067 000 01102 Contact: Craig Pierce
(425) 299-2600
TABLE OF CONTENTS
SECTION PAGES
A. Project Summary ..... ......... ......... .................. ........ ... .................. 3
B. Parcel (Vicinity) Map ......... ............................. ......... ......... ......... ........... ....... ......... ......... 1
C. Site Development Plans..,—,--,,,—., ....... ......... ......... ......... ...... ........ ....,..,, 6
D. Aerial Photo ......... ......... ............................ .-....... .,,..,,..,..,.. ., „......... ....... .......- 1
E. Stormwater Control System Summary and Calculations.................................................................. 2
F. Drainage Basin Description and Maps ............................ ......... ......... ...... ......... ,.. 3
G. Grading & Erosion Control Summary and Soils Map ... ...... ....-... ,, -...........,..,....,,.,..............,.....,..... 4
H. Operation and Maintenance Guidelines .............. ..-.., ................... ,. 6
R.4MEngineering, Inc,
Engineering and Drainage Report Maplewood Drive Short Plat
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Page i
A. PROJECT SUMMARY:
This report provides engineering design information for the proposed construction of a single family
residence 2- lot short subdivision; the project is located 20226 Maplewood Dr (91St PI W) in the City of
Edmonds.
Existing Conditions. The total site is about 32,029 sf (0.735 acres) in size; and currently occupied by a single
family residence, detached outbuilding and lawn/landscaped area. The site is bordered by Maplewood Dr
along the east, and single family houses to the north, west and south (see attached aerial photo- section D).
The site contains a crest that generally slopes to east or to west with most of the elevation change along
the western portion of the slope (slopes west 4% to 10%). Run-off from the site generally sheet flows in a
westerly or easterly direction divided by of the site. No existing pipe/catchbasin system or channel was
discovered in the westerly direction; in the easterly slope direction a pipe/catchbasin system is lactated
along the westerly edge of Maplewood Dr that collects sheet flow runoff from the site. Additional discussion
of the local drainage basin and downstream path is discussed in section F of this report.
Developed Conditions. The proposed project includes removal of the existing house and outbuilding form
the site. Infrastructure improvements include a driveways; walkways; patios; stormwater collection,
conveyance and individual lot detention tanks systems to control stormwater runoff; and connection of the
typical utilities (water, sewer, gas, electric, and communication services).
Existing trees will be cleared during site grading activities to install the utilities along the frontage of the lots
and the individual lot access driveways. During the building permit phase, each lot will be cleared for the
building pad and install individual driveway, utility connections and individual lot detention pipes for each
house; landscaping and lawn around the new houses will stabilize the lots upon house construction. Each
lot will include a storm drainage detention pipe system (or other City approved storm control system) for
the single family residence, driveway and patio impervious surfaces areas of each individual lot.
All disturbed pervious (lawn and landscape) areas will preserve or restore the health and water -holding
capacity of the soils by compost -amending (Per DOE BMP T5.13: Post -Construction Soil Quality and Depth).
See section E for additional evaluation of the storm drainage control systems.
RAM Engineering, Inc.
Engineering and Drainage Report
RAM No. 15-028
Page A-1
Maplewood Drive Short Plat
April 1, 2016
underground detention tank (on each lot) per the City's drainage manual will be provided to control
stormwater quantity control. See civil site development plans and section E for additional sizing
calculations and construction details.
5.6 Small Site Minimum Requirement #6 — Runoff Treatment. The project does not propose to
create/replace more than 5,000 sf of pollution -generation impervious surface onsite. The project will create
about 2,800 sf (2 individual lot driveways at 1,400 sf each) pollution generation impervious surfaces; a
majority of the site's impervious surface is rooftop and walkway/patio areas (non -pollution generation
surfaces). Thus, no basic or enhanced water quality treatment system is require. The site's stormwater
control system will include a sump and a control tee that will provide some water quality and oil/water
separation of the collected runoff.
5.7 Small Site Minimum Requirement #7 —Flow Control. Individual onsite storm detention tanks on each
lot will provide flow control of the site's stormwater runoff. The detention tank systems have been design
to meet the flow control standards of a Small Site- Category 2 project in a creek or lake basin (less than an
acre of disturbance and between 5,000 sf and 10,000 sf of impervious surface). Per Edmonds Stormwater
Code Supplement (5.7.3.2 Simplified Sizing Approach) "a pre -sized approach for sizing flow control BMPs
has been developed for Small Site Projects in Edmonds with between 2,000 and 10,000 square feet of new
and replaced impervious surface area." The detention tank has be sized using the City of Edmonds Simplified
Sizing Approach; an overview of the proposed storm drainage control facilities are provided in section E.
5.8 Small Site Minimum Requirement #8 — Wetland Protection. No wetlands are known to exist on or
adjacent to the site.
5.9 Small Site Minimum Requirement #9 — Operation and Maintenance. An operation and maintenance
summary is provided in section H.
5.10 Small Site Minimum Requirement #10 — Offsite Analysis and Mitigation. See section F. Drainage Basin
Description and Maps for a qualitative analysis.
5.11 Small Site Minimum Requirement #11— Financial Liability. Cost estimates and bonds will be provided
by the applicant during final construction permit approval.
R.4MEngineering, Inc.
Engineering and Drainage Report
RAM No. 15-028
Page A-3
Maplewood Drive Short Plat
April 1, 2016
C. SITE DEVELOPMENT PLANS
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RAM Engineering, Inc.
Engineering and Drainage Report Maplewood Drive Short Plat
RAM No. 15-028 April 1, 2016
Page C-1
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RAM Engineering, Inc.
Engineering and Drainage Report Maplewood Drive Short Plat
RAM No. 15-028 April 1, 2016
Page C-1
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April 1, 2016
E. STORMWATER CONTROL SYSTEM SUMMARY AND CALCULATIONS:
The project proposes to create and/or replace approximately 10,000 sf of impervious surface (two lots at
5,000 sf each). To mitigate the development of the site, individual lot stormwater detention tank systems
will be installed to control the drainage runoff. All of the on-site impervious surfaces shall be collected
and routed to the on-site detention systems. The site is located within the Hindley Creek watershed basin
which per Edmonds code is a Creek -basin (See Figure A, City of Edmonds Watershed Map at the end of
this section). Per City standards a project with greater than 2,000 sf of effective impervious area shall
detain the 10 -year developed storm and release at 0.25 cfs/acre of impervious, or follow the simplified
sizing guidelines of the E72 -A Edmonds handout. The project may follow the design guidelines of Table 1,
shown on the following page for a maximum area of 5,000 sf of impervious area for each lot. During the
individual building permits of each lot the final proposed lot impervious will be confirmed and the
individual detention pipe systems sized.
Below is the E72 -A summary simplified sizing chart for individual systems under 5,000 sf of new
impervious surface:
Each Lot: 5,000 sf = Requires 112 ft of 18" Detention Pipe
Now: bluhiple pipes in parallel connected lo"Cther I nt:ulifolded) can be used to meet length mquimntenls, if site has coilsu'ainls.
RAMEngineering, Inc..
Engineering and Drainage Report
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Maplewood Drive Short Plat
April 1, 2016
Table 1
Detention Pipe Look -Up Table
Category 1 Small Site Projects
Contributing Ne►v PiusLength
of Tie (ft) Foy Gwen Inside Diameter
Replaced Impervious���
Surface Area (sf)
18 -inch
24 -inch
30 -inch .�.�
.��.�..I.I.�
36 -inch
..�. 2.000
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15
500..............
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12
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61
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33
2
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3,500
74
38
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95
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32
23
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112
56
35
25
sf— Square Iccl
Orifice Size:
0.5 (1/2) inch diameter
= 0.75 (3/4) inch dianteter
0.625 (5/5) Inch diameter
V
_ 0.875 (7/8) incil dlUmeter
Now: bluhiple pipes in parallel connected lo"Cther I nt:ulifolded) can be used to meet length mquimntenls, if site has coilsu'ainls.
RAMEngineering, Inc..
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Maplewood Drive Short Plat
April 1, 2016
FIGURE
CROSS—SECTION of TYPICAL DETENTION SYSTEM
CATEGORY 1 SMALL SITE PROJECTS
AVE TEDEPTH TO PREVENT DAMAGE TO PIPE
F,UNOFF FINISHED GRADE
FROM
SITE coN1ROL cATcl1 a+�N
O5OZ TO 0.75% SLOPE SEE FIGURE 2
DETENTION PIPE LENGTH
REFER TO TABLE 1
FIGURE 2
DETAIL OF CONTROL CATCH BASIN
RIM
LACKING ELEVATION S' MIN. MEASURED FROM
UO THE TOP OF THE
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DETENTION PIPE `M;
7
N EL
RITIGE SIZE PER TABLE 1
RAM Engineering, Inc.
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Maplewood Drive Short Plat
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F. DRAINAGE BASIN DESCRIPTION:
The site is located in the Hindley Creek watershed basin. The Hindley Creek basin is an urban basin that
collects stormwater runoff from primarily residential areas in the central portion of the City (see watershed
map in previous section).
An evaluation of the topography in the area reveals that stormwater runoff from the site would sheet flow
in a westerly or easterly direction due to a crest in the natural grades found onsite. Both the westerly and
easterly paths are within the Hindley Creek watershed basin. Due to the fact a majority of the proposed
impervious is within in the easterly portion and the easterly portion has an existing pipe and catch basin to
connect to, the proposed site detention systems will connect to the easterly system. The easterly system
collects in pipes and catch basins located along the easterly boundary of the site (along the west side of
Maplewood Dr). The pipe system along the west side of Maplewood Dr directs collected runoff south about
150 ft to Sierra St and then is directed west along Sierra St 200 ft and then back south to an open channel
about 100 feet (450 ft from the site). The open channel continues in a south/westerly direction and then
re-enters a pipe system in about 900 ft from the site. The piped system continues west along Highland Dr
crossing under 12th Ave N about 1,700 ft downstream of the site. The pipe system continues west along 12th
PI N and between and behind private residence and continues back north following Olympic Ave; the pipe
system then turns back west and daylights to the open channel of Hindley Creek about 0.6 miles from the
site (near a residence at 603 Olympic Ave). Hindley Creek continues in a westerly direction and eventually
outlets to Puget Sound about 1.6 miles from the site. A majority of the % mile downstream is contained in
pipes or well define channels. No apparent flooding or system inadequacies within a % mile downstream of
the site were discovered during research of the downstream system.
See the Watershed Map in the previous section and Downstream Drainage Exhibit on the following page for
the local downstream path.
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F-2. Watershed Basin Map
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RAM Engineering, Inc.
Engineering and Drainage Report Maplewood Drive Short Plat
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Page F-2
ra. Downstream Drainage and|it Map
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Maplewood Drive So4 Plat
Aprl{2fe
G. GRADING & EROSION CONTROL SUMMARY:
The project will require grading to construct the proposed driveways, buildings and utilities (including the
individual lot stormwater detention tanks systems). Standard erosion control measures are proposed to be
used during construction. The primary erosion and sediment control BMP during construction will be
proper soil stabilization methods. Exposed soils shall be stabilized by application of effective BMPs that
protect the soil from the erosive forces of raindrops, flowing water, and wind. Applicable practices include,
but not limited to, temporary and permanent seeding, sodding, mulching, plastic covering, erosion control
fabrics, matting, soil application of polyacrylamide (pam), the early application of gravel base on areas to be
paved, and dust control. The contractor shall select a soil stabilization method best suited for the particular
situation. Stock piles must be stabilized and protected with sediment trapping measures. In addition, site
containment of exposed soils shall be sustained by using silt fence barriers along the down-slope boundaries
of the site's disturbance areas. See the site development plan for details.
Soils: In accordance with the City of Edmonds Soil Map the on-site soils consist of Alderwood - Urban Land
Complex, 2 to 8 percent slopes (soil # 5). Alderwood soils are moderately deep over a hardpan and are
moderately well drained; see the full SCS soils description and site specific geotechnical evaluation report
attached.
Construction Stormwater Pollution Prevention Plan (SWPPP): The following is a summary of the site's
erosion control measures that evaluates the typical DOE 13 elements of a SWPPP:
Element 1: Mark Clearing Limits: Clearing limits have been delineated on the engineering site development
plans and shall be clearly marked prior to construction.
Element 2: Establish Construction Access: A construction access has been delineated on the engineering
site development plans.
Element 3: Control Flow Rates: Due to the relatively small site size of the project site (less than one acre),
no flow control system (ie: temporary pond) is proposed. During construction silt fencing will
provide attenuation of site runoff, and upon project completion and site stabilization
(established lawns and landscape of exposed soils) the installed storm systems (detention
tanks and collection and roof drain systems) will provide flow control.
Element 4: Install Sediment Controls: Filter fabric fence has been delineated and detailed on the
engineering site development plans. At a minimum, silt fence will be installed along the down
gradient perimeter of the disturbed area that will receive sediment -laden runoff.
Element 5: Stabilize Soils: Soils will be stabilized per the TESC notes listed on the engineering site
development plans.
Element 6: Protect Slopes: Exposed slopes shall be stabilized per the TESC notes listed on the engineering
site development plans.
Element 7: Protect Drain Inlets: Drain inlet protection will be installed on all catch basins that will receive
RAMEngineering, Inc.
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sediment -laden runoff. See the engineering site development plans for locations and detail.
Element 8: Stabilize Channels and Outlets: This element is not applicable since there are no temporary
channels or outlets proposed.
Element 9: Control Pollutants: Pollutants shall be managed as described in the TESC notes listed on the
engineering site development plans.
Element 10: Control De -Watering: Highly turbid or contaminated de -watering water shall be handled
separately from stormwater. The water from all de -watering systems for trenches and
foundations shall be treated or disposed prior to discharging from the site.
Element 11: Maintain BMPs: BMPs shall be maintained and removed at the end of the project as follows:
i. All temporary and permanent erosion and sediment control BMPs shall be inspected,
maintained and repaired in accordance with the Drainage Manual or as approved or
required by the City to assure continued performance of their intended function in
accordance with BMP specifications.
ii. The applicant may remove temporary BMPs when they are no longer needed.
iii. All temporary erosion and sediment control BMPs shall be removed within 30 days after
construction is completed and the City has determined that the site is stabilized.
Element 12: Manage the Project: The owner of the site is responsible for managing the installation and
maintenance of the site BMPs.
Element 13. Protect Low Impact Development BMPs: Not site specific LID BMPs are proposed for the short
plat construction.
Grading QuantityApproximation: The below listed grading quantities have been estimated using the
AutoCAD 3D modeling of the site; estimated quantities are for permitting purposes only.
Estimated grading site development quantities:
Cut: 300 CY
Fill: 300 CY
Conclusion: The final site development construction plans will include specific grading and drainage
improvement notes and details. With proper installation, maintenance and inspections of the proposed
construction the project should have minimal impact to the surrounding environment.
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G-3 Soils Map
.�
rCity of Edmonds
Soil Map Units (SCS 1983)
LEGEND
... City of Edmonds Boundary
Soil Map Unite
SOIL NAME
Alderwood Gravelly sandy loam, 2-8 % slopes
Alderwood Gravelly sandy loam, 8-15 % slopes
Alderwood Gravelly sandy loam, 15-25 % slopes
Alderwood roan amend co rex. s s -
11101, Alderwood Urban land tonplex, 8-15 % slopes
Alderwood-Everett Gravelly sandy loams, 25-70
Custer fine sandy loam
Everett gravelly sand loam, 0-8 % slopes
Everett gravelly sand loam, 8-15 % slopes
Everett gravelly sand loam, 15-25 % slopes
Fluvaquents, tidal
Kitsap silt loam, 0-8 % slopes
Kitsap sift loam, 8-25 % slopes
00 McKenna gravelly silt loam, 0-8 % slopes
01110 Mukitteo muck
no Pits
Urban land
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SOIL SURVEY OF
SNOHOMISH COUNTY AREA, WASHINGTON
UNITED STATES DEPARTMENT OF AGRICULTURE,
SOIL CONSERVATION SERVICE
Alderwood - Urban Land Complex, 2 to 8 percent slopes (soil # 5)
This map unit is on till plains. Areas are irregular in shape and are 100 to 1,000 acres in size. The native
vegetation is mainly conifers. Elevation is 50 to 550 feet. The average annual precipitation is about 40
inches, the average annual air temperature is about 50 degrees F, and the average frost -free season is 170
to 190 days.
This unit is about 60 percent Alderwood gravelly sandy loam and about 25 percent urban land. The
components of this unit are so intricately intermingled that it was not practical to map them separately at the
scale used.
Included in this unit are small areas of McKenna and Norma soils and Terric Medisaprists in depressional
areas and drainageways on plains. Also included are small areas of soils that are very shallow over a
hardpan; small areas of Everett, Indianola, and Ragnar soils on terraces and outwash plains; and soils that
have a stony and bouldery surface layer. Included areas make up about 15 percent of the total acreage.
The Alderwood soil is moderately deep over a hardpan and is moderately well drained. It formed in glacial
till. Typically, the surface layer is very dark grayish brown gravelly sandy loam about 7 inches thick. The
upper part of the subsoil is dark yellowish brown and dark brown very gravelly sandy loam about 23 inches
thick. The lower part is olive brown very gravelly sandyloam about 5 inches thick. A weakly cemented
hardpan is at a depth of about 35 inches. Depth to the hardpan ranges from 20 to 40 inches.
Permeability of the Alderwood soil is moderately rapid above the hardpan and very slow through it. Available
water capacity is low. Effective rooting depth is 20 to 40 inches. Runoff is slow, and the hazard of water
erosion is slight. A seasonal perched water table is at a depth of 18 to 36 inches from January to March.
Urban land is areas that are covered by streets, buildings, parking lots, and other structures that obscure or
alter the soils so that identification is not possible.
The Alderwood soil in this unit is used mainly for parks, building sites, lawns, gardens, and woodland.
The main limitations of the Alderwood soil for homesites and septic tank absorption fields are the depth to the
hardpan and the seasonal perched water table. Onsite waste disposal systems often fail or do not function
properly during periods of high rainfall. Drainage is needed if buildings with basements and crawl spaces are
constructed. Topsoil need to be stockpiled during site preparation and subsequently used to cover the
exposed material. Additions of fertilizer and peat are desirable prior to seeding grass for lawns.
This map unit is in capability subclass IVe.
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H. OPERATION AND MAINTENANCE GUIDELINES:
These guidelines are intended to provide operation and maintenance instructions for the project's storm
drainage control facilities. The owner is responsible for maintenance of storm drainage facilities within
the property (private property owner system); the owner is not responsible for maintenance within the
public right-of-way (City system).
Private Property Owners: Private property owners are responsible for properly maintaining the stormwater
infrastructure on their property to ensure it operates as designed. The City has developed an inspection
program to ensure private property owners are properly maintaining their stormwater systems.
City System: City crews perform maintenance activities on the entire storm drainage system, including
inspection and cleaning of catch basins, street sweeping, emergency flooding response, creek
maintenance, inspection and monitoring of private stormwater detention systems.
Operation and Maintenance Requirements for private property owner system:
This manual is not comprehensive; although it explains the intended operation of the various
components of the drainage system, and suggests a routine of inspection and maintenance, it cannot
anticipate every problem. Once a historical record of maintenance is established, it may be prudent to
alter the routine. It is recommended that maintenance records be kept, and that the records be
reviewed periodically.
Concept of Operation: The drainage design is shown and described in the site development engineering
plans and report. The approved site development plans and report should be retained by the owner and
used as a reference to identify drainage facilities outlined in this manual.
Conveyance Systems: The design objective in pipe sizing was to convey the 100 -year storm without the
water surface exceeding the ground elevation. Frequent overtopping of the pipe system in a particular
area might indicate a downstream blockage. Overtopping of the drain systems at the yard drains or
cleanouts is an indication that maintenance is required.
The following pages outline standard general maintenance criteria for the project's drainage facilities.
For additional and updated maintenance information visit the Washington State Department of
Ecology's web -site at: http://www.ecy.wa.gov/programs/wq/wghome.html
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No. 3 — Closed Detention Systems (Tanks/Vaults)
Maintenance
Defect
Conditions When Maintenance Is Needed
Results Expected
Component
When Maintenance Is
Performed
Storage Area
Plugged Air Vents
One-half of the cross section of a vent is
Vents open and
blocked at any point or the vent is damaged.
functioning.
Debris and Sediment
Accumulated sediment depth exceeds 100
All sediment and
of the diameter of the storage area for 112
debris removed from
length of storage vault or any point depth,
storage area.
exceeds I Vlo of diameter,
(ExampW 72-InCh storage tank would
require cleaning when sediment reaches
depth of 7 inches for more than 1/2 length of
tank)
Joints Between
Any openings or voids allowing material to
All joint between
Tank/Pipe Section
be transported Into facility,
tank1pipe sections
(Will require engineering analysis to
detemilne structural stability).
are sealed.
Tank Pipe Bent Out
Any part of tank/pipe is bent out of shape
Tank/pipe repaired or
of Shape
more than 10% of its design shape (Review
replaced to design,
required by engineer to determine structural
shabbily).
Vault Structure
Cracks wider than 1/2 -Inch and any
Vault replaced or
Tto
Includes Cracks In
evidence of soil particles entenng, the
design
Wall, Bottom,
structure, through the cracks, or
c
sfuct�lecIl ations and is
Damage to Frame
maintenancefinspection personnel
Ify sound
structurally
and/or Top Slab
determines that the vault is not structurally
sound.
Cracks wider than 1/2 -inch at the joint of any
No cracks more than
inlettoutlet pipe or any evidence of soil
114 -inch wide at the
particles entering the vault through the walls.
joint of the inlet/outlet
pipe.
ManholeCover
Not In Place
Cover is missing or only partially In place.
Manhole is closed.
Any open manhole requires maintenance.
Locking Mechanism
Mechanism cannot be opened by one
Mechanism opens
Not Working
maintenance person with proper tools. Bolts
with proper loots.
into frame have less than 1/2 incl, of thread
(may not apply to self-locking lids).
Cover Difficult to
One maintenance person cannot remve lid
Cover can be
Remove
after applying nonnal lifting pressure, Intent
removed and
is to keep cover from sealing off access to
reinstalled by one
maintenance.
maintenance person.
Ladder Rungs Unsafe
Ladder is unsafe due to missing rungs,
Ladder meets design
misalignment, not securely attached to
standards Allows
structure wall, rust, or cracks.
maintenance person
safe access.
Catch Bash"Catch
Basins"
I
See "Catch Basins" (No, 5).
See "Catch Basins*
I
(No. 5).
Volume V— Ritnoff Treannent BMPs — December 2014
4-36
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 15-028
Page H-2
Maplewood Drive Short Plat
April 1, 2016
No. 4 - Control Structure/Flow Restrictor
Maintenance
Defect
Condition, When Maintenance is Needed
Results Expected
Component
When Maintenance
is Performed
General
Trash and Debris
Material exceeds 25% Of Sump depth or 1
Control structure
(includes Sediment)
toot below orifice plate,
orifice is not blocked.
All trash and debris
removed,
Structural Damage
Structure is not securely attached to
Structure securely
manhole wall.
attached to wall and
outlet pipe.
Structure is not in upright position (allow tip
Structure in correct
to 10% frorn plumb),
position- —
Connections to outlet pipe are not watertight
Connections to oullet
and show signs of rust,
pipe are water tight;
structure repaired or
replaced and works
as desiogned,
Any holes --other than designed holes --in the
Structure has no
structure,
holes other than
designed holes.
Cleanout Gate
Damaged or Missing
Cleanout gate is riot watertight or is missing.
Gate is watertight
and works as
Gate cannot be moved up and down by one
Grate moves up arid
maintenance person.
down easily and is
-wa, e fgl I
Chain/rod leading to gate is missing or
Chain is in place and
damaged.
works as designed.
Gate is rusted over 50% of its surface area.
Gate is repaired or
replaced to meet
design standards.
Orifice Plate
Damaged or Missing
Control device is not working properly due to
Plate is in place and
massing, out of place, or bent orifice plate,
works as designed.
Obstructions
Any trash, debris, sediment, or vegetation
Plate is free of all
blocking the plate,
obstructions and
works as designed.
Overflow Pipe
Obstructions
Any trash or debris blocking (or having the
Pipe is free of all
potential of Nocking) the overflow pipe.
obstructions and
works as designed.
Manhole
See "Closed
See "Closed Detention Systems" (No. 3).
See "Closed
Detention Systems"
Detention Systems"
(No. 3),
(No. 3),
Catch Basin
See 'Catch Basins"Basins"
(No. 5).
1
See -Catch Basins"
(No. 5),
(No. 5).
Volume V - Runoff Ty-eannent BMPs - December 2014
4-37
RAMEngineering, Inc,
Engineering and Drainage Report
RAM No. 15-028
Page H-3
Maplewood Drive Short Plat
April 1, 2016
No. 5 — Catch Basins
Maintenance
Defect
Conditions When Maintenance is Needed
Results Expected When
Component
Maintenance Is
performed
General
Trash &
Trash or debris which is located immediately
No Trash or debris located
Debris
in front of the catch basin opening or is
Immediately in front of
blocking intetting capacity of the basin by
catch basin or on grate
more than 10%.
opening.
Trash or debris (in the basin) that exceeds 60
No trash or debris in the
rercerit of the sump depth as measured from
catch basin.
hibottom of basin to invert of the lowest
into or out of the basin, but In no case
Fipe
ess, than a, minimum of six inches clearance
from the debris surface to the invert of the
lowest pipe.
Trash or debris in any inlet or outlet pipe
Inlet and outlet pipes free
blocking more than 113 of ft height,
of trash or debris.
Dead animals or vegetation that could
No dead animals or
generate odors that could cause complaints
vegetation present within
or, dangerous gases (e,g,, methane).
the catch basin,
Sediment
Sediment (in the basin) that exceeds 60
No sediment In the catch
percent of the sump depth as measured from
basin
the bottom of basin to Invert of the lowest
rl pe Into or out of the basin, but in no case
ess than a minimum of 6 Inches clearance
from the sediment surface to the invert of the
lowest pipe.
Structure
Top slab has holes larger than 2 square
Top slab is free of holes
Damage to
inches or cracks wider than 1/4 inch
and cracks,
Frame and/or
Top Slab
(intent is to make sure no material is running
into basin).
France not sitting flush on top slab, i,e,,
Frame is sitting flush on
separation of more than 314 !rich of the frame
the riser rings or top slab
from the trap stab France not securely
and firmly attached.
attached
Fractures or
Maintenance person judges that structure is
Basin replaced or repaired
Cracks in
unsound.
to design standards.
Basin Walls/
Bottom
Grout fillet has separated or cracked Oder
Pipe is regrouted and
than 112 inch and lon?er than I root at the
secure at basin wall.
joint of ! pipe or any ewdence of
soil particles entering catch basin through
cracks,.
Settlementt
If failure of basin has created a safety,
Basin replaced or repaired
Misalignment
function, or design problem.
to design standards.
Vegetation
Vegetation growing across and blocking more
No vegetation blocking
than 10% of the basin opening.
opening to basin.
Vegetation growing in inlet/outlet pipe Joints
No vegetation or root
that is more than W inches tall and less than
growth present,
six inches apart.
Contamination
See "Detention Ponds" (No. 1).
No pollution present
and Pollution
Volume
V — Runoff Treatment BMPs — December 2014
4-38
R4M Engineering, Inc.
Engineering and Drainage Report
RAM No. 15-028
Page H-4
Maplewood Drive Short Plat
April 1, 2016
No. 5 — Catch Basins
Maintenance
Defect
Conditions When Maintenance is Needed
Results Expected When
Component
Needed
Maintenance is
General
Trash and
Trash or debris that is plugging more
performed
Catch Basin
Cover Not in
Cover is missing or only partially in place,
Catch basin cover is
Cover
Place
.................
Any open catch basin requires maintenance.
closed
Locking
Mechanism
Mechanism cannot be o ened by one
tools. Bolts
Mechanism opens with
tools.
Not working
maaitenance, person witf, proper
into Imine have less than V2 inch of thread,
proper
Cover Difficult
One maintenance person Cannot remove lid
Cover can be removed by
to Remove
after apptying normal lifting pressure.
one maintenance person.
(intent is keep cover from sealing ott access
Barrier replaced or repaired to
to maintenance,)
design standards.
Ladder
Ladder Rungs
Ladder is unsafe due to missing rungs, not
Ladder meets design
Unsafe
securely attached to basin wall,
standards and allows
misalignment, rust cracks, or sharp edges.
maintenance person safe
access,
Metal Grates
Grate opening
Grate with opening wider than 7/8 inch.
Gra, le opening meets
(it Applicable)
Unsafe
design standards.
...................
Trash and
Trash and debris that is blocking more than
Grate free of trash and
Debris
20% of grate surface inletting capacity,
debris.
Damaged or
Grate missing or broken member(s) of the
Grate Js in place and
Nit sshig'
grate.
meets design standards.
No. 6 — Debris Barriers (e.g., Trash Racks)
Maintenance
Defect
Condition When Maintenance is
Results Expected When
Components
Needed
Maintenance Is Performed
General
Trash and
Trash or debris that is plugging more
Barrier Cleared to design flow
Debris
than 20% of the openings in the barrier.
capacity.
Metal
Damaged/
Bars are bent out of Shape more than 3
Bars in place with no bends more
Missing
inches,
than 314 inch.
Bars..Bars
are missing or entire barrier
Bars in place according to design.
missing_
Bars are loose and rust is causing 50%
Barrier replaced or repaired to
deterioration to any part of barrier.
design standards.
Inlet/Outlet
Debris barrier missing or not attached to
Barrier firmly attached to pipe
I
Pipe
pipe
I
Volume V— Runoff Treatment BMPs — December 2014
4-39
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 15-028
Page H-5
Maplewood Drive Short Plat
April 1, 2016
Edmonds City Code and Community Development Coder
18.30.090 Inspection and maintenance roles and responsibilities.
Proper inspection and maintenance of storm water facilities (including construction BMPs) is essential for the
protection of the city's MS4 and the environment. Inspection and maintenance of all storm water facilities shall be
required in accordance with the storm water supplement.
A. Storm Water Maintenance and Inspection Standards. Storm water facilities shall be inspected and maintained
per the requirements of the storm water supplement. For systems which do not have a maintenance standard, the
owner shall develop a standard based on guidelines from the manufacturer, designer, or a registered professional
engineer and submit the standards to the director for approval.
B. Ownership. Storm water facilities are either privately or publicly owned and maintained. All storm water
facilities that serve commercial and industrial sites are private. Storm drainage facilities or controls that are
privately owned by a homeowner's association or similar organization also are private.
C. Maintenance and Inspection. All privately owned storm drainage facilities or controls shall be maintained by the
owner, or the homeowner or owner association ("owner") if one is established as part of a residential or
commercial development. All private storm drainage facilities shall be regularly inspected to ensure proper
operation and shall monitor the facility or control as required or as set forth in the storm water supplement. The
owner shall maintain records of inspection and maintenance, disposal receipts, and monitoring results. The
records shall catalog the action taken, the person who took it, the date said action was taken, how it was done,
results of any monitoring effort, and any problems encountered or follow-up actions required. The records shall be
made available to the city upon request. The owner shall maintain a copy of the Stormwater Operations and
Maintenance Manual (if required) on site, and shall make reference to such document in real property records
filed with Snohomish County, so others who acquire real property served by the privately owned storm drainage
facilities or controls are notified of their obligation to maintain such facilities or controls.
D. When an inspection identifies an exceedance of the maintenance standard, maintenance shall be performed:
1. Within one year for wet pool facilities and retention/detention facilities;
2. Within six months for typical maintenance;
3. Within nine months for maintenance requiring revegetation; and
4. Within two years for maintenance that requires capital construction of less than $25,000.
E. Disposal of Waste from Maintenance Activities. Disposal of waste from maintenance activities shall be
conducted in accordance with the Minimum Functional Standards for Solid Waste Handling, Chapter 173-304 WAC,
guidelines for disposal of waste materials from storm water maintenance activities, and where appropriate, the
Dangerous Waste Regulations, Chapter 173-303 WAC.
F. City Inspection. The regular inspection of privately owned storm drainage facilities or controls is essential to
enable the city to evaluate the proper operation of the city's MS4 and the environment. The city shall have access
to private storm water facilities for inspection to ensure they are properly operated and maintained in accordance
with ECC 7.200.100. The city may offer an incentive program to owners to encourage the proper maintenance of
private storm drainage facilities. [Ord. 3792 § 1, 2010].
R.4MEngineering, Inc..
Engineering and Drainage Report
RAM No. 15-028
Page H-6
Maplewood Drive Short Plat
April 1, 2016