Drainage Report.pdfIFIECEIVED
Select Homes 7th Ave South OCT 19 2017
2-Lot Short Plat BUILDING
612 7t" Avenue S.
Edmonds, WA 98020
CITY COPY
Storm Drainage Report
Prepared for:
Select Homes
Date: February 15, 2017
Update: October 17, 2017
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Prepared by: Rob Long, PE
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RAM Engineering, nc.
16531 13t" Ave W, Suite A108, Lynnwood WA 98037
(425) 678-6960 RAMengineeringinc.com Job No. 16-033
Select Homes 7th Ave South 2-Lot Short Plat
612 7th Avenue S.
Edmonds, WA 98020
Introduction: This summary report provides site design information for a single family 2-lot short
plat by Select Homes. This report includes storm drainage analysis to support permit review and
approval. The property is located on the west side of 7t" Ave S W and south of Cedar St, in the
northwest 1/4 of Section 25, T 27 N, R 3 E, W.M.
Site Address: 612 7th Avenue S. Applicant: Select Homes
Edmonds, WA 98020 16513 13th Ave W, Suite A108,
Lynnwood WA 98037
Tax Parcel Number: 270325-002-035-00 Contact: Kayla Clark
(425) 742-6044
TABLE OF CONTENTS
SECTION
PAGES
A. Project Summary ............................................................................................................................... 3
B. Parcel (Vicinity) Map.......................................................................................................................... 1
C. Site Plan............................................................................................................................................. 1
D. Aerial Photo....................................................................................................................................... 1
E. Stormwater Control System Summary ............................................................................................... 1
F. Drainage Basin Description and Maps............................................................................................... 3
G. Grading and Erosion Control Summary (SWPPP Evaluation)............................................................ 2
H. Operation and Maintenance Guidelines............................................................................................ 5
I. Geotechnical Engineering Report...................................................................................................... 1
RAMEngineering, Inc Select Homes 7th Ave South
Engineering and Drainage Report 2-Lot Short Plat
RAM No. 16-033 October 17, 2017
A. PROJECT SUMMARY:
This report provides engineering information for the proposed construction of a 2-lot single family residence
short plat; the project is located on the west side of 7th Ave S and south of Cedar St (216 7th Ave S) in the
City of Edmonds. The applicant, Select Homes proposes to remove the existing residence and construct two
single family residence on the site. This report provides the evaluation for the proposed 2-lot short plat.
Existing Conditions. The total site consists of about 17,911 sf (0.411 acres) and is currently occupied by an
existing single family residence with a large access drive off 7th Ave S. The existing house is surrounded by
open grass lawn and landscape areas. The site is surrounded by single family residences to the north, west,
and south; and 7th Ave S to the south (see attached aerial photo- section D).
The site is located at the top of a small knoll that generally slopes off in all directions. A majority of the site's
drainage runoff would sheet flow southwesterly, westerly and northwesterly direction. No stream or
wetlands were discovered on or immediately adjacent to the site; Shellabarger Creek is located about 380
feet south of 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 the construction two single residence and associated
driveway and utilities. Both lots will utilize separate private driveways off of 71h Ave S for access. All existing
structures and impervious surface onsite will be removed/replaced with the site development; landscaping
and grass lawn around the new residence will stabilize the site upon building construction. New
infrastructure improvements include a stormwater conveyance and separate infiltration trenches for each
lot; water; sewer; power; and communications. Two individual lot infiltration trench systems will be
designed and sized to meet compliance with the LID performance standard of the Edmonds Community
Development Code (ECDC). 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 BMPT5.13: Post -Construction
Soil Quality and Depth). Due to the fact, the pollution generating driveway area are less than 5,000 sf (+/-
2,850 sf) no water quality treatment system will be provided. A full overview of the proposed storm
drainage control facilities, offsite/downstream analysis and grading and erosion control measures are
discussed in the following sections of this report.
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page A-1
Summary of Minimum Requirements for Category 2 Project:
5.1 Minimum Requirement #1 — Preparation of Stormwater Site Plan. The proposed site development
consists of disturbing about 0.411 acres of land and creating/replacing about 10,000 sf (Lot 1=4,400 sf and
Lot 2 = 5,600 sf) of hard surface area. Thus, the project is classified as a Category 2 project per the City's
classification system. The civil site development plans and this report have been prepared to address the
projects impacts.
5.2 Minimum Requirement #2 — Construction Stormwater Pollution Prevention. A construction
Stormwater Pollution Prevention Plan (SWPPP) has be incorporated into the site development plans. A
summary of the site's erosion control measures that evaluates the typical 13 elements of a SWPPP are
included in section G. The total site disturbance area of the project is less than one acre, thus a formal
Notice of Intent application for NPDES coverage will not be made to the Department of Ecology. The short -
plat construction grading quantities are estimated to be 100 CY of cut and 100 CY of fill.
5.3 Minimum Requirement #3 — Source Control of Pollution. Specific source controls are not required for
single family residential sites. General requirements for these sites include preventing the discharge of
pollutants to the City's storm drainage system per Edmonds City Code Chapter 7.200 (Illicit Discharges). This
includes common household items such as pesticides, herbicides, fertilizers, detergents and fluids from
vehicle maintenance.
Single family residences shall incorporate DOE's S411 BMPs for landscape and lawn vegetation
management. Lawn and vegetation management can include control of objectionable weeds, insects, mold,
bacteria, and other pests with pesticides. Examples include weed control on golf course lawns, access roads,
and utility corridors and during landscaping; sap stain and insect control on lumber and logs; rooftop moss
removal; killing nuisance rodents; fungicide application to patio decks, and residential lawn/plant care. It is
possible to release toxic pesticides such as pentachlorophenol, carbamates, and organometallics to the
environment by leaching and dripping from treated parts, container leaks, product misuse, and outside
storage of pesticide contaminated materials and equipment. Poor management of the vegetation and poor
application of pesticides or fertilizers can cause appreciable stormwater contamination.
5.4 Minimum Requirement #4 — Preservation of Natural Drainage Systems and Outfalls. The site is located
at the top of a local knoll that slopes in the southwest, west and northwesterly directions. There are no
concentrated flows or existing defined conveyance systems downgradient of the site; any site runoff leaves
the site as sheet -flow. The frontage improvements along 7th Ave S eliminates any upstream run-on from
properties east of the site. The proposed development will install infiltration trenches and amend the
disturbed site soils; thus, reducing the site developments runoff to a de minimis amount. Each infiltration
system will have a catchbasin near the edge of 7th Ave S that will provide a safe and certain overflow route
to the City's storm drainage system within 7th Ave S. The City's storm drainage system within 7th Ave S along
the project's frontage is within the project's Shellabarger watershed, thus maintaining the natural outfall
watershed basin. The site is located within the Shellabarger watershed basin and eventually discharge to
the Puget Sound (via Shellabarger Creek) per the City of Edmonds maps (see section F).
5.5 Minimum Requirement #5 — Onsite Stormwater Management. The developed site conditions include
new/replaced hard surface for the roof tops, driveways and walkway/patio areas for the proposed
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page A-2
residences. All rooftop and exterior area collection drains shall convey stormwater run-off to the on -site
infiltration trench systems on each lot. Two individual lot infiltration trench systems will be designed and
sized to meet compliance with the LID performance standard (MR #5) of the Edmonds Community
Development Code (ECDC). Additionally, 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 civil site development plans and section E for additional sizing
calculations and construction details.
5.6 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 2,850 sf
pollution generation hard surfaces (driveways); most the site's hard surface is rooftop and walkway/patio
areas (non -pollution generation surfaces). Thus, no basic or enhanced water quality treatment system is
required. The site's stormwater control system will include a sump and a floatable tee that will provide
some water quality and oil/water separation of the collected runoff.
5.7 Minimum Requirement #7 —Flow Control. Two infiltration trenches (one on each lot) will provide
flow control of the site's stormwater runoff. The infiltration trenches shall be designed at building permit
application for each individual lot and meet the flow control standards of a Category 2 project in a creek or
lake basin and meet full flow control (due to the fact the project proposed 10,000 sf of hard surface area).
Each lot stormwater infiltration system shall be designed to fully mitigate the increased hard surfaces and
be in full compliance with the LID Standard and full flow control (match flow durations between 8 percent
of the 2-year flow through the full 50-year flow). The final design of each system will be completed during
the building permit review of each individual lot; a summary overview of the proposed storm
5.8 Minimum Requirement #8— Wetland Protection. No wetlands are known to exist on or adjacent to the
site.
5.9 Minimum Requirement#9—Operation and Maintenance. An operation and maintenance summary is
provided in section H.
RAMEngineering, Inc
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page A-3
B. PARCEL (VICINITY) MAP
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Engineering and Drainage Report
RAM No. 16-033
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2-Lot Short Plat
October 17, 2017
Page B-1
C. SITE PLAN
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RAM Engineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page C-1
D. AERIAL PHOTO (City of Edmonds GIS, 2015 photo)
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page D-1
E. STORMWATER CONTROL SYSTEM SUMMARY AND CALCULATIONS:
The project proposes to create and/or replace 10,000 sf of hard surface with the complete site
development (Lot 1 =4,400 sf and Lot 2 = 5,600 sf). To mitigate the development of the site, individual lot
stormwater infiltration trench systems will be installed to control the drainage runoff (flow control). The
project applicant has elected to meet the LID Performance Standard to comply with ECDC 18.30.060.D.b
(ii) and (iii), stormwater discharges shall match developed discharge durations to pre -developed durations
for the range of pre -developed discharge rates from 8 percent of the 2-year peak flow to 50 percent of the
2-year peak flow from the project site. Additionally, the project proposes to add/replace 10,000 sf of hard
surface and thus subject to also meet Minimum Requirement No. 7 and match flow durations between 8
percent of the 2-year flow through the full 50-year flow.
The following is a summary of the proposed new/replaced hard surface areas:
Hard Surface Summary:
Lot 1 (House 3,880 + Driveway 1,570 + Sidewalk/Patio 150) = 5,600 sf
Lot 2 (House 3,000 + Driveway 1,250 + Sidewalk/Patio 150) = 4,400 sf
Lot Impervious = 10,000 sf (0.230 ac)
A site specific geotechnical evaluation was made to assess the use of infiltration and LID measures onsite.
The evaluation determined infiltration is feasible onsite and recommends a long-term infiltration design
rate of 4.0 in/hr.
The infiltration trenches will be located at the easterly end of each lots access driveway. As stated above
the infiltration trenches will be designed for the total hard surface for the complete build out of the site;
the total hard surface created will be 10,000 sf (0.230 ac). Final design sizing and calculations of each
individual stormwater detention system will be completed at the building permit stage for each lot.
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page E-1
F. DRAINAGE BASIN DESCRIPTION:
The site is located within the City of Edmonds Shellabarger watershed basin. The Shellabarger basin is a
centralized urban basin that collects stormwater runoff from primarily residential areas in the City Edmonds
and ultimately discharges flows westerly to Puget Sound via the Shellabarger Creek (see attached watershed
map).
The proposed stormwater infiltration trench systems are designed to infiltrate most the site stormwater
flows into the underlying outwash soils. Flows that don't infiltrate into the soils will sheet flow off in a
southwesterly, westerly or northwesterly direction; all within the Shellabarger watershed basin. The
infiltration systems include a collection catch basin that will overflow into 7th Ave S in the event of an
extraordinary rainfall event. The existing storm drainage systems in 7th Ave S directs the flows north and
northwesterly to Dayton St and then back south again along 3`d Ave S and eventually entering Shellabarger
Creek between Walnut St and Howell Way. Shellabarger Creek continues in a westerly direction and
eventually discharges into the Puget Sound about one mile west of the site
A majority of the downstream conveyance system within a % mile of the site consists of a man-made pipe
and catch basin system; some site runoff flows south/southwesterly and enters the Shellabarger Creek
channel southwest of the site. No apparent flooding or system inadequacies within a % mile downstream
of the site were discovered during site visits or research of the downstream system.
Due to the fact, the site sits atop a local knoll and the improvements of 7th Ave S the site does not receive
any upstream run-on.
See attached watershed and downstream drainage facility map for the local downstream path.
RAMEngineering, Inc
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page F-1
F-2. Watershed Basin Map
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R.4MEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
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Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page F-2
F-3. Downstream Drainage Facility Map (City of Edmonds GIS)
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Engineering and Drainage Report
RAM No. 16-033
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Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page F-3
G. GRADING and EROSION CONTROL SUMMARY:
The project will require grading to construct the proposed buildings and utilities (including the stormwater
infiltration trench 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 project's site specific geotechnical engineering study by Earth Solutions NW,
LLC the on -site soils consist of loose to medium dense poorly graded sand (Unified Soil Classification System:
SP) outwash deposits. Overall soil relative density increases with depth. The subject site is underlain by
outwash (Ova) deposits; Alderwood/Everett series soils. Alderwood/Everett soils are well drained soil and
are categorized as a hydrologic group A/B soil. Earth Solutions NW, LLC. Recommends a long term design
infiltration rate of 4.0 inches per hour. Full soils description is included in the project's site specific
geotechnical engineering study by Earth Solutions NW, LLC.
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.
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 underlying outwash soils no flow control system (ie: temporary
pond) is proposed. During construction silt fencing will provide attenuation of site runoff and
upon project completion and stabilization (established lawns and landscape of exposed soils),
the infiltration storm system 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.
R.4MEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page G-1
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
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:
L 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: During construction the proposed infiltration trench
systems areas shall be protected from sediment accumulation, sediment -laden runoff and
soils, and compaction from construction equipment. Soils restoration and/or replacement
may be needed if soils are compacted or contaminated with sediment.
Grading Quantity Approximation: 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: 100 CY
Fill: 100 CY
Conclusion: The final site development construction plans 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.
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page G-2
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 large storm events 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 catch -basins is an
indication that maintenance is required.
Stormwater Infiltration Trench System. The private onsite infiltration trench systems consist of excavated
trench filled with drain rock per the City Standard detail (Handout #E72 B, Figure A-3). The infiltration
trench system has been designed to infiltrate most storm event; if an extraordinary event was to occur or
multiple back to back large storm events occurred the upstream catch -basins may overtop and overflow
into the street system. If regular overtopping of the catchbasin is experienced the system shall be
thoroughly cleaned and inspected. Over a period of time siltation of the infiltration bed can occur
(especially if the system and upstream catchbasin are not inspected and cleaned regularly) and
replacement of the rock in the infiltration system may be required.
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page H-1
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.htmI
MAINTENANCE REQUIREMENTS
ECDC Section 18.30.090 requires privately -owned
stormwater management facilities, such as LID
BMPs be properly maintained. The owner of the
property is the responsible party for such
maintenance. The system must be kept in good
working order. The entire system should be
inspected once per year. An improperly maintained
BMP may cause private property or street Flooding.
Contact the City Engineering Division for
maintenance information.
The City may make periodic inspections of BMPs to
ensure they are operating properly. ECDC Section
18.30.100 contains the enforcement provisions the
City can use to ensure the system is properly
maintained.
General Infiltration Maintenance Criteria
Provision should be made for regular and perpetual maintenance of the infiltration basin/trench, including
replacement and/or reconstruction of the any media that are relied upon for treatment purposes.
Maintenance should be conducted when water remains in the basin or trench for more than 24 hours after
the end of a rainfall event, or when overflows occur more frequently than planned. For example, off-line
infiltration facilities should not have any overflows. Infiltration facilities designed to completely infiltrate
all flows to meet flow control standards should not overflow.
Removal of accumulated debris/sediment in the basin/trench should be conducted every 6 months or as
needed to prevent clogging, or when water remains in the pond for greater than 24 hours after the end of a
rainfall event.
R.4MEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page H-2
No. 2 — Infiltration
Maintenance
Defect
Conditions When Maintenance Is
Results Expected When
Component
Needed
Maintenance Is
Performed
General
Trash & Debris
See "Detention Ponds" (No 1)
See "Detention Ponds-
(No- 1).
Poisonous/Noxious
See "Detention Ponds" (No 1)
See "Detention Ponds"
Vegetation
(No. 1).
Contaminants and
See 'Detention Ponds- (No 1)
See "Detention Ponds"
Pollution
(No. 1).
Rodent Boles
See "Detention Ponds- (No 1)
See "Detention Ponds -
(No. 1)
Storage Area
Sediment
Water ponding in infiltration pond after
Sediment is removed
rainfall ceases and appropriate time
and/or facility is cleaned
allowed for infiltration Treatment basins
so that infiltration system
should infiltrate Water Quality Design Stomn
•.-,orks according to
Volume .within 48 hours. and empty within
design
24 hours after cessation of most rain
events.
(A percolation test pit or test of facility
indicates facility is only working at 9y% of
its designed capabilities Test every 2 to 5
years If two inches or more sediment is
present, remove)
Filter Bags (if
Filled with
Sediment and debris fill bag more than 12
Filter bag is replaced or
applicable)
Sediment and
full
system is redesigned.
Debris
Rock Filters
Sediment and
By casual inspection, little or no v:ater flows
Gravel in rock filter is
Debris
through filter during heavy rain storms
replaced.
Side Slopes of
Erosion
See "Detention Ponds" (No. 1).
See 'Detention Ponds"
Pond
(No. 1).
Emerggent
Tree Growth
See "Detention Ponds" (No. 1).
See "Detention Ponds'
Overtfov: pillway
(No. 1).
and Berms over 4
feet in height.
Piping
See "Detention Ponds" (No. 1).
See "Detention Ponds"
(No. 1).
Emergency
Rock Missing
See 'Detention Ponds' (No. 1).
See "Detention Ponds"
Overflo.v Spillway
(No. 1).
Erosion
See "Detention Ponds" (No. 1).
See "Detention Ponds'
(No- 1)
Pre -settling
Facility or sump
6' or designed sediment trap depth of
Sediment is removed.
Ponds and Vaults
filled with Sediment
sediment.
and/or debris
Volute V - Rrrr;off Treatment B.t1Ps - Decentb e,• 2014
4-35
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page H-3
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 inletting 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
percent of the sump depth as measured from
catch basin.
the bottom of basin to invert of the lowest
pipe into or out of the basin, but in no case
less 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 1/3 of its 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
pipe into or out of the basin, but in no case
less 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 114 inch
and cracks
Frame and/or
Top Slab
(Intent is to make sure no material is running
into basin).
Frame not sitting flush on top slab, i.e.,
Frame is sitting flush on
separation of more than 3/4 inch of the frame
the riser rings or top slab
from the top slab. Frame 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 wider
Pipe is regrouted and
than 1/2 inch and longer than 1 foot at the
secure at basin wall.
joint of any inlet/outlet pipe or any evidence of
soil particles entering catch basin through
cracks.
Settlement/
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 six inches tall and less than
growth present.
sic inches apart.
Contamination
See "Detention Ponds' (No. 1).
No pollution present.
and Pollution
Volume V— Runoff Treatment BMPs— December 2014
4-38
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page H-4
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 inletting 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
percent of the sump depth as measured from
catch basin.
the bottom of basin to invert of the lowest
pipe into or out of the basin, but in no case
less 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 1/3 of its 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
pipe into or out of the basin, but in no case
less 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 114 inch
and cracks.
Frame and/or
Top Slab
(intent is to make sure no material is running
into basin).
Frame not sitting flush on top slab, i.e.,
Frame is sitting flush on
separation of more than 3/4 inch of the frame
the riser rings or top slab
from the top slab. Frame 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 wider
Pipe is regrouted and
than 1/2 inch and longer than 1 foot at the
secure at basin wall.
joint of any inlet/outlet pipe or any evidence of
soil particles entering catch basin through
cracks.
Settlement/
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 six 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
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page H-5
I. GEOTECHNICAL ENGINEERING REPORT
Geotechnical Engineering Study.
Prepared by: Earth Solutions NW, LLC
Revision Date: June 6, 2017
Pages: 58
(attached under separate cover)
RAMEngineering, Inc.
Engineering and Drainage Report
RAM No. 16-033
Select Homes 7th Ave South
2-Lot Short Plat
October 17, 2017
Page 1-1