HomeMy WebLinkAboutPermit File BLD-2021-0668 3010 Georgia Place (3) tift'o`E1ERR1C / 2
Y o ��FWAS �•� ' 1 Storm Water Drainage Report
.f, w imum Requirements 1 through 9
A' , ENGINEERING DEPARTMENT
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Official Use '°`I '. (Information to Inspectors)
Required Storm Water Facility and other related requirements:
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Project Address: _3010 Georgia Place Submittal Date: .) .o9.Zol 1
Parcel Number: _ P10895 Revision Number: cS
Permit Number: _BLD-2021-0 Reviewer:
Acceptance Date C A): c 5 i3-2-c2_I
FRONT OF REPORT:
Submittal Checklist: (All items listed below are required for a complete submittal)
o Cover Sheet (Preparer to Provide): Project title, Location, Revision dates, Engineer's Stamp
o TAB 1: Minimum Requirement#1 - Preparation of Stormwater Site Plans
o TAB 2: Minimum Requirement#2 - Construction Stormwater Pollution Prevention (SWPP)
o TAB 3: Minimum Requirement#3- Source Control of Pollution
o TAB 4: Minimum Requirement#4- Preservation of Natural Drainage Systems and Outfalls
o TAB 5: Minimum Requirement#5-On-site Stormwater Managements
o TAB 6: Minimum Requirement#6- Runoff Treatment
o TAB 7: Minimum Requirement#7- Flow Control
o TAB 8: Minimum Requirement#8-Wetland Protection
o TAB 9: Minimum Requirement#9-Operation and Maintenance
o APPENDIX 1 - Survey performed by a Professional Land Surveyor
o APPENDIX 2 - Flow Control Exempt
o APPENDIX 3 - Model Soil Management Plan for BMP T5.13
o APPENDIX 4 - Determining Construction Site Sediment Damage Potential (Appendix 7)
o APPENDIX 5 - Site Plan with all applicable information (Minimum Size 11x17 - 30 scale)
o APPENDIX 6 - Documented Site Photos (North, South, East and West)
o APPENDIX 7 - Drainage BMP Facility Maintenance Covenant, if applicable. To be recorded prior to the
Temporary Certificate of Occupancy, Certificate of Occupancy or Final Acceptance. FLOW CONTROL
EXEMPT
Stormwater Management Requirements:
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
o Refer to the 2012\14 Department of Ecology Manual, as amended in 2014 for further required
information.
o See also, City of Anacortes Municipal Code 19.76 for additional information
o See also, current Engineering Development Standards, Chapter 2- Storm Drainage for additional
information.
Protect Description and Summary:
Summary Table
Existing Proposed
Development Type Single Family Home
Number of Lots 1
Lot Acreage in SF 21,344 SF
Soil Type(s) Coveland Gravely Loam HG C/D
Site Sediment Transport Scor- Hig Low) High 190
Depth to Ground Water Table (Fee and Inches) N/A Flow Control Exempt
(See completed Soils Analysis(Volume 1, Chapter 3.1.1)
Infiltration Rate during Rainy Season (Inch\Per Hour) N/A Flow Control Exempt
Impervious Surface (on-site) 0 sf 6,813 sf
Impervious Surface (off-site) 0 0
New and Replaced Hard Surface Total (SF) 0 6,813 sf
Lot Coverage (Percentage) 0 32%
BMP (Required Minimum Requirement 5) BMP T5.13 Post Construction Soils
- -R Pe
Water Quality Method (Minimum Requirement 6) None Exempt
Water Quantity Method (Minimum Requirement 7) N/A Exempt
Existing Site Conditions Summary:
(Additionally, provide information on previous permits, if any, like Grade and Fill, Clear and Grade, topography,
vegetation, drainage, Critical Areas adjacent to the site and how it may affect this project if soils are disturbed,
Soils Type (Included in Soils Analysis Report), Erosion Problem Areas, Construction PhasinglSequence)
The existing site is undeveloped and covered in blackberry and brush. The site slopes at and average
of 30% with some steeper slopes from the top to the bottom with a flat area in the northeast corner of
the site. An existing 12" drainage pipe extends into the site in the northeast corner and collects water
from a short swale and water from neighboring properties to the west.
The north 30 feet of the property is within an ingress, egress and utility easement. It is graded but not
used to often. Sanitary sewer lies within the easement but the storm lies just to the south onto this
property.
Single family homes lie to the east and west of this site as well as to the north. Georgia Place lies to
the south at the top of the property.
Erosion could be significant due to the steep slope of the site.
Developed Conditions Summary:
(Additionally, to be shown on the site plan. Identify cut and fill areas, proposed slopes of all hard
surfaces, proposed contours)
The proposal is a 3,525 square foot house along will patios, retaining walls and driveway to Georgia
Place. There will not be significant grading out side the house footprint and retaining walls. The
ground out side these areas will maintain the existing slope. All top soil and cuts for the house and
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
base of the retaining walls. Fill within the retaining walls. The total hard surface will be 6,813 square
feet.
Drainage Basin (2007 Storm Comp Plan —City website\publicworks\engineering\comprehensive plans):
What Drainage Basin are you in? G9 Identify any downstream drainage issues (Storm Comp Plan: No. If so,
describe:
The City Stormwater Management Plan identifies this site in Basin G9 including the area east of
Georgia Place to about Baltimore and north of the forest lands. This basin is small and discharges to
Guemes Channel at Dakota Avenue. The outfall system was replace from Oakes Avenue to the outfall.
No current capacity issues are known for the downstream pipe.
Complete the Applicability Requirements —Flow Chart (Figure 1-2.4.1 Attached, Figure 1-2.4.2 Attached
and Figure 1-2.5.1 Attached)
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
Figure 1-2.4.1 Flow Chart for Determining Requirements for New
Development
Start Here
Does the site have 35% Yes See Redevelopment Minimum
or more of existing t Requirements and Flow Chart
impervious coverage? (Figure 1-2.4.2).
No
Does the project convert
acres or more of vegetation to
Does the project result in lawn or landscaped areas, or
5,000 square feet, or No convert 2.5 acres or more of
greater, of new plus to native vegetation to pasture?
replaced hard surface
area?
\NO
Yes
Yes
Does the project result in 2,000
T square feet, or greater, of new plus
All Minimum Requirements replaced hard surface area?
apply to the new and replaced
hard surfaces and converted No
vegetation areas. Yes
Does the project have land
Minimum Requirements#1 disturbing activities of 7,000
through #5 apply to the new square feet or greater?
YeS
and replaced hard surfaces
and the land disturbed. No
V
Minimum Requirement#2
applies.
MAIMFigure I-2.4.1
_ Flow Chart for Determining Requirements for
' M New Development
DEPARTMENT OF Revised June 2015
ECOLOGY Please see http.//www.ecy.wa.gov/copyright.htm/for copyright notice including permissions,
State of Washington limitation of liability,and disclaimer.
2014 Stormwater Management Manual for Western Washington
Volume I- Chapter 2 - Page 37
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
Figure_ Q- . .1 Flew Chart for Daterminiing LOD MR #5 RequireiMeintS
Does the project discharge to Flow Control Exempt Waters(per Minimum Requirement (MR)#7)?
,Yes
REQUIRED: Implement the following BMPs No
where feasible:
• BMP T5.13 Post-Construction Soil Quality V Na(the
and Depth Does the project project
11. BMP T5.10A, B, or C: Downspout Full trigger only MRs#1 - triggered
Infiltration. Downspout Dispersion #5?(Per Figure 3.2 or only MR#2)
Systems, or Perforated Stub-out Figure 3,3 in Appendix No additional
Connections 1 of the 2013-2015 requirements
• BMP T5.11 or T5.12:Concentrated Flow WvVA Phase II Permit
Dispersion or Sheet Flow Dispersion &Phase I Permit).
NOT REQUIRED:Achievement of the LID Na(the project triggered
Performance Standard.Applying the other Yes only MRs#1 -#O)
EMPs in List#1 or List#2. V
Is the project inside the UGA?
Did the project developer choose to meet
the LID Performance Standard? Yes v No
is the project on a parcel
p Na of 5 acres or larger?
REQUIRED: For each Did the project developer No
Yes
surface, consider the choose to meet the LID T
BMPs in the order Performance Standard? REQUIRED: Meet the LID
listed in List#1 for that Performance Standard through
type of surface. Use Yes the use off BMP(s)in the
the first BMP that is 2014 SWVIMVWV except for
considered feasible. Yes No Rain Gardens(the use of
Bioretention is acceptable).
NOT REQUIRED:
Achievement of the LID If The project can't meet the
Performance Standard. REQUIRED: For each LID Performance Standard, it
surface, consider the BMPs must seek and be granted an
REQUIRED:Meet the LID Performance in the order listed in List#2 exception/variance.
Standard through the use of any BMP(s)in for that type of surface. Use
the 2014 SV'NIMVWVexcept for Rain Gardens the first BMP that is REQUIRED: Apply BMP T5.13
(the use of bioretention is acceptable). considered feasible. Post-Construction Soil Quality
and Depth.
REQUIRED for Projects Triggering MR#1-9': NOT REQUIRED:
Apply BMP T5.13 Post Constn_iction Soil Achievement of the LID NOT REQUIRED:Applying the
Quality and Depth,
Performance Standard. BMPs in List#1 or List#2.
NOT REQUIRED:Applying the BMPs in List
#1 or List#2. *Recommended byEcologyfor projects triggering MRs#1 -#5.
Figure 1-2.5. 1
Flow Chart for Determining LID MR #5
'VW" Requirements
DEPARTMENT OF
Revised June 2015
ECOLOGY Please see hUtpiAvtww.ecy. ,a.gov/copyright.hfm(for copyright notice including permissions,
State of Washington limitation of liability, and disclaimer_
2014 Stonrwater Management Manual for Western Washington
Volume 1- Chapter 2 - Page 60
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 1 (MINIMUM REQUIREMENT#1)
• 1-2.5.1 Minimum Requirement#1 — Prepare a Stormwater Site Plan
- 1.3— Preparation of a Stormwater Site Plan
- 1.3.1 —Stormwater Site Plans: Step-by-Step
Note: The level of detail needed for each step depends upon the project size. Provide a narrative
description of each step.
1-3.1.1 Step 1 - Site Analysis: Collect and Analyze Information on Existing Conditions
Site analysis shall be submitted as part of the Existing Conditions Summary above. Part of the
information in this step should be used to help prepare the Construction Stormwater Pollution
Prevention Plan. Purpose of the Site Analysis is to provide for a Low Impact Development site
design that is intended to compliment the predeveloped conditions of the site.
The site is a steep slope with an average grade of 30% from Georgia Place to the toe of the
slope at the 12" storm inlet pipe. No soils report was completed due to the steep slopes
precluding any reasonable infiltration system.
1-3.1.2 Step 2 - Prepare Preliminary Development Layout
Based upon the analysis of existing site conditions, locate the buildings, roads, parking lots,
landscaping features, on-site stormwater management BMP's, and preliminary location of
stormwater treatment and retention/detention facilities for the proposed development.
BMP's will include covering soil stock piles and protecting down slope properties with silt
fencing. A quarry spall or crushed rock construction entrance will be shown at the
Georgia Place entrance. Grading will only be in the area of the house foundation and
retaining wall areas and exposed to erosion until the foundation is complete and
backfilled.
1-3.1.3 Step 3 - Perform Off-site Analysis (at Local Agency's Option): Use additional Sheets, if necessary,
Ecology recommends that local governments require an off-site analysis for projects that add
5,000 SF or more of new hard surfaces, or convert% acres of vegetation to lawn or landscape
areas, or convert 2.5 acres of forested area to pasture.
Off-site analysis extends to mile downstream of the project site.
The storm inlet pipe a the bottom of the site drains to the northeast and down the
unimproved Erie Avenue to the north. A portion of the system is an open ditch down Eire
Avenue to West 3rd Street where it enters a 12" storm pipe and continues flowing north
before discharging to an open ditch from West 2nd Street to Oakes Avenue. Then east
down Oakes Avenue for one block (300 feet) before entering the storm system and Dakota
Avenue and flowing north 740 feet before entering Guemes Channal. The distance from
the site to Oakes Avenue is 900 lineal feet or a total of 2,040 feet to Guemes Channel a flow
exempt body of water.
This site is FLOW CONTROL EXEMPT.
1-3.1.4 - Determine Applicable Minimum Requirements
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
Establish project size thresholds for the application of Minimum Requirements to new
development and redevelopment projects. Figures 2.4.1 (Attached) and 2.4.2 (Attached)
provide the same thresholds in a flow chart format. Based on the preliminary layout, determine
whether Minimum Requirements#1 through #5 apply to the project; or, whether Minimum
Requirements#1 through #9 apply.
Please note, that Minimum Requirement#1 through #5 may trigger additional Minimum
Requirements, such as Flow Control.
We are adding or replacing 6,813 square feet within the lot with roof, patios and driveway
which triggers minimum requirements 1 through 9.
1-3.1.5 Step 5 - Prepare a Permanent Stormwater Control Plan
(Refer to this section of the Ecology Manual for requirements.)
A storm water plan is provided in the developed site plan in Appendix 5. The drainage
system will be described in minimum requirement#5 below. The options for a perforated
stub out are discussed in Minimum Requirement#5 below.
1-3.1.6 Step 6 - Prepare a Construction Stormwater Pollution Prevention Plan (MR#2—13
Elements)
Refer to Chapter 11-3—Planning for a detailed description of each element. See also attached
Tables 4.1.1 (Source Control BMP's by SWPPP Element) and Table 4.2.1 (Runoff Conveyance
and Treatment BMP's by SWPPP Element).
See 13 Elements of a SWPPP.
1-3.1.7 Step 7 - Complete the stormwater site plan
The Stormwater Site Plan encompasses the entire submittal to the Local Agency with drainage
review authority. Refer to this section of the Manual for further clarification of each item and
what is required. See below:
• Project Overview
• Existing Conditions Summary
• Off-site Analysis Report
• Permanent Stormwater Control Plan
• Construction Stormwater Pollution Prevention Plan
• Special Reports and Studies
• Other Permits
• Operation and Maintenance Manual
• Declaration of Covenant for Privately Maintained Flow Control and Treatment Facilities.
(See attached Drainage BMP Maintenance Covenant BMP Agreement)
• Declaration of Covenant for Privately Maintained On-site Stormwater BMP's (See
attached Drainage BMP Maintenance Covenant BMP Agreement)
• Bond Quantities Worksheet, if applicable
The project overview has been provided at the beginning of this report along with an
existing conditions description. Maps are included in the attachments.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
1-3.1.8 Step 8 - Check Compliance with all Applicable Minimum Requirements
A Stormwater Site Plan as designed and implemented should specifically fulfill all Minimum
Requirements applicable to the project. The Stormwater Site Plan should be reviewed to check
that these requirements are satisfied.
To take place during review and during and after construction.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 2 (MINIMUM REQUIREMENT#2)
• 1-2.5.2 Minimum Requirement#2—Construction Stormwater Pollution Prevention Plan (SWPP)
- All projects are required to complete Minimum Requirement 2.
- Refer to the 13 Elements of the SWPP (See document below, complete and attach)
- See attached Table 4.1.1, Table 4.2.1 and Table
- Provide Engineering Calculations as an attachment for Sediment Ponds\Traps, Diversions,
Waterways and Runoff/Stormwater Detention Calculations.
Table 4.1.1 Source Control BMP's by SWPPP Element
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
Element II Element/2 Element/5 ElemsntiG Elament/9 Element011 Element/12 Element/13
BLIP or Element Herne Preserve Establish ProtectProtect Control Maintain Manage the ProteetLow
Vegetation/Mark Connection Sole Slopes Pollutants BLIP' Protect Impact
ClearinaLln:la Access tievelonment
BLIP C101: Preserving NaturalVegetedon ✓
BLIP C102:Buller Zones
BLIP C103:High►isibllty Plastic or Metal ✓ ✓
Fence
BLIP C105: SmbllzedConstruction ✓
Entrance/Exit
BMPC106:Wheel Wash ✓
Hp C10T:Construction RoadlParkkrg ✓
Area Stebllrition
BMP C120:Temporary and Permanent ✓ ✓
Seeding
BLIP C121:Mulching ✓ ✓
BLIP C122: line and Blankets ✓ s/
BHP C123:Plan*Covering ✓
BLIP C124: Sodding ✓
BLIPC125:Tapsolling/Con ostilg ✓
BNP C125:PolyacryktrrkIn for Soil Erasion ✓
Protection
BLIP C130: Surface Roughening ✓ ✓
BLIP C121;Gradient Terraces ✓ ✓
BLIP C140: Gust Control ✓
BLIP C100:Materiels On Hand ✓ ✓
BHP C101:Concrete Hendlkrg ✓
BLIP C152: Se outting and Sedating ✓
Palutkn Prevention
BMP C157: Material Galvuly,Storage end ✓
Containment
BLIP C154:Concrete Mahout Area ✓
BLIP C100:Certlid Erosion and ✓ ✓
Ss dinsnt Control Lead
BLIP C162:Schsduing ✓
Table 4.2.1 Runoff Conveyance and Treatment BMP's by SWPPP Element
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
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Version Date: October 7, 2019 Previous Version Date: February 20, 2019
13 Elements of SWPPP
(Construction Stormwater Pollution Prevention Plan)
Please check off boxes to show that each element has been read and understood. Provide details where
applicable and if certain aspects are unnecessary or exempt, clearly justify. Details of the 13 Elements and the
correlating BMPs are listed Above from the 2014 Stormwater Management Manual for Western Washington
(SWMMWW). A link is provided on the City of Anacortes website, under Planning, Community, & Economic
Development Department, as well as under Stormwater on the Engineering Division of Public Work's page.
Owner Name: Bonnie VAnSickle
Site Address: 3010 Georgia Place
Prepared By: Dale Herrigstad PE
The Stormwater checklist or building permit determined that:
❑ The 13 elements must be addressed ❑ These elements must be addressed
for construction activity adding under for construction activity adding 2,000
2,000 sq. ft. of hard surface area. sq. ft. or more of hard surface area.
This means that an attached narrative
and site plan are required with this
document.
Under each element, provide the BMP's that will be applicable to your project. Use the attached Tables
provided.
ELEMENT 1: Preserve Vegetation/Mark Clearing Limits
❑ Before beginning land disturbing activities, including clearing and grading, clearly mark all clearing
limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area.
❑ Retain the duff layer, native top soil, and natural vegetation in an undisturbed state to the maximum
degree practical.
A high visibility construction fence BMP C103 will be installed at the perimeter of the construction site
or where silt fence is used. BMP will be installed as first step of construction.
BMP to be monitored daily and repaired as needed.
ELEMENT 2: Establish Construction Access
❑ Limit construction vehicle access and exit to one route, if possible.
❑ Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize
tracking onto roads.
❑ Locate wheel wash or tire baths on site, if the stabilized construction entrance is not effective in
preventing tracking sediment onto roads.
❑ If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more
frequently as necessary (ex: wet weather). Remove sediment from roads by shoveling, sweeping, or
pick up and transport the sediment to a controlled sediment disposal area.
❑ Conduct street washing only after sediment is removed in accordance with the above bullet.
❑ Control street wash wastewater by pumping back on site or otherwise preventing it from discharging
into systems tributary to waters of the State.
The construction entrance will be limited to one location at Georgia Place with BMP C105 or C107
(Construction Entrance.)
Any dirt or mud that is tracked onto the roadway will be clean immediately.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
To be installed prior to construction. BMP to be monitored daily and repaired as needed.
ELEMENT 3: Control Flow Rates
❑ Protect properties and waterways downstream of development sites from erosion and the associated
discharge of turbid waters due to increases in the velocity and peak volumetric flow rate of stormwater
runoff from the project site.
❑ Where necessary to comply with the bullet above, construct stormwater retention or detention facilities
as one of the first steps in grading. Assure that detention facilities function properly before constructing
site improvement (e.g. impervious surfaces).
❑ If permanent infiltration ponds are used for flow control during construction, protect these facilities from
siltation during the construction phase.
A silt fence BMP C233 is to be installed along the North and east property lines. The majority of the
site will be disturbed. Schedule BMP C162.
ELEMENT 4: Install Sediment Controls
❑ Design, install, and maintain effective erosion controls and sediment controls to minimize the discharge
of pollutants.
❑ Construct sediment control BMPs (sediment ponds, traps, filters, etc.) as one of the first steps in
grading. These BMPs shall be functional before other land disturbing activities take place.
❑ Minimize sediment discharges from the site. The design, installation and maintenance of erosion and
sediment controls must address factors such as the amount, frequency, intensity and duration of
precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of
soil particle sizes expected to be present on the site.
❑ Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment
removal BMP, before the runoff leaves a construction site or before discharge to an infiltration facility.
Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet
the flow control performance standard in Element#3, bullet#1.
❑ Locate BMPs intended to trap sediment on-site in a manner to avoid interference with the movement of
juvenile salmonids attempting to enter off-channel areas or drainages.
❑ Provide and maintain natural buffers around surface waters, direct stormwater to vegetated areas to
increase sediment removal, and maximize stormwater infiltration.
❑ Where feasible, design outlet structures that withdraw impounded stormwater from the surface to avoid
discharging sediment that is still suspended lower in the water column.
Per BMP C233 a silt fence will be installed as noted in element 3. To be installed prior to the start of
construction. BMP to be monitored daily and repaired as needed. The site has a 30% slope down to
the north. BMP C162 Scheduling.
ELEMENT 5: Stabilize Soils
❑ Stabilize exposed and unworked soils by application of effective BMPs that prevent erosion. Applicable
BMPs include, but are not limited to: temporary and permanent seeding, sodding, mulching, plastic
covering, erosion control fabrics and matting, soil application of polyacrylamide (PAM), the early
application of gravel base early on areas to be paved, and dust control.
❑ Control stormwater volume and velocity within the site to minimize soil erosion.
❑ Control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize
erosion at outlets and to minimize downstream channel and stream bank erosion.
❑ Soils must not remain exposed and unworked for more than the time periods set forth below to prevent
erosion.
o During the dry season (May 1 —Sept 30): 7 days
o During the wet season (Oct 1 —Apr 30): 2 days
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
❑ Stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather
forecast.
❑ Stabilize soil stockpiles from erosion, protect with sediment trapping measures, and where possible, be
located away from storm drain inlets, waterways, and drainage channels.
❑ Minimize the amount of soil exposed during construction activity.
❑ Minimize the disturbance of steep slopes.
❑ Minimize soil compaction and, unless infeasible, preserve topsoil.
Stabilize exposed and unworked soils by application of effective BMPs that prevent erosion.
Applicable BMPs include, but are not limited to: temporary and permanent seeding, sodding, mulching
and plastic covering. Install plastic covering per BMP C123 on Soils Stockpiles. BMP to be monitored
daily and repaired as needed. Refer to Table 4.1.1 in MR#2.
ELEMENT 6: Protect Slopes
❑ Design and construct cut-and-fill slopes in a manner to minimize erosion. Applicable practices include,
but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope
steepness, and roughening slope surfaces (Ex: track walking).
❑ Divert off-site stormwater (run-on) or ground water away from slopes and disturbed areas with
interceptor dikes, pipes, and/or swales. Off-site stormwater should be managed separately from
stormwater generated on the site.
❑ At the top of slopes, collect drainage in pipe slop drains or protected channels to prevent erosion.
o *Temporary pipe slope drains must handle the peak volumetric flow rate calculated using a 10-
minute time step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition.
Alternatively, the 10-year, 1-hour flow rate predicted/indicated by an approved continuous runoff
model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing
land cover condition for predicting flow rates from tributary areas outside the project limits. For
tributary areas on the project site, the analysis must use the temporary or permanent project
land cover condition, whichever will produce the highest flow rates. If using the Western
Washington Hydrology Model (WWHM) to predict flows, bare soil areas should be modeled as
"landscaped" area.
o Where 15-minute time steps are available in an approved continuous runoff model, they may be
used directly without a correction factor.
❑ Place excavated material on the uphill side of trenches, consistent with safety and space
considerations.
❑ Place check dams at regular intervals within constructed channels that are cut down a slope.
❑ Consider soil types and its potential for erosion.
❑ Stabilize soils on slopes, as specified in Element 5.
❑ BMP combinations are the most effective method of protecting slopes with disturbed soils. Ex: Use both
mulching and straw erosion control blankets.
The site grade is at approximately 30% and open excavation should be limited for the construction of
each house site and retaining wall improvements. An existing swales lies along the bottom of the site
directing flow to the existing 12" storm pipe.
ELEMENT 7: Protect Drain Inlets
❑ Protect all storm drain inlets made operable during construction so that stormwater runoff does not
enter the conveyance system without first being filtered or treated to remove sediment.
❑ Clean or remove and replace inlet protection devices when sediment has filled one-third of the available
storage (unless a different standard is specified by the product manufacturer).
❑ Where possible, protect all existing storm drain inlets so that stormwater runoff does not enter the
conveyance system without first being filtered or treated to remove sediment.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
❑ Keep all approach roads clean. Do not allow sediment and street wash water to enter storm drains
without prior and adequate treatment unless treatment is provided before the storm drain discharges to
waters of the State.
❑ Inlets should be inspected weekly at a minimum and daily during storm events.
Per detail 1-40.20-00 Storm Drain Inlet protection devices will be installed at existing catch basins in the
immediate vicinity of the project.
To be installed prior to the start of any construction. Nearest CB is east of the entrance on Georgia
Place at the end of the dead end road. Provide Wattles dam BMP C235 at entry to storm culvert at the
bottom of the site.
BMP to be monitored daily and repaired as needed.
ELEMENT 8: Stabilize Channels and Outlets
❑ Design, construct, and stabilize all on-site conveyance channels to prevent erosion from the following
expected peak flows:
o *Channels must handle same peak volumetric flow rate as temporary pipe slope drains listed in
Element 6, above.
❑ Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent
streambanks, slopes, and downstream reaches at the outlets of all conveyance systems.
❑ The best method for stabilizing channels is to completely line the channel with a blanket product first,
then add check dams as necessary to function as an anchor and to slow the flow of water.
The existing ditch of channel along the bottom downslope of the property is stable now with
vegetation and should be left undisturbed.
ELEMENT 9: Control Pollutants
❑ Design, install, implement, and maintain effective pollution prevention measures to minimize the
discharge of pollutants.
❑ Handle and dispose of all pollutants, including waste materials and demolition debris that occur on-site
in a manner that does not cause contamination of stormwater.
❑ Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum
products, and other materials that have the potential to pose a threat to human health or the
environment. On-site fueling tanks must include secondary containment. Secondary containment
means placing tanks or containers within an impervious structure capable of containing 110% of the
volume contained in the largest tank within the containment structure. Double-walled tanks do not
require additional secondary containment.
❑ Conduct maintenance, fueling, and repair of heavy equipment and vehicles using spill prevention and
control measures. Clean contaminated surfaces immediately following any spill incident.
❑ Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that prevents
discharge to surface water, such as closed-loop recirculation or upland land application, or to the
sanitary sewer, with local sewer district approval. Wheel wash or tire bath wastewater should not
include wastewater from concrete washout areas.
❑ Apply fertilizers and pesticides in a manner and at application rates that will not result in loss of
chemical to stormwater runoff. Follow manufacturers' label requirements for application rates and
procedures.
❑ Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources. The sources for this
contamination include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete
washing and curing waters, waste streams generated from concrete grinding and sawing, exposed
aggregate processes, dewatering concrete vaults, concrete pumping, and mixer washout waters. Adjust
the pH of stormwater if necessary to prevent violations of the water quality standards.
❑ Assure that washout of concrete trucks is performed off-site or in designated concrete washout areas
only. Do not wash out concrete trucks onto the ground, or into storm drains, open ditches, streets, or
streams. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
spillage or concrete discharge to surface waters of the State is prohibited. Do not use upland land
applications for discharging wastewater from concrete washout areas.
❑ Obtain written approval from Ecology and provide to the City before using chemical treatment other
than CO2 or dry ice to adjust pH.
❑ Woody debris may be chopped and spread on site.
❑ Conduct oil changes, hydraulic system drain down, solvent and de-greasing cleaning operations, fuel
tank drain down and removal, and other activities which may result in discharge or spillage of pollutants
to the ground or into stormwater runoff using spill prevention measures, such as drip pans.
❑ Clean contaminated surfaces immediately following any discharge or spill incident. Emergency repairs
may be performed on-site using temporary plastic placed beneath and, if raining, over the vehicle.
Per BMP C154 a Concrete Washout Area is to be installed onsite to capture contaminated water from
concrete washouts. To be installed prior to foundation / concrete installation.
BMP to be monitored daily and repaired as needed.
Contractor is to provide spill prevention kits for excavation and concrete crews are required on Site.
ELEMENT 10: Control De-Watering
❑ Discharge foundation, vault, and trench dewatering water, which have characteristics similar to
stormwater runoff at the site, into a controlled conveyance system before discharge to a sediment trap
or sediment pond.
❑ Discharge clean, non-turbid de-watering water, such as well-point ground water, to systems tributary to,
or directly into surface waters of the State, as specified in Element 8, provided the de-watering flow
does not cause erosion or flooding of receiving waters or interfere with the operation of the system. Do
not route clean dewatering water through stormwater sediment ponds. Note that"surface waters of the
State" may exist on a construction site as well as off site; for example, a creek running through a site.
❑ Handle highly turbid or contaminated dewatering water separately from stormwater.
❑ Other treatment or disposal options may include:
1. Infiltration
2. Transport off-site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that
does not pollute state waters.
3. Ecology-approved on-site chemical treatment or other suitable treatment technologies.
4. Sanitary or combined sewer discharge with local sewer district approval, if there is no other
option.
5. Use of a sedimentation bag with outfall to a ditch or swale for small volumes of localized
dewatering.
❑ Construction equipment operation, clamshell digging, concrete tremie pour, or work inside a cofferdam
can create highly turbid or contaminated dewatering water.
❑ Discharging sediment-laden (muddy) water into waters of the State likely constitutes a violation of water
quality standards for turbidity. The easiest way to avoid discharging muddy water is through infiltration
and preserving vegetation.
If dewatering is needed all discharge will be directed to a temp. sed. trap BMP C240 prior to discharge
to the city storm drainage system. The sediment trap will be designed for a typical 7,000 sf impervious
area or 0.16 acres where the developed 2 year flow is 0.04 cfs X 2080 sf/cfc flow= 83 sf surface area
plan or 9'x9' square surface pond area minimum.
ELEMENT 11: Maintain BMPs
❑ Maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to
assure continued performance of their intended function in accordance with BMP specifications.
❑ Remove all temporary erosion and sediment control BMPs within 30 days after achieving final site
stabilization or after the temporary BMPs are no longer needed. Some temporary erosion and sediment
control BMPs are bio-degradable and designed to remain in place following construction such as
compost socks.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
❑ Provide protection to all BMPs installed for the permanent control of stormwater from sediment and
compaction. All BMPs that are to remain in place following completion of construction shall be
examined and placed in full operating conditions. If sediment enters the BMPs during construction, it
shall be removed and the facility shall be returned to the conditions specified in the construction
documents.
❑ Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting from
removal of BMPs or vegetation.
BMP'S to be monitored daily and repaired as needed and or as required by the City of Anacortes.
Weekly reports are required to be submitted to the building department.
ELEMENT 12: Manage the Project— Projects subject to Minimum Requirements 1-9 must have a Certified
Erosion and Sediment Control Lead (CESCL) for site inspections. Projects subject to Minimum Requirements
1-5 do not require the inspector to be certified. By the initiation of construction, the SWPPP must identify the
CESCL or inspector, who shall be present on-site or on-call at all times.
❑ Phase development projects to the maximum degree practicable and take into account seasonal work
limits to prevent soil erosion and prevent transporting sediment from the site during construction.
❑ Inspection and monitoring — Inspect, maintain, and repair all BMPs as needed to assure continued
performance of their intended function.
❑ Maintain, update, and implement the SWPPP.
❑ Clearing and grading activities for developments shall be permitted only if conducted using an approved
site development plan (e.g., subdivision approval).
❑ From Oct 1 through Apr 30, clearing, grading, and other soil disturbing activities is permitted only if
shown that the site operator will prevent silt-laden runoff from leaving the site through a combination of
the following:
1. Site conditions including existing vegetative coverage, slope, soil type, and proximity to
receiving waters.
2. Limit activities and the extent of disturbed areas.
3. Proposed erosion and sediment control measures.
Weather conditions can influence the seasonal limitation on site disturbance. The City of Anacortes has
the authority to take enforcement action per AMC 19.76 Stormwater.
❑ The following activities are exempt from the seasonal clearing and grading limitations:
1. Routine maintenance and necessary repair of erosion and sediment control BMPs;
2. Routine maintenance of public facilities or existing utility structures that do not expose the soil or
result in the removal of the vegetative cover to soil
3. Activities where there is 100% infiltration of surface water runoff within the site in approved and
installed erosion and sediment control facilities.
BMP's to be monitored daily and repaired as needed and the responsibility of the owner. Project does
require a certified CESCL.
ELEMENT 13: Protect Low Impact Development BMPS
❑ If implementing any bioretention facilities or rain gardens, refer to the applicable BMP sections of the
Manual for requirements.
No LID BMPS are proposed due to Flow Exempt.
Dale Herrigstad July 31, 2021
Applicant Signature Date
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 3 (MINIMUM REQUIREMENT#3)
• 1-2.5.3 Minimum Requirement#3—Source Control of Pollution
All known, available and reasonable source control BMP's must be applied to all projects. Source
control BMP's must be selected, designed, maintained according to the reference Ecology Manual.
The intent of source control BMP's is to prevent stormwater from coming in contact with pollutants.
They are a cost-effective means of reducing pollutants in stormwater, and, therefore, should be
considered in all projects.
All Commercial Properties, Industrial Properties, and Multi-Family Properties, Boatyards, Sand and
Gravel Mining Operations are required to comply with this Minimum Requirement.
Refer to Chapter IV-2.1 Applicable (Mandatory) Operational Source Control BMP's
During construction of the site will be open and subject to erosion. BMP's as described in the
erosion control plan and SWPPP must be constructed at the source to limit erosion and sediment
laden runoff. The primary source for erosion is the driving path for the transportation of
material to and from the site. A construction entrance and gravel construction route will limit
erosion and silt laded storm water.
Single Family Residential Construction Projects and Residential Subdivisions are Exempt from
this Minimum Requirement
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 4(MINIMUM REQUIREMENT#4)
• Minimum Requirement#4— Preservation of Natural Drainage Systems and Outfalls
Natural drainage patterns shall be maintained and discharges from the project shall occur at the natural
location, to maximum extent practicable. The manner by which runoff is discharged from the project site
must not cause a significant adverse impact to downstream receiving waters and down gradient
properties. All outfalls require energy dissipation.
The objective is to preserve and utilize drainage systems to the fullest extent because of the multiple
stormwater benefits these systems provide; and to prevent erosion at the downstream of the discharge
location.
Refer to the reference manual for supplemental guidelines and additional information under this
section.
Will this project disturb the Natural Drainage System or Outfall of the project Site? NO. If yes,
refer to section 1.2.5.4 for Supplemental Guidelines for additional information.
No change in drainage is proposed for this site. Drainage will discharge to the north to an
existing drainage system.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 5 (MINIMUM REQUIREMENT #5)
• Minimum Requirement#5—On-site Stormwater Management
Project thresholds that trigger Minimum Requirements#1 through #5, shall utilize the On-site
Stormwater Management BMP's from List#1 for all surfaces within each type of surface in List#1; or,
Demonstrate compliance with the LID Performance Standard. Projects selecting this option cannot use
Rain Gardens. They may choose to use Bioretention BMP's as described in Chapter V-7— Infiltration
and Bioretention Treatment Facilities to achieve the LID Performance Standard.
Refer to this section of the reference Manual for all Feasibility or Infeasibility Criteria for List#1
and List#2.
Is this project Flow Control Exempt?Yes (See Appendix l-E: Flow Control-Exempt Surface Water).
If yes, provide reasoning from the applicability section of 1-2.5.7 Minimum Requirement#7: Flow
Control). If No, then the project triggers Minimum Requirement#7 (1-2.5.7) and possibly Minimum
Requirement#8 (1-2.5.8).
The flow from this site is a stable drainage system to Guemes Channel, a flow control exempt
body of water.
If the project is Flow Control Exempt, select from the list below (Skip List 1 and List 2).
o BMP T5.13 Post Construction Soils Quality and Depth
o BMP T5.10A: Downspout Full Infiltration, or;
o BMP T5.10B Downspout Dispersion Systems, or;
o BMP T5.10C: Perforated Stub-out Connections, or;
o BMP T5.11 Concentrated Flow Dispersion, or;
o BMP T5.12 Sheet Flow Dispersion
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
All sites are required to utilize BMP T5.13— Post Construction Soil Quality and Depth.
For each surface, consider the BMP's in the order listed for that type of surface. Use the first BMP that
is considered feasible. No other on-site Stormwater Management BMP is necessary for that surface.
Feasiblity shall be determined by evaluation against:
1. Design criteria, limitations and infeasiblity criteria identified for each BMP in this manual, and;
2. Competing needs criteria listed in Chapter V-5—On-site Stormwater Management.
Lawn and Landscaped Area:
• BMP T5.13: Post-Construction Soil Quality and Depth. (Attach Detail in Report)
Refer to this site for requirements and specifications. All projects are required to utilize this BMP.
http://www.soilsforsalmon.orq/pdf/Soil BMP Manual.pdf
See Appendix 3 for the "Model Soil Management Plan for BMP T5.13" to be submitted with
Drainage Report and Application Material.
An alternate document acceptable to the City of Anacortes is a Test Report provided by the Soils
Supplier that identifies the soils to be used meet the specifications outlined under Minimum
Requirement 5. The specifications are in both WSDOT and CSI Formats. For specifications, refer to
the above referenced PDF.
This submittal can be a deferred submittal since most projects are not sure who the supplier will be
at the time of building permit application. For projects that trigger Minimum Requirements 1 through
5, the Test Report will be provided to the Building Department. Projects triggering Minimum
Requirements 1 through 9, the Test Report will be provided to the Engineering Department.
BMP T5.10C: Perforated Stub-out Connections
Roof downspouts will be collect to the northeast corner of the house and pass through
the perforated stub-out prior to discharging to the storm system at W 2nd Street.
o BMP T5.12: Sheet Flow Dispersion
Sheet flow dispersion will be provided for the alley in Minnesota Avenue with two dispersion
trenches for each 700 square feet of paved surfacing.
Dale Herrigstad July 31, 2021
Applicant Signature Date
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
TAB 6—(MINUMUM REQUIREMENT 6 - RUNOFF TREATMENT)
Refer to 1.2.5.6 and provide the required information for this Minimum Requirement.
Threshold requirements for determining the applicability of runoff treatment.
Projects in which the total of pollution-generating hard surface (PGHS) is 5,000 square feet or more
in a threshold discharge area of the project, or
Projects in which the total of pollution-generative pervious surfaces (PGPS)-not including permeable
pavements-is three-quarters (3/4) of an acre or more in a threshold discharge area,and from
which there will be a surface discharge in a natural or man-made conveyance system from the site.
The total PGHS projected for this site is 1,661 square feet of paved driving surface and less than the
5,000 square foot threshold.
Treatment is Not required.
TAB 7—(MINUMUM REQUIREMENT 7— FLOW CONTROL)
Refer to 1.2.5.7 and provide the required information for this Minimum Requirement.
Threshold requirements for determining the applicability of flow control.
• Projects in which the total of effective impervious surfaces is 10,000 square feet or more in a
threshold discharge area, or
• Projects that convert 3/4 acres or more of vegetation to lawn or landscape, or convert 2.5 acres
or more of native vegetation to pasture in a threshold dis-charge area,and from which there is a
surface discharge in a natural or man-made conveyance system from the site, or
• Projects that through a combination of effective hard surfaces and converted vegetation areas
cause a 0.10 cubic feet per second increase in the 100-year flow frequency from a threshold
discharge area as estimated using the Western Washington Hydrology Model or other approved
model and one-hour time steps (or a 0.15 cfs increase using 15-minute time steps).
As discussed above with the downstream is enclosed or a manmade swale designed for
conveyance with no capacity issues.
This site is FLOW CONTROL EXEMPT.
TAB 8—(MINUMUM REQUIREMENT 8—WETLAND PROTECTION)
Refer to 1.2.5.8 and provide the required information for this Minimum Requirement.
There are no wetlands down stream of this site before discharge to the Guemes Channel.
TAB 9—(MINUMUM REQUIREMENT 9—OPERATION AND MAINTENANCE)
Refer to 1.2.5.9 and provide the required information for this Minimum Requirement.
There are no maintenance requirements for a perforated stub out.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
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APPENDIX 2—Soils Report
A soils report for infiltration was not completed due the steep slopes on the site and no reasonable
opportunity for infiltration. Also the project is flow control exempt.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
APPENDIX 3— Model Soil Management Plan for BMP T5.13
An alternate document acceptable to the City of Anacortes is a Test Report provided by the Soils Supplier that
identifies the soils to be used meet the specifications outlined under Minimum Requirement 5. The
specifications are in both WSDOT and CSI Formats. For specifications, refer to the above referenced PDF.
This submittal can be a deferred submittal since most projects are not sure who the supplier will be at the time
of building permit application. For projects that trigger Minimum Requirements 1 through 5, the Test Report will
be provided to the Building Department. Projects triggering Minimum Requirements 1 through 9, the Test
Report will be provided to the Engineering Department.
DIFFERRED SUBMITTAL UNTIL END OF PROJECT WITH PLACEMENT OF SOILS.
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
DEFERRED SUBMITTAL: PROVIDE A TEST REPORT FROM SOILS SUPPLIER TO THE BUILDING DEPT.
PROJECT INFORMATION "Model Soil Management Plan for BMP T5.13" age # of pages
Complete all information on page 1; only site address and permit number on additional pages.
Site Address / Lot No.: 5304 Sterling Drive /Lot #55 Skyline No.3.
Permit Type: Permit Number:
Permit Holder: Phone:
Mailing Address:
Contact Person: Phone:
Plan Prepared By:
ATTACHMENTS REQUIRED (Check off required items that are attached to this plan)
Site Plan showing, to scale: Areas of undisturbed native vegetation (no amendment required)
New planting beds and turf areas (amendment required)
Type of soil improvement proposed for each area
Soil test results (required if proposing custom amendment rates)
Product test results for proposed amendments
AREA # (should match Area # on Site Plan)
PLANTING TYPE Turf Undisturbed native vegetation
Planting Beds Other:
SQUARE FOOTAGE OF THIS AREA: square feet
SCARIFICATION inches (depth) of scarification needed to achieve finished total 12" loosened depth.
Subsoil will be scarified
PRE-APPROVED inches of compost or imported topsoil applied
AMENDMENT METHOD: X 3.1 (conversion factor, inches to cubic yards) PRODUCT:
Topsoil import = cu. yards per 1,000 sq. ft.
Amend with compost X ,000s sq.ft. in this area
Stockpile and amend = cubic yards of amendment -* QUANTITY: CU. YDS.
( cu. yds. stockpiled) (needed to cover this area to designated depth)
CUSTOM AMENDMENT Attach test results and calculations.
Topsoil import inches organic matter or topsoil import PRODUCT:
Topsoil & compost lift X 3_1
Amend = cu. yards / 1,000 sq. ft.
Stockpile and amend X ,000s sq.ft. in this area
( cu. yds. stockpiled) = cubic yards of amendment — --> -i — —* QUANTITY: CU. YDS.
MULCH ,000 sq.ft. PRODUCT:
X 6.2 (conversion, to give 2 inch mulch depth)
= cubic yards of mulch — —> —f --> —* QUANTITY: CU. YDS.
TOTAL AMENDMENT/TOPSOIL/MULCH FOR ALL AREAS (complete on page 1 only, totaling all areas/pages in this Plan)
❑ Product #1: ❑ Quantity: cu. yds.
❑ Test Results: % organic matter C:N ratio <25:1 (except mulch, or <35:1 for native plants) "stable" (yes/no)
❑ Product#2: ❑ Quantity: cu. yds.
❑ Test Results: % organic matter C:N ratio <25:1 (except mulch, or <35:1 for native plants) "stable" (yes/no)
❑ Product #3: ❑ Quantity: cu. yds.
❑ Test Results: % organic matter C:N ratio <25:1 (except mulch, or <35:1 for native plants) "stable" (yes/no)
Date: Inspector: Approved: Revisions Required:
Date: Inspector: Approved: Revisions Required:
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
APPENDIX 4— Determining Construction Site Sediment Damage Potential (Appendix 7— NPDES Phase
II Permit)
Note: See attached. All projects within the City of Anacortes are required to complete that document under
Appendix 4.
Western Washington Phase II Stormwater Permit
i. APPENDIX 7 — Determining Construction Site
Sediment Damage Potential
The following rating system allows objective evaluation of a particular development site's potential to
discharge sediment. Permittees may use the rating system below or develop alternative process
designed to identify site-specific features which indicate that the site must be inspected prior to clearing
and construction. Any alternative evaluation process must be documented and provide for equivalent
environmental review.
Step one is to determine if there is a sediment/erosion sensitive feature downstream of the development
site. If there is such a site downstream complete step two, assessment of hydraulic nearness. If there is
a sediment/erosion sensitive feature and it is hydraulically near the site then go to step three to
determine the construction site sediment transport potential.
ii. STEP 1 —Sediment/Erosion Sensitive Feature Identification
Sediment/erosion sensitive features are areas subject to significant degradation due to the effect of
sediment deposition or erosion. Special protection must be provided to protect them.
Sediment/erosion sensitive features include but are not limited to:
i. Salmonid bearing fresh water streams and their tributaries or freshwater streams that
would be Salmonid bearing if not for anthropogenic barriers;
ii. Lakes;
iii. Category I, II, and III wetlands;
iv. Marine near-shore habitat;
v. Sites containing contaminated soils where erosion could cause dispersal of
contaminants; and
vi. Steep slopes (25% or greater) associated with one of the above features.
Identify any sediment/erosion sensitive features, and proceed to step two. If there are none the assessment
is complete.
iii. STEP 2— Hydraulic Nearness Assessment
Sites are hydraulically near a feature if the pollutant load and peak quantity of runoff from the site will not
be naturally attenuated before entering the feature. The conditions that render a site hydraulically near
to a feature include, but are not limited to, the following:
i. The feature or a buffer to protect the feature is within 200 feet downstream of the site.
ii. Runoff from the site is tight-lined to the feature or flows to the feature through a channel
or ditch.
August 1, 2013, Modified January 16, 2015 Appendix 7- Determining Sediment Damage
Potential Page 1 of 3
Version Date: October 7, 2019 Previous Version Date: February 20, 2019
A site is not hydraulically near a feature if one of the following takes place to provide attenuation
before runoff from the site enters the feature:
iv. Sheet flow through a vegetated area with dense ground cover
v. Flow through a wetland not included as a sensitive feature
vi. Flow through a significant shallow or adverse slope, not in a conveyance
channel, between the site and the sensitive feature.
Identify any of the sediment/erosion sensitive features from step one that are hydraulically near
the site, and proceed to step three. If none of the sediment/erosion sensitive features are
hydraulically near the site, the assessment is complete.
vii. STEP 3— Construction Site Sediment Transport Potential
Using the worksheet below, determine the total points for each development site. Assign points
based on the most critical condition that affects 10% or more of the site.
If soil testing has been performed on site, the results should be used to determine the
predominant soil type on the site. Otherwise, soil information should be obtained from the
county soil survey to determine Hydrologic Soil Group (Table of Engineering Index Properties
for step 1.D) and Erosion Potential (Table of Water Features for step 1.E)
When using the county soil survey, the dominant soil type may be in question, particularly when
the site falls on a boundary between two soil types or when one of two soil types may be present
on a site. In this case, the soil type resulting in the most points on the rating system will be
assumed unless site soil tests indicate that another soil type dominates the site.
Use the point score from Step 3 to determine whether the development site has a high potential
for sediment transport off of the site.
Total Score Transport Rating
<100 Low
❑100 High
A high transport rating indicates a higher risk that the site will generate sediment contaminated
runoff.
Construction Site Sediment Transport Potential Worksheet
A . Existing slope of site ( average , weighted by aerial extent) : Points
2 % or less . . 0
> 2-5 % 5
> 5- 10 % 15
> 10- 15 % 30
> 15 % 50
B . Site Area to be cleared and/or graded :
< 5 , 000 sq . ft 0
5 , 000 sq . ft . — 1 acre 30
> 1 acres 50
C . Quantity of cut and/or fill on site :
< 500 cubic yards 0
500 — 5 , 000 cubic yards 5
> 5 , 000 — 10 , 000 cubic yards 10
> 10 , 000 — 20 , 000 cubic yards 25
> 20 , 000 cubic yards 40
D . Runoff potential of predominant soils ( Natural Resources Conservation Service) : Hydrologic
soil group A 0
Hydrologic soil group B 10
Hydrologic soil group C 20
Hydrologic soil group D 40
E. Erosion Potential of predominant soils ( Unified Classification System) : GW, GP , SW,
SP soils 0
Dual classifications (GW-GM , GP-GM , GW-GC ,
GP-GC , SW-SM , SW-SC , SP-SM , SP-SC) 10
GM , GC , SM , SC soils 20
ML , CL , MH , CH soils 40
F . Surface or Groundwater entering site identified and intercepted 1 :
Yes 0
No 25
G . Depth of cut or height of fill > 10 feet :
Yes 25
No 0
H. Clearing and grading will occur in the wet season ( October 1 — May 1 ) : Yes 50
No 0
TOTAL POINTS 190
1 If no surface or groundwater enters site , give 0 points .
APPENDIX 5-SITE ECS PLAN
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H VISIBILITY
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EASEMENT EA ENT j ``"--
GEORGIA PL. _" "c�R
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BMP C123 CONSTRUCTION
BMP C154 'I TEMPORARY SOIL ENTRANCE
CONCRETE CRUSHED ROCK
WASH-OUT STOCKPILE LOCATION. BASE
GRAPHIC SCALE 01 0 Georgia covER WITH STRAW
1 i i 15 30 r Place `
OR VISQUEEN
IN Asi
1 inch =30 ft.
HERRIGSTAD ENGINEERING & SURVEYING ECS PLAN
4320 WHISTLE LAKE ROAD
ANACORTES, WA 913221 299-8804 3010 Georgia Place
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APPENDIX 7— Drainage BMP Facility Maintenance Covenant
Note: To be recorded prior to: 1) Temporary Certificate of Occupancy; 2) Final Certificate of Occupancy, and
or; 3) Final Acceptance of the project.
This is Covenant is required for any Permanent Stormwater Facility constructed on a project site. The applicant
should work with the the City of Anacortes Engineering Department on formalizing the document for recording.