HomeMy WebLinkAboutPermit File BLD-2018-0500 1016 27th Street (11) -0E@ROW111-
NOV 0 6 2018
HERRIGSTAD ENGINEERING PS - -�
Civil Engineer CITY OF ANACORTES
4320 Whistle Lake Road Dale Herrigstad, P.E.
Anacortes, WA 98221 (360) 299-8804
1018-1020 27th Street
Anacortes Family Center
DRAINAGE ANALYSIS
July 24, 2018 51 ROUL(Aki1
I1evised September 29, 2018 L II.VI.le
Revised November 5, 2018
R Job # 2017-117
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Prepared By: /0I� i
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Owner:
Anacortes Family Center
2702 Commercial Avenue
Anacortes WA 98221
The stormwater plan will be based on the requirements of the 2014 DOE Stormwater
Management Manual for Western Washington, as required by the City of Anacortes
Drainage Ordinance.
2
TABLE OF CONTENTS
Page SECTION TITLE
2 PROJECT DESCRIPTION
2 EXISTING CONDITIONS
3 DOE Stormwater Management Manual Minimum Requirements
3 Minimum Requirement#1: Prepare a Stormwater Site Plan
4 Minimum Requirement#2: Construction Stormwater Pollution Prevention
(SWPP)
4 Minimum Requirement#3: Source Control of Pollution
4 Minimum Requirement#4: Preservation of Natural Drainage Systems and
Outfalls
4 Minimum Requirement#5: On-site Stormwater Management
5 Minimum Requirement#6: Runoff Treatment
6 Minimum Requirement#7: Flow Control
7 Minimum Requirement#8: Wetland Protection
8 Minimum Requirement#9: Operation and Maintenance
ATTACHMENT A Existing Site &Erosion Control Drawing
ATTACHMENT B Developed Site Drawing
ATTACHMENT C Soils report
ATTACHMENT D DOE Manual Flow Chart Figure I-2.4.1
ATTACHMENT E Soil amendment requirements
ATTACHMENT F 13 Elements of SWPPP
PROJECT DESCRIPTIONEl -47
This project is to construct a 4,409 square foot building and 4,832 square feet of
walkways,porch,patios and parking areas for a total of 9,241 square foot total
impervious area on a 12,500 square foot site at 1018-1020 27th Street that includes the
alley way and some of 27th Street right-of-way used for parking. See ATTACHMENT
B.
EXISTING SITE CONDITIONS
The 12,500 square foot or 0.29 acre site is currently developed with two existing homes
and shed (1,944 sf—0.04 acres) that will be removed. The remainder of the site is grass.
The site slopes at an average from the west down to the east at 2%over the site. See
ATTACHMENT A.
Linda Spicher, Septic System Designer, completed a soils report p Y g p ep rt for the site and is
included in ATTACHMENT C. The underlying restrictive soil layer was found on site
at 17"and 24"on the north side of the site and 19"on the south side of the site. The
water table was found at 9", 18"and 11"respectively.
3
J
DOE Stormwater Management Manual Minimum requirements:
According to the 2014 DOE manual figure I-2.4.1 Flow Chart:
Does the site have 35%or more of existing impervious coverage—No
Does the site add 5000 square feet of new impervious surfaces—Yes
Does the site convert%acres or more of native vegetation to lawn—No
Does the project have 2,000 square feet of new impervious surfaces—Yes
Minimum requirements#1 through#9 apply to this project. (See flow chart in
ATTACHMENT D)
Minimum Requirement#1: Prepare a Stormwater Site Plan.
Volume 1, Chapter 3 steps (page 3-1).
Step 1. Collect and Analyze Information on Existing Conditions.
The site slopes at 2% across the site. The site is developed with two single family
homes and a shed with the remainder of the site in grass. An apartment lies to the
west and multi-unit shelter to the east. 27th Street to the south and alley to the
north.
The site soils as discussed above are found to be shallow with a restrictive layer at
17"to 24"below the surface with a water table at 9"to 18". The soils report is
included in ATTACHMENT C.
Step 2. Prepare a Preliminary Development Layout.
During construction all 12,500 square feet of the lot will be disturbed. A
proposed layout is attached as ATTACHMENT B.
Step 3.Perform an offsite analysis:
Storm water from this site sheets to the northeast and into the alley drainage
system. A large apartment building borders the uphill property where roof water
1' 09I.15 is collected and taken to the storm drainage system and not affecting the property.
"Il'1E The enclosed drainage system beginning in the alley flows north to 26th Street in
►t.► c $b.stN an 18" storm pipe. Drainage turns west for %2 a block then north through the
w1 Lrc "hoc w..alikagialospital property in a 24" and 36" storm pipe and back to an 18"pipe north of the
fthejz- (5 Hospital property from 24th Street to 22nd Street. At 22nd Street the Stormwater
Er
j, ‘14 flows east to Fidalgo Bay in a 27" concrete pipe to"Q"Avenue, a 30" concrete
E � pipe to "R"Avenue and a 36"concrete pipe to the outfall at the Anacortes Marina
Inek
and approximately 3,540 feet from the project site.
'ilr�C�N20, v clegi
v. s 54121,4 046 The City of Anacortes 2007 Storm Water Management Plan identifies the basin
B for this drainage as F3 and the Bay outlet as#41. At approximately 'A mile AS usr
Issme ,downstream from this site brings the downstream system to 24th Street where the
modal shows ample volume passing by the hospital.
PM, RAM 'IDS LUX
1N M FJT'C Step 4.Determine and Read Applicable Minimum Requirements.
C.FP, Threshold requirements: See DOE flow chart 2.4.1 in ATTACHMENT C.
The total new impervious area is over 5,000 square feet at 9,241 square feet.
Minimum requirements 1 through 9 are required.
Step 5.Prepare a Permanent Stormwater Control Plan
4
A storm water plan is provided in the developed site plan in Attachment B. LID
options will be addressed in Minimum Requirements#5 below.
Step 6. Prepare a Construction Stormwater Pollution Prevention Plan.
See minimum requirement#2 below for SWPPP.
Step 7. Complete a Stormwater Site Plan:
The project overview has been provided at the beginning of this report along with
an existing conditions description. Maps are included in the attachments. Offsite
analysis is provided in section step 3 above.
Step 8. Check compliance with all applicable minimum requirements:
To take place during review and during and after construction.
Construction completion report stamped and signed by the engineer of record.
Minimum Requirement #2: Construction Stormwater Pollution Prevention (SWPP)
This project must meet the 13 elements of a SWPP because the site exceeds the threshold
of 2,000 square feet of new impervious surfacing. See the attached SWPPP plan. See
ATTACHMENT F.
Minimum Requirement#3: Source Control of Pollution
During construction the site will be open and subject to erosion. BMP's as described in
the erosion control plan must be constructed at the source to limit erosion and sediment
laden runoff. The most common erosion source is exposed soils to rain. Covering the
slopes as discussed in the SWPPP shall be implemented.
Minimum Requirement#4: Preservation of Natural Drainage Systems and Outfalls
This site surface water naturally drains to the northeast and onto the alley to the North.
The site does not infiltrate to any great degree due to shallow water table.
Minimum Requirement#5: On-site Stormwater Management
As indicated above the impervious soil layer was found on site at 17"to 24" in depth as
shown in the report. The water table was found at 9"to 18"respectively. The entire site
will be completely disturbed. See developed site plan in ATTACHMENT B.
BMP T5.13: Post-Construction Soil Quality and Depth,Lawn and landscaping
areas:
All disturbed site soil will be amended as required by the post construction soil
quality and depth requirements and will be implemented at the building permit
stage. The design guidelines for the soil requirements are included in
ATTACHMENT E.
•
LIST#2 because the site triggered Minimum requirements#1 through#9.
ROOFS:
1. BMP T5.30: Full Dispersion—Requires native vegetation on site and there is
no native vegetation on this site. Full dispersion is not feasible do to no native
vegetation on this property.
BMP T5.10A: Downspout full infiltration—Minimum setbacks shall be 10 feet
from any structure and 3 feet from pavement and 3 feet or more of permeable
5
soils to the seasonal high ground water table. The ground water table is a
maximum of 18" below the ground surface. Infiltration is not feasible.
2. BMP T5.14A: Rain Gardens or BMP T7.30: Bioretention Cells,Swales,
and Planter Boxes—Not feasible if the Rain Garden or Bioretention facility
cannot be located on slopes less than 8% and if minimum of 1 foot vertical
separation to the seasonal high table, bedrock or other impervious layer can not be
achieved below rain garden or Bioretention cell.
Rain garden and Bioretention is not feasible due to the shallow water table of no
greater than 18".
3. BMP T5.10B: Downspout Dispersion Systems—A vegetated flow path of at
least 50 feet must be maintained between the outlet of the trench and any slope
steeper that 15%and 25 feet to any structure or property line. Downspout
dispersion is not feasible due to close proximity parking lots and property lines.
4. BMP T5.10C: Perforated Stub Out Connections—Do not place perforated r) Gd+ws-
stub outs above slopes greater than 20% and maintain at least 1 foot of separation
from the bottom of the trench and the seasonal water table. Not feasible due to "'Co M-
shallow water table of 18".
OTHER HARD SURFACES (driveways and patios)
1. BMP T5.30: Full Dispersion—65%of the site must be maintained in a
forested or native condition. There is no native vegetation.
BMP T5.15: Permeable Pavements—Not feasible when within 50 feet of the
top of slopes greater than 20%. Also must maintain at least one foot of separation
to the ground water or an underlying impermeable layer. Not feasible due to
shallow impermeable layer of 24" and water table at 18".
BMP T7.30: Bioretention Cells, Swales,and Planter Boxes—Not feasible if
the Bioretention facility cannot be located on slopes less than 8%and if minimum
or 1 foot vertical separation to the seasonal high table, bedrock or other
impervious layer. Bioretention is not feasible.
BMP T5.12: Sheet Flow Dispersion—A vegetated flow path of at least 50 feet
must be maintained between the outlet of the trench and any slope greater than
15%. Not feasible due to no flow paths of 50 feet.
BMP T5.11: Concentrated Flow Dispersion—Do not place the discharge point
on or above slopes greater than 20% and maintain a vegetated flow path of at
least 50 feet between the discharge point and any property line, structure or steep
slope. Not feasible to no flow paths of 50 feet.
6
Minimum Requirement#6: II.turnoff Treatment
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 including parking area is 4,832 square feet and less
than the 5,000 square foot threshold. The roof is covered with a backed enamel coating
and not a PGHS surface. 2012 Manual V-4.1.3 Flows Requiring Treatment.
The total disturbed site is 0.35 acres and less than the 3/4 acre PGPS threshold.
Water quality treatment is not required.
Minimum Requirement#7: Flow Control
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).
The new impervious area of 9,241 square feet(0.21 acres) (0.10 acre roof and
0.11 acre parking and sidewalks) is BELOW the threshold discharge area
of 10,000 square feet. The overall disturbed area is 12,500 square feet
(0.29 acres).
The overall site is less than 3/4 of an acre
The increase in flow for the 100-year flow frequency is
100 year PREDEVELOPED (forested) 0. 1144 cfs
100 year DEVELOPED 0. 2113cfs WA:A.1$
t14 , m��c5
Increase in runoff is 0.0969 cfs and LESS than the 0.10 cfs ��N �
1AN
Flow Control is NOT required. No ‘SS- feelk £ C"c
WWHI'42 012
PROJECT REPORT Y�`�
7
Project Name : default [ 5 ]
Site Name : Anacortes Family Center
Site Address : 1020 27th Street
City : Anacortes
Report Date : 7/24 /2018
Gage : Burlington
Data Start : 1948/10/01
Data End : 2009/09/30
Precip Scale : 0 . 83
Version Date : 2016/02/25
Version : 4 . 2 . 12
PREDEVELOPED LAND USE
Pervious Land Use acre
C , Lawn , Flat . 25
Pervious Total 0 . 25
Impervious Land Use acre
ROOF TOPS FLAT 0 . 04
Impervious Total 0 . 04
Basin Total 0 . 29
MITIGATED LAND USE
Pervious Land Use acre
C , Lawn , Flat . 08
Pervious Total 0 . 08
Impervious Land Use acre
ROOF TOPS FLAT 0 . 1
DRIVEWAYS FLAT 0 . 11
Impervious Total 0 . 21
Basin Total 0 . 29
Flow Frequency Return Periods for Predeveloped. POC #1
Return Period Flow (cfs)
2 year 0 . 02233
5 year 0 . 037785
10 year 0 . 051199
25 year 0 . 072399
50 year 0 . 091707
100 year 0 . 114413
Flow Frequency Return Periods for Mitigated. POC #1
Return Period Flow (cfs)
2 year 0 . 072272
5 year 0 . 102887
10 year 0 . 125685
25 year 0 . 157476
50 year 0 . 183399
100 year 0 . 211305
8
Minimum Requirement#8: Wetland Protection
There are no wetlands on this site. The downstream system is enclosed to a discharge
point 3,500 feet downstream to Fidalgo Bay.
Minimum i'equirement#9: Operation and Maintenance
The drainage system within this project will remain private and the responsibility of the
homeowners for which it serves.
SEDIMENT TRAP DESIGN
The sediment trap will be designed for the developed 2-year runoff event and provided
with 2080 square feet of surface area per cfs (2 year) inflow.
The 2-year flow rate as shown above is 0.072 cfs x 2080 SF/cfs= 150 sf of surface area.
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GRAPHIC SCALE
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IN .1 ( IN FEET )
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Existing & Erosion Control Site Plan
HERRIGSTAD ENGINEERING & SURVEYING 1018-1020 27th Street, Anacortes
4320 WHISTLE LAKE ROAD
ANACORTES, WA 98221 299-8804 A T T A C H V' C \ T A
ALLEY PAVEMENT SECTION
I 2' ASPHALT
I 2' CTSC EX. STEEL BLDG �
6' GRAVEL BORROW z I
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n NEW SSMH OVER EXISTING 6' — " EX. CB TYPE1 �'�"
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o EXIST. SSCO EXIST, 6' SD I.E. 8' PVC
ADD IRON EXTEND 8' PVC SS TEl
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x \ASE
BUILDING x x _ _ — —
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' — — I EX. BURLINGTON CB \ I,E 61.06'
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LID
GRAPHIC SCALE
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( IN FEET )
1 inch = 30 ft.
Developed Site Plan
HERRIGSTAD ENGINEERING & SURVEYING 1018-1020 27th Street, Anacortes
4320 WHISTLE LAKE ROAD
ANACORTES, WA 98221 299-8804 A T T A C H N E N T 3
ATTACHMENT C
Soils Report
Linda Spicher, Septic System Designer
(360)708-3004
Project/Client: Anacortes Family Center Page of
Site Address: 1018 — 1020 27th Street, Anacortesff
/
Parcel Numbers: 57346 & 57345 or ft-Airy
'�PII!
Contractor/Builder: Strandberg Design •,'��''"=' � ` ,.j
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Date on Site: 04/09/18 o/
A"•�r , .. s.ti*sacKEn'
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Map Unit, Natural Resources Conservation Service: #20 EXPIRES 09.29.18
Bow-Urban land complex soils are very deep and somewhat poorly drained.
Permeability is slow, and available water capacity is high. Runoff is medium, and the
hazard of water erosion is slight.
Hydrologic Soil Group: C/D
Soil Typel Loading Rate2
Soil Log 1
0 — 13 brown silt loam w/clay pockets, disturbed 5 0.4
13 — 17 medium sandy clay loam, fine roots to 9" 6 0.2
observed water table at 12"
anticipated water table at 9"
Soil Log 2
0— 11 brown fine sandy silt loam w/clay pockets,
disturbed 5 0.4
11 — 18 dark brown ashy silt loam w/ clay pockets,
disturbed, roots 5 0.4
18 —24 gray sandy silty clay, fine roots 7 not suitable
strong roots, no mottles
observed water table at 18"
anticipated water table at 18"
I One of seven numerical classifications of fine earth particles and rack fragments as described in WAC
247-272A-0220(2)(e).
2 From Chapter 247-272A WAC: "Hydraulic Loading Rate" means the amount of effluent applied to a
given treatment step, in this chapter expressed as gallons per square foot per day(gal/sq.ft./day).
ATTACHMENT C
Page .Z of S
Soil Tvpe3 Loading Rate4
Soil Log 3
0 — 11 dark brown silt loam 5 0.4
11 - 16 red medium sandy ashy silt loam,
mottles, roots 6 0.2
16— 19 gray gravelly sandy silty clay, fine roots 7 not suitable
observed water table at 16"
anticipated water table at 11"
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EXPIRES 09.29-,8
3 One of seven numerical classifications of fine earth particles and rack fragments as described in WAC
247-272A-0220(2)(e).
4 From Chapter 247-272A WAC: "Hydraulic Loading Rate"means the amount of effluent applied to a
given treatment step, in this chapter expressed as gallons per square foot per day(gal/sq. ft./day).
ATTACHMENT C
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EXPIRES 09-29- LiI
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HERRIGSTAD ENGINEERING & SURVEYING 1018-1020 27TH STREET
4320 WHISTLE LAKE ROAD SOILS TEST LOCATIONS
ANACORTES, WA 98221 299-8804 4-5-2018
ATTACHMENT C
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0 40 80 163 240 I
r Corner czr�rdiaiti: WGSB4 Edge tics: l 9 Zone 10N WGSS4 `,
Imp projection: Web Mercator e
1) us A NaturaI Resources Web Soil Survey 411012018
�-- National! Cooperative Soil Sunee Page 1 of 3
�� Conservation Se��oo� � �
peto o
Skagit County Area, Washington
20—Bow-Urban land complex, 0 to 8 percent slopes
Map Unit Setting If
• National map unit symbol: 2hv1 i
• Elevation: 0 to 450 feet •
• Mean annual precipitation: 20 to 60 inches 1
• Mean annual air temperature: 48 to 50 degrees F „/ �4, ' taf
• Frost-free period: 150 to 220 days !:y {; 406
• Farmland classification: Not prime farmland : '1
Map Unit Composition DMiGNEIt VA
• Bow and similar soils: 60 percent pCF1RES 09-29-
r8
• Urban land: 35 percent
• Minor components: 5 percent
• Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Bow
Setting
• Landform:Terraces, hilislopes
• Parent material: Volcanic ash, glaciolacustrine deposits, and glacial drift
Typical profile
• Hi - 0 to 7 inches: gravelly ashy loam
• H2 - 7 to 17 inches: very gravelly ashy loam
• H3 - 17 to 31 inches: clay loam
• H4 - 31 to 60 inches: silty clay
Properties and qualities
• Slope: 0 to 8 percent
• Depth to restrictive feature: More than 80 inches
• Natural drainage class: Somewhat poorly drained
• Capacity of the most limiting layer to transmit water(Ksat): Moderately low to moderately high
(0.06 to 0.20 in/hr)
• Depth to water table: About 6 to 18 inches
• Frequency of flooding: None
• Frequency of ponding: None
• Available water storage in profile: High (about 10.4 inches)
Interpretive groups
• Land capability classification (irrigated): None specified
• Land capability classification (nonirrigated): 4w
• Hydrologic Soil Group: C/D
• Forage suitability group: Seasonally Wet Soils (G002XN202WA)
• Hydric soil rating: Yes
Description of Urban Land
Interpretive groups
• Land capability classification (irrigated): None specified
• Land capability classification (nonirrigated): 8
• Hydric soil rating: No
Minor Components
Bellingham, undrained
• Percent of map unit: 5 percent
• Landform: Depressions
• Hydric soil rating: Yes
ATTACHMENT C
Start Here
Dees the site have 35% Yes See Redevelopment Minimum
or more of existing Requirements and Flow Clam
impervious coverage? (Figure I-2.4.2).
No
ry Does the project convert 3la
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
'! square feet,or greater,of new plus
replaced hard surface area?
All Minimum Requirements !
apply to the new and replaced .
hard surfaces and converted
{ vegetation areas. i
Yes No
v.
Does the project have land
Minimum Requirements#1 disturbing activities of 7,000
through#5 apply to the new 41
Ya•es
square feet or greater?
and replaced hard surfaces
and the land disturbed. No
V
0.oqAEI Minimum Requirement#2
applies.
6nu.. (�-u-N.ac> etliE Sawv< LoNc..t.-sthl-- Qs'1.s.114C
CAA-N..14,40XX 1^2..4.2
lel Figure I- .4.YZ-
Flow Chart for Determining Requirements for
New-Dsrverturrrnerd .taco et-'i
OEPARTMEENT OF Revised June 2016
ECOLOGY Please see hplAvwnu_ecy.w a.ga tleopyrigshthrmf for copyright notice inducting permissions,
i State of Washington limitation of liability,anr1 disclaimer_
ATTACHMENT D
ATTACHMENT E
4 PAGES
BMP T5.13: Post-Construction Soil Quality and Depth
Purpose and Definition
Naturally occurring (undisturbed) soil and vegetation provide important stormwater func-
tions including: water infiltration; nutrient, sediment, and pollutant adsorption; sediment
and pollutant biofiltration; water interflow storage and transmission; and pollutant decom-
position. These functions are largely lost when development strips away native soil and
vegetation and replaces it with minimal topsoil and sod. Not only are these important
stormwater functions lost, but such landscapes themselves become pollution generating
pervious surfaces due to increased use of pesticides, fertilizers and other landscaping
and household/industrial chemicals, the concentration of pet wastes, and pollutants that
accompany roadside litter.
Establishing soil quality and depth regains greater stormwater functions in the post devel-
opment landscape, provides increased treatment of pollutants and sediments that result
from development and habitation, and minimizes the need for some landscaping chem-
icals, thus reducing pollution through prevention.
Applications and Limitations
Establishing a minimum soil quality and depth is not the same as preservation of nat-
urally occurring soil and vegetation. However, establishing a minimum soil quality and
depth will provide improved on-site management of stormwater flow and water quality.
Soil organic matter can be attained through numerous materials such as compost, com-
posted woody material, biosolids, and forest product residuals. It is important that the
materials used to meet the soil quality and depth BMP be appropriate and beneficial to
the plant cover to be established. Likewise, it is important that imported topsoils improve
soil conditions and do not have an excessive percent of clay fines.
This BMP can be considered infeasible on till soil slopes greater than 33 percent.
Design Guidelines
. Soil retention. Retain, in an undisturbed state, the duff layer and native topsoil to
the maximum extent practicable. In any areas requiring grading remove and stock-
pile the duff layer and topsoil on site in a designated, controlled area, not adjacent
to public resources and critical areas, to be reapplied to other portions of the site
where feasible.
. Soil quality.All areas subject to clearing and grading that have not been covered
by impervious surface, incorporated into a drainage facility or engineered as struc-
tural fill or slope shall, at project completion, demonstrate the following:
1. A topsoil layer with a minimum organic matter content of 10% dry weight in
planting beds, and 5% organic matter content in turf areas, and a pH from 6.0
2014 Stormwater Management Manual for Western Washington 1 OF 4
Volume V- Chapter 5-Page 911 ATTACHMENT E
to 8.0 or matching the pH of the undisturbed soil. The topsoil layer shall have
a minimum depth of eight inches except where tree roots limit the depth of
incorporation of amendments needed to meet the criteria. Subsoils below the
topsoil layer should be scarified at least 4 inches with some incorporation of
the upper material to avoid stratified layers,where feasible.
2. Mulch planting beds with 2 inches of organic material
3. Use compost and other materials that meet these organic content require-
ments:
a. The organic content for"pre-approved" amendment rates can be met
only using compost meeting the compost specification for BMP T7.30:
Bioretention Cells, Swales, and Planter Boxes (p.959),with the excep-
tion that the compost may have up to 35% biosolids or manure.
The compost must also have an organic matter content of 40% to 65%,
and a carbon to nitrogen ratio below 25:1.
The carbon to nitrogen ratio may be as high as 35:1 for plantings com-
posed entirely of plants native to the Puget Sound Lowlands region.
b. Calculated amendment rates may be met through use of composted
material meeting (a.) above; or other organic materials amended to
meet the carbon to nitrogen ratio requirements, and not exceeding the
contaminant limits identified in Table 220-B, Testing Parameters, in
WAC 173-350-220.
The resulting soil should be conducive to the type of vegetation to be established.
. Implementation Options: The soil quality design guidelines listed above can be
met by using one of the methods listed below:
1. Leave undisturbed native vegetation and soil, and protect from compaction
during construction.
2. Amend existing site topsoil or subsoil either at default"pre-approved" rates,
or at custom calculated rates based on tests of the soil and amendment.
3. Stockpile existing topsoil during grading, and replace it prior to planting.
Stockpiled topsoil must also be amended if needed to meet the organic mat-
ter or depth requirements, either at a default"pre-approved" rate or at a cus-
tom calculated rate.
4. Import topsoil mix of sufficient organic content and depth to meet the require-
ments.
2014 Stormwater Management Manual for Western Washington 2 OF 4
Volume V- Chapter 5-Page 912 ATTACHMENT E
More than one method may be used on different portions of the same site. Soil that
already meets the depth and organic matter quality standards, and is not com-
pacted, does not need to be amended.
Planning/Permitting/Inspection/Verification Guidelines & Procedures
Local governments are encouraged to adopt guidelines and procedures similar to those
recommended in Guidelines and Resources For Implementing Soil Quality and Depth
BMP T5.13 in WDOE Stormwater Management Manual for Western Washington. This
document is available at: http://www.soilsforsalmon.orq/pdf/Soil BMP Manual.pdf
Maintenance
. Establish soil quality and depth toward the end of construction and once estab-
lished, protect from compaction, such as from large machinery use, and from
erosion.
. Plant vegetation and mulch the amended soil area after installation.
. Leave plant debris or its equivalent on the soil surface to replenish organic matter.
. Reduce and adjust, where possible, the use of irrigation, fertilizers, herbicides and
pesticides, rather than continuing to implement formerly established practices.
Runoff Model Representation
Areas meeting the design guidelines may be entered into approved runoff models as
"Pasture" rather than "Lawn."
Flow reduction credits can be taken in runoff modeling when BMP T5.13: Post-Con-
struction Soil Quality and Depth is used as part of a dispersion design under the con-
ditions described in:
. BMP T5.10B: Downspout Dispersion Systems (p.905)
. BMP T5.11: Concentrated Flow Dispersion (p.905)
. BMP T5.12: Sheet Flow Dispersion (p.908)
. BMP T5.18: Reverse Slope Sidewalks (p.937)
. BMP T5.30: Full Dispersion (p.939) (for public road projects)
3 OF 4
2014 Stormwater Management Manual for Western Washington
Volume V- Chapter 5-Page 913 ATTACHMENT E
Figure V-5.3.3 Planting bed Cross-Section
Mulch
•
Loose soil with
visible dark
organic matter
17--PC �✓
r � _
4"
Loose or
fractured
subsoil
Reprinted from Guidelines and Resources For Implementing Soil Quality and
Depth BMP T5.13 in WDOE Stormwater Management Manual for Western
Washington,2010,Washington Organic Recycling Council NOT TO SCALE
rsMIE
Figure V-5.3.3
6111 Planting Bed Cross—Section
DEPARTMENT OF Revised January2016
ECOLOGY Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions,
State of Washington limitation of liability,and disclaimer.
2014 Stormwater Management Manual for Western Washington 4 OF 4
Volume V- Chapter 5-Page 914 ATTACHMENT E
. ‘.�Y o� Planning, Community, & Economic Development Department
rr,G PO Box 547, Anacortes, WA 98221
PH: 360.299.1984
,p9' 5, 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 on Pg. 236 of 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:Anacortes Family Center
Site Address: 1018-1020 27th Street
Prepared By:Dale Herrigstad,PE
The Stormwater checklist or building permit determined that:
❑ The 13 elements must be addressed for ❑✓ These elements must be addressed for
construction activity adding under 2,000 construction activity adding 2,000 sq. ft.
sq. ft. of hard surface area. or more of hard surface area. This means
that an attached narrative and site plan
are required with this document.
Under each element, explain the best management practices (BMPs) used or justify reasoning
for those that will not be used. If needed, please attach a narrative to further explain plans or
justification.
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 temporary chain link construction fence will be installed at the perimeter of the construction site.
This will be installed prior to beginning construction.
BMP to be monitored daily and repaired as needed.
Page 1 of 8
March, 2017
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.
ElIf 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.
Per BMP C105 a Stabilized Construction Entrance will be installed at the alley. Crushed rock parking along 27th Street.
Any dirt or mud that is tracked onto the roadway will be clean immediately.
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.
Property to have silt fence(BMP C233)or wattles(BMP C235)installed to protect down hill adjacent properties.
Wattles will be installed along gravel parking as condition require.
Also a Sediment trap(BMP C240)in the rear of the project will be installed.
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
Page 2 of 8
March, 2017
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.
0✓ 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 on the downhill side of the site per the site plan.
To be installed prior to the start of construction.
BMP to be monitored daily and repaired as needed.
ELEMENT 5: Stabilize Soils
❑s 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.
I] 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
❑✓ 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.
0✓ Minimize the amount of soil exposed during construction activity.
I]✓ 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,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. Install plastic covering per BMP C123 on Soils Stockpiles.BMP to be monitored daily and repaired as needed.
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).
Page 3 of 8
March, 2017
❑ 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.
There are no steep slopes on this projext
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.
❑✓ 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.
Storm Drain Inlet protection(BMP C220)or wdot stnd plan 140.20-00 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.
BMP to be monitored daily and repaired as needed.
Page 4 of 8
March, 2017
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.
O Provide stabilization, including armoring material, adequate to prevent erosion of outlets,
adjacent streambanks, slopes, and downstream reaches at the outlets of all conveyance
systems.
0 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.
No stormwater runoff will be conveyed off site via channels,swales,or streams.
If needed,temporary sed.trap(BMP C240)to be installed and any runoff will be channeled or conveyed to trap.
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.
Page 5 of 8
March, 2017
0✓ 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 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.
O Obtain written approval from Ecology and provide to the City before using chemical treatment
other than CO2 or dry ice to adjust pH.
CI Woody debris may be chopped and spread on site.
0✓ 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.
0✓ 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 to provide Spill Prevention Plan,Kits,Etc.
All fuel,lubricants,paint,and/or other hazardous material shall be stored in a lockable,covered storage container if kept 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.
0✓ 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.
I]✓ Handle highly turbid or contaminated dewatering water separately from stormwater.
0✓ 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.
0✓ Construction equipment operation,clamshell digging, concrete tremie pour,or work inside a
cofferdam can create highly turbid or contaminated dewatering water.
ElDischarging sediment-laden (muddy)water into waters of the State likely constitutes a violation
Page 6 of 8
March, 2017
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 temporary sediment trap(BMPC240).
If pond is not adequate then Baker tanks or trailers will be required.
ELEMENT 11: Maintain BMPs
E✓ 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.
El 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.
El Remove or stabilize trapped sediment on site. Permanently stabilize disturbed soil resulting
from removal of BMPs or vegetation.
BMP to be monitored daily and repaired as needed.
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. Management details starting on Pg. 250.
El 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.
C✓ 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:
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March, 2017
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 to be monitored daily and repaired as needed.A Certified Erosion and Sedimentation Control Lead
CESCL is yet to be determined for this project CESCL personnel are trained in and responsible
for the proper maintenance of the erosion control BMPs. The CESCL will work with the City of Anacortes
Inspector to maintain all BMPs. Install 24 hour contact info on sign as noted on plans.
ELEMENT 13: Protect Low Impact Development BMPS
❑ If implementing any bioretention facilities or rain gardens,see Pg. 253 for requirements.
Dale Herrigstad o; ^Y',aoe
- ;��•a•>••m•^-��•�^•�•®�mm=-�^ November 5,2018
Applicant Signature Date
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March, 2017