|
RECORD DRAWING MAY 2024
<br />0
<br />_>
<br />J
<br />NOTES:
<br />1. Yard drains to be constructed from High Density Polyehtylene (HDPE) in accordance with ASTM C-14 otherwise
<br />shown on the plans or noted in the specifications.
<br />2. Cutout hole size is equal to outlet pipe outside diameter plus yard drain wall thickness.
<br />3. Connection to outlet pipe to be mortared and made flush with inside of the yard drain wall.
<br />4. Cast iron bell grate. Fits into bell recess and extends flush with face of bell. The grate shall have slots (holes) that
<br />constitute 50 percent open area for drainage unless otherwise specified on the plans or noted in the
<br />specifications. Inlet bell area shall be finished to assure non -rocking fit with any cover position.
<br />5. Washed drain rock. 6 inches minimum depth.
<br />6. Varies, 12 inches for 4"-8" pipe, 18 inches for larger pipe. 7. Special cast yard drain may be required for multiple pipe connections. 6" PVC
<br />Cap or
<br />C
<br />8. Provide cleanout (per this detail) upstream of yard drain when grate to pipe IE is greater than 42" Plug
<br />1-4
<br />NOTE:
<br />HDPE Wyes or Tees may be used for
<br />roof/footing/yard drain systems with pipes 8" or less 6" min dia Clean -out
<br />and not used in structural area (e.g. driveways, Stand -pipe
<br />paved area) or locations were surface water is to be 6" Wye to 6",8", or 12"
<br />collected. Clean outs required upstream of each Yard system
<br />Wye or Tee. Wye tie-in
<br />(as req'd: 4'4', 4"-6",
<br />eo-a 4"-8", 4"-12")
<br />From Yard
<br />Drain
<br />6",8", or 12" Tee
<br />Yard system
<br />DROP CONNECTION
<br />Provide
<br />Downspout
<br />debris barrier
<br />(typ. All homes)
<br />All homes in West
<br />Basin to be dispersed
<br />via Splash block
<br />dispersion.
<br />Contractor to
<br />connect to Yard
<br />5 Drain & Yard CB
<br />--- From Yard
<br />CLEANOUT Drain
<br />From Yard Drain l�
<br />6" Wye to
<br />6",8", or 12"
<br />Yard system
<br />DROP CONNECTION
<br />2x4 Drain Marker painted GREEN stencil
<br />w/ 3" high WHITE letters "DRAIN'.
<br />Locate at pipe end.
<br />Note depth to invert w/ indelible black
<br />marker.
<br />Rim El: See Profile
<br />12" min to Top of Riser
<br />F a T
<br />2 U
<br />� A o
<br />-�
<br />i l ���i i
<br />y \' C, -
<br />i l r r�l
<br />18" of BMP \ o c
<br />T5.13 Soils V" n
<br />- o
<br />\ 41/� 1 � o c
<br />i ` 2
<br />q a r��i
<br />18" min
<br />12'' Dia Yard CB (concrete pipe or HDPE
<br />N-12 or equivalent) in accordance with
<br />ASTM C-14. Use Solid Lid. Lid at surface
<br />or max 4" bury with location marker
<br />Closed Bottom: HDPE Cap or
<br />Grouted Base where indicated on
<br />site plan per lot
<br />6" min Clean Rock for all others
<br />SECTION A
<br />4"/6" Cap. Drill two
<br />1 " dia holes near
<br />top (opposite sides)
<br />To Cleanout via Yard Drain
<br />Conveyance System per
<br />plan and profile
<br />4"/6" PVC Tee to 4"/6" PVC or
<br />HDPE (DWV) yard drain (typ)
<br />Fine mesh Screen, 1 /10'' to 1 /4''
<br />rust-poof hardware cloth.
<br />4" min explosed height.
<br />SS straps/band clamps.
<br />4" PVC cap bottom.
<br />YD YD YD YD YD YD YD YD T�
<br />Para Uraln C_,IeanOUT 4 /6 lee
<br />\�S,ee clenaout configuration options Yard Drain Coryveyance
<br />�
<br />Perf. Pipe to be placed a' bye based on lot configuration) o System Pipe (pipe is profiled
<br />and Ian on dis la ed
<br />p � plan)
<br />through vegetated
<br />areas at frontage.
<br />French Drain installation through yard
<br />connection reminescent of BMP T5.1 OC
<br />Perforated Stub -Out Connections i O
<br />12" Dia Yard CB (concrete pipe or HDPE N-12 or I ��
<br />equivalent) in accordance with ASTM C-14. Use Solid ����-- '--�% 2x4 Drain Marker
<br />Lid. Lid at surface or max 4" bury with location marker }
<br />Roof Drains Provide
<br />Downspout
<br />debris barrier or
<br />equal (typ. All
<br />homes)
<br />RD RD RD RD RD RD
<br />Building o
<br />ROOF -YARD DRAIN CONNECTIONS 20
<br />SCALE: NTS
<br />UNDERGROUND UTILITY NOTE
<br />Underground utility locations shown hereon are based
<br />upon surface indicators. No underground location
<br />service was utilized for their location. The use of this
<br />map for their exact location is not warranted. Prior to
<br />construction user should call the utility location service
<br />at 1-800-424-5555 48 hours before construction.
<br />0
<br />r
<br />LJ
<br />r
<br />A PORTION OF SECTION 18, TOWNSHIP 28 NORTH, RANGE 05 EAST, W.M.
<br />NOTES
<br />[1]. Soils per Bioretention Soil Media detail. Mix to be certified prior to placement. Compact to 85% proctor per ASTM D1557.
<br />[2]. Uniformly graded coarse aggregate WSDOT spec 9-03.1 (4)C 'crushed washed stone'- AASHTO size number 67, (or equivalent)
<br />[3]. Uniformly graded coarse aggregate, with a wash loss of no more than 0.5%, WSDOT spec 9-03.12(5) 'Gravel Backfill for Drywells', (or
<br />equivalent)
<br />RECORD DRAWING
<br />This Record Drawing has been prepared, in part,
<br />based on "As -Built" information provided by
<br />others. Though the as -built information and this
<br />drawing are based on the best available
<br />information, no presumption should be made
<br />regarding the drawing's accuracy.
<br />Jim Knappert 05/16/2024
<br />Permit Inspector
<br />NOTE: Riprap to be placed at all inlets.
<br />* RIPRAP: Crushed or Broken
<br />A
<br />Rock meeting WSDOT 9-13.4(2)
<br />Class A "Well -Graded" (or
<br />P-ni d\/n -nt1
<br />----------CLASSA
<br />---------
<br />Approx Size[i]
<br />Percent Passing
<br />tinj----
<br />----
<br />18.000
<br />---Smaller]___
<br />100.000
<br />-----
<br />--16.000---1----
<br />--- ---
<br />80-95----
<br />50-80----
<br />----12.000---
<br />8.000
<br />1
<br />----
<br />15-50
<br />---- ---
<br />4.000
<br />----
<br />15 max.
<br />[1] Approximate Size is determined by the
<br />following calculation:
<br />Size = (Length + Width + Thickness) /3
<br />Debris Barriers
<br />required on all open
<br />pipe inlets/outlets per Riprap*
<br />DCSS 4-2.3(8) -I'min above
<br />pipe crown
<br />RECORD DRAWING
<br />This Record Drawing has been prepared, in part, based on
<br />information gathered during construction and historical
<br />documents. Although the information and this drawing are
<br />based on the best available information, no presumption
<br />s a regarding the drawing's accuracy.
<br />05 03 2024
<br />gned By Date
<br />TYLER FOSTER, P.E.
<br />Print Name and Title
<br />8' �.�.....�....�.-
<br />Fi/terfabric
<br />l"min thick Riprap*
<br />underrock (embed 6')
<br />SECTION A -A
<br />(OR POINT DISPERSION PAD)
<br />2'
<br />min
<br />Chanel bottom
<br />r
<br />ARiprao
<br />/Rock
<br />Armour/
<br />0
<br />0
<br />Q
<br />0
<br />30" min
<br />\ /A
<br />V
<br />Op t/ona/
<br />L-A a/rgnment
<br />PLAN VIEW
<br />Bio-cell bottom Riprap*
<br />and side slopes 1' min above
<br />per Plan pipe crown
<br />511erfabric �l"min thick Riprap*
<br />underrock (embed 6')
<br />SECTION B-B
<br />RIPRAP PAD (PIPR OUTFALL ARMOURING
<br />SCALE: NTS per 2019 SMMWW, VOI.V.Ch.1.4.3
<br />0
<br />m
<br />2 12"CAS depth
<br />Direct Surface to French Drain
<br />Direct Surface to French Drain
<br />� 9
<br />y
<br />�i � i i �� i✓a a o o
<br />'aoo
<br />V
<br />//j/j/j/j Ja�� a�� a�� a /j�
<br />\�\�\\�\�\� 12 1\�\ Subgrade to
<br />////////// a �a o, �a ////,scarifedpriortoCAs'////
<br />/\ Ca o a \/` ,X\�\/
<br />� a � � a /A VA/VA costa//ation �� �� �A VA
<br />of/�
<br />% �% % � a a °(� (��� ,O* A% �% �%
<br />6 pen`orated i \
<br />����������� ��o o a01001o%D%recttO,iOUtt)7\7/��/�����/
<br />�� // �� �� �� ao o o� V// V// V// V// V//%
<br />�A�A�/�A�/�A�/�A���6 ,min'. o a / 3/4„- I-I12"C/ean�V��V��V��V��V�
<br />\����������� i� o 0-) a o �� ��/
<br />������������',j/////v
<br />�'. Ate' o '� \ A /
<br />/V�/V�>/// /V�/V�/ �%\ V�/\ /�S�fines/ /VA/VA/VA
<br />// // // // // // //// //
<br />\//�//�//�//��
<br />��/A ���A��A/���A���A��A�� /rencateirati/��
<br />// // // // // // // //� //� //i�///�///�//��//� 148NL or ������� /XV
<br />,</y</�//��/��/�v/%
<br />equivalent/
<br />Nalive sub soils
<br />21 French Drain Yard Connections
<br />SCALE: NTS
<br />Filter Sand Specification Table
<br />U.S. Sieve
<br />Number
<br />Percent
<br />Passing
<br />#4
<br />95-100
<br />#8
<br />70-100
<br />#16
<br />40-90
<br />#30
<br />25-75
<br />#50
<br />5-30
<br />#100
<br /><2
<br />#200
<br />j <1
<br />4x8 Sand Specification Table
<br />U.S. Sieve
<br />Number
<br />Percent
<br />Passing
<br />3/8"
<br />100
<br />#4
<br />90-100
<br />#8
<br />0-10
<br />#10
<br />0-5
<br />#100
<br />0-0.5
<br />#200 (wet sieve)
<br />0-0.5
<br />3" Coarse Compost
<br />Side slopes
<br />per plan Top of BSM: See Elevation
<br />Specified in grading plans
<br />�T •T..T.•=•=•T-•T •T-•=•=•=•T-•T •T •T-•=�
<br />• • • • •
<br />�T-LT.�i. _y�..�..LT..L!T..ti!Y=i• --e!• .L!• .LY .L!Y:.L!Y .ti!Y - =v • - • ' - - • • • -
<br />�a`yO`NANW92 va�a�iavava�a�avavava -
<br />biorerenTion )oii ivieaia t i
<br />[L
<br />4" Filter Sand I
<br />2" 4x8 Sand 6" Sand (See Spec Table)
<br />6" Filter. 8" clean, uniformly graded coarse aggregate[2]
<br />Reservoir Layer. Cean crushed, 22'-12' uniformly graded (washed
<br />drain rock) [3] Specified depth includes Filter layer. See
<br />each Cell Section for Total Depth
<br />Gravel Depth includes Filter.
<br />35 BIO-CELL MATERIALS TYPICAL SECTION
<br />SCALE: NTS
<br />Length & Width per Plan
<br />min. area: Cell A= 4,032 sf
<br />Contractor to provide Cell B= 700 sf
<br />2" drop at EOP for Flow Cell C= 300 sf
<br />Entrance to Cell. 100 Year storm
<br />3" Coarse Bioretention Cell Plantings per Recommended DOE
<br />5 a Clean chip, coarse Compost Plant List. See Drainage Report for Comprehensive
<br />edim nt filter List Cell A=1'
<br />:x. Cell B=0.5' 0. Fr d
<br />�
<br />�
<br />\.�\. I/�//3,1 max
<br />Cell C,= 0.25'
<br />1.5 Bioretention Soil Media
<br />6" Sand
<br />Cell A: 4' Gravel [2]&[3]
<br />Cell B: 3.0' Gravel [2]&[3]
<br />Cell C: 0.5' Gravel [21&[31
<br />Subgrade to be se�ROY
<br />1�' riot to ravel lC
<br />p g p �/�
<br />55 BIORETENTION CELL
<br />SCALE: NTS
<br />eTop of BSM Elevation:
<br />/;Cell A = 518.5
<br />`�CellB=517.0
<br />j"Cell C = 512.75
<br />DMil PVC Liner or
<br />�uivalent per
<br />OE V-1.3.3 w/
<br />eotechnical
<br />QQrova I.
<br />Naive i iii or .y
<br />Structural Soil
<br />Bioretention Cell to consist
<br />of materials specified in
<br />Bioretention Cell Materials,
<br />Typical Section Detail
<br />UNDERDRAIN PIPE NOTE:
<br />Underdrains shall be slotted, thick-walled plastic pipe. The slot opening should be smaller than the
<br />smallest aggregate gradation for the gravel filter bed (see
<br />Materials Section Detail) to prevent migration of the material into the drain. This configuration
<br />allows for pressurized water cleaning and root cutting if necessary.
<br />• Underdrain pipe recommendations: Minimum pipe diameter: 4 inches (See Plan for pipe sizes)
<br />• Slotted subsurface drain PVC per ASTM D1785 SCH 40.
<br />•
<br />Slots should be cut perpendicular the Ion axis of the pipe and be 0.04 to 0.069 inches b 1
<br />p p g pp Y
<br />inch long and be spaced 0.25 inches apart (spaced longitudinally). Slots should be arranged in
<br />four rows spaced on 45-degree centers and cover'/2 of the circumference of the pipe. See
<br />Underdrain Aggregate Filter and Bedding Layer for aggregate gradation appropriate for this
<br />slot size.
<br />Underdrains should be sloped at a minimum of 0.5 percent unless otherwise specified b an
<br />p p p Y
<br />engineer.
<br />Perforated PVC or flexible slotted HDPE pipe cannot be cleaned with pressurized water or root
<br />cut-ting equipment, are less durable and are not recommended. Wrapping the underdrain pipe in
<br />filter fabric increases chances of clogging and is not recommended. A 6-inch rigid non -perforated
<br />observation pipe or other maintenance access should be connected to the underdrain every 250
<br />to 300 feet to provide a clean -out port, as well as an observation well to monitor dewatering rates.
<br />.....I _
<br />6,oCBioretention Materials Section ��o�o�o�o�o��C
<br />��tov o� c o� o� o 0 0 0 0 0
<br /><(per Detail����/��/���
<br />o�6 o,D_6I ���� U17d&1ated
<br />���� Under -drain Pipe
<br />6" min
<br />SECTION
<br />Flow
<br />Fes_
<br />///////
<br />ISO
<br />TYPICAL UNDER -DRAIN SECTION & PIPE
<br />SCALE: NTS
<br />See Plan
<br />Ann n
<br />ROCK DETENTION CHAMBER
<br />23
<br />SCALE: 1 "=3'
<br />fling course: 4"
<br />t h k 8„ -4"
<br />>rmly graded
<br />rse aggregate
<br />�rvior Layer, 12.0'
<br />comp depth clean
<br />hed, 22'-12'
<br />>rmly graded.
<br />mum 0.40 porosity
<br />tired .
<br />:itive till soil
<br />compacted
<br />b-grade
<br />30Mil PVC Liner or
<br />quivalent per
<br />DOE V-1.3.3 w/
<br />.7eotechnical
<br />Approval.
<br />SECTION
<br />en
<br />---------------------------------
<br />BIORETENTION SOIL MEDIA PROCEDURE NOTE:
<br />Two acceptable criteria for Bioretention Soil Media (BSM
<br />or CAS):
<br />• Default Bioretention Soil Media
<br />• Custom Bioretention Soil Mix.
<br />L
<br />Default Bioretention Soil Media Design Criteria for Custom Bioretention Soil Mixes Projects which
<br />Projects which use the following requirements for the bioretention soil media
<br />prefer to create a custom Bioretention Soil Mix rather than using the default
<br />do not have to test the media for its saturated hydraulic conductivity
<br />requirements above must demonstrate compliance with the following
<br />Mineral Aggregate
<br />criteria using the specified test method:
<br />Percent Fines: A range of 2 to 4 percent passing the #200 sieve is ideal and
<br />fines should not be above 5 percent for a proper functioning specification •
<br />CEC >- 5 meq/100 grams of dry soil; USEPA 9081
<br />according to ASTM D422. •
<br />pH between 5.5 and 7.0
<br />Aggregate Gradation
<br />5 - 8 percent organic matter content before and after the saturated
<br />The aggregate portion of the BSM should be well -graded. According to
<br />hydraulic conductivity test; ASTM D2974(Standard Test Method for Moisture,
<br />ASTM D 2487-98 (Classification of Soils for Engineering Purposes (Unified Soil
<br />Ash, and Organic Matter of Peat and Other Organic Soils)
<br />Classification System)), well -graded sand should have the following
<br />•
<br />g radation coefficients:
<br />2-5 percent fines passing the 200 sieve; TMECC 04.1 1-A
<br />• Coefficient of Uniformity (Cu - D60/D10) equal to or greater than 4, and •
<br />Measured (Initial) saturated hydraulic conductivity of less than 12 inches
<br />• Coefficient of Curve (Cc = (D30)2/D60 x DI 0) greater than or equal to 1
<br />per hour; ASTM D 2434 (Standard Test Method for Permeability of Granular
<br />and less than or equal to 3.
<br />Soils (Constant Head)) at 85% compaction per ASTM D 1557 (Standard Test
<br />The sand gradation below is often supplied as a well -graded utility or
<br />Method s for Laboratory Compaction Characteristics of Soil Using Modified
<br />screened. With compost this blend provides enough fines for adequate
<br />Effort). Also, use Appendix V-B, Recommended Procedures for ASTM D
<br />water retention, hydraulic conductivity within recommended range (see
<br />2434 When Measuring Hydraulic Conductivity for Bioretention Soil Mixes.
<br />below), pollutant removal capability, and plant growth characteristics for •
<br />Design (long-term) saturated hydraulic conductivity of more than 1 inch
<br />meeting design guidelines and objectives. Where existing soils meet the
<br />per hour. Note: Design saturated hydraulic conductivity is determined by
<br />aggregate gradation below, those soils may be amended rather than
<br />applying the appropriate infiltration correction factors as explained above
<br />importing mineral aggregate.
<br />under "Determining Bioretention soil mix infiltration rate."
<br />•
<br />If compost is used in creating the custom mix, it must meet all of the
<br />specifications listed below for compost.
<br />General Guideline for Mineral Aggregate Gradation
<br />Sieve Size
<br />Percent Passing
<br />3/811
<br />100
<br />#4
<br />95-100
<br />#10
<br />75-90
<br />#40
<br />25-40
<br />#100
<br />4-10
<br />#200
<br />2-5
<br />COMPACT BSM TO 857o PER ASTM D1557
<br />Infiltration rates for the initial placement of Bioretention
<br />Soil Media is to be within 6 to 12 inches per hour to
<br />Compost to Aggregate Ratio, Organic Matter Content, ensure vegetation survival.
<br />Cation Exchange Capacity
<br />• Compost to aggregate ratio: 60-65 percent mineral
<br />aggregate, 35 - 40 percent compost.
<br />• Organic matter content: 5 - 8 percent by weight.
<br />• Cation Exchange Capacity (CEC) must be > 5
<br />milliequivalents/100 g dry soil Note: Soil mixes
<br />meeting the above specifications do not have to be
<br />tested for CEC. They will readily meet the minimum
<br />CEC.
<br />Compost
<br />To ensure that the BSM will support healthy plant growth and root development, contribute to biofiltration of pollutants, and not restrict infiltration when used in the proportions
<br />cited herein, the following compost standards are required.
<br />• Meets the definition of "composted materials" in WAC 173-350-220 (including contaminant levels and other standards), available online at
<br />http://www.ecy.wa.gov/programs/swfa/organics/soil.html
<br />• Produced at a composting facility permitted by the WA Department of Ecology. A current list of permitted facilities is available at
<br />http://www.ecy.wa.gov/programs/swfa/compost/
<br />• The compost product must originate a minimum of 65 percent by volume from recycled plant waste as defined in WAC 173-350-100 as "Type I Feedstocks." A maximum of 35
<br />percent by volume of other approved organic waste as defined in WAC 173-350-100 as "Type III", including postconsumer food waste, but not including biosolids, may be
<br />substituted for recycled plant waste. Type II and IV feedstocks shall not be used for the compost going into bioretention facilities or rain gardens.
<br />• Stable (low oxygen use and CO2 generation) and mature (capable of supporting plant growth) by tests shown below. This is critical to plant success in a bioretention soil
<br />mixes.
<br />• Moisture content range: no visible free water or dust produced when handling the material.
<br />• Tested in accordance with the U.S. Composting Council "Testing Methods for the Examination of Compost and Composting" (TMECC), as established in the Composting
<br />Council's "Seal of Testing Assurance" (STA) program. Most Washington compost facilities now use these tests.
<br />• Screened to the size gradations for Fine Compost under TMECC test method 02.02-B (gradations are shown in the specification in an appendix of the Low Impact
<br />Development Technical Guidance Manual for Puget Sound)
<br />• pH between 6.0 and 8.5 (TMECC 04.1 1-A). If the pH falls outside of the acceptable range, it may be modified with lime to increase the pH or iron sulfate plus sulfur to lower
<br />the pH. The lime or iron sulfate must be mixed uniformly into the soil prior to use in the bioretention area.
<br />• Manufactured inert content less that I % by weight (TMECC 03.08-A)
<br />• Minimum organic matter content of 40% (TMECC 05.07-A)
<br />• Soluble salt content less than 4.0 mmhos/cm (TMECC 04.10-A)
<br />• Maturity greater than 80% (TMECC 05.05-A "Germination and Vigor')
<br />• Stability of 7 or below (TMECC 05.08-B "Carbon Dioxide Evolution Rate")
<br />• Carbon to nitrogen ratio (TMECC 04.01 "Total Carbon" and 04.02D "Total Kjeldahl Nitrogen") of less than 25:1. The C:N ratio may be up to 35:1 for plantings composed entirely
<br />of Puget Sound Lowland native species and up to 40:1 for coarse compost to be used as a surface mulch (not in a soil mix).
<br />Soo BIORETENTION SOIL MEDIA
<br />SCALE: NTS
<br />Design Criteria:
<br />Soil Retention: The duff layer and native topsoil should be retained in an undisturbed state to the maximum extent practicable. In an areas requiring grading remove and stockpile the duff
<br />Y p p Y q gg g p
<br />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.
<br />Soil quality: The resulting soil should be conducive to the type of vegetation to be established. All areas subject to clearing and grading that have not been covered b impervious surface
<br />a y g Yp g 1 g g g Y p -
<br />incorporated into a drainage facility or engineered as structural fill or slope shall, at project completion, demonstrate the following:
<br />•loss-on-ignition
<br />A to soil la erwith a minimum or anic matter content of ten percent d weight in planting beds and 5 0 organic matter content based on a test in turf areas and a
<br />p Y g p dry g p g - � g () -
<br />pH from 6.0 to 8.0 or matching the pH of the original undisturbed soil. The topsoil layer shall have a minimum depth of eight inches except where tree roots limit the depth of
<br />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
<br />stratified layers, where feasible.
<br />• Planting beds must be mulched with 2 inches of organic material.
<br />• Quality of compost and other materials used to meet the organic content requirements:
<br />1. The organic content for "pre -approved" amendment rates can be met only using compost meeting the compost specification for Bioretention (BMP T7.30), with the exception that
<br />the compost may have up to 35% biosolids or manure.
<br />2. Compost used in bioretention areas should be stable, mature and derived from yard debris, wood waste, or other organic materials that meet the intent of the organic soil
<br />amendment specification. Biosolids and manure composts can be higher in bioavailable phosphorus than compost derived from yard or plant waste and therefore are not allowed
<br />in bioretention areas due to the possibility of exporting bio-available phosphorus in effluent.
<br />3. The compost must also have an organic matter content of 35% to 65%, and a carbon to nitrogen ratio below 25:1.
<br />4. The carbon to nitrogen ratio may be as high as 35:1 for plantings composed entirely of plants native to the Puget Sound Lowlands region.
<br />• Calculated amendment rates may be met through use of composted material meeting the requirements above; or other organic materials amended to meet the carbon to nitrogen
<br />ratio requirements, and not exceeding the contaminant limits identified in Table 220-B, Testing Parameters, in WAC 173-350-220.
<br />Implementation Options:
<br />Option 1: Leave native soil undisturaea, uiiu NiorecT iivin co«,paction auring conbiiuction.
<br />Option 1 is only applicable to sites that have the original, undisturbed soil native to the site. This will most often be forested land that is being left undisturbed in the current project.
<br />Option 2: Amend disturbed soil according to the following procedures:
<br />a. Scarify subsoil to a depth of one foot.
<br />b. In planting beds, place three inches of compost and till in to an eight -inch depth.
<br />c. In turf areas, place two inches of compost and till in to an eight -inch depth.
<br />d. Apply two to four inches of arborist wood chip, coarse bark mulch, or compost mulch to planting beds after final planting.
<br />(Alternatively, disturbed soil can be amended on a site -customized manner so that it meets the soil quality criteria set forth above, as determined by a licensed
<br />engineer, geologist landscape architect or other person as approved by Snohomish County).
<br />Option 3: Disturbed Soil.
<br />Stockpile existing topsoil during grading and replace it prior to planting. Stockpiled topsoil must be amended if needed to meet the organic matter and depth
<br />requirements by following the procedures in option (4). Remove forest duff layer and topsoil and stockpile separately, in an approved location prior to grading.
<br />Cover soil and duff piles with woven weed barrier (available from nursery supply stores) that sheds moisture yet allows airflow.
<br />Option 4: Import topsoil mix with 10% min soil organic matter content.
<br />Import topsoil mix of sufficient organic content and depth to meet the organic matter and depth requirements.
<br />NOTE: All yards, landscape areas, or disturbed areas to receive 12 inches of Compost Amended Soils meeting the criteria of BMP
<br />T5.13. Careful removal of 9 inches of the onsite Forest Duff** could meet this requirement if properly protected and cared for during
<br />the Construction Process.
<br />**Ignition testing of organics shall confirm that forest duff meets BMP T5.13 Specifications by an independent soils lab.
<br />Note: Grading with Heavy Equipment may render this layer unsuitable.
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