HomeMy WebLinkAboutR-401455REFERENCE 11-C: BIORETENTION SOIL MEDIA STANDARD SPECIFICATIONS
6.8.1.2 INSTALLATION
BIORETENTION SOIL MEDIA STANDARD
SPECIFICATIONS
11-C.1 COMPOST
Compost products shall be the result of the biological degradation and transformation of uncontaminated
biological organic materials under controlled conditions designed to promote aerobic decomposition.
Compost shall be stable with regard to oxygen consumption, carbon dioxide generation, and seed
germination and seedling vigor. Compost shall be mature with regard to its suitability for use in
stormwater facilities and BMPs, post -construction soil amendment, general landscaping, or an erosion
control BMP as defined below.
Compost shall be tested at a minimum in accordance with the U.S. Composting Council "Testing Methods
for the Examination of Compost and Composting" (TMECC), as established in the Composting Council's
"Seal of Testing Assurance" (STA) program. Most Washington compost facilities now use these tests. All
tests must be done on compost screened to specification for its intended use.
11-C.LA SPECIFICATION 1 COMPOST
1. Compost must be produced at a facility that is permitted by the jurisdictional health authority.
Permitted compost facilities in Washington are included on a list available at
<http://www.ecy.wa.goy/pro,grams/swfa/organics/soil.html>.
2. Compost must meet the definition of "composted material" in WAC 173-350-100, and must comply
with testing parameters and other standards including not exceeding contaminant limits identified in
Table 220-B. Testing Parameters, in WAC 173-350-220; and "Physical contaminants" (as defined in
WAC 173-350-100) content less than 1% by weight (TMECC 03.08-A) total, not to exceed
0.25 percent film plastic by dry weight.
3. The compost product must originate a minimum of 65 percent by volume from recycled plant waste
comprised of "yard debris," "crop residues," and "bulking agents" as those terms are defined in
WAC 173-350-100. A maximum of 35 percent by volume of "post -consumer food waste" as defined
in WAC 173-350-100 may be substituted for recycled plant waste. Biosolids, manure, and/or bedding
straw or wood chips or shavings containing animal excreta are not allowed.
4. Wood waste from chemically treated lumber and manufactured wood products containing adhesives
or any other chemical is not allowed; painted and stained wood are not allowed; and only sawdust
from virgin lumber allowed. No other toxic or otherwise harmful materials are allowed.
5. For high -density residential subdivision development, multi family, commercial, and industrial
projects, and road projects considered high ADTprojects,l the Manufacturer or Vendor shall provide
to the end buyer a list of feedstock sources by percentage by volume in the final compost product.
6. Compost shall have a moisture content that has no visible free water or dust produced when handling
the material.
1 Land uses as described in Bullets 1, 2, and 3, SWDM Section 1.2.8.1, Subsection A "Basic WO Treatment Areas, Required Treatment
Menu."
2017 City of Renton Surface Water Design Manual
11-C-1
REFERENCE 11: MATERIALS
12/1/2016
7. Compost shall have an organic matter content of 40 percent to 65 percent by dry weight as determined
by loss of ignition test method ASTM D 2974, or by U.S. Composting Council TMECC 05.07A
"Loss -On -Ignition Organic Matter Method (LOI)."
8. Compost shall have a carbon to nitrogen ratio below 25:1, although 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. The carbon to nitrogen ratio shall be calculated on a dry weight basis using TMECC 5.02A
("Carbon to Nitrogen Ratio"), which uses TMECC 04.01A, "Organic Carbon" divided by the dry
weight of "Total N" (TMECC 04.02D).
9. Compost pH shall be between 6.0 and 8.5 when tested in accordance with U.S. Composting Council
TMECC 04.11-A, "1:5 Slurry pH."
10. Soluble salt content shall be less than 4.0 dS/m (mmhos/cm) when tested in accordance with
U.S. Composting Council TMECC 04.10 `Electrical Conductivity, 1:5 Slurry Method, Mass Basis."
11. Compost maturity indicators from a cucumber bioassay (TMECC 05.05-A "Germination Seedling
Emergence and Relative Growth) must be greater than 80% for both emergence and vigor").
12. Stability shall be 7-mg CO2 - C/g OM/day or below in as determined by U.S. Composting Council
TMECC 05.08-13 "Carbon Dioxide Evolution Rate," to establish low oxygen use and low CO2
generation rates.
Compost shall be screened to the Fine Compost size gradation specification in Section 11-C. LC of this
Reference.
11-C.LB SPECIFICATION 2 COMPOST
1. Specification 2 Compost manufacturing, feedstocks, and testing are all identical to Specification 1
Compost except that:
a) A maximum of 35 percent by volume of biosolids or manure may be substituted for recycled plant
waste.
b) Compost may be fine or coarse gradation depending on use and need to meet other screened
material quality criteria.
c) Carbon to Nitrogen ratio may be up to 40:1 for coarse compost to be used as a surface mulch (not
in a soil mix).
11-C.1.0 COMPOST SCREENING SIZE GRADATIONS
Where compost gradation is specified, it must meet the following size gradations when tested in
accordance with the U.S. Composting Council "Test Methods for the Examination of Compost and
Composting" (TMECC) Test Method 02.02-B.
Fine Compost shall meet the following gradation by dry weight:
Minimum percent passing 2" sieve 100%
Minimum percent passing 1 " sieve 99%
Minimum percent passing 5/8" sieve 90%
Minimum percent passing 1/4" sieve 75%
12/1/2016
CALL 48 HOURS
BEFORE YOU DIG
1- 800- 424- 5555
Coarse Compost shall meet the following gradation by dry weight:
Minimum Percent passing 3" sieve
100%
Minimum Percent passing 1" sieve
90%
Minimum Percent passing 3/4" sieve
70%
Minimum Percent passing 1/4" sieve
40%
i BergerABAM
N%Wldw
33301 9th Avenue South, Suite 300
Federal Way, Washington 98003-2600
(206) 431-2300 Fax:(206) 431-2250
11-C-2
2017 City of Renton Surface Water Design Manual
11-C.LD COMPOST ACCEPTANCE REQUIREMENTS
The Contractor shall submit the following information to the King County Department of Permitting and
Environmental Review (DPER) Engineer for approval:
1. If the manufacturer is not exempt under Table 220-A, "Terms and Conditions for Solid Waste Permit
Exemptions," a copy of the Solid Waste Handling Permit issued to the compost manufacturer by the
Jurisdictional Health Department in accordance with WAC 173-350 (Minimum Functional Standards
for Solid Waste Handling) or for biosolids composts a copy of the Coverage Under the General Permit
for Biosolids Management issued to the manufacturer by the Department of Ecology in accordance
with WAC 173-308 (Biosolids Management).
2. The Applicant shall provide written verification and lab analyses that the material complies with the
processes, testing, and standards specified in WAC 173-350 and these Specifications. An independent
Seal of Testing Assurance (STA) Program certified laboratory2 or a laboratory accredited by WA
Ecology3 for the specified methods shall perform the analyses. Lab analysis shall be for the compost
delivered on site for project use.
3. A copy of the STA laboratory's Seal of Testing Assurance STA certification as issued by the
U.S. Composting Council, or a copy of the Ecology -certified laboratory's accreditation for the
specified methods.
11-C.2 BIORETENTION SOIL MIX SPECIFICATIONS
Follow the specification below for the approved default bioretention soil mix. Alterations to this
specification require an approved adjustment.
11-C.2.A DEFAULT BIORETENTION SOIL MIX
Bioretention Soil Mix (BSM) shall be a well -blended homogeneous mixture of Bioretention Mineral
Aggregate and Bioretention Compost measured on a volume basis composed of-
0 35 to 40 percent by volume Specification 1 Compost per Section 11-C.1.A above and
Section 11-C.2.B below.
0 60 to 65 percent by volume Bioretention Mineral Aggregate per Section 11-C.2.0 below.
Projects which prefer to create a custom Bioretention Soil Mix rather than using the default requirement
above must demonstrate compliance with criteria as described in Ecology's Stormwater Management
Manual for Western Washington (2014) Volume V - Runoff Treatment BMPs, except that any more
stringent compost criteria required by this Reference 11-C are applicable.
11-C.2.B BIORETENTION COMPOST
Bioretention Compost shall be Specification 1, Fine Compost per Sections 11-C.LA and 11-C.LC of this
Reference. Fine Specification 1 Compost shall be used for Bioretention Soil Mix and for any compost used
to amend bioretention cell soil.
2 A list of STA certified laboratories can be found at <http://coma ostingcouncil.org/labs/>.
3 A list of WA Ecology accredited laboratories can be found at <httD://www.ecy.wa.gov/programs/eap/labs/>. Only laboratories
certified for the specified methods may be used for compost testing.
2017 City of Renton Surface Water Design Manual
11-C-3
REFERENCE 11: MATERIALS
11-C.2.0 BIORETENTION SOIL MIX AGGREGATE
Aggregate Gradation
12/1/2016
The following table provides a gradation guideline for the aggregate component of a Bioretention Soil Mix
specification in western Washington. This sand gradation is often supplied as a well -graded utility or
screened. With compost, this blend provides enough fines for adequate water retention, hydraulic
conductivity within recommended range (see below), pollutant removal capability, and plant growth
characteristics for meeting design guidelines and objectives.
TABLE 11-C.2.A BIORETENTION SOIL MIX
MINERAL AGGREGATE GRADATION
Sieve Size
Percent Passing
3/8"
100
#4
95-100
#10
75-90
#40
25-40
#100
1 4-10
#200
2-4
Where existing soils meet the above aggregate gradation, those soils may be amended rather than
importing mineral aggregate.
11-C.3 BIORETENTION MULCH
Mulch may only be composed of either chipped wood as defined in Section 11-C.3.A, or compost as
defined in Section 11-C.3.B. Mulch may not be made of synthetic materials including but not limited to
recycled tire material, virgin rubber material, plastics; or pre -or post -consumer cardboard.
11-C.3.A ARBORIST' S WOOD CHIP MULCH
12/1/2016
Arborist Wood Chip Mulch shall be coarse ground wood chips (approximately 1/2" to 6" along the longest
dimension) derived from the mechanical grinding or shredding of the above -ground portions of trees. It
may contain wood, wood fiber, bark, branches, and leaves, but may not contain visible amounts of soil. It
shall be free of weeds and weed seeds including but not limited to plants on the King County Noxious
Weed list available at: <www.kin cg ounty.gov/weeds>, and shall be free of invasive plant portions capable
of re -sprouting, including but not limited to horsetail, ivy, clematis, knotweed, etc. It may not contain
more than 0.5% by dry weight of manufactured inert material (plastic, concrete, ceramics, metal, etc.).
Arborist Wood Chip Mulch, when tested, shall meet the following loose volume gradation:
TABLE 11-C.3.A ARBORIST WOOD MULCH GRADATION
Sieve Size
Percent Passing
1 inch
100
2"
95-100
1"
70-100
5/8
0-50
No. 4
1 0 - 30
11-C-4
2017 City of Renton Surface Water Design Manual
REFERENCE 11-C: BIORETENTION SOIL MEDIA STANDARD SPECIFICATIONS
Prior to delivery, the Applicant shall provide the following:
1. The source of the product and species of trees included in it;
2. A sieve analysis verifying the product meets the above size gradation requirement;
3. A representative sample of the product for County approval.
11-C.3.B COMPOST MULCH SPECIAL REQUIREMENTS
• Compost Mulch for Bioretention must meet the Specification 1 compost requirements of
Section 11-C.1.A, except that the gradation must be Coarse Compost per Section 11-C.LC
• Compost Mulch for other facilities and BMPs must meet either Specification 1 or Specification 2
compost of Section 11-C. LA or 11-C.1.B respectively, except that the gradation must be Coarse
Compost per Section 11-C.1.C.
2017 City of Renton Surface Water Design Manual
11-C-5
12/1/2016
TABLE 6.8.1.C. UNDERDRAIN AGGREGATE
Sieve Size
Percent Passing
3/ inch
100 percent
'/ inch
30 to 60 percent
U.S. No. 8
20 to 50 percent
U.S. No. 50
3 to 12 percent
U.S. No. 200
0 to 1 percent
CIVIL PERMIT SET
V3
DESIGN BY: BERGERABAM DATE 10/22/2018
Excavation
Soil compaction can lead to facility failure; accordingly, minimizing compaction of the base and sidewalls
of the bioretention area is critical. Excavation should never be allowed during wet or saturated conditions
(compaction can reach depths of 2-3 feet during wet conditions and mitigation is likely not be possible).
Excavation should be performed by machinery operating adjacent to the bioretention facility and no heavy
equipment with narrow tracks, narrow tires, or large lugged, high pressure tires should be allowed on the
bottom of the bioretention facility. If machinery must operate in the bioretention cell for excavation, use
light weight, low ground -contact pressure equipment and rip the base at completion to refracture soil to a
minimum of 12 inches. If machinery operates in the facility, subgrade infiltration rates must be field tested
and compared to design rates. Failure to meet or exceed the design infiltration rate will require revised
engineering designs to verify achievement of treatment and flow control benefits that were estimated in the
Stormwater Site Plan.
Prior to placement of the bioretention soil mix, the finished subgrade shall:
• Be scarified to a minimum depth of 3 inches.
• Have any sediment deposited from construction runoff removed. To remove all introduced sediment,
subgrade soil should be removed to a depth of 3-6 inches and replaced with bioretention soil mix.
• Be inspected by the responsible engineer to verify required subgrade condition.
Sidewalls of the facility, beneath the surface of the bioretention soil mix, can be vertical if soil stability is
adequate. Exposed sidewalls of the completed bioretention area with bioretention soil mix in place should
be no steeper than 3H:1 V. The bottom of the facility should be flat.
Soil Placement
Onsite soil mixing or placement shall not be performed if bioretention soil mix or subgrade soil is
saturated. The bioretention soil mixture should be placed and graded by machinery operating adjacent to
the bioretention facility. If machinery must operate in the bioretention cell for soil placement, use light
weight equipment with low ground -contact pressure. If machinery operates in the facility, subgrade
infiltration rates must be field tested and compared to design rates. Failure to meet or exceed the design
infiltration rate will require revised engineering designs to verify achievement of treatment and flow
control benefits that were estimated in the Stormwater Site Plan.
The soil mixture shall be placed in horizontal layers not to exceed 12 inches per lift for the entire area of
the bioretention facility.
Compact the bioretention soil mix to a relative compaction of 85 percent of modified maximum dry
density (ASTM D 1557). Compaction can be achieved by boot packing (simply walking over all areas of
each lift), and then apply 0.2 inches (0.5 cm) of water per 1 inch (2.5 cm) of bioretention soil mix depth.
Water for settling should be applied by spraying or sprinkling.
Temporary Erosion and Sediment Control (TESC)
Controlling erosion and sediment are most difficult during clearing, grading, and construction;
accordingly, minimizing site disturbance to the greatest extent practicable is the most effective sediment
management. During construction:
• Bioretention facilities should not be used as sediment control facilities and all drainage should be
directed away from bioretention facilities after initial rough grading. Flow can be directed away from
the facility with temporary diversion swales or other approved protection. If introduction of
construction runoff cannot be avoided see below for guidelines.
• Construction on bioretention facilities should not begin until all contributing drainage areas are
stabilized according to erosion and sediment control BMPs and to the satisfaction of the engineer.
• If the design includes curb and gutter, the curb cuts and inlets should be blocked until bioretention soil
mix and mulch have been placed and planting completed (when possible), and dispersion pads are in
place.
Every effort during design, construction sequencing and construction should be made to prevent sediment
from entering bioretention facilities. However, bioretention areas are often distributed throughout the
project area and can present unique challenges during construction.
Erosion and sediment control practices must be inspected and maintained on a regular basis.
6.8.1.3 VERIFICATION
If using the default bioretention soil mix, pre -placement laboratory analysis for saturated hydraulic
conductivity of the bioretention soil mix is not required. Verification of the mineral aggregate gradation,
compliance with the compost specifications, and the mix ratio must be provided.
If using a custom bioretention soil media, verification of compliance with the minimum design criteria
cited above for such custom mixes must be provided. This will require laboratory testing of the material
that will be used in the installation. Testing shall be performed by a Seal of Testing Assurance, AASHTO,
ASTM or other standards organization accredited laboratory with current and maintained certification.
Samples for testing must be supplied from the bioretention soil mix that will be placed in the bioretention
areas.
If testing infiltration rates is necessary for post -construction verification use the Pilot Infiltration Test
(PIT) method or a double ring infiltrometer test (or other small-scale testing allowed by the local
government with jurisdiction). If using the PIT method, do not excavate bioretention soil mix (conduct test
at level of finished bioretention soil mix elevation), use a maximum of 6 inch ponding depth and conduct
test before plants are installed.
R-401455
IN COMPLIANCE WITH CITY OF RENTON STANDARDS
DEVELOPMENT ENGINEERING
Ann Fowler 12/14/2018 01
SURFACE WATER UTILITY
rstraka 12/14/2018
SYM REVISION BY APPROVED DATE SYM REVISION BY APPROVED DATE DRAWN DATE SUBTITLE CURRENT REVISION SYMBOL DATE
ACCEPTABILITY 10/09/18
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