HomeMy WebLinkAboutD_Stormwater Adjustment 2020-1_Earlington Townhomes_20200303.pdf
March 3, 2020
Ms. Sunshine Kapus
Polygon LWH, LLC
11624 SE 5th Street
Bellevue, WA 98005
Email: sunshine.kapus@polygonhomes.com
RE: Earlington Townhomes (C17004096) - Adjustment 2020-01
CONTECH Engineered Solutions, StormFilter w/MetalRx Media for Enhance Treatment
Dear Ms. Kapus:
The City of Renton has completed review of the adjustment request for Earlington Townhomes
(C17004096) in accordance with the City adopted 2017 City of Renton Surface Water Design
Manual (RSWDM). As the Applicant, you are requesting an adjustment from the 2017 RSWDM
Section 6.1.2, Enhanced Basic Water Quality Menu, to use CONTECH Engineered Solutions
StormFilter with MetalRx Media within facilities that are in public right of way and private
property.
Findings:
1. The project is a zero lot line 60 unit multi-family project and is located at 8220 S 132nd
Street.
2. The storm facilities within public right of way will be publicly maintained and those
within private property will be privately maintained.
3. The project is vested to the City adopted 2017 City of Renton Surface Water Design
Manual (RSWDM).
4. The CONTECH Engineered Solutions StormFilter with MetalRx Media received
Washington State Department of Ecology Conditional Use Level Designation (CULD) for
Basic and Dissolved Metals (Enhanced) Treatment in October 1, 2014 and has
continually received annual extensions CULD approval with the most recent approval
scheduled to expire July 1, 2020.
5. The City of Renton requires a Two-Year Maintenance and Defect Bond be provided to
the City at the project construction completion which will be used to monitor the
performance of the system.
Ms. Sunshine Kapus
March 3, 2020
Page 2 of 2
The use of CONTECH Engineered Solutions StormFilter with MetalRx Media to provide
enhanced basic water quality treatment is approved for the Earlington Townhomes with the
following conditions of use that are required by the Department of Ecology (CULD approval).
Conditions:
1. Design, assemble, install, operate, and maintain CONTECH Engineered Solutions
StormFilter with MetalRx Media in accordance with applicable CONTECH Engineered
Solutions manuals, documents, and the Ecology Decision.
2. Discharges from the CONTECH Engineered Solutions StormFilter with MetalRx Media
system shall not cause or contribute to water quality standards violations in receiving
waters.
3. If Department of Ecology CULD approval has been rescinded during the Two-Year
Maintenance and Defect Period following construction completion, then the Applicant
must find another method to provide Enhanced basic water quality treatment for the
project.
If you have any questions about this adjustment, please contact Brianne Bannwarth,
Development Engineering Manager, at (425) 430-7299 or Joseph Farah, Surface Water Utility
Engineering Manager, at (425) 430-7248.
Sincerely,
BRIANNE BANNWARTH, PE JOSEPH FARAH, PE
Development Engineering Manager Surface Water Utility Engineering Manager
cc: Ron Straka, PE, Utility Systems Director
Justin Johnson, PE, Assist. Development Engineering Manager
Richard Marshall, Surface Water/Waste Water/Special Projects Manager
Gary Fink, Surface Water Civil Engineer III
Enclosures: - Stormwater Adjustment Request
- CULD for Basic (TSS) and Dissolved Metals (Enhanced) Treatment for CONTECH Engineered Solutions Storm
Water Management StormFilter with MetalRx Media
• 12100 NE 195th Street, Suite 300
• Bothell, Washington 98011
• Ph 425.885.7877
• www.coredesigninc.com
MEMORANDUM
To: Ann Fowler
City of Renton
From:
Gary R. Sharnbroich, P.E.
Core Design Inc.
14711 NE 29th Place, Suite 101
Date: December 7, 2018
Subject: Earlington Townhomes Water Quality
This memo addresses a change to the required water quality treatment level onsite. Under the approved
civil plans, the project was originally designed to be subdivided as a fee-simple plat, which was
considered to be single family. The developer is now proposing to use a condominium instead of a plat to
subdivide the units. The final housing products are the same, but the way the land will be divided has
technically changed the project from single to multifamily residences.
The project was originally designed for basic water quality treatment since it was operating as a single-
family development. However, under Section 1.2.8.1 of the 2016 King County Surface Water Design
Manual (KCSWDM) any project with 50 percent or more runoff from multifamily use, are required to
comply with the Enhanced basic menu instead. Under the basic water quality requirement, the project
proposed proprietary media filters. Since the project is now under the enhanced basic treatment menu the
proprietary media is still feasible if the media mix is changed. The Contech MetalRx media has been
approved at the conditional use level for enhanced basic treatment under the Department of Ecology
(DOE) testing and is proposed for the project. Refer to the attached conditional use level designation from
the DOE.
In summary,to meet the Enhanced Basic water quality standard, the project proposes to use the Contech
Stormfilter with MetalRx media.
Sincerely,
Core Design Inc.
Gary R. Sharnbroich, P.E.
Project Engineer
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October 2019
CONDITIONAL USE LEVEL DESIGNATION FOR BASIC (TSS) AND
DISSOVLED METALS (ENHANCED) TREATMENT
For
CONTECH Engineered Solutions
Stormwater Management StormFilter®
with MetalRx™ media
Ecology’s Decision:
Based on Contech Engineered Solutions application, Ecology hereby issues conditional use
level designation (CULD) for the Stormwater Management StormFilter® using MetalRx™
media cartridges:
1. Conditional Use Level Designation (CULD) for Basic Treatment (total suspended
solids) and for Dissolved Metals (“Enhanced”) treatment.
• Sized at a hydraulic loading rate of no greater than 1 gallon per minute (gpm) per
square foot (sq ft.) of media surface, per Table 1.
• Using Contech’s MetalRx media. Specifications for the media shall match the
specifications provided by the manufacturer and approved by Ecology.
Table 1. StormFilter design flow rates for 18-inch
diameter cartridges with MetalRx media, operating at 1
gpm/sq ft.
Effective cartridge height (in) Cartridge flow rate
(gpm/cartridge)
12 5
18 7.5
27 11.25
2. Ecology approves StormFilter systems containing MetalRx media for treatment at the
hydraulic loading rates shown in Table 1, to achieve the maximum water quality design
flow rate. The water quality design flow rates are calculated using the following
procedures:
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• Western Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
the latest version of the Western Washington Hydrology Model or other Ecology-
approved continuous runoff model.
• Eastern Washington: For treatment installed upstream of detention or retention,
the water quality design flow rate is the peak 15-minute flow rate as calculated using
one of the three methods described in Chapter 2.2.5 of the Stormwater Management
Manual for Eastern Washington (SWMMEW) or local manual.
• Entire State: For treatment installed downstream of detention, the water quality
design flow rate is the full 2-year release rate of the detention facility.
3. The use level designation expires on July 1, 2020 unless Ecology extends the date, and is
subject to the conditions specified below.
Ecology’s Conditions of Use:
StormFilter systems containing MetalRx media shall comply with the following conditions:
1. Design, assemble, install, operate, and maintain StormFilter systems containing
MetalRx media in accordance with applicable Contech Engineered Solutions manuals,
documents and the Ecology Decision.
2. Use sediment-loading capacity, in conjunction with the water quality design flow rate,
to determine the target maintenance interval.
3. Install StormFilter systems in such a manner that you bypass flows exceeding the water
quality treatment rate or you will not re-suspend captured sediments.
4. Contech Engineered Solutions commits to submitting a QAPP for Ecology review and
approval by October 1, 2014 that meets the TAPE requirements for attaining a GULD
for basic and dissolved metals treatment.
5. Contech Engineered Solutions shall complete all required testing and submit a TER for
Ecology review by January 1, 2020.
6. Contech Engineered Solutions may request Ecology to grant deadline or expiration date
extensions, upon showing cause for such extensions.
7. This CULD approval allows up to ten (10) installations of StormFilter systems
containing MetalRx media within the State of Washington for development and
redevelopment projects (as defined by the Stormwater Management Manual Western
Washington). The limit of ten sites applies to the total number of installations; whether
for basic or for dissolved metals (enhanced) treatment.
8. Maintenance: The required maintenance interval for stormwater treatment devices is
often dependent upon the degree of pollutant loading from a particular drainage basin.
Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance
cycle for a particular model/size of manufactured filter treatment device
• Typically, CONTECH designs StormFilter systems for a target filter media
replacement interval of 12 months. Maintenance includes removing accumulated
sediment from the vault, and replacing spent cartridges with recharged cartridges.
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• Indications of the need for maintenance included the effluent flow decreasing to
below the design flow rate, as indicated by the scumline above the shoulder of the
cartridge.
• Owners/operators must inspect StormFilter with MetalRx for a minimum of twelve
months from the start of post-construction operation to determine site-specific
maintenance schedules and requirements. You must conduct inspections monthly
during the wet season, and every other month during the dry season. (According to
the SWMMWW, the wet season in western Washington is October 1 to April 30.
According to SWMMEW, the wet season in eastern Washington is October 1 to June
30). After the first year of operation, owners/operators must conduct inspections
based on the findings during the first year of inspections.
• Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and
you must use methods capable of determining either a decrease in treated effluent
flowrate and/or a decrease in pollutant removal ability.
• When inspections are performed, the following findings typically serve as
maintenance triggers:
• Accumulated vault sediment depths exceed an average of 2 inches, or
• Accumulated sediment depths on the tops of the cartridges exceed an average of
0.5 inches, or
• Standing water remains in the vault between rain events, or
• Bypass during storms smaller than the design storm.
• Note: If excessive floatables (trash and debris) are present, perform a minor
maintenance consisting of gross solids removal, not cartridge replacement.
9. Discharges from the StormFilter systems containing MetalRx media shall not cause or
contribute to water quality standards violations in receiving waters.
Applicant: CONTECH Engineered Solutions
Applicant’s Address: 11835 NE Glenn Widing Dr.
Portland, OR 97220
Application Documents:
§ August 27, 2012 letter from CONTECH Engineered Solutions requesting a CULD from
Washington State Department of Ecology.
§ Application and supporting documentation. Stormwater Management StormFilter®
MetalRx™ at a Specific Flow Rate of 1 gpm/ft2.
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• Volume 1 – Technology Description
o Appendix A – Specifications
o Appendix B – Schematics
o Appendix C – Operations & Maintenance
o Volume 2 - MetalRx™ at 1 gpm/ft2
o Lab testing
o Field Testing
o Appendix A – Site Report
o Appendix B – Statistics
o QAPP
Applicant’s Use Level Request:
• General use level designation as a basic (TSS) and dissolved metals treatment device in
accordance with Ecology’s 2012 Stormwater Management Manual for Western
Washington and Technology Assessment Protocol – Ecology (TAPE January 2011
Revision).
Applicant’s Performance Claims:
Based on results from laboratory and field-testing, the applicant claims:
• The Stormwater Management StormFilter with MetalRx media operating at 1 gpm/ft2
removes greater than 80% suspended solids for influent concentrations greater than 100
mg/L, 60% dissolved zinc for influent concentrations greater than 20 ug/L, and 30%
dissolved copper for influent concentrations greater than 5 ug/L.
Recommendations:
Ecology finds that:
• CONTECH Engineered Solutions qualifies for the opportunity to demonstrate, through
field-testing in the Pacific Northwest, whether the StormFilter system with MetalRx
media can attain Ecology’s basic and dissolved metals treatment goals.
Findings of Fact:
Laboratory testing
• Since 1992, CSF® leaf, XFCSF™, and MetalRx media have been widely tested to
investigate their pollutant removal capabilities for stormwater.
• In one laboratory study, Stormwater Management tested a single cartridge with XFCSF
media for TSS, copper, and zinc removal using synthetic stormwater. Test flow rate was
6.5 gpm (slightly lower than the 7.5 gpm that corresponds to a loading of 1 gpm/ft2).
Contech made synthetic stormwater using zinc and copper salts and sandy loam (USDA)
or sandy organic (USCS) sediment. Eight (8) of 14 test runs had TSS concentrations
within the TAPE assessment range. These influent TSS concentrations ranged from 22 to
68 mg/L, and TSS removal was between 89 and 95 percent. Two (2) of 14 test runs had
influent dissolved zinc in the TAPE assessment range, with a removal of 78-80 percent
(influent concentrations 0.155, 0.185 mg/L). The remaining twelve (12) runs had much
higher dissolved zinc influent concentrations, with removals ranging from 93 to 98
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percent. The influent dissolved copper concentrations for all runs were higher than the
TAPE assessment range of 0.005 to 0.02 mg/L. Influent dissolved copper ranged from
0.024 mg/L to 17.0 mg/L. Dissolved copper removal ranged from 15 to 97 percent
(average of 65 percent).
Field testing
• Contech conducted monitoring of a StormFilter system using a blend of perlite and
MetalRx media treating runoff from a 2.3-acre parking lot. Influent TSS concentration
ranged from 22 to 71 mg/L. Discrete TSS removal efficiency ranged from 68 to 78
percent (5 storm events). Removal efficiency for influent dissolved zinc in the range of
19 to 60 ug/L ranged from 41 to 77 percent, with an average of 63 percent (6 storm
events). Dissolved copper removal for a single event was 22 percent (influent 3.33 ug/L;
effluent 2.59 ug/L).
• Contech conducted monitoring of a large-scale StormFilter system using MetalRx media
treating runoff from 152 acres of airport runoff (roads, parking lots, roofs, taxiways,
landscaping). The StormFilter system is downstream of a detention pond; therefore;
influent TSS concentrations for all monitored events were lower than the lower end of the
TAPE assessment range (<20 mg/L). Dissolved zinc removal ranged from 47 to 80
percent for influent concentrations from 30 to 52 ug/L. Average dissolved zinc removal
was 68 percent (11 events). Dissolved copper removal ranged from -3 to 50 percent for
influent concentrations from 7.7 to 18 ug/L. Average dissolved copper removal was 32.3
percent (11 events).
• Contech conducted monitoring of a StormFilter system using XFCSF media treating
runoff from a 1-acre galvanized metal roof. The XFCSF media is similar to MetalRx
media, except that XFCSF media comprises slightly larger gradation of media pellets.
Contech did not monitor TSS removal for this study. Influent dissolved zinc
concentrations were all higher than the upper end of the TAPE assessment range (> 300
ug/L), and ranged from 389 to 11,600 ug/L. Dissolved zinc removal ranged from 25 to 90
percent, with an average removal of 64 percent (12 events). Influent dissolved copper
ranged from 2.1 to 18.2 ug/L. Dissolved copper removal ranged from 27 to 76 percent,
with an average removal of 55 percent.
Other StormFilter system MetalRx media matters to be addressed by the company:
1. Test the system under normal operating conditions, such that pollutants partially fill the
settling basin. Results obtained for “clean” systems may not be representative of typical
performance.
2. Conduct field-testing at sites that are indicative of the treatment goals.
3. Conduct testing to obtain information about maintenance requirements in order to come up
with a maintenance cycle.
4. Conduct loading tests on the filter to determine maximum treatment life of the system.
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Technology Description: Download at: http://www.conteches.com/Products/Stormwater-
Management/Treatment/Stormwater-Management-StormFilter.aspx
Contact Information:
Applicant: Jeremiah Lehman
Contech Engineered Solutions
11835 NE Glenn Widing Drive
Portland, OR, 97220
503-258-3136
jlehman@conteches.com
Applicant website: www.conteches.com
Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html
Ecology: Douglas C. Howie, P.E.
Water Quality Program
(360) 407-6444
douglas.howie@ecy.wa.gov
Revision History
Date Revision
November 7, 2012 Original Draft use-level-designation document: CULD for basic and
dissolved metals (enhanced).
November 2016 Revised Contech contact information
April 2017 Revised TER submittal and Expiration dates
October 2019 Revised TER submittal and Expiration dates
Attachments
August 27, 2012 letter from Contech Engineered Solutions.
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