Contech Modular Wetland Linear Stormwater Bioretention

Conditions of use

1. All configuration options for the Modular Wetland Systems Linear are approved for pollution reduction. Selection of a specific configuration is the responsibility of the project designer.
2. Use of Modular Wetland Systems Linear does not exempt a project or site from required flow control requirements, operations and maintenance requirements, or other applicable requirements of the Stormwater Management Manual.
3. For use in the public right-of-way, the following conditions must be met:
   • Units must meet City of Portland street design requirements, including but not limited to H-20 vehicle load rating, non-slip surface, and American with Disabilities Act tolerances specific to surface grates or vault lids. 
   • The Operations & Maintenance Plan must call for an assessment during the two-year warranty period of project-specific maintenance requirements and frequencies.
   • The following Zone 8 or Northwest region plants are allowed:
     • Bluestem, Turkey Foot Bluestem - Andropogon gerardii 
     • Bluestem, Lindheimer's / Seacoast Bluestem - Schizachyrium scoparium 
     • Canna, Canna Tropicana, Canna Lilly - Canna X generalis 
     • Cape Lily, Powell's Crinum Lily - Crinum X powellii 
     • Daylily - Hemerocallis hybrids 
     • Gaura, White "Whirling Butterflies" - Gaura lindheimeri 
     • Grass, Vetiver - Vetiveria zizanioides (L.) 
     • Heavenly Bamboo, Dwarf - Nandina domestica "Nana"
     • Heavenly Bamboo, Moon Bay - Nandina domestica "Moon Bay"
     • Indiangrass, Yellow Indiangrass - Sorghastrum nutans 
     • Iris, African / Fortnight Lily / Morea Iris - Dietes iridioides
     • Joe Pye Weed, Queen-of-the-Meadow - Eupatorium fistulosum 
     • Lavender - Lavandula L. 
     • Lily, Lily-of-the-Nile / African Lily / African Blue Lily - Agapanthus spp 
     • Muhlygrass, Lindheimer's / Blue - Muhlenbergia lindheimeri 
     • Muhlygrass, Gulf / Mist Grass / Hairawn Muhly - Muhlenbergia capillaris 
     • Oregon Grape, Creeping - Mahonia repens
     • Oregon Grape, Cascade - Mahonia nervosa
     • Purple Coneflower - Echinacea purpurea
     • Society Garlic, Pink Agapanthus - Tulbaghia violacea 
     • Rose Campion, Mullein Pink, Dusty Miller - Lychnis coronaria 
     • Rush, Japanese Sweet Flag - Acorus gramineus 
     • Rush, Spreading - Juncus patens
     • Rye, Giant Wild - Leymus condensatus 
     • Sage, Russian - Perovskia atriplicifolia 
     • Sea Oats - Chasmanthium paniculatum / Uniola paniculata 
     • Sedge, Umbrella Plant - Cyperus involucratus 
     • Sedge, Brome Hummock - Carex bromoides
     • Sedge, Slough - Carex obnupta
     • Spiraea, Japanese - Spiraea japonica
     • Spiraea, Birchleaf - Spiraea betulifolia
     • Spiraea, Mountain - Spiraea densiflora
4. Modular Wetland Systems-certified providers must be utilized for activation, inspection and maintenance of installed systems. 

Project designer responsibilities

1. Ensuring that the conditions of use are met.
2. Ensuring that the project meets all applicable requirements of the Stormwater Management Manual, such as the Stormwater Infiltration and Discharge Hierarchy, in order to use Modular Wetland Systems Linear.
3. Ensuring that the design and installation of the units are appropriate for the project goals, site conditions, long-term maintenance requirements, and any other site-specific design requirements on private property or for use in the public right-of-way.

4. Sizing units to meet the current Stormwater Management Manual presumptive design approach and pollution reduction requirements. The pollution reduction capacity is flow-based and assumes a treatment flow intensity of 0.19 inches per hour and a 0.90 runoff coefficient using the Rational Method with a treatment rate of 1 gpm/square foot. The treatment capacity for Modular Wetland Systems Linear units are provided in Table 1.

   Table 1. Modular Wetland Systems Linear sizing to meet City of Portland pollution reduction requirements

   Unit size (ft)	Treatment Capacity (cfs)	Maximum Drainage Area (acres)
   4 x 4	0.051	0.31
   4 x 6	0.071	0.42
   4 x 8	0.112	0.66
   4 x 13	0.139	0.82
   4 x 15	0.170	0.99
   4 x 17	0.200	1.17
   4 x 19	0.230	1.35
   4 x 21	0.261	1.52
   6 x 8	0.142	0.83
   8 x 8	0.224	1.31
   8 x 12	0.336	1.97
   8 x 16	0.448	2.62
   8 x 20	0.561	3.28
   8 x 24	0.673	3.93

5. Each site plan must undergo Modular Wetland Systems review before the City of Portland can approve the unit(s) for site installation. A letter that certifies that the project has been designed to manufacturer's specification must be submitted to the Bureau of Environmental Services prior to the appropriate design milestone. For public improvements, including public works permits, the letter must be submitted to the Bureau of Environmental Services prior to 60% plan review. For installation on private property, the letter must be submitted prior to building permit plan approval. The project designer is highly encouraged to work with Modular Wetland Systems  prior to the appropriate review milestone in order to maximize placement and performance of the unit(s).  
6. If the project designer wants to use plants in public facilities not approved under the Conditions of Use, the project designer is required to get written approval from the City of Portland Environmental Services Revegetation Program and Modular Wetland Systems prior to 90% plan review.
7. If the project designer wishes to vary from these conditions of approval, the project designer must use the Performance Design Approach.  

Approval conditions

1. The Bureau of Environmental Services may at any time suspend or revoke approval if the performance of the technology does not meet performance criteria, or if the performance criteria change due to the local, state, or federal pollution reduction standards.  
2. If any changes, updates, or revisions have occurred to the Modular Wetland Systems Linear, the applicant must obtain Washington State Department of Ecology Technology Assessment Protocol General Use Level Designation certification and re-apply following submission guidelines in effect at the time of application.  

More information on the product can be found on the manufacturer's product website. 

Approved: June 2016 under the requirements of the 2014 Stormwater Management Manual.