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Silva cell 11-8-13MSC Metropolitan St. Louis Sewer District 2350 Market Street St. Louis, MO 63103-2555 (314) 768-6200 November 8, 2013 Ms. Brenda Guglielmina DeepRoot Green Infrastructure, LLC P.O. Box 927 Decatur, GA 30031-0927 RE: Silva Cell System: St. Louis MSD Submission Dear Ms. Guglielmina: The Metropolitan St. Louis Sewer District (MSD) has reviewed your application regarding the Silva Cell for use as a Best Management Practice for stormwater management. Silva Cell may be used to supplement permeable pavement as a stand-alone water quality BMP, subject to the following provisions: • The Silva Cell is approved for use on new development and redevelopment sites of any size (including roadway projects) in which permeable pavement is used. • The Silva Cell shall be designed and applied in accordance with the details attached to this letter. When supplemented with permeable pavement, the permeable pavement may manage a larger upstream tributary area (up to a ratio of 4:1) as a stand-alone BMP, regardless of the saturated hydraulic conductivity of the underlying soil. • Channel Protection Volume (CPv) storage may be provided within the void space of the soil media, ponding zone, and within the rock layer of the permeable pavement. • Project specific design calculations and maintenance plans furnished by DeepRoot LLC must be included within the project's "Stormwater Management Facilities Report" prepared by the consulting engineer. • The initial installation of the Silva Cell under this design criteria in the MSD shall include the following: 1) A manufacturer's or vendor's representative must be onsite during the proprietary BMP installation to ensure the product's installation requirements are met. 2) Shop drawings indicating elevations of flowlines, weirs, pipe inverts, etc. will be required prior to installation. 3) The manufacturer or vendor must arrange for an as -built survey of the proprietary BMP to be performed by a Missouri -registered Professional Land Surveyor once the device has been installed, and prior to any testing or monitoring. 4) The manufacturer or vendor must perform quarterly inspections of the proprietary BMP during its' first year of operation, which will include visual inspections and quantitative analysis of the service's sediment removal efficiency, especially as compared to its design efficiency. MSD requests to be invited to these inspections to further enhance familiarity and understanding of the device. 5) Formal reports shall be submitted to MSD, including as-builts and at each quarterly inspection. The reports shall include summaries, quantitative analysis mentioned in item 4, photographs of the structure, inlet, internal conditions of the structure, the filters, and outfall conditions, etc. The reports shall also evaluate the performance of the owner's adherence to the approved maintenance program, and offer suggestions for any areas of improvement. MSD reserves the ability to withdraw or modify this approval based on subsequent information, including information indicating that this BMP does not satisfy MSD rules, requirements, or construction specifications. Sincerely, Jason Peterein, P.E. Principal Engineer (BMP Committee Chairman) Engineering/Planning — Development Review Metropolitan St. Louis Sewer District Pc: Brenda Guglielmina — DeepRoot, LLC File liloalad Jai uoilualaJoi8 �Loz lsnOnd L-VS 1IV134 GEOGRID, 12" EXTENSION DOWNWARD PAST EDGE OF SILVA CELL DECK. AFFIX TO SILVA CELL FRAME WITH ZIP TIES MSD TYPE 4 GEOTEXTILE FABRIC, 14' MIN EX NSION DOWNWARD PAST EDGE OF SILVA DECK. TURN ,A D ROOT PACKAGE AND INSTALL SOIL LIFT TO F SURFACE ELEVATION TREE TRUNK, SIZE VARIES 2" MULCH ABOVE TREE PIT CURB AND STREET PER PROJECT SPECIFICATION TREE ROOT PACKAGE, SIZE VARIES DEEPROOT UB 24-2 ROOT BARRIER ANGLE OF REPOSE. VARIES PER PROJECT SPECIFICATIONS PLANTING SOIL, TAMPED TO MAX. 85% COMPACTION BELOW ROOT PACKAGE 6" THICK SAND (ASTM C-33 FINE AGGREGATE) MSD TYPE 4 GEOTEXTILE FABRIC ON COMPACTED SUBGRADE 6" THICK "o GRAVEL (ASTM C-33 ND. 6 OR 67), COMPACTED TO 95% SUBGRADE BELOW GEOTEXTLE AND AGGREGATE BASE COURSE. COMPACTED TO 95% DEEPROOT UB 24-2 ROOT BARRIER CONCRETE CURB, SIZED PER PROJECT SPECIFICATIONS, POSITIONED OVER CELL POSTS. ATTACH TO PAVING PERVIOUS PAVING. PER PROJECT SPECIFICATION 12" MIN. AGGREGATE BASE COURSE, PER PROJECT SPECIFICATIONS MSD TYPE 4 GEOTEXTILE FABRIC, 18" MIN. OVERLAP PAST EXCAVATION 6" MIN PONDING SPACE BETWEEN SILVA CELL DECK AND BIORETENTION SOIL SURFACE .t11#ii#1iE11Li{E##{g1HE#N41i1#If I:/:I 6 MIN, PLANTING SOIL PER MSD BIORETENTION SOIL MIX (BSM) SPECS., INSTALLED IN 8" LIFTS (2 LIFTS PER CELL) TO 4" FROM TOP OF FRAME SILVA CELL BASE SLOPE TO 0%1 (FLAT/NO GRADE) OVER ENTIRE BASE SURFACE AREA 6" THICK 3/8" Q GRAVEL (ASTM C-33 NO.8), COMPACTED TO 95% 4"0 SCHEDULE 40 PVC PERFORATED PIPE, 3/8"0 HOLES, TWO SIDES, FACING DOWN, 2" OFF BOTTOM OF EXCAVATION. CONNECT TO OVERFLOW FOR DRAINAGE TO OFF -SITE RECEIVING AREA OR DEVICE TYPICAL SECTION SCALE: NTS CLEANOUT/OBSERVATION WELL 18" MIN PAVING BASE COURSE, PER PROJECT SPECS. BACKFILL, INSTALLED IN 8" LIFTS. WITHIN 4-6" FROM TOP OF DECKS, COMPACTED TO 95% SCREW CELL DECKS TO FRAMES AFTER SNAPPING IN PLACE (TYP) GEOGRID. 'J' 6" MIN. BELOW BACKFILL AT BASE. OVERLAP 12" MIN. AT TOP OF CELLS. 3/16" x14" ZIP TIES, ATTACHING GEOGRID TO SILVA CELLS AT EACH LEVEL AND AT CELL DECK INVERT ELEVATION SHALL NOT BE ABOVE BOTTOM OF BSM ANCHOR EACH SILVA CELL TO GROUND WITH 4 - 10" SPIKE, <10MM DIA., SEE CELL BASE FOR SPIKE HOLES. MARK UNDER - DRAINAGE PIPE LOCATION IN BASE TO PREVENT SPIKES FROM PUNCTURING PIPE ON INSTALLATION NOTES: (1) BIORETENTION SOIL MIX (BSM) = 80% SAND. 10% FINE GROUND MULCH, 10% 'TOPSOIL", OR MIX PER MSD LANDSCAPE GUIDE FOR BMPS. (2) SEE MSD LANDSCAPE GUIDE FOR MULCH & VEGETATION. TREES PLANTED IN BSM SHOULD BE ANCHORED. (3) 90TH PERCENTILE (P=1.14") RAINFALL EVENT. (4) OPTIONAL WHERE SAND CONTENT OF BSM IS HIGH (>130%). }i.0a4eJ .0j. UOiTU IGJO!8 21.OZ 1Sf19f V z—vg 7ivi]a TREE TRUNK, SIZE VARIES 2" MULCH ABOVE TREE PIT DEEPROOT UB 24-2 ROOT BARRIER MSD TYPE 4 GEOTEXT1LE FABRIC, 14" MIN EXTENSION DOWNWARD PAST EDGE OF SILVA DECK. TURN TOWARD ROOT PACKAGE AND INSTALL SOIL LIFT TO FINAL SURFACE ELEVATION 6" THICK SAND (ASTM C-33 FINE AGGREGATE) 6" MIN PLANTING SOIL PER MSD BIORETENTION SOIL MIX (BSM) SPECS., INSTALLED IN 6" LIFTS (2 LIFTS PER CELL) TO 4" FROM TOP OF FRAME 6" THICK 3/8"0 GRAVEL (ASTM C-33 NO.8), COMPACTED TO 95% 6" THICK 1"0 GRAVELI (ASTM C--33 NO. 6 OR 67). COMPACTED TO 95% (OPTIONAL) CURB STOP, PER PROJECT SPECIFICATIONS CONCRETE CURB, SIZED PER PROJECT SPECIFICATIONS, POSITIONED OVER CELL POSTS. ATTACH TO PAVING. PERVIOUS PAVING, PER PROJECT SPECIFICATION 12" MIN. AGGREGATE BASE COURSE. PER PROJECT SPECS. MSD TYPE 4 GEOTEXTILE FABRIC, 18" MIN. OVERLAP PAST EXCAVATION 6" MIN PONDING SPACE BETWEEN SILVA CELL DECK AND BIORETENTION SOIL SURFACE • • - • %✓ ••I�✓��I�v#• * • v��I�• ✓ `J "'WV MSD TYPE 4 GEOTEXTILE FABRIC ON COMPACTED SUBGRADE PLANTING SOIL SILVA CELL BASE SLOPE TO 0% (FLAT/ NO GRADE) OVER ENTIRE BASE SURFACE AREA 4"0 SCHEDULE 40 PVC PERFORATED PIPE, 3/8"0 HOLES, TWO SIDES, FACING DOWN. 2" OFF BOTTOM OF EXCAVATION. CONNECT TO OVERFLOW FOR DRAINAGE TO OFF -SITE RECEIVING AREA OR DEVICE TYPICAL SECTION SCALE N1S NOTES: (1) BIORETENTION SOIL MIX (BSM) = 80% SAND, 10% FINE GROUND MULCH, 10% "TOPSOIL", OR MIX PER MSD LANDSCAPE GUIDE FOR BMPS. (2) SEE MSD LANDSCAPE GUIDE FOR MULCH & VEGETATION. TREES PLANTED IN BSM SHOULD BE ANCHORED. (3) 90TH PERCENTILE (P=1.14") RAINFALL EVENT. (4) OPTIONAL WHERE SAND CONTENT OF BSM IS HIGH (>804 PAVING BASE COURSE, PER PROJECT SPECS. SCREW CELL. DECKS TO FRAMES AFTER SNAPPING IN PLACE (TYP) 3/16" x14" ZIP TES, ATTACHING GEOGRID TO SILVA CELLS AT EACH LEVEL AND AT CELL DECK BACKFILL, INSTALLED IN 8" LIFTS. WITHIN 4-6" FROM TOP OF DECKS. COMPACTED TO 95% GEOGRID. V 6" MIN. BELOW BACKFILL AT BASE. OVERLAP 12" MIN. AT TOP OF CELLS. ANCHOR EACH SILVA CELL TO GROUND WITH 4 - 10" SPIKE, <10MM DIA., SEE CELL BASE FOR SPIKE HOLES. MARK UNDER - DRAINAGE PIPE LOCATION IN BASE TO PREVENT SPIKES FROM PUNCT- URING PIPE ON INSTALLATION