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Home My WebLink AboutR-391915NOTE: M C') O 0 LJ,J C.2.4.4 USE OF GRAVEL FILLED TRENCHES FOR BASIC DISPERSION Where dispersion of concentrated flows through 50 feet of vegetation is not feasible, such as on a small or highly constrained site, a gravel filled trench (also called a dispersion trench) may be used to "unconcentrate" flows. Dispersion trenches provide some storage for runoff, promote infiltration, and spread concentrated flows so that a shorter vegetated flowpath length can be used at the trench outlet. This BMP is more expensive than the simple dispersion systems described above, and must be carefully constructed to be effective. Uses: Roofs, driveways, lawns, pasture, etc. from which runoff is concentrated in a downspout, yard drain, pipe, drainage tile, etc. Design Specifications Figure C.2.4.13 (p. C-56) shows two types of dispersion trenches that may be used, a "simple 10—foot trench" and a maximum "50—foot trench with notch board." The 50—foot trench with notch board is further detailed in Figure C.2.1.D (p. C-35). These gravel filled trenches must meet the following specifications for basic dispersion: 1. No more than 700 square feet of impervious surface (or 5,000 square feet of non—native pervious surface) may be drained to a simple 10—foot dispersion trench. Up to 3,500 square feet of impervious Q surface (or 25,000 square feet of non—native pervious surface) may be drained to a 50—foot trench with J notch board. Smaller lengths of trench with notch board may be used at a ratio of 10 feet of trench n per 700 square feet of impervious surface (or 5,000 square feet of non—native pervious surface). 2. A "vegetated flowpath segment" of at least 25 feet in length must be available along the flowpath that runoff would follow upon discharge from a dispersion trench. This length must be increased to 50 T feet if the discharge is toward a steep slope hazard area or a landslide hazard area steeper than 15%. Z All or a portion of the vegetated flowpath segment may be within the buffer for the steep slope hazard Oarea or landslide hazard area. I-_ 3. The simple 10—foot trench illustrated in Figure C.2.4.13 must be at least 2—feet wide by 18—inches deep. z The maximum 50—foot trench with notch board detailed in Figure C.2.1.D must be at least 2—feet wide w by 24—inches deep. 4. All trenches must be filled with 3/4 to 1 1 /2—inch washed rock. 5. All trenches must be placed at least 10 feet from any building and must be parallel as possible to the contour of the ground. A setback of at least 5 feet must be maintained between any edge of a trench and the property line. 6. For purposes of maintaining adequate separation of flows discharged from adjacent dispersion devices, the outer edge of the vegetated flowpath segment for the dispersion trench must not overlap with other flowpath segments, except those associated with sheet flow from a non—native pervious surface. LO T ~ 0 PROPOSED STORM CONNECTION: ALL LOTS w LJ — 600 SQ. FEET OF DRIVEWAY GRADE TOWARDS = STREET; OR DRAIN ON THE LOT TO AN AREA DRAIN U) AND CONNECT TO THE PROVIDED STORM STUB — COLLECT ROOF AREA FROM HOUSE AND CONVEY THROUGH A PERFORATED PIPE CONNECTION INTO THE AND CONNECT TO THE PROVIDED STORM STUB SFCTTON C2 FT.OW CONTROL RMPs FIGURE C.2.4.B TYPICAL GRAVEL -FILLED DISPERSION TRENCII FOR BASIC DISPERSION ° ° o level outlet 6" min .J 4' pert pipe V°a°°°.,3.o�°o;o°` 18„min ° 11/2" - 3/4" washed rock O up 0,L.G c � 24" min —►I TRENCH X-SECTION NTS slope small catch basin or yard drain 25-FoolVegetated l- Flowpat1 Segment ` <_700 sq. ft. Simple 1 D-foot trench Type I CB >700 sq. ft. / 25 FaotYegetat6r FI owpath'Seg ment -------------- Maximum 50-foot trerch w/notch board (see Figure C.21.D, p. C-32) PLAN VIEW OF ROOF NTS 1/9/2009 2909Sufa Wale, Design Manual—Appe dixC C-56 OFFE ENGINEERS 13932 SOUTHEAST 159TH PLACE RENTON, WASHINGTON 98058 PHONE: 425-260-3412 CONTACT: DARRELL OFFE, P.E. Renton 14 Plat Maximum Impervious per Lot ** Maximum Mitigation -Max. 40% Imp. Impervious Lot Area reduced impervious A//owed on Lot Perforated Restrictive Lot # (M. cm. (M. Pie Connection Covenant 1 14833 5933 4000 yes yes 2 15286 6114 4000 yes yes 3 9743 3897 4000 yes yes 4 9743 3897 4000 yes yes 5 8988 3595 3500 yes yes 6 7720 3088 3088 yes yes 7 7901 3160 3088 yes yes 8 8986 3594 3500 yes yes 9 9516 3806 3600 yes yes 10 9513 3805 3600 yes yes 11 9529 3812 3600 yes yes 12 9980 3992 3600 yes yes 13 13750 5500 3600 yes yes 14 9056 3622 3600 yes yes 15 9000 3600 3600 yes yes 153544 54376 * maximum impervious surface allowed under Restrictive Covenant BMP ** maximum impervious allowed on lot is EITHER 4,000 sq. feet OR column (3) whichever is less. J-4. 27460 018 SURVEYED: TERRANE SURVEYING 4 REVISED PER CITY COMMENTS DLO 2/2018 DESIGNED: D.L. OFFE, P.E. 3 REVISED PER CITY COMMENTS DLO 1/2018 2 REVISED PER CITY COMMENTS DLO 9/2017 DRAW": D.L. OFFE, P.E. 1 REVISED PER CITY COMMENTS DLO 2/2017 CHECKED: NO. REVISION BY DATE APPR APPROVED: SCALE: ONE INCH AT FULL SCALE IF NOT ONE INCH SCALE ACCORDINGLY VERTICAL: NAVD 1988 HORIZONTAL: NAD 1983/1991 DATU M EXISTING UTILITY LOCATIONS SHOWN HEREON ARE APPROXIMATE ONLY. IT SHALL BE THE CONTRACTOR'S RESPONSIBILITY TO DETERMINE THE EXACT VERTICAL AND HORIZONTAL LOCATION OF ALL EXISTING UNDERGROUND UTILIITES PRIOR TO COMMENCING CONSTRUCTION. NO REPRESENTATION IS MADE THAT ALL EXISTING UTILITIES ARE SHOWN HEREON. THE ENGINEER ASSUMES NO RESPONSIBILITY FOR UTILITIES NOT SHOWN OR UTILITIES NOT SHOWN IN THEIR PROPER LOCATION. CALL BEFORE YOU DIG: 811 2 LOT DRAINAGE NOTES: a. SINGLE FAMILY RESIDENCES AND OTHER IMPROVEMENTS CONSTRUCTED ON THE LOTS CREATED BY THIS SUBDIVISION MUST IMPLEMENT THE FLOW CONTROL BEST MANAGEMENT PRACTICES AS LISTED IN THE TABLE BELOW AS WELL AS ANY DECLARATION OF COVENANTS AND GRANTS OF EASEMENT. COMPLIANCE WITH THIS STIPULATION MUST BE ADDRESSED IN THE "SINGLE FAMILY RESIDENCE BUILDING PERMIT DRAINAGE REVIEW" WHEN ANY APPLICATION IS MADE FOR A BUILDING PERMIT FOR THE LOT. b. COMPLIANCE WITH THE BMP REQUIREMENT MUST BE ADDRESSED IN THE SINGLE FAMILY RESIDENTIAL BUILDING PERMIT DRAINAGE REVIEW WHEN AN APPLICATION IS MADE FOR A SINGLE FAMILY RESIDENTIAL BUILDING PERMIT FOR THE LOT. c. ALL CONNECTIONS TO THE DOWNSTREAM DRAINAGE SYSTEM SHALL BE VIA A PERFORATED PIPE CONNECTION. d. ALL INDIVIDUAL FLOW CONTROL BMP's SHALL BE PRIVATELY OWNED, MAINTAINED AND KEPT IN GOOD REPAIR BY EACH LOT %R CITY OF 17 3 RENTON Planning/Building/Public Works Dept. GRAPHIC SCALE 0 25 50 100 I inch = 50 feet R-391915 IN COMPLIANCE WITH CITY OF RENTON STANDARDS RENTON 14 PLAT KENDALL HOMES, INC. LOT DRAINAGE CONTROL PLAN & DETAILS 6201 NE 4th STREET W I — a J n DATE: 02/13/2018 Tf FIELDBOOK: L PAGE: O DRAWING NO: Z SHEET: 15 OF:2 Q LU CJ