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HomeMy WebLinkAboutBuilding Miscellaneous 2007-6-25 • 5-25c f�/�tA8 /41 R_D . . 53cr nste_ OLSON & June 25, 2007. MORRIS . . House Plan#0591, Thurston Place Subdivision ,. . Roof Drainage Drywell .• A division of L.B.Olson&Associates,Inc. . • .. . • • Consulting Engineers The storm drainage system that is intended to serve house plan#0591, to be Land Surveyors constnicted within Thurston Place Subdivision,is proposed to be by a private Urban Planners drywell system. The drywell, calculations attached, has been sized to handle storm water runoff that will be generated by the roof drainage area of 1,922 square feet. The runoff was calculated by use of the Rational Method based on a 5 year storm event. 380 Q Street Suite 200 The soil permeability rate used for these calculations was taken from the average Springfield,Oregon 97477 of a series of permeability tests that were conducted on the site. Included with (541)302-9790 this letter are the results of the above stated permeability tests. Fax:(541)485-3253 olsonandmorris.com With proper maintenance,the proposed drywell is designed to have a 20 year life expectancy and shall be located on the parcel to adhere to state and local building codes. Drywell Calculation Summary: < Soil Permeability = 17 in/hr < Parcel Area =0.044 ac < Runoff Coefficient(50% impervious) =0.90 < Rainfall Intensity =2.7 in/hr (from otak IDF curves 5-year) . Refer to the attached Standard Drywell Calculation Sheets for drywell size and calculations. Also refer to attached detail for drywell construction., . If you have any questions or comments in regards to the above letter, feel free to contact this office at your convenience. Respectfully, - 4'71.441(// `., , Wade R. 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Sa .y y0 a — N 9 :21::::::::eltit.ilic 0 rx E V d' V V V 7 V V O V V C V O O O rn J .� Q -114 o 0 0 0 o 0 0 0 0 0 0 0 0 O O O .r L . >t -4d 0 0 0 0 0 0 0 0 0 0 0 0 6 N c4 N �fl "„ry, E -- yt 'n N lc N.a' ^Y a 3- — r :li g i ' U Q tr' " t SiY ..;ga T 0 e.��y tra PAS'''. O Q a 4. Ft r4 ' � 1;11�Lij ' O " N N F.,' ? ' C N 2 ? '� C , N i5 r y[1y © :. . z III, ., �p tin . cd ctl s.0 i L1 4 -g0:<:-°-4/4.,..,--',1 yo a xo, : : v' a_ n � gym. ice' _., ,[��sE. DRYWELL CONFIGURATION INSPECTION/MAINTENANCE PORT 12" NATIVE SOIL elL�l i INHUhli el( +!�!�� d! ��4°ROOF DRAIN .res GEOTEXTILE FABRIC ALONG SIDES AND � � �. OVER TOP OF DRAIN ROCK • 1•016 FleY,V EXISTING NATIVE 1:•^� SOIL �!� �+ :.� 24" DIAMETER HDPE PERFORATED CHAMBER 3.5' IN HEIGHT 1 1/2" DIA. DRAIN ROCK NATIVE BASE • 24" 24"HDPE PERFORATED CHAMBER 1 1/2" DIA. DRAIN ROCK, CLEAN 1101.1(38% VOIDS) 4"ROOF DRAIN GEOTEXTILE FILTER FABRIC • 0.5' min Drywell Permeability Test Highbanks Subdivision Test Date 1/24/2006 Roof Drain Drywells Pre-test depth to water 4.4 ft. Time(min) I Depth to Water(ft) 0 4.6 4 4.7 Test Pit 1 4.72 4.7 x 4.68 `m 4.66 3 4.64 w e tSeriesl p ! Y 1 2 Time(min) The soil within the test pit was a silty clay loam material to the 4.5 foot depth and bar run material to the bottom of the test pit at 5.0 feet. The test pit had 0.4 feet of standing water in the bottom indicating that the soils are saturated. The test pit was 2.0 feet wide and 5.6 feet long. Water was pumped into the test pit at a rate of approximately 150 gallons per minute with only a gain of 0.10 feet in the depth of water in the bottom of the pit. At this point a measurement was taken and the time started. The drawdown was timed until the depth of water reached the original pre-test depth of 4.60 feet from a fixed point at the top of the pit. The above permeability test report shows that the soil at a depth of 5 feet,the saturated soil has a permeability rate of 18.0 inches per hour. Soil types for this site are as follows:(from SCS Soil Survey of Lane County) • Soil Type#25-Chapman loam Soil Type#26-Chapman-Urban land complex • Drywell Permeability Test Highbanks Subdivision Test Date 1/24/2006 Roof Drain Drywells Pre-test depth to water 4.7 ft. Time(min) Depth to Water(ft) 0 3.69 5 3.90 10 4.08 15 4.23 20 4.31 Test Pit 2 .ca 3.9 a 31 ti' 0 3.5 34 ,.k�i 3.3 . 1 2 3 4 5 Time(min) The soil within the test pit was a silty clay loam material to the bottom of the test pit at 5.1 feet. The test pit had 0.53 feet of standing water in the bottom indicating that the soils are saturated. The test pit was 2.0 feet wide and 8.3 feet long. Water was pumped into the test pit until the depth of water reached approximately 1.0 feet above the pre-test water surface,at this point a measurement was taken and the time started. The drawdown was timed for 20 minutes with measurements taken from a fixed point at the top of the pit at 5 minute intervals. The above permeability test report shows that the soil at a depth of 5 feet,the saturated soil has a permeability rate of 22.3 inches per hour. Soil types for this site are as follows:(from SCS Soil Survey of Lane County) Soil Type#25-Chapman loam Soil Type#26-Chapman-Urban land complex Drywell Permeability Test Highbanks Subdivision Test Date 1/24/2006 Roof Drain Drywells Pre-test depth to water 5.0 ft. Time(min) I Depth to Water(ft) 0 3.10 5 3.20 10 3.31 15 3.40 20 3.46 Test Pit 3 3.5 .. 3.2 +Series! 3.1 3.0 1 2 3 4 5 • Time(min) The soil within the test pit was a silty clay loam material to the bottom of the test pit at 5.1 feet. The test pit had 0.1 feet of standing water in the bottom Indicating that the soils are saturated. The test pit was 2.0 feet wide and 5-1 feet long. Water was pumped into the test pit until the depth of water reached approximately 2.0 feet above the pre-test water surface,at this point a measurement was taken and the time started. The drawdown was timed for 20 minutes with measurements taken from a fixed point at the top of the pit at 5 minute intervals. The above permeability test report shows that the soil at a depth of 5 feet,the saturated soil has a permeability rate of 13.0 inches per hour. Soil types for this site are as follows:(from SCS Soil Survey of Lane County) Soil Type#25-Chapman loam Soil Type#26-Chapman-Urban land complex