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Home My WebLink AboutBuilding Construction Specification 2007-6-25 i- OLSON & M\ORR!S A division of l.B. Olson & Associates. Inc. Consulting Engineers land Surveyors Urban Planners 380 Q Street Suite 200 Springfield, Oregon 97477 (541) 302-9790 Fax: (541) 485-3253 olsonandmorris.com -~ loT {~ 100'/ 5?/! 71 ifV.?'...~ ~\D .,\(\,~ June 25, 2007. House Plan #0591;Thurston Place Subdivision Roof Drainage Drywell The storm drainage system that is intended to serve house plan #0591, to b" constructed within Thurston Place Subdivision, is proposed to be by a private 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. The soil permeability rate used for these calculations was taken from the average .ofa series of permeability tests that were conducted on the site. Included with tlris letter are the results of the above stated permeability tests. 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 Parcel Area Runoff Coefficient (50% impervious) Rainfalllntensity (from otak IDF curves 5-year) = 17 inlhr = 0.044 ac =0.90 = 2.7 inIhr 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. ;/:2w Wade R. Holaday, P.E. "- ~ [Gliel'( [i>}$Jl~ : Troy Cummins, Thurston Place Subdivision Roof Drain Drywell (Plan #0591) ~~="1'=co:"~..,__ ~'~ - --::r=-:-_""''''-7':=~~?'-~'- He :"_. ",'~>,:1fRk~~'."~';;sf<] ;Sa;0WvhWA+rER'iRl!JN0Er~ifE0w..llit\orE';~i0i;;1.~;f~;;h;!i:l J~~~ '~'",=J '~~' I' ",' ~."f..:,,1 1',1= 'k".[.~'. """-a" <<::::::, [.... 0.900 0.044 acres 2,700 in!hr 0.1 07 cfs Imopervious area from House Plans: 1,922 sf 5 Year storm event ~~\(~1(1'{EN@Htfsiz'E#Jti.~~~~twi~t1 Soil Type: SCS #25 - Chapman loam Soil Type: SCS #26 - Chapman-Urban land complex 8.500 ft 4.500 ft 5.500 ft 17.0000 inlhr 0.00039 ftlsec 0.015 cfs IS'E0R%GEIM.@TiJN:rE@F.~0R'Z;WEI3j?':r~B___~ TRENCH PIPE 24.000 210.375 cf 203.295 cf 77.252 cf v= 7.080 cf 1.,,,,,,,,-,""7""""~~~'"=~=''''''='-:=r>:''''____''' .~.",-~.:n ifJ9[A'llilS;I;0R'AGEj,V0IiUME:;!fI\",%1 :ffi,~~-gI~~;:~:f,::~f fl1.'{,Vi.. "",.,-"'<'_.' ... ,~,. .~-,~ 84.332 cf 5 10 ]5 20 25 30 40 50 60 90 120 \50 180 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 0,04 ~Sife~'e'a,:::;r,fi - ~' I"" ;-,,~,;->:''2'if;1, ._';li;!r\>.(f,>}""}~Ji'_".~.M~E !:EenntaEil'ifi' ~,';w"';"{'<.- .',' l'i.~..1.1~""~, f$li'f~i)j:.fc~~ . x:!tl", ~~@{~l11v~ju 1922.000 sf 17.0000 in/hr 2.000 fI+~3'2j cf .2.70 1.85 1.50 1.25 1.10 0,95 0,79 0,69 0.6] 0,52 0,46 0,4] 0,39 0;11 32,08 0,01505 4,52 0.Q7 43,96 0,01505 9,03 0,06 53,46 0,01505 13,55 0,05 59,40 0,01505 18,06 0,04 65,34 0,01505 22,58 0,04 67,72 0,01505 27,09 0.Q3 75,08 0,0]505 36,]3 0.Q3 81.97 0,01505 45,16 J 0,02 86,96 0,01505 54,19 0,02 111.20 0,0]505 81.28 0,02 131.16 0,01505 108,38 0,02 146,12 .0,01505 135.47 0,02 166,80 0,01505 ]62,56 2 year 5 year 10 year Time 2,10 2,70 3,70 5 1.45 1.85 2.80 10 1.30 1.50 2,25 15 0,98 1.25 1.87 20 0,75 1.10 1.62 25 0,68 0,95 1,45 30 0,63 0.79 1.20 40 0.55 0,69 1.02 50 0,50 0,61 0.90 60 0,42 0,52 0,66 90 0,36 0.46 0,54 120 0,33 0,4] 0.44 150 0,31 0,39 0,38 180 Client Troy Cummins, Thurston Place Subdivision Project Roof Drain Drywell (plan #0591) .~ ~ DRYWELL CONFIGURATION INSPECTION/MAINTENANCE PORT 12" NATIVE SOIL ~ 4"ROOF DRAIN. GEOTEXTILE FABRIC ALONG SIDES AND OVER TOP OF DRAIN ROCK EXISTING NATIVE . SOIL " 24" DIAMETER HDPE PERFORATED CHAMBER 3.5' IN HEIGHT 1 1/2" DIA. DRAIN ROCK NATIVE BASE --7 24" 1 1/2" DIA. DRAIN ROCK, CLEAN (38% VOIDS) 24"HDPE . PERFORATED CHAMBER 4"ROOF DRAIN GEOTEXTILE FILTER FABRIC 0.5' min .~ Drywell Permeability Test Highbanks Subdivision Roof Drain Drywells Test Date 1/24/2006 Pre-test depth to water 4.4 ft. Time (min) o 4 Depth to Water (ft) 4.6 4.7 Test Pit 1 4.72 4.7 is 4.68 di 4.66 ~ 4.64 ..B 4.62 ~ 4.6 (g 4.58 4.58 4.54 l-+--serie~ll 2 Time (min) The soil within the lest 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 lest 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 p()int 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 Roof Drain Drywells Test Date 1/24/2006 Pre-lest depth to water 4.7 ft. Time (min) o 5 10 15 20 Depth to Waler (ft) 3.69 3.90 4.08 4.23 4.31 Test Pit 2 4.4 4.3 _4.2 ~41 .! 4:0 ... ~ 3.9 .s 3.8 = 3.7 g.. 3.6 c 3.5 3.4 3.3 I-.-Sertes11 2 3 Time (min) .4 5 The soil within the test pit was a silty clay loam material to the bottom of the test pit at 5.1-fee1. 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 Roof Drain Drywells Test Date 1/24/2006 Pre-lest depth to water 5.0 ft. Time (min) o 5 10 15 20 Depth to Water (ft) 3.10 3.20 3.31 3.40 3.46 Test Pit 3 3.5 l-+-serieS11 3.4 ~ 3.3 -;; ;;: 3.2 B ~ 3.1 m o 3.0 2.9 2 3 Time (min) 4 5 The soil within the test pit was a silty clay loam material to thet>oUom of the test pit at 5.1 feet. The test pit had 0.1 feel of standing water in the bottom indicating that the soils are saturated. The test,pit was 2.0 feet wide an~ 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 drnwdown 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 pem1eability rate of 13.0 inches per hour. Soil types for this site are as foll~ws: (from SCS. Soil Survey of Lane Co~nty) Soil Type #25 - Chapman loam Soil Type #26 - Chapman-Urban land complex