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Home My WebLink AboutLUA-06-087_Misc0 " C 0 E L "' " ID > 0 "' "' 0 0 N " N >, 0 2 I - ~I w z ~ w I ' \ l / w z «I I w NE 1~~ - 2 r-L__=-___j_,.Y JI- ~ z: w ' / c-' > u--~, y _J ...., <r ~~ H--~,1---...L.--...L.----'---, B '~ NE 4TH ST - Design JDZ -·--~---- LJW z > ~ 1.------ -' " > ::, " IW c-V, cow !'.:> " SE 116Tc ST I 1--../ w / V, w > " I c-co !'.: Drawn 5/12/06 Date Site Development Associates, LLC 1&lZ2 llothel'Wr:s'(NE: lothel,W~ 9f!011 I I --- 107-016-06 omce: <125.-411&.6533 Faic -425.-486.65?3 www~.com Project No. I SE w V, w > <J: l> < r1 \ I I _J Project Loc0 tion ;: co ---< I fl V, r1 128TH ST f--- w V, w > <J: I c- "' N EB LANGLEY MEADOWS '----- - NT S 1----------------------j Saale VICINITY MAP 2 Figure No. Rc\Prnjects\ 107(0ffe)\01 6--06 (Langley Meadows)\Dwg\Flguces\ TIR\LM-flg01.dwg I f---- f------ f------ f------ f---- r ;f ~-'~'~'J'~· ~2~0~05~-~1~2~:03~P~M~L~oo~t~S~o,~·~' ~,~,.~,~··~rno~,~,,~=~=~==~;;--;;~;;;;::r=~:::;1:.;;;~;;:T-;.;~-;:-;;;:;-;:;;--r-----,;;;:ir.i'cv"7,~;;;:::;;--[::::::::::::::::::::::J }' I-WISON $IJRVEYlMG -... -"" ,·.,a· .i/l/lll/f~.IA,, ~ CITY OF LANGLEY MEADOW j,~:,~:JT=·-=====~~~====+,~+i ~--~-~i~-~-gi~-=·=;:~'~jl I __ 1 1 ~ 1 ~ RENTON I RENTON, WASHINGTON ::_w,oo, --• -fl J ReaSION • BY DATr. ~· : "" ~ ---I ;-I I 1::--•,, I .. ---1--1- -' _ ... _ : .•PPR I -• ' g ' 0 if i : / j / ;i C I cc; ~ < l a· 0 • 0 l ti' ~ ~ " l VI Ilg' 0 0 • ~ 0 U1 0 11 ... 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Site Development Associates, LLC 1832.2 &ofhell Way HE; Bo!hel, Woshlrigton 9801 \ Offk:&; ffl.'IM.6533 Fax: 425A86.6593 www.idoi,ngl.--i;.com " 0 ,, -j i5 z 0 -n -j I m z _;:, z m :a: (/) m (') -j i5 z _w ~ " ~ w z ~I "'' rn: " "' " 0 ,, -a, i51 z, 0 -n _, I m CJ) -~ CJ) m _:a: CJ) m <:i i5 z _'t. ~ " ';;: z es m "' m " "' (·' ~ § ks,=,=e;~c=o,=,=rn=,---D-RA_I_N_A_G_E_B_A_S_I N-S-------l;;o"rn"',o:;;";,;c':;;";;-----,r;;o;;;SA;aw;;;, ;;;,,,--------,,r;;rn;;;,:;;cK;;;,;;-o,;;;,c----j I I I =3 I I • \ 1 1 AND SITE CHARACTERISTICS wee ,oz ''° lsev. so. I DATE I oescs,eno, =._J -0 C ~ a:, 0) 0 -a:, 0 _J ~ .i;;; t2 J e-.~ £ ·-A. ~ \ D FIGURE 4 in all areas. Klaber-Cinebar silt foams, 0 to 8 percent slopes, is an example. This survey includes miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. Table 4 gives the acreage and proportionate extent of each map unit. Other tables (see "Summary of Tables") give properties of the soils and the limitations, capabilities, and potentials for many uses. The "Glossary" defines many of the terms used in describing the soils or miscellaneous areas. Map Unit Descriptions 1-Alderwood gravelly loam, 6 to 15 percent slopes. This moderately well drained soil is in glacially modified areas on foothills and in valleys. It is moderately deep to ortstein. It formed in dense glacial till. The native vegetation is mainly confers and shrubs. Elevation is 50 to 800 feet. The average annual precipitation is about 45 inches, and the average annual air temperature is about 50 degrees F. The average frost-free period is about 200 days. Typically, the surface is covered with a mat of needles, twigs, and moss 1.5 inches thick. When mixed to a depth of 6 inches, the surface layer is dark brown gravelly loam. The upper 14 inches of the subsoil is dark yellowish brown very gravelly loam. The lower 13 inches is dark yellowish brown very gravelly sandy loam. Grayish brown ortstein that crushes to very gravelly sandy loam is at a depth of about 33 inches. Below the ortstein is grayish brown, dense glacial till that crushes to very cobbly fine sandy loam. The depth to dense glacial till ranges from 20 to 40 inches. In some areas the surface layer is gravelly sandy loam. In other areas the soil has 15 to 35 percent rock fragments in the subsoil or is 40 to 60 inches deep to cemented glacial till. Included in this unit are small areas of Beausite, Everett, Lynnwood, Norma, and Ovall soils and Alderwood soils that have slopes of more than 15 percent or less than 6 percent. Included areas make up about 15 percent of the total acreage. Permeability is moderately rapid in the upper part of the Alderwood soil and very slow in the ortstein. Available water capacity is low. The effective rooting depth is 20 to 40 inches. Water is perched above the ortstein from December through May. In most areas, runoff is slow and the hazard of water erosion is slight. In areas used as pasture or cropland, however, runoff is medium and the hazard of erosion is moderate. This unit is used mainly as woodland. It also is used as pasture or cropland. In the areas used as pasture or cropland. the main limitations are the slope and the muddiness caused by seasonal wetness. Proper stocking rates, pasture rotation, and restricted grazing during short wet periods help to keep the pasture in good condition and help to control runoff and erosion. Grazing when the soil is wet results in compaction of the surface layer and poor tilth. Douglas fir is the main woodland species. Among the trees of limited extent are red alder, western redcedar, western hemlock, and Pacific madrone. The common forest understory plants are salal, Oregongrape, western brackenfern, western swordfern, and evergreen huckleberry. On the basis of a 100-year site curve, the mean site index for Douglas fir is 146. On the basis of a 50-year site curve. it is 111. The highest average growth rate in unmanaged, even-aged stands of Douglas fir is 153 cubic feet per acre per year, occurring at age 60. The main limitation affect'lng timber harvesting is the muddiness caused by seasonal wetness. The use of wheeled and tracked equipment when the soil is wet causes excessive rutting. Using low-pressure ground equipment can minimize damage to the soil. Unsurfaced roads are soft when wet and are subject to deep rutting during rainy periods. Rock for road construction is not readily available. Equipment and logs on the surface result in a moderate degree of soil compaction when the soil is moist and a moderate degree of puddling when the soil is wet. Carefully laying out roads and skid trails. properly timing their use, and using low-pressure ground equipment can reduce the degree of compaction and puddling. A moderate reduction in productivity can be expected from unmanaged fires in undisturbed areas. Seedling establishment, seedling mortality, and the hazard of windthrow are the main concerns affecting timber production. A low content of moisture in the surface layer during the growing season hinders the survival of planted and naturally established seedlings. Because most of the roots are concentrated in the organic mat, loss of this layer after logging greatly reduces natural fertility and the available water capacity. Reforestation can be accomplished by planting Douglas fir or red alder seedlings. If seed trees are available, natural reforestation of cutover areas by red alder occurs periodically. Seedlings that are planted or naturally established in the less fertile subsoil grow poorly and lack vigor. When openings are made in the canopy, the uncontrolled invasion and growth of competing plants can delay the establishment of seedlings. Competing vegetation can be controlled by mechanical or chemical means. Because the rooting FIGURE 4 (CONTINUED) depth is restricted by the ortstein, trees are occasionally subject to windthrow when the soil is wet and winds are strong. This unit is in capability subclass IVe. 2-Alderwood gravelly loam, 15 to 30 percent slopes. This moderately well drained soil is on glacially modified foothills. It is moderately deep to ortstein. It formed in dense glacial till. The native vegetation is mainly conifers and shrubs. Elevation is 50 to 800 feet. The average annual precipitation is about 40 inches, and the average annual air temperature is about 50 degrees F. The average frost-free period is about 200 days. Typically, the surface is covered with a mat of needles, twigs, and moss 1.5 inches thick. When mixed to a depth of 6 inches, the surface layer is dark brown gravelly loam. The upper 14 inches of the subsoil is dark yellowish brown very gravelly loam. The lower 13 inches is dark yellowish brown very gravelly sandy loam. Grayish brown ortstein that crushes to very gravelly sandy loam is at a depth of about 33 inches. Below the ortstein is grayish brown, dense glacial till that crushes to very cobbly fine sandy loam. The depth to dense glacial till ranges from 20 to 40 inches. In some areas the surface layer is gravelly sandy loam. In other areas the soil has 15 to 35 percent rock fragments in the subsoil, has weathered bedrock at a depth of 40 to 60 inches, or is 40 to 60 inches deep to cemented glacial till. Included in this unit are small areas of Everett, Kanaskat, Lynnwood, and Ovall soils and Alderwood soils that have slopes of more than 30 percent or less than 15 percent. Included areas make up about 15 percent of the total acreage. Permeability is moderately rapid in the upper part of the Alderwood soil and very slow in the ortstein. Available water capacity is low. The effective rooting depth is 20 to 40 inches. Water is perched above the ortstein from December through May. Runoff is slow, and the hazard of water erosion is slight. This unit is used as woodland. Douglas fir is the main woodland species. Among the trees of limited extent are red alder, western redcedar, western hemlock, and Pacific madrone. The common forest understory plants are salal, Oregongrape, western brackenfern, western swordfern, and evergreen huckleberry. On the basis of a 100-year site curve, the mean site index for Douglas fir is 146. On the basis of a 50-year site curve, it is 111. The highest average growth rate in unmanaged, even-aged stands of Douglas fir is 153 cubic feet per acre per year, occurring at age 60. The main limitation affecting timber harvesting is the muddiness caused by seasonal wetness. The use of wheeled and tracked equipment when the soil is wet causes excessive rutting. Using low-pressure ground equipment can minimize damage to the soil. Unsurfaced roads are soft when wet and are subject to deep rutting during rainy periods. Rock for road construction is not readily available. Equipment and logs on the surface result in a moderate degree of soil compaction when the soil is moist and a moderate degree of puddling when the soil is wet. Carefully laying out roads and skid trails, properly timing their use, and using low-pressure ground equipment can reduce the degree of compaction and puddling. A moderate reduction in productivity can be expected from unmanaged fires in undisturbed areas. Steep skid trails and firebreaks are subject to rilling and gullying unless adequate water bars are provided or a protective plant cover is established. Seedling establishment, seedling mortality, and the hazard of windthrow are the main concerns affecting timber production. A low content of moisture in the surface layer during the growing season hinders the survival of planted and naturally established seedlings. Reforestation can be accomplished by planting Douglas fir or red alder seedlings. If seed trees are available, natural reforestation of cutover areas by red alder occurs periodically. Seedlings that are planted or naturally established in the less fertile subsoil grow poorly and lack vigor. When openings are made in the canopy, the uncontrolled invasion and growth of competing plants can delay the establishment of seedlings. Competing vegetation can be controlled by mechanical or chemical means. Because the rooting depth is restricted by the ortstein, trees are occasionally subject to windthrow when the soil is wet and winds are strong. This unit is in capability subclass IVe. 3-Alkiridge sandy loam, 8 to 30 percent slopes. This moderately well drained soil is in cirque basins and on the adjacent valley floors. It is moderately deep to dense glacial till. It formed in volcanic ash, pumice, and cinders over dense glacial till. The native vegetation is mainly conifers and shrubs. Elevation is 2,700 to 3,700 feet. The average annual precipitation is about 80 inches, and the average annual air temperature is about 42 degrees F. The average frost-free period is about 120 days. Typically, the surface is covered with a mat of needles, litter, and moss 1 inch thick. When mixed to a depth of 7 inches, the surface layer is dark brown sandy loam. The upper 11 inches of the subsoil is dark brown gravelly sandy loam. The lower 19 inches is dark yellowish brown and olive brown very gravelly loam. Brown, dense glacial till that crushes to very gravelly FIGURE 4 (CONTINUED) Site Development Associates, LLC SECTION 2 CONDITIONS AND REQUIREMENTS SUMMARY LANGLEY MEADOWS 107-016-006 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY Site Development Associates, LLC TASK 1 -SUMMARY OF CORE REQUIREMENTS Core Requirement #1 -Discharge at Natural Location The existing topography of the site can generally be described as gently sloping toward the east. Stormwater appears to follow the ground topography, and leave the site across the east property boundary. The proposed development calls for stormwater to be routed through a detention facility, which will discharge to the eastern property boundary, maintaining the natural discharge location. Core Requirement #2 -Offsite Analysis A Level 1 downstream analysis was performed for the project, and is included in Section 3 of this report. A discussion of the upstream drainage area is also included. Core Requirement #3 -Flow Control This project proposes the creation of a significant amount of impervious surface area, and therefore, is subject to the flow control requirements of the King County Surface Water Design Manual (KCSWDM). Specifically, this project will be required to meet the Level 2 flow control criteria, as outlined in the KCSWDM. The design of the proposed flow control facility is covered in Section 4 of this report. Core Requirement #4 -Conveyance System The proposed development will be required to meet the conveyance system criteria outlined in the KCSWDM. Specifically, the system must be sized to convey flows from the 25-yr design-storm event, and enough of the 100-yr design storm that significant flooding problems are not created. The design of the proposed conveyance system is covered in Section 5 of this report. Core Requirement #5 -Erosion and Sediment Control In order to protect the downstream waters from erosion or sediment inundation, a number of Best Management Practices (BMP's) will be implemented throughout the construction process. These BMP's will include stabilization of exposed soils during and after grading activity occurs, installation of silt control measures (i.e. filter-fabric perimeter fencing, rock-lined construction entrance), and construction of a temporary sedimentation facility. Section 8 of this report will serve as the project's construction stormwater pollution prevention plan (SWPPP). LANGLEY MEADOWS 107-016-006 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY •• Ii' .. Site Development Associates, LLC Core Requirement #6 -Maintenance and Operations Maintenance and operations guidelines for this project are outlined in Section 1 O of this report. Core Requirement #7 -Financial Guarantees and Liability The project will be bonded per the City of Renton's guidelines prior to the commencement of construction activity. Core Requirement #8 -Water Quality This project proposes stormwater treatment which meets the "Basic" water quality treatment criteria outlined in the KCSWDM. Specifically, the project calls for the construction of a permanent wetpool within the proposed stormwater detention/treatment vault. A further discussion of this facility, along with design calculations, are included in Section 4 of this report. LANGLEY MEADOWS 107-016-006 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY Site Development Associates, LLC TASK 2 • SUMMARY OF SPECIAL REQUIREMENTS Special Requirement #1 -Other Adopted Area-Specific Requirements This project does not lie within an identified critical drainage area, or other area for which specific drainage requirements apply. Special Requirement #1 is not applicable to this project. Special Requirement #2 -Flood Hazard Area Delineation This project does not lie within or adjacent to an identified flood hazard area. Special Requirement #2 is not applicable to this project. Special Requirement #3 -Flood Protection Facilities This project does not propose construction of a flood protection facility, or rely on an existing flood protection facility. Special Requirement #3 is not applicable to this project. Special Requirement #4 -Source Controls This project does not require a commercial building permit or commercial site development permit. Special Requirement #4 is not applicable to this project. Special Requirement #5 -Oil Control This project will not have "High Use" characteristics, and does not propose the redevelopment of an existing "High Use" site. Special Requirement #5 is not applicable to this project. TASK 3 -SUMMARY OF ADDITIONAL REQUIREMENTS The project is not subject to any additional requirements in addition to the core and specific requirements listed above. LANGLEY MEADOWS 107-016-006 SECTION 2 CONDITIONS & REQUIREMENTS SUMMARY ... Site Development Associates, LLC LANGLEY MEADOWS 107-016-006 SECTION 3 OFF-SITE ANALYSIS SECTION 3 OFF-SITE ANALYSIS •• ~- Site Development Associates, LLC TASK 1 STUDY AREA DEFINITION AND MAPS The project is located within the City of Renton, and consists of the following five tax parcels, totaling 11.09 acres: Prooertv Address Tax Parcel Number Area (acres) 698 Hoauiam Avenue NE 1023059113 2.39 No address listed 1023059151 0.35 12208 142"0 Avenue SE 1023059371 0.47 12226 142"" Avenue SE 1023059049 4.56 12220 142 00 Avenue SE 1023059179 3.32 Total Area = 11.09 acres The off-site study area includes these parcels, as well as three upstream parcels, which lie adjacent to the southeast of the site. The study area also includes a large downstream wetland area to the east of the project site, and the remainder of the downstream flowpath to the southeast of the project site. Figure 5 of this report shows the general vicinity of the project site, and downstream analysis map. LANGLEY MEADOWS 107-016-006 SECTION 3 OFF-SITE ANALYSIS Site Development Associates, LLC TASK 2 -RESOURCE REVIEW Adopted Basin Plans (including Critical Drainage Areas) The project site does not appear to be within an adopted basin plan area or critical drainage area. Finalized Drainage Studies No Finalized drainage studies were located in the vicinity of this project Basin Reconnaissance Summary Reports King County's Basin Reconnaissance Summary Reports were not consulted for this project. FEMA Floodplain/Floodway Maps The project site is shown on FEMA Flood Insurance Rate Map Number 53033C0982, and does not appear to be within a flood hazard area. A portion of this map has been included in Appendix 3-A. Other Offsite Analysis Reports This project is tributary to a large wetland area which exists immediately east of the project site. The recently constructed Shamrock Subdivision, which lies further to the east, is also tributary to this wetland area, and shares the same downstream system. The Level 1 downstream analysis for the Shamrock Subdivision has been included in Appendix 3-A. Sensitive Areas Folio Maps King County's Sensitive Areas Folio Maps have not been consulted for this project. The project site is not expected to contain any of the sensitive areas listed in the folio maps. Drainage Complaints and Studies No King County drainage complaints were researched for this report, since downstream complaints have already been addressed by the Shamrock Subdivision listed above, as well as other downstream projects referenced by the Shamrock report. Additionally, Langley Meadows is discharging to a large wetland area, which, in conjunction with the proposed detention facility, is expected to attenuate flow enough to avoid aggravation of any downstream problems. LANGLEY MEADOWS 107-016-006 SECTION 3 OFF-SITE ANALYSIS z 0 ... rn .... - Site Development Associates, LLC Road Drainage Problems No roadway drainage problems were identified in the vicinity. The existing roadway drainage along the site frontage appears to be operational and clear of debris. Migrating River Studies The project site is not within a Migrating River Study area. LANGLEY MEADOWS 1 07-016-006 SECTION 3 OFF-SITE ANALYSIS ·-··· Site Development Associates, LLC TASK 3 -FIELD INSPECTION The Langley Meadows site and surrounding vicinity were visited on May 10, 2006. The conditions at the time of the visit were warm and clear, and no recent precipitation had occurred . No surface water was observed on the project site during the visit. The project site generally slopes downward to the east. Stormwater runoff appears to follow the existing ground topography, exiting the project site across the east property boundary. The east edge of the project is shown in Photo #1 below: Photo #1 (looking north a long east boundary line) After leaving the project site, surface runoff enters a large, off-site wetland area which lies immediately east of the site. Photo #'s 2 & 3 show the vicinity of the wetland and project site. LANGLEY MEADOWS 107-016-006 SECTION 3 O FF -SITE A NALYSI S Site Development Associates , LLC LANGLEY MEADOWS 10 7 -0 16-006 Photo #2 (l ooking east at w etl and from property line ) Photo #3 (lookin g wes t fro m wetl and) (La ng ley Mead ows behind trees) SECTION 3 O FF-SI TE A NALYS IS Site Development Associates, LLC The wetland system continues to the south, and runoff follows the same downstream flowpath that was outlined in the approved downstream analysis for the Shamrock development. The Shamrock downstream analysis has been included in Appendix 3-A of this report. The exhibits in the Shamrock report have been modified slightly to show the location of the Langley Meadows site. Three single-family residences lie immediately adjacent to the southwest corner of the project site. A portion of these lots, specifically the back yards, appear to be tributary to the project site. All three lots face 142"d Ave. SE, and it is likely that the roof and footing drains from these lots drain toward the fronting road. TASK 4 -DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS No specific problems were noted on the Langley Meadows project site itself, since the primary method of conveyance is overland sheet flow. Immediately off-site, stormwater runoff enters a large wetland area, which appears to have been recently enhanced during the development of the Shamrock subdivision to the East. Any problems that may have existed downstream of the wetland area are assumed to have been resolved as part of the Shamrock development. TASK 5 -MITIGATION OF EXISTING OR POTENTIAL PROBLEMS No specific problems were identified during the site investigation. The detention facility should outfall to a rock-lined splash pad, to keep erosion in the wetland area to a minimum. LANGLEY MEADOWS 107-016-006 SECTION 3 OFF-SITE ANALYSIS •• ~r Site Development Associates, LLC APPENDIX 3-A RESOURCE REVIEW DOCUMENTS LANGLEY MEADOWS 107-016-006 SECTION 3 OFF-SITE ANALYSIS A 21 B C APPAOXl.'v!A TE SCALE l"J Fl ET so, "" 122°09"22"' ~7030·00 ,------JOINS PA~EL 0669 -~---------- CITY OF RENTON ~ '°"'"'"' I I "°'" ~00,1 Is srnm \ I NATIONAL FLOOD INSURANCE PROGRAM sour><E'<S' na,,., CITY OF RENTON FLOOD INSURANCE RATE MAP KING COUNTY, WASHINGTON AND INCORPORATED AREAS tL~,J T:l'IST ~TF!l:ET l 6\~ rr 1C 2 2 ~ " ~10 'I QI~ ~ >--z I::;:;;.:: '--' CITY OF RENTON 530088 I I ~ SOVTHE.<.SJ I 126TH $1AEET I 0 & I ~ I 530088 I 0,,,,,~s, ''°'" ~ f/<o:rfc";-I ZONE X $;,£ 128TH -~TAffT so~~HEA..~r STRfH 1SEF. M"P '"'OEX FOR PAN~~$ Nor PAINlfOJ ~U_IBER Pp,ML sc1ff1:< --::: MAP HUMBER 53633GOS82 F MAP REVISED: MAY 16, 1995 Fedeul Emergtncy Management Agency n.011·iin...i<'"c...,.c11;,·_.,.,.,..,,,...-.-.....,..,1,,.,.,-.,,.,P • -""no:teo _..,,g F-MrT °"""--'"" Thoo .._ -..,. 'fleCt """"- ,,, .--., __ <h ""'' ..... ....,, "'-·--"''""""'"°"- ••• '""""-Fo, "'* ,_, ..-..,,. '""'"""""" ""'°"' --F'-<I .._._._. p._,..,, food mopo ""'°"" '"° Fe;MA Flood"'°" St°'*•-..."'""--•~ Shamrock LEVEL 1 DOWNSTREAM ANALYSIS King County, Washington Prepared For: Prepared For: Cam West Real Estate Development, Inc. Prepared By: Schwin Chaosilapakul Ben Rutkowski Reviewed By: Rebecca Cushman, PE Issued July 29, 2002 Revised September 12, 2003 Revised January 19, 2004 Revised May 26, 2004 Shamrock -Level 1 Downstream Analysis Table of Contents 1 INTRODUCTION ................................................................................................. 1 2 SITE .................................................................................................................... 2 3 UPSTREAM DRAINAGE ANALYSIS ................................................................. 2 3.1 Upstream Basin .................................................................................................................. 2 4 DOWNSTREAM DRAINAGE ANAL YSIS ........................................................... 3 4. 1 On site Runoff ...................................................................................................................... 3 4.2 Offsite Runoff ...................................................................................................................... 4 4.3 Downstream Capacity ........................................................................................................ 4 4.4 Downstream Drainage Problems ...................................................................................... 7 5 RESOURCES USED FOR ANALYSIS ............................................................... 8 5.1 Sensitive Areas Folio ......................................................................................................... 8 5.2 King County Basin Reconnaissance Program ................................................................ 8 5.3 Soils Survey for the King County Area ............................................................................ 8 5.4 King County Community Planning Area .......................................................................... 8 6 DRAINAGE CONCEPT ....................................................................................... 9 Appendix .................................................................................................................. A Existing Conditions Exhibit Developed Conditions Exhibit Downstream Drainage Exhibit Tributary Areas Exhibit Soils Map and Legend, Hydrologic Soils Group Table Sensitive Areas Folio King County Basin Reconnaissance Program King County Community Planning Area Complaints Excerpt.from Sienna Improvement Plans (6 Sheets) Shamrock -Level 1 Downstream Analysis 1 INTRODUCTION Shamrock is a 34.5 acre site spanning both King County and the City of Renton jurisdictions. The total proposed project will contain 129 lots. The King County portion of the project proposes to create 118 single-family lots (74 lots will utilize Low Impact Development) on an approximately 29.8 acre property. This Technical Infonnation Report (TIR) is for the King County and Renton portions of the project. The Vicinity Map below shows the City of Renton boundary. The part of the site outside the City of Renton boundary is subject to King County DOES review. The site is north of 128 1 h Street SE, west of 148 1h Avenue SE. The property is within Section 10, Township 23 North, Range 5 East, W.M., King County, Washington. Please see the Vicinity Map below. NE 4th ST SE !J7nd sr ~ SE rJJ,~ crl -: ~I ,---/ _] I --=r -1 -:j .--+-~__J- I VICINITY MAP Not to Scale Site visits were performed on July 2, 2001 and July 15, 2002 and July 14, 2003 to observe the upstream and downstream drainage conditions. The following analysis is based on these site visits and related research of available records. May 26, 2004 Job# 01-159 /rRIAD ,,,.,,,,11, Page 1 • Shamrock -Level 1 Downstream Analysis 2 SITE The existing site is a wholesale nursery with two residences and several outbuildings that will be demolished (see Existing Conditions Exhibit, in Appendix). The site generally slopes from the east to west. An onsite wetland exists on the northwestern portion of the site . Slopes range from 2-12 % with pasture ground cover. The site exists within two basins. 3 UPSTREAM DRAINAGE ANALYSIS 3. 1 Upstream Basin There are several upstream areas that are tributary to the site. Areas I and 2 are tributary to the portion of the site that is within the May Creek sub-basin. Please see Section 5 in the Technical Information Report (TIR) for detention/water quality issues. Area 3 is hibutary to the Lower Cedar River sub-basin portion of the site located in both King County and the City of Renton. Please sec Section 5 in the TIR for detention/water quality issues. Area 4 is tributary to the wetland only and will not affect drainage. Areas 5 and 6 were previously assumed to be tributary. However, additional topography revealed that it is not tributary. Upstream from the southeast section of the site is a development called Morgan Place which contributes approximately 3 acres. The site contains slopes ranging from 2-10%, predominately in the westerly direction consisting primarily of pasture, some light forest, wetland and two existing houses. Refer to the Tributary Areas Exhibit at the end of this report. May 26, 2004 Job#01-159 Page 2 Shamrock -Level 1 Downstream Analysis 4 DOWNSTREAM DRAINAGE ANALYSIS Refer to the Downstream Drainage Exhibil and Upstream Tributary Map from the Loken/Johnson Report, Sheets I and 2 from the approved King County Project L02SR037 and Sheets I 0, 11 and 15 from the approved City of Renton Project of Sienna at the end of this report. 4. 1 Onsite Runoff Approximately 17.0 acres of the northern portion of the site slope from east to west. Slopes range from 2-12 %. This northern portion of the site is tributary to two onsite wetlands located in the northwestern portion and north-central portion of the site. The northwestern wetland discharges to the north and south, whereas the north-central wetland discharges to the north only. The remainder of the site drains in a southwest to south direction over gentle slopes. Runoff is collected in an existing detention pond located n01ih of the intersection of SE 128 1h Street and 146'h Ave. SE. Specifically, at the southeast comer of the southernmost parcel of the site. Runoff from the pond discharges south offsite beneath SE 128'h Street through a 42- ineh pipe. May 26, 2004 Job# 01-159 /TRIAD " " ' ' --· Page 3 Shamrock -Level 1 Downstream Analysis 4.2 Offsite Runoff North Discharge from the north half(+/-) of the onsite northwestern wetland flows offsite to the north through a 12-inch CMP and a 6-inch concrete culvert and into a pond in the adjacent property. The pond discharges north into a wetland, then to Honey Dew (Honey) Creek which, according to the December 1990 King County Sensitive Areas Map Folio, is an unclassified stream in the May Creek Sub-Basin. The nrn1h-central wetland discharges to the north and connects with the off-site wetland described above. Honey Dew Creek combines with May Creek over two miles downstream (north) of the site. May Creek is in the Cedar River Drainage basin and ultimately discharges into Lake Washington. Runoff to the south flows through a 42-inch pipe then into a ditch behind a residence at 14415 SE !28th St. The ditch ranges from 2 to 3 feet deep and then travels under a driveway via an 18-inch culvert. The storm water enters the north property line ofa new development (Sienna). The !low is then picked up by the 36-inch bypass conveyance pipe within the Sienna development and continues in a southerly direction until passing the quarter-mile downstream point at its intersection with SE I 32"d Street. From there, the flow continues to travel in the 36-ineh pipe approximately 200 feet west on SE I 32"d Street before changing course to the south on 144th Avenue SE. The flow then travels south on 144th Avenue SE for approximately 600 feet where it connects to a 24-inch cross culvert. The flow then continues to the west in a defined stream channel. 4.3 Downstream Capacity The Sienna proj eel included the design of an upstream bypass conveyance line. The sizing of this pipe system was based on assumptions made of the upstream basin. These assumptions were made based on limited topography. As a result of more detailed topography, it is found that the original assumptions arc conservative. Please see the Tributary Areas Exhibit located at the end of this report. May 26, 2004 Job#01-159 /rRIAD . "'"(''"' ----- Page 4 ) Shamrock -Level 1 Downstream Analysis The following is an excerpt from the Final Corrected Technical Infomiation Report provided to King County under Pem1it #L02SR037 dated September 16, 2002. Begin Excerpt Conveyance for Upstream Flows The KCRTS I 5-minute time step was used to determine the overall flows tributary to the pipe system conveyance. 6 7. 2 acres upstream area has been recently developed. Those areas pertaining to new development were modeled using the information obtained from previous Technical Information Reports. The remaining areas were modeled using approved Technical Information Reports, Aerial maps and actual survey. All of NE 41h Street right-of- way was assumed impervious. An additional 781 efs from the JOO-year outflow of the detention pond from the City of Renton approved project of Sienna was added at CB 4 making the total flows piped at 75.41 cfs. Please see the upstream tributary map. The following is the ground cover breakdown of the I 59. 43-acre tributary area upstream and the KCRTS 15-minute time step printout. Till Forest: 74.94 acre Till Pasture. 9. 76 acre Till Grass: 33.86 acre Flow Frequency Analysis Time Series File:jan28.tsf Project Location:Sea-Tac Wetland: 4.81 acre Impervious: 36.06 acre ----1'!.nnual Peak Flow Rates--------Flow Frequency Analysis------- Flow Rate Rank Time of Peak -Peaks Rank Return Prob (CFS) (CFS) Period 20.50 6 2/09/01 12,30 67.60 1 100.00 0.990 14.40 7 1/05/02 15,00 44.13 2 25.00 0.960 44.13 2 12/08/02 17, 15 25. 62 3 10.00 0.900 13.82 8 8/23/04 14,30 24.49 4 5.00 0.800 25. 62 3 11/17 /04 5:00 21.65 5 3.00 0.667 21.65 5 10/27 /05 10,45 20.50 6 2.00 0.500 24. 49 4 10/25/06 22,45 14.40 7 1.30 0.231 67.60 1 1/09/08 6,30 13. 82 8 1.10 0.091 Computed Peaks 59.78 50.00 0.980 This conveyance system has been designed to convey.flows up to the I 00-year storm without overt op ping. May 26, 2004 Job# 01-159 /rRIAD . ,,,,,c,,,,. ---· Page 5 Shamrock -Level 1 Downstream Analysis Freeboard Tables from Storm Sewer Output Upstream Tributary Pipe System Catch Basin Rim Elev. outfall-/ 410.00 I-upstream 410.00 2 415.80 3 420.10 4 421.84 5 428.50 6 430.65 7 431.32 8 432.52 9 433.00 10 431.25 End Excerpt HGL Elev. Free board 409.08 0.92 409.10 0.90 409.96 5.84 411.96 8.14 419.37 2.46 423.27 5.23 424. 72 5.92 425.43 5.88 429.49 3.02 430.17 2.82 430.88 0.37 Additional survey and analysis of the onsite wetland located on the west property line of Shamrock determined that approximately 22 acres of assumed tributary area to the bypass conveyance system flows to the north as apposed to the south. Therefore, the designed flows to the bypass conveyance system are more conservative with less t1ibutary area. May 26, 2004 Job#01-159 ftRIAP -- Page 6 Shamrock -Level 1 Downstream Analysis 4.4 Downstream Drainage Problems North According to King County Water & Land Resources Division, there have been no recent problems downstream of this project. The complaints that have been documented arc associated with downstream properties near the East Renton project. These complaints are over 12 years old. King County suggests not following up on any complaints before 1990 due to their age, development that has occurred, etc. Additionally, no complaints have been documented at those addresses for 12 years, so the problem most likely has been corrected. The complaints arc linked to a private home drainage system and a private road washout due to no drainage system rather than flooding, or erosion of the large drainage course that our site will discharge to. Since no complaints have been documented at this location in the last 12 years, it is assumed that corrections have been made as a result of subsequent development. According to complaints compiled by the King County Water and Land Resources Division, several instances of flooding have been reported in areas near the downstream drainage path of the site. Problems of flooding and drainage in these areas seem to have been alleviated with the recent installation of a 36-inch pipe system shown in the Downstream Drainage Exhibit. Details of complaints are included at the end of this report. Since the installation of the 36-inch conveyance system there has been one downstream complaint. This complaint comes from the resident at the address of 5511 NE 2nd Street. The resident complains of the roadside ditch overtopping. Per conversations with Ron Straka with the City of Renton, this is not considered a major issue and the City currently docs not have plans for maintenance. In addition, available topography suggests that potential over- flows from the Sienna project would flow cast along 3rd Street to Lyons Avenue, then south along the west side of Lyons Avenue rather than further east to the subject property. A copy of this complaint along with photographs can be found in the Appendix. Also see the Downstream Drainage Map #2 included at the end of this report. May 26, 2004 Job# 01-159 ltBJAD - Page 7 n NOlDNIHS't/M '.HNno:> !JNl>I SISJ.. ?ttNtt Wtf3J:l1NSMOO t 73113? ' . ' l t ~ \ ·. \i t ,. I.,· -~, >IDOIJWt'HS : I 1S3MWtt:J 118/HX:J SN0/1/GNO:J 9Nl1SIX3 11 L_J l \ '--.. \. i ·, ·,'. I i '. \ i . I @ I :~1· . . .\ "· .. ": I '; ~ I : '. :. (. .,. '·1', ~ j /'., w -' <:( (.) <f) r··· I r----.. ! r - !··--" Vl w f- <I: u 0 (/1 (/1 <:( 0 <:( ii f- v 0 0 N (Q) '6MP'JJ-L7 6f;tt0\t 7311J7\s;,1q,1'1xJ 6u,uaau,16u3\sa1u:JM0 \691, LJJrOcJd\ .3 W 7 · ,,.---;: '-z 'f' '""lW "rn:y • . LJ :. ~ [l w "'n w (!) '-------J z ~~ ~I z <? 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SC.All: HORJ'l.: 1 ·.200· YUT.: S!A WP N01 YAUD UNLESS SIC~lD AND DATED JOB NO. 01-159 SHEET NO. 3 or4 L I --i I I I I -i I -------, I tu ttttt 111 tut==~ C 1111 ·m~m II r I l-1--+ -1-1 I ~ ---;; Ill __ --I I I I I I I 1 -----,------+ --1 1 I :: I _ LJJ_l~Ll I T ___ __jt___ I I I I : :1 II i ,.~t~-Jif !frin .LL .1 ····· .~.~·-· / _____ J ___ j l-=~=-=: ~-------n__ :l_ ~, --~u-~:IrJf __ 1_/ ___ -;~_,--T-/--,-------: U --_J r ------'--=:tr-; T 11 I I 1-1, I I I I ~~ : -~--'-\ tr t-~ J/f-1----i I I --i c-Q-:cr --1 -j, 1 1 1 1 1 II SITE ,. ~ J r, n-· . I/. J_L __ J _J ______ -~- ~:>_ ... · :,.....r:-: ~ ,,1 ,,,-1,---,-- . · · · · · l v---':== f-jJ _1_ --i I I : '1 /~:-_ :: SITE ;;:_--42" F--i I I I I : f>u ... :__ -~~ --_11-+-I I I : --f----I I I I ~I -I I r -------/-1/4 Ml F P IN1i ...... r , _J___ 1 uJ _ 1 _J___]JL~-E~24··,~1AKE _ _J ~;~:E~Jf//~ r---Eilill ,-U,fT='t1rVf r~ TT/_n--~'11-=lr--~-c~EX 2:"-0UTFALL-I A'eA< -~-=_--_ 11 ~~ F--i w l J I //1_~_1_--1 I ~-t 1l ---I~---{~ r3--J-__ -1_ ___ j// / -n 1 J __ C[JII 111] , 1 1 --t-1 L j_ __ -----_j I~ -_ l__ - r' -11-1 " 1 ---1 =1 1 1 ------i -----1 I~ -i= -1 r_ ~- --j LE:--~--=-0 I 1-1 / I t=--11' f-/-=~ r-~: I L ~-u --/--j I I I , I [ _-_ l _i t -_-IT 1 ---JJ 1 / I f .J f ~ }--7 I-- ~_ J ____ J ---/-I I / 1 I I =n--'r¢?1 ~ I ,1 I "I~-3 ~1 I 11 -=l -~ I ---,, I I TOTAL SITE AREA = 34.27 AC!: .,,,,,,,_ . ...,r..,,..,;11,,,., '"0,-., ,,.._,, .,,,.-~"'"''·""'XKJ-4,.. '""'""''·'·~c:,d·,---,c,· ~.,x:z~,LQ,A?.Q,,... ,,, __ _ -@- SCALE: 1" = 400' Fl.OW LEGEND ---PIP£ Fl.OW __...___ SHEET Fl.OW - · , · -SHALLOW Fl.OW DITCH Fl.OW !r1JJM? - ~ ~ <I "' f... c:i-~ ill <I ~ ~ "' f... ~ 0 Cl ~ ~ I ~ ,1~14 1,sc,, .. ,... >It" O<l-iJond.WA~3 425 S21.84411 '25.821,,.81 tu &ooUSOT~IDlln. -·-"""' "' iii )C ~~ (.) ~ f...o~ "' <I 11.J ~ "' :!E ::e f: ~ "' ~~~ :t: g Cl) - !ti ::,; "' ..J :z 0 ... " ~ "' ~ ,.: ... ~ 0 \) " "' >c g <J<J<J<l<}1<]<1 CDfMD F. Mg. NCP PROJECT Ill.NAGER #fC1t A.. 1'WW'l ,u PROJECT SURVIYOi iorc:eo~ PROJg(j fNGINEER PROJECT WbSCAi'E ARCl!mcT FIRS!' SUS1tmAL »ATE: SCAl.l: IIORI1.:P·•4b0' l'EIIT.,N/A STAMP NOT VAlJll UNLESS SIGNBP ARD llAtEll JOB NO. 01-159 SHEET NO © 2004 TRIAD ASSOCIATES! 4,,4 Site Development Associates, LLC SECTION 4 FLOW CONTROL & WATER QUALITY ANALYSIS & DESIGN LANGLEY MEADOWS 107-016-006 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates, LLC PART 'A' -EXISTING SITE HYDROLOGY The existing site topography can best be described as gently falling to the east. The existing land cover consists of a handful of single-family homes, detatched garages, and driveways, surrounded by landscaping and lawn area. In the existing condition, stormwater runoff is expected to follow the existing ground topography, and flow overland to the east. The existing drainage basins and site hydrology are outlined in Figure 4 of this document. PART 'B' -DEVELOPED SITE HYDROLOGY The proposed development calls for the installation of an underground pipe network to collect and convey flow from the surface streets. All roof and lot runoff is intended to be directed to this system. The pipe network will convey surface runoff to an underground stormwater detention and treatment vault near the east edge of the site. The vault will contain live detention storage, as well as a permanent wetpool for stormwater treatment. Detained and treated flow will be discharged to the existing off-site wetland area. The proposed drainage basins and site hydrology are outlined in Figure 5 of this document. PART 'C' -PERFORMANCE STANDARDS The proposed detention facility has been designed in conformance with Level-Two flow control standards, as outlined in the 2005 edition of the King County Surface Water Design Manual (KCSWDM). The level-two flow control standard essentially stipulates that the peak flowrates and peak flow durations in the post-developed condition shall not exceed the existing peak flowrates and peak flow durations. This condition shall be applied to flowrates ranging from Y, of the 2-yr design storm to the 50-yr design storm. In order to simplify the facility design process. the peak release rates are allowed to exceed the existing flowrates as long as the exceedence is not greater than 10%, does not occur for more than half of the analysis range, and does not exceed the existing flowrate at Y, of the 2-yr storm event. Design of the stormwater detention and treatment facilities will be performed using King County's KCRTS hydrologic modeling software. LANGLEY MEADOWS 107-016-006 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates. LLC PART 'D' -FLOW CONTROL SYSTEM Flow control for this project will be provided by an underground detention vault. A detail of the detention vault is included in Figure 6 of this report. Design of the detention vault is performed as follows: Step 1 -Determine the pre-developed hydrologic conditions: 0 Land Use Summary r:l ~ -Area--- Till Forest 10.65 acres Till Pasture 0.00 acres Till Grass 0.72 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres' Wetland/ 0.00 acres lmperviousL 0.3~~ 1Total- 1 ~es/ Scale Factor : 1.00 Hourly Reduced ? Time Series: '-IP_r_e_de_v_.t_s...c~ _________ __,_I >_>...,l Compute Time Series l Modify User Input ! File for computed Time Series [.TSF] Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow Rate Rank Time of (CFS) 0 .779 2 2/09/01 0.275 7 1/05/02 0.652 3 2/28/03 0.094 8 8/26/04 0.381 6 1/05/05 0.620 4 1/18/06 0.567 s 11/24/06 1.10 1 1/09/08 Computed Peaks LANGLEY MEADOWS 107-016-006 Peak 18:00 16:00 3:00 2:00 8:00 16:00 4:00 9:00 -----Flow Peaks (CFS) 1.10 0.779 0.652 0 .620 0. 567 0 .381 0 .275 0. 094 0.992 Frequency Analysis------- Rank 1 2 3 4 5 6 7 8 Return Prob Period 100.00 0.990 25.00 0. 960 10.00 0.900 5. 00 0.800 3.00 0.667 2.00 0.500 1. 30 0.231 1.10 0.091 50.00 0.980 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates, LLC Step 2 -Determine the post-developed hydrologic conditions: ~ Land Use Summary GJ (g) Area -? - Till Forest 0.00 acres Till Pasture, 0.00 acres Till Grass 4.75 acres Outwash Forest 0.00 acres Outwash Pasture 0.00 acres Outwash Grass 0.00 acres Wetland 0.00 acres Impervious 6.94 acres ~ Total 11.69 acres Scale Factor : 1.00 Hourly Reduced Time Series: !Dev.ts~ J»I Compute Time Series I Modify User Input I r File for computed Time Series (.TSF] Flow Frequency Analysis Time Series File:dev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- Flow -----Flow Frequency Analysis--- Rate Rank Time of (CFS) 2.11 6 2(09(01 1. 70 B 1/05(02 2. 54 3 2/27/03 1. 82 7 8(26/04 2.19 5 10/28/04 2.23 4 1/18/06 2.64 2 10/26/06 4.28 1 1/09/08 Computed Peaks LANGLEY MEADOWS 107-016-006 Peak - 2:00 16:00 7:00 2:00 16:00 16:00 0:00 6:00 Peaks Rank (CFS) 4.28 1 2.64 2 2. 54 3 2.23 4 2.19 5 2.11 6 1. 82 7 1 .70 8 3. 74 Return Prob Period 100.00 0.990 25. 00 0.960 10.00 0.900 5.00 0.800 3.00 0.667 2.00 0.500 1.30 0.231 1.10 0.091 50.00 0.980 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates, LLC Step 3 -Calculate the required detention facility dimensions: Type of Facility: Detention Vault Facility Length: Facility Width: Facility Area: Effective Storage Depth: Stage O Elevation: Storage Volume: Riser Head: Riser Diameter: Number of orifices: Orifice # Height (ft} 1 o.oo 2 4.30 472. 00 38.00 17936. 7.00 44 7. 00 125552. 7.00 12.00 2 Diameter (in) 1. 75 3. 25 Top Notch Weir: None Outflow Rating Curve: None ft ft sq. ft ft ft cu. ft ft inches Full Head Discharge (CFS) 0.220 0. 471 Pipe Diameter (in) 6.0 Stage/Storage/Discharge Performance Stage Elevation Storage Discharge Percolation (ft) (ft} (cu. ft} (ac-ft} (cfs) (cfs) 0. 00 447 .00 o. 0.000 0.000 0.00 0.02 447 .02 359. 0.008 0.011 0.00 0.04 447 .04 717. 0.016 0.016 0.00 0.05 447 .05 897. 0.021 0.019 o.oo 0. 07 447.07 1256. 0.029 0.022 0 .00 0 .09 447.09 1614. 0.037 0.025 0.00 0.11 447.11 1973. 0 . 045 0 .027 0.00 0 .13 44 7 .13 2332. 0.054 0 .030 0.00 0 . 15 447.15 2690 . 0.062 0 . 032 0.00 0 .26 447.26 4663. 0.107 0 .043 0.00 0 . 3 8 447.38 6816. 0.156 0. 051 0. 00 0. 50 447.50 8968. 0.206 0.059 0. 00 0.62 447.62 11120. 0.255 0.065 0.00 0.74 447.74 13273. 0.305 0.071 0.00 0.86 447 .86 15425. 0.354 0.077 0.00 0.98 447.98 17577. 0 .404 0.082 0.00 1. 09 448.09 19550. 0. 44 9 0.087 0.00 1.21 448.21 21703. 0.498 0.092 0 .oo 1. 33 448.33 23855. 0.548 0.096 0.00 1. 45 448.45 26007. 0 .597 0.100 0.00 1. 57 448.57 28160. 0 . 646 0.104 0.00 1 .69 448.69 30312. 0. 696 0 .108 0.00 1. 81 448.81 32464. 0 .745 0 .112 0 .00 1. 93 448.93 34616. 0.795 0 .115 0 .00 2 .04 449 .04 36589. 0.840 0.119 0 .oo 2. 16 449 .16 38742. 0.889 0.122 0. 00 2.28 449 .28 40894. 0 .939 0.125 0.00 2 .40 449 .40 43046. 0 .988 0.129 0.00 2.52 449 .52 45199 . 1.038 0 .132 0.00 2 .64 449 . 64 47351. 1 .087 0.135 0.00 2.76 449 .76 49503. 1 .136 0 .138 0.00 2.87 449 .87 51476. 1 .182 0 .141 0.00 2.99 449 .99 53629 . 1 .231 0 . 144 0.00 3.11 450 . 11 55781. 1 .281 0 .147 o.oo 3. 23 450 .23 57933. 1 . 330 o. 149 0.00 3 .35 450 .35 60086. 1 .379 0 .152 0.00 3 . 47 450 .47 62238 . 1.429 0 .155 0.00 3 .59 450 .59 64390. 1 .478 0 .157 0. 00 3. 71 450.71 66543. 1 .528 o. 160 0.00 LANGLEY MEADOWS SECTION 4 107-016-006 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN •• ~ Site Development Associates, LLC Stage/Storage/Discharge Performance Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) lac ft) (cfs) (cfs) 3. 82 450.82 68516. 1.573 0.162 0 .00 3. 94 450.94 70668. 1 .622 0 .165 0 .00 4 . 06 451. 06 72820 . 1 . 672 0 .167 0 .00 4 .18 451.18 74972. 1 .721 o .170 0 .00 4.30 451.30 77125. 1 . 771 o .172 0.00 4.33 451.33 77663. 1 .783 0. 176 o .00 4.37 451.37 78380. 1 .799 0 .184 0.00 4.40 451.40 78918. 1 .812 o. 198 0.00 4. 44 451.44 79636. 1 .828 0 . 217 o.oo 4 .47 451.47 80174. 1.841 0 .240 0.00 4 .50 451.50 80712. 1.853 0 .269 0.00 4. 54 451. 54 81429. 1.869 0 .299 0.00 4.57 451.57 81968. 1.882 0 .327 0 .oo 4.60 451.60 82506. 1. 894 0. 336 o .oo 4.72 451.72 84658. 1.943 0 .367 o .00 4.84 451.84 86810. 1.993 o .394 0 .00 4. 96 451.96 88963. 2.042 0 .418 o .00 5.08 452.08 91115. 2.092 0 .440 0 .00 5.20 452.20 93267. 2 .141 0.461 0.00 5.32 452.32 95420. 2 .191 0 .480 0.00 5 .44 452.44 97572. 2 .240 0.499 0.00 5 .55 452.55 99545. 2.285 0.517 0.00 5. 67 452.67 101697. 2.335 0.533 0.00 5. 79 452.79 103849. 2.384 0.550 0.00 5.91 452 .91 106002. 2.433 o. 565 0.00 6. 0·3 453 .03 108154. 2.483 0 .581 0 .00 6 .15 453 .15 110306. 2.532 0 .595 0 .oo 6 .27 453 .27 112459. 2 .582 0 .610 0 .00 6 . 38 453 .38 114432 . 2 .627 0 .624 0 .00 6 .50 453 .50 116584. 2 .676 0 . 637 o .00 6 . 62 453 .62 118736 . 2 .726 0.650 0. 00 6. 74 453.74 120889. 2.775 0.663 0 .00 6. 86 453.86 123041. 2.825 0.676 0.00 6.98 453.98 125193. 2.874 0.688 0.00 7.00 454.00 125552. 2.882 0.691 0 .00 7.10 454.10 127346. 2 .923 1.010 0. 00 7 . 20 454 .20 129139 . 2 .965 1.580 0 .oo 7 .30 454 .30 130933. 3. 006 2.320 0 .00 7 . 4 0 454 .40 132726 . 3. 047 3 .120 0 .00 7 . so 454 .50 134520 . 3. 088 3 .410 o .oo 7.60 454.60 136314. 3.129 3.680 0 .oo 7.70 454.70 138107. 3.171 3.920 0 .00 7.80 454.80 139901. 3.212 4.150 0.00 7.90 454.90 141694. 3.253 ' .360 o.oo 8.00 455.00 143488. 3.294 4.570 0.00 Stage/Discharge Performance at Significant Storm Events Hyd Inflow Outflow Target Cale 1 4 .28 1.10 2.85 2 2 . 11 ******* 0.83 3 2 .54 ******* 0 .56 4 2 . 64 ******* 0.60 5 2 .23 ******* 0 .46 6 2.19 ******* 0 .25 7 1. 70 ******* 0 .16 8 1. 82 ******* o. 14 LANGLEY MEADOWS 107-016-006 Peak Stage Elev 7.37 454.37 7 .04 454.04 5 .87 452.87 6 .18 453 .18 5 .18 452 .18 4 .48 451 .48 3 . 85 450 . 85 2 .74 44 9. 74 Storage (Cu-Ft} (Ac-Ft) 132132 . 126355. 105321. 110933 . 92958. 80295. 69093. 49063. 3.033 2.901 2 . 418 2 .547 2 .134 1 . 843 1 .586 1.126 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN ...... Site Development Associates, LLC KCRTS Routing Instructions Route Time Series through Facility Inflow Time Series File:dev.tsf Outflow Time Series File:RDOut Inflow/Outflow Analysis Peak Inflow Discharge: 4.28 Peak Outflow Discharge: 2.86 Peak Reservoir Stage: 7. 37 Peak Reservoir Elev: 454 .37 Peak Reservoir storage: 132132. Duration Comparison Analysis Duration Comparison Anaylsis Base File: predev.tsf New File: rdout.tsf Cutoff Units: Discharge in CFS 3 .033 CFS at CFS at Ft Ft Cu-Ft Ac-Ft 6 :00 on Jan 10 :00 on Jan -----Fraction of Time--------------Check of Cutoff Base New %"Change Probability 0 .191 0.79E-02 0.53E-02 -32.2 0.79E-02 0.236 0 . 57E-02 0. 44E-02 -23 . 9 0.57E-02 0.281 0 .44E-02 0 .39E-02 -11. 8 0 .44E-02 0.326 0 . 33E-02 0 .37E-02 10 .3 0 .33E-02 0. 372 0 .25E-02 0 .29E-02 16 .2 0 .25E-02 0.417 0 .18E-02 0 .23E-02 30. 0 0 . 18E-02 0.462 0.12E-02 0. 15E-02 18. 7 0. 12E-02 0. 507 0.90E-03 0 .12E-02 30. 9 0 . 90E·· 03 0 .553 0.64E-03 0 .BOE-03 25. 6 0.64E-03 0 .598 0.38E-03 0.34E-03 -8.7 0.38E-03 0 .643 0.20E-03 0.21E-03 8.3 0.20E-03 0 .688 O.llE-03 0.49E-04 -57.1 0.llE-03 0.733 0 .82E-04 0.33E-04 -60.0 0.82E-04 0. 779 0 .16E-04 0.16E-04 0.0 0.16E-04 Maximum positive excursion= 0.035 cfs 9.3%) occurring at 0.382 cfs on the Base Data:predev.tsf and at 0.417 cfs on the New Data:rdout.tsf Maximum negative excursion= 0.055 cfs (-23.3%) occurring at 0.237 cfs on the Base Data:predev.tsf and at 0.182 cfs on the New Data:rdout.tsf LANGLEY MEADOWS 1 07-016-006 Base 0.191 0.236 0.281 0.326 0.372 0. 417 0 .462 0 .507 0 .553 0 .598 0 . 643 0 .688 0 .733 0 . 779 9 in Year 8 9 in Year 8 Tolerance------- New %Change 0.171 -10.5 0.182 -23 .1 0 .229 -18 .6 0.348 6 . s 0 .401 7 .8 0 .449 7 . 8 0. 4 99 B .o 0 .543 7.1 0 .568 2. 8 0 . 595 -0 .5 0.651 1 .3 0.675 -1 .8 0.681 -7 .1 0.834 7 .1 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates, LLC Duration Comparison Analysis {continued) ~ Paused -Duralion Analysis -KCRTS 1-l@l(RI co +--0----','-------------- 0 "' f=:'[,1C 1ut ,:iui- TargE:<t dur • ~ "'+---------~----------------------0 ~)._ '0 " " ~,) ""+-----------------',,~---------------0 "' 0 oo•-=====~----------'c-;;:----._'.!:::=----0----------- ------· -,_ '.'-·---.:-~~ 10 ,, 0>-,-,--,-,,,..,.-r,---r--,-,rrn-,.,---i----,--r,,-,TTr---,-,---,--,--,-TTT,---,C-1'"",:"T ... "'<'4) ""TTTn 10 ,, LANGLEY MEADOWS 107-016-006 10 '3 10 ,, 10 ,, 10° Probabrl1ty Exceedence SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN Site Development Associates, LLC PART 'E' -WATER QUALITY SYSTEM Water quality for this project will be attained through the use of permanent wetpool storage inside the detention vault. A detail of the detention/treatment facility is included in Figure 6 of this report. Design of the water quality facility is performed as follows: Step 1: Identify required wetpool volume factor (f). f= 3 ----'=--Per KCSWDM 6.4.1.1 Step 2: Determine rainfall (R) for the mean annual storm. R = 0.47 Per KCSWDM Fig. 6.4.1.A Step 3: Calculate runoff from the mean annual storm (V,) for the developed site. V, = (0.9A; + 0.25A,9 + 0.1 OA" + 0.01 A;,) x (R / 12) where: A; = Impervious Surface Area = 302,306 s.f. A,, = Till Grass Area = A" = Till Forest Area = A;, = Outwash Area V, = 12,682 c.f. Step 4: Calculate required wetpool volume (V"). vb= , xv, v. = 38,047 c.f. LANGLEY MEADOWS 107-016-006 = 206,910 s.f. 0 s.f. 0 s.f. SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN •• ~ .. Site Development Associates, LLC APPENDIX 4-A SUPPORTING DOCUMENTS FOR HYDROLOGIC MODEL LANGLEY MEADOWS 107-016-006 SECTION 4 FLOW CONTROL & WATER QUALITY FACILITY ANALYSIS & DESIGN t L ID C C ID " "' (D ~ ID > 0 V) ~ ~ 0 -' ::, <( N " ;--. '° 0 0 N 0 n "' 0 ::, I.._ 1_--. -__ _ ON-SITE HYDROLOGIC CONDITIONS -1 TOTAL BASIN AREA: 11.69 AC. I TOTAL BASIN AREA WITHIN PROJECT BOUNDARY: 10.65 AC. I (ASSUME I 00% FORESTED) I I EXISTING PVMT IN 142ND AVE. R-0-W: 0.32 AC. I I I I I I ----, I I I ON SITE I BASIN ' UNDISTURBED I I : I AREA I I I ----~ ' I I ' ii I ~L.___ I I ,_____ ---.-_J ---------- ~~~gn !!~r! LANGLEY MEADOWS Drawn Stte Development Associates, LLC Date '"""'""'woyNeBothol.w""*"100 '"'" EXISTING HYDROLOGIC 107-018-08 Offlco<'5<&"33 ""''"·"'·"" www.sda-.com CONDITIONS Sheet: FIGURE 5 Project No. q.\ PrnLPdc::\ 1 n7(()ff,:,J\:: n1 Fi-nFi (I nnnlPV MPnrlnwc::l\ nwn\ nP<::inn\ flrninnnP rlwn <:;,-.r,1,:,· 4n ~ m C C 0 y ~ " 0 > 0 V) m 0 _, :, <'. co n , .. w 0 0 N 0 n >. 0 :, ...... I I I I I I I I I I I I I I I -, -, T -. : ;-1 e i ® ! -: n·-------~;;;=====~========~ : : © ~ ~ ~-1--~--.--------~---1 ® i © -------- L ___ ~---I ------+------@ ~ i Cg) ® : @ --------1 ® ! ® : -----'-------© . r--------, ! : ® ® ! ® I. I 1 ~ -------'1--------I -----.-...--------- ® I @ Ot,I_SITI: __ : ______ _ ' BASIN I • ® ' © UNDISTURBED t---------' AREA ' ----_J _____ _ I ® I ® ! ® 1------~ ' --®---l--® --~-1--------------1-------: : : ® I I e e e G @ 8 8 e © ® ® © ' --------~ ® 1 ---~--- © --------, ® -------1 ® ® ® ® @) :------- ' _______ , ______ _ I ® I.. . ........_~ ® : ® _______ / ------ ' © ~ ® I @ @ @ ' ® I ® -------,------- ® ' I ' ' ® -------1-------- ® , ' © I ! © ;ill-® ~·:------~ D-\ 8r~:~~•~\ 1 n /(r,p_\\ o\1 /'; nc (1 ~~-1~. u-~..r~ .. ~'.\ I"'\ ... -\ r,~~:r,.o\ r,,.-· '"··-,J. .. -'-"'---'-· ~n ® ® ® I ----J ® - Design KJM Drawn Date 107-016-06 Project No. !!Hill! ON-SITE HYDROLOGIC CONDITIONS TOTAL BASIN AREA = IMPERVIOUS LOT AREA CALCULATION: TOTAL LOT AREA = IMPERVIOUS LOT AREA (METHOD 'A') = ( /~% O, TOTAL LOT AREA) IMPERVIOUS LOT AREA (METHOD 'B') (69 LOIS@ .3,000 S 0 /LOT) 11.69 AC. 8.44 AC. 6.33 AC. 4.75 AC. NOTE THE IMPERVIOdS L01 COVERAGE USED FOR DESIGN OF THf fl OW CONTROL FP,CILITY SH.Al L cl[ THE LESSER OF METHODS 'A' A~D 'H' AROV[ TOTAL IMPERVIOUS AREA TABULATION: IMPERVIOUS ROAD/SIDEWALK AREA = IMPERVIOUS LOT AREA = TOTAL IMPERVIOUS AREA = 2.53 AC. 4.41 AC. 6.94 AC. rn TOTAL IMPERVIOUS AREA = 6.9 TOTAL LANDSCAPE/LAWN AREA = 4.7 TOTAL BASIN AREA = 11.6 C LANGLEY MEADOWS Site Development Associates, LLC 18322 Bothel Wcrv NE; llolhel. Wannglon 98011 Office: "25 . .c&.6533 F<K 425."86.6593 www.Woe~heen..com PROPOSED HYDROLOGIC CONDITIONS Sheet: FIGURE 6 S ECTl ON 3.2 RUNOFF COl\·1PU T AT10N ,\ND /\NALY S1S METHODS FI GU RE 3.2.2.A RA INFALL REG IONS AN D REG IONAL SCALE FACTO RS ST 1.1 ST 1.1 ST 1 .0 Rainfall Regions and Regional Scale Factors 0 f(~:::::a In corporat ed AreaO ~ R iver/LakeO Major RoadO 0 1/24 /2005 ST 1.0/ LA 0 .9 LA 1.0 LA 1.2 H CO UNfY KINO CO U Hl Y 3-22 2005 Surface Water Desi gn Manual 3.2.2 KCRTSiRUNOFF FILES METHOD-GENERATING TIME SERIES . TABLE 3.2.2.B EQUIVALENCEJlETWEEN SCS SOIL TYPES AND KCRTS SOIL TYPES ' . SCS Soil Type scs KCRTS Soil Notes Hydro logic Group Soil Group Alderwood (AgB, AgC, AgD) C Till Arents, Alderwood Material (AmB, AmC) C Till Arents, Everetl Material (An) B Outwash 1 Beausite (BeC, BeD, BeF) C Till 2 Bellingham (Bh) D Till 3 Brisco! (Br) D Till 3 Buckley (Bu) D Till 4 Earlmont (Ea) D Till 3 Edgewick (Ed) C Till 3 Everett (EvB, EvC, EvD, EwC) A/B Outwash 1 Indianola (lnC. lnA, lnD) A Outwash 1 Kitsap (KpB, KpC, KpD) C Till Klaus (KsC) C Outwash 1 Neilton (NeC) A Outwash 1 Newberg (Ng) B Till 3 Nooksack (Nk) C Till 3 Norma (No) D Till 3 Orcas (Or) D Wetland Oridia (Os) D Till 3 Ovall (OvC, OvD, OvF) C Till 2 Pilchuck (Pc) C Till 3 Puget (Pu) D Till 3 Puyallup (Py) B Till 3 Raqnar (RaC, RaD, RaC, RaE) 6 Outwash 1 Renton (Re) D Till 3 Salal (Sa) C Till 3 Sammamish (Sh) D Till 3 Seattle (Sk) D Wetland Shalcar (Sm) D Till 3 Si (Sn) C Till 3 Snohomish (So, Sr) D Till 3 Sultan (Su) C Till 3 Tukwila (Tu) D Till 3 Woodinville (Wo) D Till 3 Notes: 1. Where outwash soils are saturated or underlain at shallow depth ( <5 feet) by glacial till, they should be treated as till soils. 2. These are bedrock soils, but calibration of HSPF by King County DNRP shows bedrock soils to have similar hydrologic response to till soils. 3. These are alluvial soils, some of which are underlain by glacial till or have a seasonally high water table. In the absence of detailed study, these soils should be treated as till soils. 4. Buckley soils are formed on the low-permeability Osceola mudflow. assumed to be similar to that of till soils. Hydrologic response is 2005 Surface Water Design Manual 1/24/2005 3-25 • '-.····· • !W·· . Site Development Associates, LLC SECTION 5 CONVEYANCE SYSTEM ANALYSIS & DESIGN LANGLEY MEADOWS 107-016-006 SECTION 5 CONVEYANCE SYSTEM ANALYSIS & DESIGN Site Development Associates, LLC CONVEYANCE SYSTEM ANALYSIS & DESIGN The Langley Meadows project is currently seeking preliminary approval only. A design of the conveyance system will be provided at the final design stage of the project. LANGLEY MEADOWS 107-016-006 SECTION 5 CONVEYANCE SYSTEM ANALYSIS & DESIGN Site Development Associates, LLC SECTION 6 SPECIAL REPORTS & STUDIES LANGLEY MEADOWS 107-016-006 SECTION 6 SPECIAL REPORTS & STUDIES --~··· Site Development Associates, LLC SPECIAL REPORTS & STUDIES LANGLEY MEADOWS 107-016-006 SECTION 6 SPECIAL REPORTS & STUDIES Site Development Associates, LLC LANGLEY MEADOWS 107-016-006 SECTION 7 OTHER PERMITS SECTION 7 OTHER PERMITS Site Development Associates, LLC OTHER PERMITS LANGLEY MEADOWS 107-016-006 SECTION 7 OTHER PERMITS Site Development Associates, LLC SECTION 8 CSWPPP ANALYSIS & DESIGN LANGLEY MEADOWS 107-016-006 SECTION 8 CSWPPP ANALYSIS & DESIGN •• ~- Site Development Associates, LLC CSWPPP ANALYSIS & DESIGN This section of the report, along with the Temporary Erosion and Sediment Control (TESC) Plan included in the engineering drawings, is intended to serve as the construction Stormwater Pollution Prevention Plan (SWPPP) for the project. The SWPPP is outlined in conformance with the 2001 edition of the Washington State Department of Ecology's Stormwater Management Manual for Western Washington (DOE Manual). STEPS 1&2-DATA COLLECTION &ANALYSIS The topography of the site has been described previously in this report as being gently sloping toward the east. No significant slopes currently exist on the project site, and none are expected to be created. The topography of the site is shown in the engineering planset, as well as in Figure 5 of this report. Soils on the project site have been identified previously in this report as being of the Alderwood variety, which is generally considered to be a till soil, with moderate to high runoff potential and little capacity for infiltration. The existing ground cover at the project site consists of a handful of single-family residences and associated driveways, surrounded by landscaping and lawn area. A critical wetland area lies immediately to the east of the project site. This wetland area appears to have been recently enhanced by the construction of the nearby Shamrock subdivision. Proper erosion and sediment control practices shall be implemented to ensure that the construction of Langley Meadows does not affect the adjacent wetland area. STEP 3 -CONSTRUCTION SWPPP DEVELOPMENT AND IMPLEMENTATION The development and implementation of this SWPPP shall consist of 12 specific elements, as outlined in the DOE Manual. They are: 1. Mark Clearing Limits Clearing limits will be flagged or fenced by the contractor or project surveyor prior to commencement of construction activity. 2. Establish Construction Access A stabilized rock construction entrance will be installed at the entrance to the plat at the onset of construction. LANGLEY MEADOWS 107-016-006 SECTION 8 CSWPPP ANALYSIS & DESIGN Site Development Associates. LLC 3. Detain Flows Prior to significant clearing, the permanent detention facility shall be constructed, so that it can be used for temporary sediment control. A temporary sediment riser shall be installed in order to ensure proper sediment control. Once the facility is constructed, the site shall be cleared and graded, and all surface water controls shall direct runoff to this facility. When final grading is complete and the site is stabilized, the temporary sediment riser shall be replaced with a permanent flow control structure. 4. Install Sediment Controls Filter fabric fencing (silt fence) shall be installed around the downstream perimeter of the site in order to keep sediment-laden stormwater from leaving the site. The fencing shall be inspected periodically to ensure its continued effectiveness. 5. Stabilize Soils The temporary erosion and sediment control plan calls for the stabilization of exposed soils through mulching or hydroseeding when the soils are not to be worked for a significant period of time. The plan also calls for the establishment of permanent vegetation through hydroseeding once the site has reached final grade. 6. Protect Slopes The project does not propose the creation of any significant slopes. 7. Protect Drain Inlets The temporary erosion and sediment control plan calls for a filter fabric sock to be installed at all nearby catch basin inlets. Filter fabric protection shall be placed in all new catch basins as they are installed. 8. Stabilize Channels and Outlets All temporary interceptor swales shall contain check dams whenever a drop of 2 vertical feet occurs. Water discharged from the sedimentation facility shall outfall onto a rip-rap splash pad. LANGLEY MEADOWS 107-016-006 SECTION 8 CSWPPP ANALYSIS & DESIGN •• !Ir Site Development Associates, LLC 9. Control Pollutants All waste materials shall be disposed of in an approved location, in accordance with City of Renton standards. In order to reasonably prevent a contamination event (such as a fuel spill), all major vehicle maintenance shall occur off-site to the greatest extent practicable. The contractor shall provide a vehicle staging area near the entrance to the site where all fueling and maintenance activity is likely to take place. This is intended to contain the area in which a contamination event is likely to take place. The contractor shall immediately contain and clean- up an area in which a contamination event occurs. 10. Control Dewatering No significant dewatering is expected to occur during this project. 11. Maintain BMPs All BMPs should be monitored and maintained regularly to ensure adequate operation. A TESC supervisor shall be identified at the beginning of the project to provide monitoring and direct the appropriate maintenance activity. As site conditions change, all BMPs shall be updated as necessary to maintain compliance with County standards. 12. Manage the Project The project will begin with a pre-construction conference in which an on-site TESC supervisor shall be identified. The on-site supervisor shall monitor all TESC facilities regularly and maintain a log of inspections and improvements to demonstrate compliance with City standards. The project is not large enough to be effectively phased, therefore, it will be important that the entire site is in conformance with City of Renton erosion control standards at all times. The TESC supervisor shall notify Site Development Associates of any problems with the proposed erosion control elements, or if any revisions to the plan need to be made. Additional erosion control materials, such as filter fabric fencing, cover plastic, and straw bales, shall be kept on-site at all times in the event that an erosion control feature needs to be replaced or installed. LANGLEY MEADOWS 107-016-006 SECTION 8 CSWPPP ANALYSIS & DESIGN •• ~ Site Development Associates, LLC SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES, AND COVENANTS LANGLEY MEADOWS 107-016-006 SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES, AND COVENANTS •• ,,,.: Site Development Associates, LLC BOND QUANTITIES, FACILITY SUMMARIES, AND COVENANTS A bond quantities worksheet will be provided at the final design stage of the project. A facility summary and discussion of any required covenants will also be provided at that time. LANGLEY MEADOWS 107-016-006 SECTION 9 BOND QUANTITIES, FACILITY SUMMARIES, AND COVENANTS Site Development Associates, LLC SECTION 10 OPERATIONS & MAINTENANCE MANUAL LANGLEY MEADOWS 1 07-016-006 SECTION 10 OPERATIONS & MAINTENANCE MANUAL ··,v·- Site Development Associates, LLC OPERATIONS & MAINTENANCE MANUAL The following pages have been selected from the current King County Stormwater Management Manual, and shall serve as the operations and maintenance manual for the project LANGLEY MEADOWS 107-016-006 SECTION 10 OPERATIONS & MAINTENANCE MANUAL Site Development Associates, LLC NO. 3 -CLOSED DETENTION SYSTEMS (PIPES/TANKS) Maintenance Component Storage Area Manhole Catch Basins Defect Plugged Air Vents Debris and Sediment Joints Between Tank/Pipe Section Tank Pipe Bent Out of Shape Cover Not in Place Locking Mechanism Not Working Cover Difficult to Remove Ladder Rungs Unsafe LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed One-half of the cross section of a vent is blocked at any point with debris and sediment Accumulated sediment depth exceeds 10% of the diameter of the storage area for Yi length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than Y:, length of tank. Any crack allowing material to be transported into facility Any part of tank/pipe is bent out of shape more than 10% of it's design shape Cover is missing or only partially in place. Any open manhole requires maintenance. Mechanism cannot be opened by one maintenance person with proper tools. Bolts into frame have less than Y:, inch of thread (may not apply to self~locking lids.) One maintenance person cannot remove lid after applying 801bs of lift. Intent is to keep cover from sealing off access to maintenance. King County Safety Office and/or maintenance person judges that ladder is unsafe due to missing rungs, misalignment, rust, or cracks. See "Catch Basins" Standards No. 5 Results Expected When Maintenance is Performed Vents free of debris and sediment All sediment and debris removed from storage area. All joint between tank /pipe sections are sealed Tank/ pipe repaired or replaced to design. Manhole is closed. Mechanism opens with proper tools. Cover can be removed and reinstalled by one maintenance person. Ladder meets design standards allows maintenance person safe access. See "Catch Basins" Standards No.5 SECTION 10 OPERATIONS & MAINTENANCE MANUAL •• !If: Site Development Associates, LLC NO. 4 -CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component General Cleanout Gate Orifice Plate Overflow Pipe Manhole Catch Basin Defect Trash and Debris (Includes Sediment) Structural Damage Damaged or Missing Damaged or Missing Obstructions Obstructions LANGLEY MEADOWS 107-016-006 Condition When Maintenance is Needed Distance between debris build-up and bottom of orifice plate is less than 1-1/2 feet. Structure is not securely attached to manhole wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. Structure is nol in upright position (allow up to 10% from plumb). Connections to outlet pipe are not watertight and show signs of rust. Any holes--other than designed holes--in the structure. Cleanout gate is not watertight or is missing. Gate cannot be moved up and down by one maintenance person. Chain leading to gate is missing or damaged. Gate is rusted over 50% of its surface area. Control device is not working properly due to missing, out of place, or bent orifice plate. Any trash, debris, sediment, or vegetation blocking the plate. Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Results Expected When Maintenance is Performed All trash and debris removed. Structure securely attached to wall and outlet pipe. Structure in correct position. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. Structure has no holes other than designed holes. Gate is watertight and works as designed. Gate moves up and down easily and is watertight. Chain is in place and works as designed. Gate is repaired or replaced to meet design standards .. Plate is in place and works as designed. Plate is free of all obstructions and works as designed. Pipe is free of all obstructions and works as designed. See "Closed Detention Systems" Standards No. 3 See "Closed Detention Systems· Standards No. 3 See "Catch Basins" Standards No. 5 See 'Catch Basins" Standards No. 5 SECTION 10 OPERATIONS & MAINTENANCE MANUAL ••"'·· Site Development Associates, LLC NO. 5 -CATCH BASINS Maintenance Component General Defect Trash & Debris (Includes Sediment) Structure Damage to Frame and/or Top Slab Cracks in Basin Walls/ Bottom Sediment! Misalignment LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed Trash or debris of more than 1/2 cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the basin by more than 10% Trash or debris (in the basin} that exceeds 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. Trash or debris in any inlet or outlet pipe blocking more than 1/3 of its height. Dead animals or vegetation that could generate odors that could cause complaints or dangerous gases (e.g., methane}. Deposits of garbage exceeding 1 cubic foot in volume Corner of frame extends more than 3/4 inch past curb face into the street (If applicable). Top slab has holes larger than 2 square inches or cracks wider than 1/4 inch (intent is to make sure all material is running into basin}. Frame not sitting flush on top slab, i.e., separation of more than 3/4 inch of the frame from the top slab. Cracks wider than 1/2 inch and longer than 3 feet, any evidence of soil particles entering catch basin through cracks, or maintenance person judges that structure is unsound. Cracks wider than 1/2 inch and longer than 1 foot at the joint of any inlet' outlet pipe or any evidence of soil particles entering catch basin through cracks. Basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Results Expected When Maintenance is performed No Trash or debris located immediately in front of catch basin opening. No trash or debris in the catch basin. Inlet and outlet pipes free of trash or debris. No dead animals or vegetation present within the catch basin. No condition present which would attract or support the breeding of insects or rodents. Frame is even with curb. Top slab is free of holes and cracks. Frame is sitting flush on top slab. Basin replaced or repaired to design standards. No cracks more than 1/4 inch wide at the joint of inleUoutlet pipe. Basin replaced or repaired to design standards. SECTION 10 OPERATIONS & MAINTENANCE MANUAL Site Development Associates, LLC NO. 5 • CATCH BASINS (CONTINUED) Maintenance Component Catch Basin Cover Ladder Metal Grates (If Applicable) Defect Fire Hazard Vegetation Pollution Cover Not in Place Locking Mechanism Not Working Cover Difficult to Remove Ladder Rungs Unsafe Trash and Debris Damaged or Missing. LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed Presence of chemicals such as natural gas, oil and gasoline. Vegetation growing across and blocking more than 10% of the basin opening. Vegetation growing in inleUoutlet pipe joints that is more than six inches tall and less than six inches apart. Nonflammable chemicals of more than 1 /2 cubic foot per three feet of basin length. Cover is missing or only partially in place. Any open catch basin requires maintenance. Mechanism cannot be opened by on maintenance person with proper tools. Bolts into frame have less than 1/2 inch of thread. One maintenance person cannot remove lid after applying 80 lbs. of lift; intent is keep cover from sealing off access to maintenance. Ladder is unsafe due to missing rungs, misalignment, rust. cracks, or sharp edges. Grate with opening wider than 7/8 lnch. Trash and debris that is blocking more than 20% of grate surface. Grate missing or broken member(s) of the grate. Results Expected When Maintenance is perfonned No flammable chemicals present. No vegetation blocking opening to basin. No vegetation or root growth present. No pollution present other than surface film. Catch basin cover is closed Mechanism opens with proper tools. Cover can be removed by one maintenance person. Ladder meets design standards and allows maintenance person safe access. Grate opening meets design standards. Grate free of trash and debris. Grate is in place and meets design standards. SECTION 10 OPERATIONS & MAINTENANCE MANUAL •• g; Site Development Associates, LLC NO. 6 DEBRIS BARRIERS (E.G., TRASH RACKS) Maintenance Components General Metal Defect Trash and Debris Damaged/ Missing Bars. LANGLEY MEADOWS 107-016-006 Condition When Maintenance is Needed Trash or debris that is plugging more than 20% of the openings in the barrier. Bars are bent out of shape more than 3 inches. Bars are missing or entire barrier missing. Bars are loose and rust is causing 50% deterioration to any part of barrier. Results Expected When Maintenance is Performed. Barrier clear to receive capacity flow. Bars in place with no bends more than 3/4 inch. Bars in place according to design. Repair or replace barrier to design standards. SECTION 10 OPERATIONS & MAINTENANCE MANUAL •• .,,. Site Development Associates, LLC NO. 9-GATES Maintenance Component General Defect Damaged or Missing Members Openings in Fabric LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed Missing gate or Jocking devices. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Missing stretcher bar, stretcher bands, and ties. See ~Fencingn Standard No. 8 Results Expected When Maintenance is Performed Gates and Locking devices in place. Hinges intact and lubed. Gate is working freely. Gate is aligned and vertical. Stretcher bar, bands and ties in place. See "Fencingn Standard No. 8 SECTION 10 OPERATIONS & MAINTENANCE MANUAL ••. : Site Development Associates, LLC N0.10-CONVEYANCE SYSTEMS (PIPES & DITCHES) Maintenance Component Pipes Open Ditches Catch Basins Debris Barriers (e.g., Trash Rack) Defect Sediment & Debris Vegetation Damaged Trash & Debris Sediment Vegetation Erosion Damage to Slopes Rock Lining Out of Place or Missing (If Applicable). LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed Accumulated sediment that exceeds 20% of the diameter of the pipe. Vegetation that reduces free movement of water through pipes. Protective coating is damaged; rust is causing more than 50% deterioration to any part of pipe. Results Expected When Maintenance is Perfonned Pipe cleaned of all sediment and debris. All vegetation removed so water flows freely through pipes. Pipe repaired or replaced. Any dent that decreases the cross section area of Pipe repaired or replaced. pipe by more than 20%. Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Accumulated sediment that exceeds 20 % of the design depth. Vegetation that reduces free movement of water through ditches. See "Ponds" Standard No. 1 Maintenance person can see native soil beneath the rock lining. See "Catch Basins: Standard No. 5 See "Debris Barriers" Standard No.6 Trash and debris cleared from ditches. Ditch deaned/ flushed of all sediment and debris so that ft matches design. Water flows freely through ditches. See ~Ponds" Standard No. 1 Replace rocks to design standards. See "Catch Basins" Standard No. 5 See ~Debris Barriers" Standard No. 6 SECTION 10 OPERATIONS & MAINTENANCE MANUAL ••. : Site Development Associates, LLC N0.11 -GROUNDS (LANDSCAPING) Maintenance Component General Trees and Shrubs Defect Weeds (Nonpoisonous) Safety Hazard Trash or Utter Damaged LANGLEY MEADOWS 107-016-006 Conditions When Maintenance is Needed Weeds growing in more than 20% of the landscaped area (trees and shrubs only). Any presence of poison ivy or other poisonous vegetation. Paper, cans, bottles, totaling more than 1 cubic foot within a landscaped area (trees and shrubs only) of 1,000 square feet. limbs or parts of trees or shrubs that are split or broken which affect more than 25% of the total foliage of the tree or shrub. Trees or shrubs that have been blown down or knocked over. Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Results Expected When Maintenance is Performed Weeds present in less than 5% of the landscaped area. No poisonous vegetation present in landscaped area. Area clear of litter. Trees and shrubs with Jess than 5% of total foliage with split or broken limbs. Tree or shrub in place free of injury. Tree or shrub in place and adequately supported; remove any dead or diseased trees. SECTION 10 OPERATIONS & MAINTENANCE MANUAL Site Development Associates, LLC NO. 12 -ACCESS ROADS/ EASEMENTS Maintenance Component General Road Surface Shoulders and Ditches Defect Trash and Debris Blocked Roadway Settlement, Potholes, Mush Spots, Ruts Vegetation in Road Surface Modular Grid Pavement Erosion Damage Weeds and Brush LANGLEY MEADOWS 107-016-006 Condition When Maintenance is Needed Trash and debris exceeds 1 cubic foot per 1,000 square feet Le., trash and debris would fill up one standards size garbage can. Debris which could damage vehicle tires (glass or metal). Any obstruction which reduces clearance above road surface to less than 14 feet. Any obstruction restricting the access to a 10 to 12 foot width for a distance of more than 12 feet or any point restricting access to less than a 10 foot width. When any surface defect exceeds 6 inches in depth and 6 square feet in area. In general, any surface defect which hinders or prevents maintenance access. Weeds growing in the road surface that are more than 6 inches tall and less than 6 inches tall and less than 6 inches apart within a 400·square foot area. Build~up of sediment mildly contaminated with petroleum hydrocarbons. Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Weeds and brush exceed 18 inches in height or hinder maintenance access. Results Expected When Maintenance is Performed Roadway free of debris which could damage tires. Roadway free of debris which could damage tires. Roadway overhead clear to 14 feet high. Obstruction removed to allow at least a 12 foot access. Road surface uniformly smooth with no evidence of settlement, potholes. mush spots, or ruts. Road surface free of weeds taller than 2 inches. Removal of sediment and disposal in keeping with Health Department recommendations for mildly contaminated soils or catch basin sediments. Shoulder free of erosion and matching the surrounding road. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access. SECTION 10 OPERATIONS & MAINTENANCE MANUAL Site Development Associates, LLC NO. 13 -WATER QUALITY FACILITIES E.) Wetvaults Maintenance Defect or Problem Component Wetvault Trash/ Debris Accumulation Sediment Accumulation in Vault Damaged Pipes Access Cover Damaged/ Not Working Ventilation Vault Structure Damaged Baffles Access Ladder Damage LANGLEY MEADOWS 107-016-006 Condition When Maintenance is Needed Recommended Maintenance to Correct Problem Trash and debris accumulated in vault, pipe Remove trash and debris from vault. or inlet/ outlet, (includes floatables and non- floatables). Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6-inches. Inlet/ outlet piping damaged or broken and in need of repair. Cover cannot be opened or removed, especially by one person. Ventilation area blocked or plugged Vault Cracks wider than 1/2-inch and any evidence of soil particles entering the structure through the cracks, or maintenance/ inspection personnel determines that the vault is not structurally sound. Baffles corroding, cracking, warping and/ or showing signs of failure as detem,ined by maintenance/ inspection staff. Ladder is corroded or deteriorated, not functioning properly, missing rungs, has cracks and/ or misaligned. Confined space warning sign missing. Remove sediment from vault. Pipe repaired and/ or replaced. Pipe repaired or replaced to proper working specifications. Remove or clear blocking material from ventilation area. A specified % of the vault surface area must provide ventilation to the vault interior (see p. 6- 82 for required%). Repair cracks wider than 1/4-inch at the joint of the inleU outlet pipe. Make repairs so that vault is structurally sound. Repair or replace baffles to specifications. Ladder replaced or repaired to specifications, and is safe to use as determined by inspection personnel. Replace sign warning of confined space entry requirements. SECTION 10 OPERATIONS & MAINTENANCE MANUAL