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LEE COMPLETE PREL TIR.pdfPRELIMINARY DRAINAGE REPORT LEE SHORT PLAT 7804 218th St. SW FIR SITE DEVELOPMENT SERVICES 3011 RAVEN CREST BELLINGHAM, WA 98226 425-481-9687 February 19, 2018 Revised August 7, 2018 Section Title Drainage Summary TABLE OF CONTENTS Section Number Minimum Requirements II Off -site Analysis III Detention Design IV WWHM Report Appendix A DRAINAGE SUMMARY SECTION I DRAINAGE SUMMARY In its current condition the lot consists of four tax parcels and is occupied by four dwellings, two of them are mobile homes and two are wood frame houses. In addition, there are two detached garages. The balance of impervious area consists of gravel driveways and parking areas, all of which accesses 218th St with a single driveway approach located on the west side of the site. Pervious area is grass and brush with sparse trees. A drainage ditch and storm drain carrying runoff from the site as well as from areas to the north are located on the east side of the site. Sloping gently to the south and the east at a grade of approximately 2%, the site is well draining without any other drainage features such as closed depressions. The proposed short plat will remove all existing structures and create four single family lots. They will all access 218th St. with a single private road located on the east side of the site. Drainage improvements will be in accordance with the 2014 DOE Stormwater Management Manual for Western Washington, hereinafter referred to as the "Manual". Site Areas: Lot Size: 38,398 SF (0.88Ac) Existiniz Impervious: Roof 4912 SF(O.I IAc) Walks: 970 SF(0.02Ac) Dwy/Parking: 6551 SF(O.15Ac) Total: 12,433 SF(0.28Ac) Existing Impervious acreage: 0.28Ac. This is 33% of lot area; therefore the project is classified as "new development". Developed Site: Roof. 4x2,700 SF* = 10,800 SF(0.25Ac) Dwy**: 3,800 SF(0.09Ac) Access Road: 4,104 SF(0.09Ac) Total Site Impervious: 18,704 SF (0.43Ac) ROW: 1429 SF (0.03Ac) Total Project Impervious: 0.46Ac Total Project Area: 0.88Ac + 0.03Ac 0.91Ac *Roof area is based on a footprint that will accommodate a three car garage and a floor area that is consistent with homes in this area. **Driveway areas are: Lot 1: 646 sf Lot 2: 646 sf Lot 3: 1023 sf Lot 4: 1485 sf All site roadways and driveways that are not over the vault will be modeled as permeable pavement. Since almost all of the anticipated driveway for Lot 4 will be over the vault, the entire driveway for that lot will be assumed as impervious. Pervious: Permeable Pavement: 4104 + 3800 — 1485 = 6419 (0.15 Ac) Impervious Area is the roof area and the driveway for Lot 4: 10,800 + 1485 = 12,285 (0.28Ac) Therefore, total pervious is the site area, less the impervious area, less the permeable pavement: 0.91 —0.28 - 0.15)=0.48Ac For modeling, the permeable pavement was entered with a square having sides of 80.12 feet, which yields the square footage of 6,419 square feet. The Effective Depth is the average depth of water in the reservoir media, plus one foot, as required for proper iteration in the model. The "Ponding Depth" is the average depth of water in the reservoir media (3"), achieved through the use of check dams. Therefore, the slope for modeling purposes can be considered flat. This was done because the slope varies throughout the roadway length. To treat the driveway for Lot 4, use a bioretention cell sized per page 7-17, Section 7, Volume 5 in the DOE Manual. This states that the size is 5% of the area draining to it. As direceted in the Manual, 2% was added for the small amount of pervious area drains to it. Overflow pond area = (0.07)(1485 sq. ft.) = 104 sq. ft. As shown by Figure 2.4.1 on the following page, the project is subject to all Minimum Requirements as defined in Volume I, Chapter 2 of the Manual. Thus detention is required and is provided in an underground vault in an easement in the southeast corner of the site. As discussed in MR#5, Section II, no individual lot BMPs are assumed to be feasible at this time, although at the time of building construction on the lots, detailed testing and house design may accommodate limited BMPs. With regard to water quality treatment of runoff is required, as the total PGIS is greater than 5000 square feet. This will be accomplished through the use of permeable pavement over a suitable treatment soil. The Lot 4 driveway will be treated with a bioretention cell since it is over the vault. Start Here Does the site have 35% or more of existing impervious coverage? No Does the project result in 5,000 square feet. or greater. of new plus replaced hard surface area? Yes All Minimum Requirements apply to the new and replaced hard surfaces and converted vegetation areas. Yes s the project convert % acres or more of vegetation to lawn or landscaped areas. or No convert 2.5 acres or more of native vegetation to pasture? See Redevelopment Minimum Requirements and Flow Chart (Figure 2.4.2) Does the project No result in 2,000 square feet, or greater. of new plus replaced hard surface area? Yes / I No IAIuiimmni Requirements Does the project have # 1 through 45 apply to land disturbing the new and replaced activities of 7,000 hard surfaces and the Yes square feet or greater? land disturbed. No Minimum Requirement #2 applies. Figure 2.4.1 - Flow Chart for Determining Requirements for New Development SECTION II MINIMUM REQUIREMENTS MINIMUM REQUIREMENTS MR#1: Preparation of Stormwater Site Plans Section I demonstrates that a Stormwater Site Plan is required, so it is included in the construction documents. The downstream analysis, required as a part of the Stormwater Site Plan, is included in this report. MR#2: SWPP A SWPPP has not been prepared for preliminary approval at this time. Consisting of 38,398 square feet, the site is less than one acre so a formal SWPPP report is not required. However, a Temporary Erosion Control Plan will be prepared with the construction drawings. Because the site is very gently sloping and the runoff paths are short (150±), silt runoff can be controlled with basic TESC measures including sheet flow through a silt fence. These and other methods will be presented with the submittal of construction drawings. MR#3: Source Control of Pollution: No significant sources of pollution will be created with this project, as it consists of access and utility construction for residential improvements on a small scale. MR#4: Preservation of Natural Drainage Systems and Outfalls: Currently the site drains in a southeasterly direction, so the runoff enters the ditch on the east property line or, in the case of the area south of the end of the ditch, it sheet flows to the adjacent properties. Using the "Water Drop" feature in AutoCAD, the runoff from the existing pavement in 218th St. was shown to sheet flow to the ditch and does not enter the sites to the east. Ultimately all of the existing runoff enters a storm drain system just south of the southeast corner of the site. With only minor routing changes, all of this runoff will continue to flow to the same downstream point after the site is developed. Specifically, the 218th St runoff will be directed via a new gutter and storm drain through the Lee Short plat, through the detention system and into the storm drain off of the southeast corner of the site, as just described. The site runoff will be captured by the same site storm drain and routed to the same point. Thus the "Natural Drainage System" is maintained to the maximum extent feasible and no downstream properties or drainage systems will be adversely impacted. As for the existing ditch off of the east side of the site, the face of the proposed retaining wall is constructed within inches of the top of the channel. In the worst case, approximately 1 square foot of channel area is removed by the wall. The cross sectional area of the wetted perimeter can be maintained by deepening the retaining wall so that the bottom width of the channel can be increased. The bottom width of the existing ditch varies, but is less than 3 feet. Since the retaining wall is close to the top of the ditch, this width can be increased. This can be detailed with the construction documents. MR#5: On -site Stormwater Management: List#2 in Volume I, Section 2.5.5 for cases requiring adherence to MR#1-9 states that dispersion or infiltration are the first priorities. Examining these in accordance with Appendix A of the City's 2017 Stormwater Addendum, the infeasibilities are discussed below. Infeasibility will be discussed for both roof and other hard surfaces (driveway and roads). BMP Infeasibility Full Dispersion A minimum vegetated flow path of 100 feet cannot be achieved for either roofs or other hard surfaces. Downspout Full Infiltration The lots do not have outwash or loam soils. Bioretention or Rain Gardens Soil logs show depth to seasonal groundwater or an impermeable layer to be variable, with some depths less than two feet. Therefore it cannot be demonstrated that individual lot bioretention or rain gardens can provide the required one foot of separation. Runoff cannot be routed to such a system from the site roadway. For detention purposes, the site will be designed assuming these BMPs are infeasible due to insufficient separation. However, a bioretention has been shown to meet the feasibility requirements for the driveway on Lot 4. Downspout Dispersion Flow paths of 50 feet for splashblocks or 25 feet for trenches cannot be maintained. Although that distance could be available in a rear yard on this site, the natural ground slopes toward the building. It cannot be considered feasible to drain roof runoff to a trench located on the west property line and dispersed toward the house. Perforated Stub -out Connection As described above, it cannot be assumed that one foot of separation to groundwater or an impermeable layer can be achieved on each lot. This determination will be made with each building permit, but this report will assume it is infeasible. MR#6: Runoff Treatment Runoff treatment is required, as the new PGIS is greater than 5000 square feet. This is being provided through the use of permeable pavement for all of the PGIS, except for the driveway on Lot 4. Although bioretention cannot be used for runoff control (Page 5-12, Vol V) it can be used for treatment (page 7-8, Vol V). Because the site consists of fill above compacted glacial till, the fill material will be removed and replaced with engineered fill that will meet the treatment requirements. MR#7. Flow Control The WWHM input and results are provided in Appendix B. The permeable pavement is being used for all PGIS, except Lot 4, as described above. Using engineered fill to replace the undocumented fill the pavement was modeled using a design infiltration rate of 3 inches per hour, as suggested by the geotechnical engineer. To qualify for treatment the measured rate must be between 9 and 6 inches per hour in order to use the 3 inches per hour. For modeling, the permeable pavement was entered with a square having sides of 80.12 feet, which yields the square footage of 6,419 square feet. The Effective Depth is the average depth of water in the reservoir media, plus one foot, as required for proper iteration in the model. The "Ponding Depth" is the average depth of water in the reservoir media (3" ), achieved through the use of check dams. Therefore, the slope for modeling purposes can be considered flat. This was done because the slope varies throughout the roadway length. Due to a relatively shallow site discharge elevation, the depth available for live storage in the vault is 3.28 feet. However the minimum depth allowed is 7 feet so that is the depth that is shown on the plans. MR#8. Wetlands Protection: This requirement does not apply here, as there are no wetlands or their buffers on or adjacent to the site. MR#9. Operation and Maintenance Requirements Maintenance and operations instructions will be provided with the construction documents after preliminary approval. OFF -SITE ANALYSIS SECTION III OFF -SITE ANALYSIS UPSTREAM: The subject parcel is located in a developed residential neighborhood along the south side of 218th Street Southwest. The subject parcel and the parcel to the east are down slope of the paved surface of 218th Street Southwest and surface water, if present, would flow on the the properties as sheet flow. A small swale intercepts this sheet flow at the approximate midpoint of the subject parcel's frontage, and directs surface water to the a 3 feet wide by 2 feet deep (measured at mid- point) gravel bottomed channel. This channel outfalls from an 18" diameter concrete culvert beneath 218th Street Southwest and flows south along the east property line of the subject parcel. Access was not permitted to the parcels to the east of the subject parcel, however they appeared to be flat and at even grade with the subject parcel. There is potential that surface water from the parcel to the east, which fronts 218th Street Southwest, could flow into the channel. The other 2 parcels along the east property did not appear to drain onto the subject property. There was no indication of uncontrolled surface water flowing onto the site or the adjacent properties to the east, west, and south of the site. ON -SITE: As described in the Drainage Summary, the parcel is a developed residential property occupied by multiple buildings. The site is relatively flat, with grades of 1-2% generally down -slope from northwest to southeast. The site is serviced by a gravel driveway. There were 4 existing buildings on the site. Some of the roof drains on the buildings were directed into the ground and some were not connected. The outlet of these roof drains could not be found. There was no indication of off -site surface water flow or indication of erosion onto adjacent properties. DOWNSTREAM: Surface water would potentially exit the site along the eastern property line as sheet flow into the drainage channel and into the 16" diameter (as measured in field) PVC pipe, which is part of the mapped City of Edmonds storm drain system which continues south of site. Surface water from the site south of the 16" diameter storm drain inlet could potentially sheet flow off the site towards the southeast corner of the site, which is the topographic low point of the site. There was no indication of uncontrolled surface water flow from the subject site. City of Edmonds GIS mapping shows this 16" diameter inlet incorrectly as 18" diameter. This storm drain continues south and it could not be determined where it enlarges to 18" diameter to match the GIS mapping which show it connecting to the city of Edmonds 18" diameter storm drain below 78th Place West. Any water form the site would end up in the city of Edmonds 18" diameter storm drain below 78th Place West. This storm drain continues south on private property approximately 900 feet where the City of Edmonds GIS mapping shows the drainage outfall to a channel. This outfall was not observed due to private property. The channel was observed below the 1/4 mile downstream point at 222nd Street Southwest. At this point the drainage crossed 222nd Street Southwest in a 18" diameter (City of Edmonds GIS) culvert and continued south as an open drain channel. A homeowner on 222nd Street Southwest stated that there had been recent storm drain improvements to alleviate stormwater flooding in the area. The downstream system appears to be operating well with no apparent capacity issues. J I I I SURFACE ` 2A 7710 7702 21807 WATER FLOW I sb 2B 21917 �21815 DIRECTION 21816 ti 310 8 2181 SITE 7812 0 21828 _ _j 21823 9> e 7623 DOWNSTREAM 7621 FLOW PATH 18"0 STORM DRAIN o 3B 2191E ?1917 —�❑ o j, 0 0 0 \� O ° O �PD13-28 / SD— o 220TH ST SW H 7710 \ 22005 I_z008 7708 v o n. 00 CO t 2 \ 1 �07S n p/ 7706 o 7808 pN� 9 10 CD p2S' 22oz6 00 co ,22 DOWNSTREAM FLOW PATH 5 �� DITCH 0 E Z 1 /4 MILE DOWNSTREAM � � 00 r` 21810 P D 13-9 O O �' ;L 21822 ° f PD13-10 21822 0 ❑ I 21,906 PD13-11 ° 0 O o) o 211920 PD13-2 O ❑ ❑ 00 ° 22012 W 7 20 21 l� i ❑ ❑ 22106 0 1 22118 w 00 1 OWNSTREAM PATH A F XX PHOTO �l 0 V SITE ALONG 218TH ST SW, LOOKING SOUTH PAVEMENT' \ 0 SITE ALONG BUILDING ON EXISTING ADJACENT SITE jp.W,;BUILDINGS ON SITE �DRAINAGE CHANNEL OUTFALL FROM 18"O ROADSIDE SWALE SHEETFLOW FROM 218TH ST SW 218TH ST SW, LOOKING SOUTH 0 V 218TH ST SW� a 4 - DRAINAGE CHANNE OUTFALL FROM 18" CONCRETE CULVER ON -SITE AT 18"0 CULVERT FROM 218TH ST SW v BUILDINGS ON ADJACENT SITES -SITE iL ON -SITE ALONG EAST PROPERTY LINE, LOOKING SOUTH "Am", IV SURFACE WATER FLOWPATH OFF SITE^ 471) M BUILDINGS 01 ADJACENT ON SITE LOOKING SOUTHEAST OFF SITE LOOKING NORTH TOWARD SITE 222ND S� SW A ��DRAINAGE ' CHANNEL FLOW PATH 2 r h 18 0CULVERT a �r'• ove " we OFF SITE AT 222ND ST SW LOOKING WEST RAINA DGE CHANNEL FLOW PATH M 4 A ,s . 180 CULVERT '0 -DRAINAGE FROM 2221ND ST SW 4 y ; ,} � A��`y� '�4�. ,.w n :i • •may°, OFF SITE AT 222ND ST SW LOOKING SOUTH 4 DETENTION DESIGN SECTION IV DETENTION DESIGN This section presents the report produced by the WHMM model. As presented in Section I, the developed area includes the right-of-way improvements. Since the site paved areas are to be permeable pavement (except the driveway for Lot 4), they were modeled using that element in the WWHM model. No underlying drain pipe was used, except as an overflow. Although the proposed design has an overflow system, it is designed to flood the subgrade prior to overflow. As shown in the access road profile, the roadway is proposed to be at an elevation that provides for a minimum of one foot of treatment soil below it. See the explanation under "Water Quality", below. The data input as well as the resulting vault and restrictor design are presented in the following pages. They show a live storage depth of 3.28 feet, with a vault width of 18 feet and a length of 80 feet. The depth was controlled by the elevation of the existing drain pipe to which the vault outfall will connect. The benefit of this shallow depth is that the bottom orifice can be 0.5 inches (0.497 inches in the WWHM output), which is the minimum value. If the vault were any deeper, a pump would be required to provide the required release rate. Because the minimum required depth of a vault is 7 feet, that is the vault height that was provided. WATER QUALITY: Water quality is provided with treatment in the soil beneath the permeable pavement. For Lot 4, the driveway is over the vault, so treatment was provided with a bioretention cell to which the driveway runoff is directed. Because the soil above the hardpan is undocumented fill, it will be removed and replaced with engineered fill that meets the requirements for treatment and, in the case of permeable pavement, the support of traffic loads. The depth to the seasonal water table controls the pavement grades, so the profile shows the water table level. The depth of the permeable pavement section is 16.5 inches (1.37 feet). When added to the required one foot of separation, the total distance from the top of the pavement to the groundwater level is 2.37 feet. This is shown in the profile. The required depth under the bioretention is 18 inches, so the pond depth was set to provide this separation to the bottom of the bioretention soil. WWHM REPORT APPENDIX A WWHM2012 PROJECT REPORT Project Name: LEE 218 Site Name: Lee Short Plat Site Address: 7804 218th St SE City : Edmonds Report Date: 8/7/2018 Gage : Everett Data Start : 1948/10/01 Data End : 2009/09/30 Precip Scale: 1.00 Version : 2015/03/18 Low Flow Threshold for POC 1 : 50 Percent of the 2 Year High Flow Threshold for POC 1: 50 year PREDEVELOPED LAND USE Name . Basin 1 Bypass: No GroundWater: No Pervious Land Use Acres C, Forest, Flat .91 Pervious Total 0.91 Impervious Land Use Acres Impervious Total 0 Basin Total 0.91 Element Flows To: Surface Interflow Groundwater MITIGATED LAND USE Name . Basin 1 Bypass: No GroundWater: No Pervious Land Use Acres C, Lawn, Flat .48 Pervious Total 0.48 Impervious Land Use Acres ROADS FLAT 0.03 ROOF TOPS FLAT 0.25 Impervious Total 0.28 Basin Total 0.76 Element Flows To: Surface Interflow Vault 1 Vault 1 Name Vault 1 Width 18 ft. Length 80 ft. Depth: 4.28 ft. Discharge Structure Riser Height: 3.28 ft. Riser Diameter: 12 in. Notch Type: Rectangular Notch Width: 0.011 ft. Notch Height: 0.836 ft. Orifice 1 Diameter: 0.497 in. Element Flows To: Outlet 1 Outlet 2 Groundwater Elevation: 0 ft. Vault Hydraulic Table Stage(ft) Area(ac) Volume(ac-ft) Discharge(cfs) Infilt(cfs) 0.0000 0.033 0.000 0.000 0.000 0.0476 0.033 0.001 0.001 0.000 0.0951 0.033 0.003 0.002 0.000 0.1427 0.033 0.004 0.002 0.000 0.1902 0.033 0.006 0.002 0.000 0.2378 0.033 0.007 0.003 0.000 0.2853 0.033 0.009 0.003 0.000 0.3329 0.033 0.011 0.003 0.000 0.3804 0.033 0.012 0.004 0.000 0.4280 0.033 0.014 0.004 0.000 0.4756 0.033 0.015 0.004 0.000 0.5231 0.033 0.017 0.004 0.000 0.5707 0.033 0.018 0.004 0.000 0.6182 0.033 0.020 0.005 0.000 0.6658 0.033 0.022 0.005 0.000 0.7133 0.033 0.023 0.005 0.000 0.7609 0.033 0.025 0.005 0.000 0.8084 0.033 0.026 0.005 0.000 0.8560 0.033 0.028 0.006 0.000 0.9036 0.033 0.029 0.006 0.000 0.9511 0.033 0.031 0.006 0.000 0.9987 0.033 0.033 0.006 0.000 1.0462 0.033 0.034 0.006 0.000 1.0938 0.033 0.036 0.006 0.000 1.1413 0.033 0.037 0.006 0.000 1.1889 0.033 0.039 0.007 0.000 1.2364 0.033 0.040 0.007 0.000 1.2840 0.033 0.042 0.007 0.000 1.3316 0.033 0.044 0.007 0.000 1.3791 0.033 0.045 0.007 0.000 1.4267 0.033 0.047 0.007 0.000 1.4742 0.033 0.048 0.007 0.000 1.5218 0.033 0.050 0.008 0.000 1.5693 0.033 0.051 0.008 0.000 1.6169 0.033 0.053 0.008 0.000 1.6644 0.033 0.055 0.008 0.000 1.7120 0.033 0.056 0.008 0.000 1.7596 0.033 0.058 0.008 0.000 1.8071 0.033 0.059 0.008 0.000 1.8547 0.033 0.061 0.008 0.000 1.9022 0.033 0.062 0.008 0.000 1.9498 0.033 0.064 0.009 0.000 1.9973 0.033 0.066 0.009 0.000 2.0449 0.033 0.067 0.009 0.000 2.0924 0.033 0.069 0.009 0.000 2.1400 0.033 0.070 0.009 0.000 2.1876 0.033 0.072 0.009 0.000 2.2351 0.033 0.073 0.009 0.000 2.2827 0.033 0.075 0.009 0.000 2.3302 0.033 0.077 0.009 0.000 2.3778 0.033 0.078 0.010 0.000 2.4253 0.033 0.080 0.010 0.000 2.4729 0.033 0.081 0.010 0.000 2.5204 0.033 0.083 0.011 0.000 2.5680 0.033 0.084 0.012 0.000 2.6156 0.033 0.086 0.013 0.000 2.6631 0.033 0.088 0.014 0.000 2.7107 0.033 0.089 0.015 0.000 2.7582 0.033 0.091 0.016 0.000 2.8058 0.033 0.092 0.018 0.000 2.8533 0.033 0.094 0.019 0.000 2.9009 0.033 0.095 0.021 0.000 2.9484 0.033 0.097 0.022 0.000 2.9960 0.033 0.099 0.024 0.000 3.0436 0.033 0.100 0.026 0.000 3.0911 0.033 0.102 0.028 0.000 3.1387 0.033 0.103 0.029 0.000 3.1862 0.033 0.105 0.031 0.000 3.2338 0.033 0.106 0.033 0.000 3.2813 0.033 0.108 0.035 0.000 3.3289 0.033 0.110 0.140 0.000 3.3764 0.033 0.111 0.326 0.000 3.4240 0.033 0.113 0.567 0.000 3.4716 0.033 0.114 0.851 0.000 3.5191 0.033 0.116 1.174 0.000 3.5667 0.033 0.117 1.530 0.000 3.6142 0.033 0.119 1.917 0.000 3.6618 0.033 0.121 2.333 0.000 3.7093 0.033 0.122 2.775 0.000 3.7569 0.033 0.124 3.243 0.000 3.8044 0.033 0.125 3.734 0.000 3.8520 0.033 0.127 4.249 0.000 3.8996 0.033 0.128 4.785 0.000 3.9471 0.033 0.130 5.342 0.000 3.9947 0.033 0.132 5.920 0.000 4.0422 0.033 0.133 6.517 0.000 4.0898 0.033 0.135 7.133 0.000 4.1373 0.033 0.136 7.767 0.000 4.1849 0.033 0.138 8.419 0.000 4.2324 0.033 0.139 9.089 0.000 4.2800 0.033 0.141 9.775 0.000 4.3276 0.033 0.143 10.47 0.000 4.3751 0.000 0.000 11.19 0.000 Name : Permeable Pavement 1 Pavement Area: 0.1474 ft. Pavement Length: 80.12 ft. Pavement Width: 80.12 ft. Pavement slope 1: 0 To 1 Pavement thickness: 0.5 Pour Space of Pavement: 0.3 Material thickness of second layer: 0.25 Pour Space of material for second layer: 0.4 Material thickness of third layer: 0 Pour Space of material for third layer: 0 Infiltration On Infiltration rate: 6 Infiltration safety factor: 0.5 Total Volume Infiltrated (ac-ft): 21.196 Total Volume Through Riser (ac-ft): 0 Total Volume Through Facility (ac-ft): 21.196 Percent Infiltrated: 100 Total Precip Applied to Facility: 0 Total Evap From Facility: 1.615 Element Flows To: Outlet 1 Outlet 2 Permeable Pavement Hydraulic Table Stage(ft) Area(ac) Volume(ac-ft) Discharge(cfs) Infilt(cfs) 0.0000 0.147 0.000 0.000 0.000 0.0139 0.147 0.000 0.000 0.445 0.0278 0.147 0.001 0.000 0.445 0.0417 0.147 0.002 0.000 0.445 0.0556 0.147 0.003 0.000 0.445 0.0694 0.147 0.004 0.000 0.445 0.0833 0.147 0.004 0.000 0.445 0.0972 0.147 0.005 0.000 0.445 0.1111 0.147 0.006 0.000 0.445 0.1250 0.147 0.007 0.000 0.445 0.1389 0.147 0.008 0.000 0.445 0.1528 0.147 0.009 0.000 0.445 0.1667 0.147 0.009 0.000 0.445 0.1806 0.147 0.010 0.000 0.445 0.1944 0.147 0.011 0.000 0.445 0.2083 0.147 0.012 0.000 0.445 0.2222 0.147 0.013 0.000 0.445 0.2361 0.147 0.013 0.000 0.445 0.2500 0.147 0.014 0.000 0.445 0.2639 0.147 0.015 0.000 0.445 0.2778 0.147 0.015 0.000 0.445 0.2917 0.147 0.016 0.000 0.445 0.3056 0.147 0.017 0.000 0.445 0.3194 0.147 0.017 0.000 0.445 0.3333 0.147 0.018 0.000 0.445 0.3472 0.147 0.018 0.000 0.445 0.3611 0.147 0.019 0.000 0.445 0.3750 0.147 0.020 0.000 0.445 0.3889 0.147 0.020 0.000 0.445 0.4028 0.147 0.021 0.000 0.445 0.4167 0.147 0.021 0.000 0.445 0.4306 0.147 0.022 0.000 0.445 0.4444 0.147 0.023 0.000 0.445 0.4583 0.147 0.023 0.000 0.445 0.4722 0.147 0.024 0.000 0.445 0.4861 0.147 0.025 0.000 0.445 0.5000 0.147 0.025 0.000 0.445 0.5139 0.147 0.026 0.000 0.445 0.5278 0.147 0.026 0.000 0.445 0.5417 0.147 0.027 0.000 0.445 0.5556 0.147 0.028 0.000 0.445 0.5694 0.147 0.028 0.000 0.445 0.5833 0.147 0.029 0.000 0.445 0.5972 0.147 0.029 0.000 0.445 0.6111 0.147 0.030 0.000 0.445 0.6250 0.147 0.031 0.000 0.445 0.6389 0.147 0.031 0.000 0.445 0.6528 0.147 0.032 0.000 0.445 0.6667 0.147 0.033 0.000 0.445 0.6806 0.147 0.033 0.000 0.445 0.6944 0.147 0.034 0.000 0.445 0.7083 0.147 0.034 0.000 0.445 0.7222 0.147 0.035 0.000 0.445 0.7361 0.147 0.036 0.000 0.445 0.7500 0.147 0.036 0.000 0.445 0.7639 0.147 0.038 0.043 0.445 0.7778 0.147 0.040 0.123 0.445 0.7917 0.147 0.042 0.226 0.445 0.8056 0.147 0.044 0.349 0.445 0.8194 0.147 0.046 0.488 0.445 0.8333 0.147 0.048 0.641 0.445 0.8472 0.147 0.051 0.808 0.445 0.8611 0.147 0.053 0.988 0.445 0.8750 0.147 0.055 1.179 0.445 0.8889 0.147 0.057 1.381 0.445 0.9028 0.147 0.059 1.593 0.445 0.9167 0.147 0.061 1.815 0.445 0.9306 0.147 0.063 2.046 0.445 0.9444 0.147 0.065 2.287 0.445 0.9583 0.147 0.067 2.537 0.445 0.9722 0.147 0.069 2.794 0.445 0.9861 0.147 0.071 3.061 0.445 1.0000 0.147 0.073 3.335 0.445 1.0139 0.147 0.075 3.616 0.445 1.0278 0.147 0.077 3.906 0.445 1.0417 0.147 0.079 4.202 0.445 1.0556 0.147 0.081 4.506 0.445 1.0694 0.147 0.083 4.817 0.445 1.0833 0.147 0.085 5.134 0.445 1.0972 0.147 0.087 5.458 0.445 1.1111 0.147 0.089 5.789 0.445 1.1250 0.147 0.091 6.126 0.445 1.1389 0.147 0.093 6.470 0.445 1.1528 0.147 0.096 6.820 0.445 1.1667 0.147 0.098 7.175 0.445 1.1806 0.147 0.100 7.537 0.445 1.1944 0.147 0.102 7.905 0.445 1.2083 0.147 0.104 8.278 0.445 1.2222 0.147 0.106 8.657 0.445 1.2361 0.147 0.108 9.042 0.445 1.2500 0.147 0.110 9.432 0.445 ANALYSIS RESULTS Stream Protection Duration Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.91 Total Impervious Area:O Mitigated Landuse Totals for POC #1 Total Pervious Area:0.48 Total Impervious Area:0.427365 Flow Frequency Return Return Period Periods for Flow (cf s ) 2 year 0.019507 5 year 0.028873 10 year 0.035285 25 year 0.043556 50 year 0.049813 Predeveloped. POC #1 100 year Flow Frequency Return Return Period 2 year 5 year 10 year 25 year 50 year 100 year 0.056137 Periods for Mitigated. Flow (cfs) 0.012534 0.02392 0.035486 0.056517 0.078293 0.106793 Stream Protection Duration Annual Peaks for Predeveloped and Mitigated Year Predeveloped Mitigated 1949 0.011 0.009 1950 0.022 0.013 1951 0.017 0.009 1952 0.014 0.008 1953 0.011 0.008 1954 0.043 0.010 1955 0.029 0.021 1956 0.026 0.024 1957 0.029 0.019 1958 0.019 0.010 1959 0.021 0.010 1960 0.019 0.013 1961 0.019 0.020 1962 0.017 0.008 1963 0.020 0.009 1964 0.017 0.007 1965 0.019 0.013 1966 0.011 0.008 1967 0.024 0.009 1968 0.028 0.015 1969 0.021 0.009 1970 0.015 0.009 1971 0.021 0.026 1972 0.019 0.010 1973 0.015 0.010 1974 0.027 0.010 1975 0.015 0.008 1976 0.015 0.010 1977 0.012 0.008 1978 0.015 0.008 1979 0.027 0.009 1980 0.017 0.008 1981 0.014 0.008 1982 0.018 0.017 1983 0.026 0.009 1984 0.019 0.031 1985 0.025 0.020 1986 0.062 0.133 1987 0.028 0.056 1988 0.015 0.016 1989 0.013 0.008 1990 0.020 0.018 POC #1 POC #1 1991 0.021 0.012 1992 0.016 0.015 1993 0.011 0.007 1994 0.010 0.011 1995 0.021 0.024 1996 0.036 0.024 1997 0.068 0.244 1998 0.013 0.009 1999 0.019 0.011 2000 0.010 0.025 2001 0.003 0.006 2002 0.020 0.014 2003 0.014 0.010 2004 0.023 0.024 2005 0.017 0.010 2006 0.039 0.018 2007 0.033 0.015 2008 0.052 0.098 2009 0.016 0.010 Stream Protection Duration Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0682 0.2444 2 0.0624 0.1329 3 0.0522 0.0978 4 0.0432 0.0558 5 0.0385 0.0315 6 0.0357 0.0264 7 0.0328 0.0252 8 0.0293 0.0242 9 0.0287 0.0238 10 0.0279 0.0237 11 0.0278 0.0235 12 0.0275 0.0211 13 0.0267 0.0205 14 0.0261 0.0201 15 0.0259 0.0193 16 0.0253 0.0184 17 0.0238 0.0184 18 0.0226 0.0170 19 0.0216 0.0156 20 0.0215 0.0154 21 0.0214 0.0149 22 0.0209 0.0148 23 0.0209 0.0137 24 0.0206 0.0135 25 0.0203 0.0132 26 0.0202 0.0125 27 0.0197 0.0121 28 0.0194 0.0114 29 0.0194 0.0109 30 0.0193 0.0104 31 0.0192 0.0102 32 0.0190 0.0101 33 0.0187 0.0100 34 0.0186 0.0099 35 0.0185 0.0099 36 0.0175 0.0097 37 0.0172 0.0096 38 0.0172 0.0095 39 0.0169 0.0095 40 0.0166 0.0093 41 0.0164 0.0090 42 0.0164 0.0089 43 0.0154 0.0089 44 0.0153 0.0088 45 0.0153 0.0087 46 0.0152 0.0087 47 0.0152 0.0086 48 0.0146 0.0086 49 0.0143 0.0083 50 0.0140 0.0083 51 0.0139 0.0082 52 0.0130 0.0082 53 0.0129 0.0082 54 0.0123 0.0081 55 0.0114 0.0079 56 0.0110 0.0079 57 0.0107 0.0078 58 0.0105 0.0076 59 0.0103 0.0074 60 0.0100 0.0070 61 0.0034 0.0061 Stream Protection Duration POC #1 The Facility PASSED The Facility PASSED. Flow(cfs) Predev Mit Percentage Pass/Fail 0.0098 22629 15479 68 Pass 0.0102 20567 9830 47 Pass 0.0106 18589 8265 44 Pass 0.0110 16820 7375 43 Pass 0.0114 15154 6750 44 Pass 0.0118 13729 6239 45 Pass 0.0122 12459 5811 46 Pass 0.0126 11308 5454 48 Pass 0.0130 10235 5103 49 Pass 0.0134 9313 4776 51 Pass 0.0138 8470 4445 52 Pass 0.0142 7687 4083 53 Pass 0.0146 6956 3809 54 Pass 0.0150 6314 3533 55 Pass 0.0154 5784 3255 56 Pass 0.0158 5283 3065 58 Pass 0.0162 4857 2877 59 Pass 0.0166 4440 2676 60 Pass 0.0170 4096 2479 60 Pass 0.0174 3700 2327 62 Pass 0.0178 3377 2188 64 Pass 0.0183 3050 2020 66 Pass 0.0187 2751 1885 68 Pass 0.0191 2505 1782 71 Pass 0.0195 2304 1678 72 Pass 0.0199 2108 1603 76 Pass 0.0203 1949 1525 78 Pass 0.0207 1825 1436 78 Pass 0.0211 1698 1354 79 Pass 0.0215 1582 1293 81 Pass 0.0219 1480 1221 82 Pass 0.0223 1398 1108 79 Pass 0.0227 1329 1019 76 Pass 0.0231 1261 958 75 Pass 0.0235 1197 887 74 Pass 0.0239 1138 836 73 Pass 0.0243 1081 791 73 Pass 0.0247 1025 766 74 Pass 0.0251 956 740 77 Pass 0.0255 915 712 77 Pass 0.0259 879 688 78 Pass 0.0263 845 658 77 Pass 0.0267 808 638 78 Pass 0.0272 767 619 80 Pass 0.0276 734 601 81 Pass 0.0280 700 568 81 Pass 0.0284 676 551 81 Pass 0.0288 655 531 81 Pass 0.0292 639 513 80 Pass 0.0296 620 493 79 Pass 0.0300 604 480 79 Pass 0.0304 587 463 78 Pass 0.0308 573 449 78 Pass 0.0312 560 431 76 Pass 0.0316 551 410 74 Pass 0.0320 539 399 74 Pass 0.0324 523 383 73 Pass 0.0328 511 369 72 Pass 0.0332 496 354 71 Pass 0.0336 473 341 72 Pass 0.0340 457 328 71 Pass 0.0344 448 310 69 Pass 0.0348 438 284 64 Pass 0.0352 426 256 60 Pass 0.0357 417 223 53 Pass 0.0361 402 218 54 Pass 0.0365 396 215 54 Pass 0.0369 385 208 54 Pass 0.0373 374 204 54 Pass 0.0377 362 202 55 Pass 0.0381 355 195 54 Pass 0.0385 349 192 55 Pass 0.0389 338 191 56 Pass 0.0393 329 189 57 Pass 0.0397 320 186 58 Pass 0.0401 310 183 59 Pass 0.0405 306 180 58 Pass 0.0409 300 179 59 Pass 0.0413 296 177 59 Pass 0.0417 288 174 60 Pass 0.0421 283 173 61 Pass 0.0425 276 173 62 Pass 0.0429 270 171 63 Pass 0.0433 260 169 65 Pass 0.0437 252 168 66 Pass 0.0441 245 164 66 Pass 0.0446 239 159 66 Pass 0.0450 234 159 67 Pass 0.0454 227 157 69 Pass 0.0458 215 156 72 Pass 0.0462 205 153 74 Pass 0.0466 200 153 76 Pass 0.0470 194 151 77 Pass 0.0474 188 150 79 Pass 0.0478 184 147 79 Pass 0.0482 176 141 80 Pass 0.0486 170 139 81 Pass 0.0490 165 135 81 Pass 0.0494 159 135 84 Pass 0.0498 152 135 88 Pass