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Home My WebLink AboutStudies APPLICANT 7/12/2021HAMLIN MIDDLE SCHOOL DRAINAGE STUDY July 9, 2021 SITE CHARACTERISTICS The subject site currently is a natural turf baseball field with dugouts and concrete walks. This proposal is to replace the existing natural turf on the baseball field with artificial turf, along with adding bleachers, new dugouts and concrete picnic areas adjacent to the baseball field EXISTING HYDROLOGY The site is relatively flat and the site drains into the existing bio-swales inside of the property. PROPOSED HYDROLOGY The proposed drainage system consists of piping the proposed impervious drainage to two treatment ponds. See attached Hydrology Map. An infiltration rale of 2" per hour was assumed to size the treatment ponds. North Basin The north basin collects the drainage from the concrete picnic areas and landscape areas (4,400 s.f.). The impervious area (20,100 s.f.) included a future restroom building and drain to a proposed treatment pond. The treatment pond was sized using the City of Eugene's Slormwaler Surface Filtration/Infiltration Facility Sizing Spreadsheet and is attached. The minimum required size for an Infiltration Rain Garden is 920 s.f. at the top of the facility. The proposed treatment pond is over 1,170 s.f. South Basin The south basin collects the drainage from the concrete picnic areas. The impervious area (5,600 s.f.) drains to a proposed treatment pond. The treatment pond was sized using the City of Eugene's Slormwaler Surface Filtration/Infiltration Facility Sizing Spreadsheet and is attached. The minimum required size for an Infiltration Rain Garden is 266 s.f. at the lop of the facility. The proposed treatment pond is over 450 s.f. CONCLUSION Based on my calculations and the proposed drainage systems are sized properly and will provide the necessary treatment. NYOVY EXPIRES DEC. 31, 2021 Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet 24 Hour Storm, N RCS Type 1 A Rainfall Distribution City of Eugene Name: Hamlin Middle School Date: 7/9/2021 Address: 98 Permit Number: Permit Total Square Footage of Drainage Area= 24509 Catchment ID: North basin or: Anthony J. Fa,mmu, TY: The Favreau Group Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) =or infiltration facilities in Class A or B soils when; no infiltration testing has been per romed use an infiltration rate of 0.5 inllrr. For all facilities use a maximum soil infiltration rate of 2.5 in/hr for lopsorgrowing medium. loose'Ym' from the dmpdown loxes below next to the design standards requirements for this facility. Pollution Reduction (PR)Yes Flow Control (FC)l No Destination(DT) No 'Ani nFlio-ationkciiiry mu91ecYxAOnae Netasiiiryh,em novtdesmotion rsqulr,norfs Total Square Footage Impervious Area= 20109 sgfl Total Square Footage Pervious Area=4400 sgfl Impervious AreaCN=l 98 Flow Control Pervious Area CN=l 135 Total Square Footage of Drainage Area= 24509 sfi Time of Concentration Post Development=min Weighted Average CN=l 96 Pre�Development CN= 85 Time of Concentration Pre�Development= 10 min Tested Soil Infiltration Rate= 1.5 rotor (Soo We 4) Destination Design=®iNhr Design Soil Infiltration Rate= 1.5 iNhr Soil Infiltration Rate R uirement Rainfall De h Dari nStorm Pollution Redugion 1.4 inches Water Qualit Flow Control 3.6inches IFlood Control Destination I 3.6inches Food Control Facility Facility Side Slop( Max. Ponding Depth in Stmonwater Facility - Depth of Growing Medium (So 7/9/2021-11:51 AM Facility Surface Facility Surface Perri Facility Bottom Facility Bottom Perri Ratio of Facility Area to Basin Vc Pollution Reduction-Calculation Results ca Peak Flow Rate to Stormwater Facility =q,3 Peak Facility Overflow Rate= 0.000 cis Total Runoff Volume to Stormwater Facilitycf Total Overflow Volume= 0 cf Max. Depth of Stormwater in Facility=in Drawdown Time=hours Yes Facility Sizing Meets Pollution Reduction Standards? VES Meets Requirement of No Facility Flooding? VES Meets Requirement for Maximum of 18 Hour Drawdown Time? Flow Control-Calculation Results Peak Flow Rate to Stormwater Facility = 0.501 cfs Peak Facility Overflow Rate= 0.489 cfs Total Runoff Volume to Stormwater Facility= 6331 cf Total Overflow Volume= 3148 cf Peak Off -Site Flow Rate Max. Depth of Stormwater in Facility= 12.0 in Filtration Facility Untlertlrain= NVl cfs Drawdown Time= 8.2 hours Pre-Devekmment Runoff Data Peak Flow Rate = 0.293 cfs Total Runoff Volume =1 4295 cf =Facility Sizing Meets Flow Control Standards? Nw Meets Requirement for Post Development offsite flow less or equal to Pre-Development Flow? ZI NW Meets Requirement for Maximum of 18 Hour Drawdown Time? Destination-Calculation Results Peak Flow Rate to Stormwater Facility = N/A cfs Peak Facility Overflow Rate= N/A cfs Total Runoff Volume to Stormwater Facility= N/A cf Total Overflow Volume= N/A cf Max. Depth of Stormwater in Facility- N/A in Drawdown Time= N/A hours N/A Facility Sizing Meets Destination Standards? N/A Meets Requirement of No Facility Flooding? L.2LAJMftts Requirement for Maximum of 30 hour Drawdown Time? 7/9/2021-11:51 AM Stormwater Surface Filtration/Infiltration Facility Sizing Spreadsheet 24 Hour Storm, N RCS Type 1 A Rainfall Distribution City of Eugene Name: Hamlin Middle School Date: 7/9/2021 Address: Water Qualit Permit Number: Permit IFlood Control Destination Catchment to: South basin or: Anthony J. Fa,mmu, TY: The Favreau Group Complete this form for each drainage catchment in the project site that is to be sized per the Presumptive Approach. Provide a distinctive Catchment ID for each facility coordinated with the site basin map to correlate the appropriate calculations with the facility. The maximum drainage catchment to be modeled per the Presumptive Approach is 1 acre (43,560 SF) =or infiltration facilities in Class A or B soils when; no infiltration testing has been per romed use an infiltration rate of 0.5 inllrr. For all facilities use a maximum soil infiltration rate of 2.5 in/hr for lopsorgrowing medium. loose'Ym' from the dmpdown loxes below next to the design standards requirements for this facility. Pollution Reduction (PR)Yes Flow Control (FC)l No Destination(DT) No 'Ani11hationkciiiry mu91ecYxAOnae Netasiiiryh,em novtdesmotion rsqulremeMs Total Square Footage Impervious Area=5600 sgfl Total Square Footage Pervious Area- 0 Sur Impervious Area CN=l 98 Pervious Area CN=l 85 Total Square Footage of Drainage Area= 5600 sfl Time of Concentration Post Development=min Weighted Average CN=l 98 Pre�Development CN= 85 Time of Concentration Pre�Development= 10 min Tested Soil Infiltration Rate= 1.5 rotor (Soo We 4) Destination Design=®iNhr Design Soil Infiltration Rate= 1.5 iNhr Soil Infiltration Rate R uirement Rainfall De h Dari nStorm Pollution Redugion 1.4 inches Water Qualit Flow Control 3.6inches IFlood Control Destination I 3.6inches Food Control Facility Facility Side Slop( Max. Ponding Depth in Stormwater Facility - Depth of Growing Medium (So 7/9/2021-11:50 AM Facility Surface Facility Surface Perri Facility Bottom Facility Bottom Perri Ratio of Facility Area to Basin Vc Pollution Reduction-Calculation Results Peak Flow Rate to Stormwater Facility cfs Peak Facility Overflow Rate= 0.000 cfs Total Runoff Volume to Stormwater =q3, Facilitycf Total Overflow Volume= 0 cf Max. Depth of Stormwater in Facility=in Drawdown Time=hours Yes Facility Sizing Meets Pollution Reduction Standards? VES Meets Requirementof No Facility Flooding? VES Meets Requirement for Maximum of 18 Hour Drawdown Time? Flow Control-Calculation Results Peak Flow Rate to Stormwater Facility = 0.121 cfs Peak Facility Overflow Rate= 0.112 cfs Total Runoff Volume to Stormwater Facility= 1568 cf Total Overflow Volume= 665 cf Peak Off -Site Flow Rate m Max. Depth of Storwater in Facility= 12.0 in Filtration Facility Underdrain= NW cfs Drawdown Time= BJ lours Pre-Development Runoff Data Peak Flow Rate = 0.06] cfs Total Runoff Volume =1 982 cf =Facility Sizing Meets Flow Control Standards? Nw Meets Requirement for Post Development offsite flow less or equal to Pre-Development Flow? NW Meets Requirement for Maximum of 18 Hour Drawdown Time? Destination-Calculation Results Peak Flow Rate to Stormwater Facility = N/A cfs Peak Facility Overflow Rate= N/A cfs Total Runoff Volume to Stormwater Facility= N/A cf Total Overflow Volume= N/A cf Max. Depth of Stormwater in Facility- N/A in Drawdown Time= N/A lours N/A Facility Sizing Meets Destination Standards? =Meets Requirement of No Facility Flooding? L.2LAJMftt, Requirement for Maximum of 30 hour Drawdown Time? 7/9/2021-11:50 AM =Em a �M��$�.�. egg.,_9CFq os me> gig p VO Y RSeiar 3 3� AIG a e�"a €$�3 nN a _a�o 22 3 e3 Ela i o a s O a m£R` s R 4P 'RI p oci9 s a b o,tl 's a s77 OG'ytR4 � Ij'� N N o ml �l �E _ g t' o� r EEEEEEEEE E�E EE rE PJ f EE EEEEE E I a I mlE I .. I EE EEEEEE EEE -I �.I _f/ \ \ E E Gv e 7L E a age 1111 a s U• _ E i 1. i II i Ie e� I NFa / ;�� P _ It C/I ua r r r sl ' r I THE FAVREAU GROUP HYDROLOGY MAP CIVIL ENGINEERING HAMLIN SCHOOL BASEBALL FIELD ..E.ORG6 (&).. p U osewimiax m TAX MAP 17-03-26-34 CITY OF SPRINGFIELD 9 REVISIONS TAX LOT 6200