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HomeMy WebLinkAboutDrainage Reports - 10/01/1981DRAINAGE REPORT FOR THE RH CONVERSION 218 PETERSON STREET FORT COLLINS, COLORADO Certification: I, David M. Frick, do hereby certify that this drainage report for the RH Conversion of 218 Peterson Street, Fort Collins, Colorado, was prepared under my supervison in accordance with City of Fort Collins specifications. David M. Frick, PE #15094 •.�STEp���•; O" Resource Consultants, Inc. P. 0. Box Q Fort Collins, Colorado 80522 October 1981 Ref : 1087 DRAINAGE REPORT FOR THE RH CONVERSION OF 218 PETERSON STREET Introduction This report presents the drainage plan for the RH conversion for 218 Peterson Street, Fort Collins, Colorado. Included are a site drainage description, proposed changes in drainage patterns, and resulting storm - water runoff rates. Site Description The site is located at 218 Peterson Street, Fort Collins, Colorado; the property is currently being used as a residence. Two structures are on the property --a house plus a garage at the rear of the lot. Access to the garage is through the alley. On the property to the south is a 2-story apartment building with a parking lot at the rear of the lot. The property to the north is a single-family residence with a garage next to the alley. At 218 Peterson Street drainage from the rear half of the house, the backyard, and the garage currently flows northwest into the alley and adjacent property to the north. The front yard and west one-half of the house drain toward the street. Fig. 1 shows the existing drainge patterns. A small amount of drainage enters the site from the lot to the south, but the roof and parking lot drainage flow to the south away from the 218 Peterson Street site. The proposed site development will include renovation of the existing house, construction of a four -car parking lot between the house and garage, and enlarging the garage to hold two cars. In addition a gravel drive and sidewalk will be installed. As shown in Fig. 2, no changes in the existing drainage conditions are planned for the west portion of the site which currently drains into Peterson Street; therefore a drainage plan for that portion of the site was not considered in this study. Drainage Calculations Computations of site drainage releases for the 2-year and 100-year storms were made utilizing the rational method. Table 1 summarizes the results of these calculations and shows peak flows for the east and west portions of the site. 1 RESOURCE CONSULTANTS INC Table 1 Summary of Drainge Calculations Area and condition Area Runoff Discharge Volume— (ac.) Coefficient (cfs) (cu.ft.) East portion of site Existing conditions 2-year 0.237 0.25 0.12 200 100-year .0.237 0.31 0.45 700 East portion of site Fully developed 2-year 0.237 0.37 0.18 300 100-year 0.237 0.46 0.67 1000 West portion of site Existing and fully developed 2-year 0.061 0.40 0.06 80 100-year 0.061 0.50 0.22 300 1/Assuming a 1-hour storm. The table shows that the 2-year flows would be increased by 0.06 cfs and the 100-year flows would be increased by 0.22 cfs as released from the site, and the runoff volumes from the site would be increased by approxi- mately 30 percent. The drainage plan for the site would consist of regrading the site to direct the storm -water flows into the proposed gravel driveway. This driveway would be at a flat slope so as to slow the storm water before it is released into the alley. This slowing of the storm water would also allow some infiltration of runoff into the gravel. The regrading would also eliminate release of drainage water onto the adjacent property as currently occurs; therefore the only release would be into the alley and this would be slowed and partially captured in the gravel driveway. Investigation of the site indicated that this control of drainage water would eliminate the potential for problems being created from increased site runoff to adjacent areas. RESOURCE CONSULTANTS INC 2 Summary and Conclusions Based on the results of this study the proposed drainage plan would be to release drainage waters from the rear portion of the property at 218 Peterson Street into the alley, with the remainder of the site drainage water flowing into Peterson Street as it currently does. Regrading of the rear portion of the site will prevent storm -water runoff from entering the property adjacent to the site, and a flat -sloped gravel driveway will minimize the impact of increased runoff into the alley. RESOURCE CONSULTANTS INC 3 I � CONCENTRATION 216I POINT � IRON PIN / FOUND �, I r 1C a g- �O m •' 3106* Walt f*** 2'f I IRON PIPE ROUND 8 i �o I"IRON PIPE FOUND I N.89a5774 WWlllii� 7900077 � LIA 0 20. i�s'sto,. ; stets -SS-� i • d TWO ORY BRICK USE l0' W/BAS ENT c IS PETER STREET n 150' 20.3, —_ _A C n 21 Via, 5. 'S6 23 II ASSUMED MORTN o 10 20 — 95 220 I NOTE Front lot line assumed to bear due north and oil other bearings shorn hereon are relative thereto. Contour lines shorn hereon are relative to an assumed elevation at the southwest Corner of the lot. IMPROVEMENT SURVEY Lot 9 — Block 152 City of Fort Collins PAVED PARKING LOT Figure # I EXISTING DRAINAGE PATTERNS CONCENTRATION POINT REBAR M BE SET l6� FRAME g BARN a 16.}. O LS�� fiARM h FNCROAGNtENT W V 1 rn M 2J, O f 1 I RON PIPE / / / 7-FOUND a► I" IRON PIPE ' FUMID 05;��COMZLCTN�NTS INC Fart CcJ I ns, Colorodo 1 216 Grading would eliminate D INAGE I 8x)e,-7IHC- -oA" r- r►rla-Y \ stormwater runoff to CO ENTRATION t _I rtE•.SIAiNG1L adjacent site. IRON-- —_, FOUND rle�t coon :.►�`+o6c�.Pllyce i REBAR TO BE SET kN 89157'4 'w (19000'PLAT1 (I�DDrACJ1— _ 16 3 I Ur Iva/. wr / 71rae e..ap Z rl�ij 'fly 0 1411' I fw}VvN� 4 fJcts a Q - 20.0 I `� FRAME _ 1 I ! g S.eys BARN S = 0.0 1 \ P a na L '^ stone Walk 11 � ' a � - ---- - - in o ° + - •� 6 e.001TIJ '10 rtiiCL IN6 o•IM`Wa TWO RY op op 40 ( BRICK OUSE j a 0 W/BA MENT -- 163' - i Ot-CL_LrIN6 UP11 q _ ta�tHe. --r l e+ oac.�rlrw s': BARN _ 0 218 PETER N STREET ��WO ENCROACHMENT 1 I f 2 - I Doll : 3 SSIot{ei orFKa& - -- % i Ip rIT*-rim Fo* a:�u.lry�. I .ter re,r�a `% DRAAAGE 1s 0' 20 3' S = 0.005 CON �E NTRATION —30 - — 0 o !, rt � i - � + I -.-� I-f•HOec1fIM4 • L. IRON PIPE N B9' S9 I E ( 190 00' PL - (t99 % R.0 t a - - -- - - -- _ �l In I$ I IRON PIPE FOUND FOUND _ V Gravel driveway will PAVED PARKING LOT slow stormwater and allow some infiltration, reducing releases from / 220 oKts—It-r— 8 uNiT s�sr" �i ; Hout,1[ fi site. NOTE Front lot line assumed to Dear due north I and oil other Dearnngs shorn hereon are relative thereto. Contour lines shown hereon are relotive to on assumed elevation of the southwest Corner of the lit. ASSUMED NORTH SCALE 1 -10 5749 —07 '01 , eL0C e\ 152- '-0aT 0._L' 5 C�L.O AADO Figure # 2 PROPOSED DRAINAGE � PLAN �I z I IRON PIPE L -� FOUND �aourlc� GONSU�-s^�-'S IyL.