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HomeMy WebLinkAboutDrainage Reports - 11/17/1999December 11, 1998 Mr. Basil Hamdan City of Fort Collins Stormwater Utility �vjj� � 2 Lo99 Development Review Division 235 Mathews Fort Collins, Colorado 80522-0580 j{ RE: Harmony Safeway Marketplace Proposed Blockbuster Video & Farmers Bank Dear Basil, As a part of the approved plan set for the Harmony Safeway Marketplace, there are two lots located in the southeast corner of the property, designated as Lots 4 and 5 . A proposed Blockbuster Video is proposed for Lot 5, and a Farmers Bank is proposed for Lot 4. This letter is intended to provide you with an overview of what the impacts development of these two lots will have on the existing drainage design, approved for the site. As is typically the case with pad sites designed with this type of project, the ultimate user generally likes to make minor changes to the approved plan. I have attached copies of the plan which was the basis of our original runoff calculations, and what the proposed site modifications include. As you can see, the changes they are requesting are minor in nature, and the original intent of our engineering and drainage design has remained in tact. Our original runoff design calculations did account for areas of imperviousness at these location. The differences are listed below. Attached is a copy of a portion of the drainage basins that were associated with the Harmony Safeway Marketplace site. As you can see Lots 4 and 5 are located within subbasins N-13, N —141 N-15, S-5, and S-6. I have also attached copies of the proposed improvements to Lots 4 and 5, which served as the basis of our original calculations with the impervious areas highlighted. Also attached is a copy of the proposed improvements for Blockbuster and Farmers Bank, with the impervious areas highlighted. To recap, subbasins designated with an N prefix were designed such that developed runoff would be directed towards the northeast corner of the site to a proposed detention pond, and then ultimately to the Golden Meadows Regional detention pond. Basins designated with a S prefix were design to release into an open channel, through proposed culverts under McMurray and Innovation Drive, and also ultimately to the Golden Meadows regional detention facility. Subbasins with an S prefix were not designed to be detained on -site, should sufficient capacity exist in the downstream conveyance system. 420 SOUTH HOWES, SUITE 202, FORT (OIIINS, (OtORADO 80521, (970) 221-4158, FAX (970) 22 1-4 159 Those portions of this project located within basins N-13,14 and 15 are small, and the developed runoff coefficient, as assumed are essentially identical. Those portions of the project located within subbasins S-5 and S-6 have been reevaluated. I have attached a copy of the calculations for the composite runoff coefficient for basins S-5 and S-6, as approved, as well as the revised calculations. As you can see, are assumptions were for a composite C value of 0.75 for basin S-5 and 0.71 for basin S-6. Given the revised site plan for lots 4 and 5, the proposed composite runoff coefficient for basin S-5 is approximately 0.63 and the proposed C value for basin S-6 is approximately 0.77. The assumed combined C value for both basins was 0.73, and the proposed C value would be 0.69. Therefore, the anticipated downstream runoff from basins S-5 and S-6 will be less than the original study anticipated. With final design, site grading for the revised site should comply with the original basin boundary lines, and that the site is graded so as not to disturb the interception swale and culverts to the south of the site. Downstream capacity should also be verified during the design process. As you recall, the storm sewer crossing of McMurray has also been modified from the original design. A copy of the UDSEWER analysis for this crossing has also been attached to this letter. The modified design is on record with the City. The attached Overall Utility plan for the Harmony Safeway Marketplace also reflects this storm sewer modification. Please call if you have any questions regarding this project, or require additional information. Sincerely, Roger Curtiss P.E. - Northern Engineering cc: Michael Davison -Wyatt & Associates " m �o DOd n Z p u �d t3 ojg fa I Ell I I 8 I I I I I u\� o00 \� 0 0 . rg \ \ ( \U .$ 4= C. 2 U . O . G k � 0 6 .e q . / a ( \ \� n C> % $/ 2 / . U QE$ 000 k\ \\ /\ 2 %% A ©© k\ \� w tntn 22 \2 co » mtn .\ / / /}kn / u%/_ 0 0 \§ ao R� ooQE / 1;dw 9 k _ . . � Ln / � �CA(AV) � �` i -���� \`1 Wq IW4' No Text STORM SEWER SYSTEM DESIGN USING UDSEWER MODEL Developed by Dr. James Guo, Civil Eng. Dept, U. of Colorado at Denver Metro Denver Cities/Counties 6 UDFCD Pool Fund Study ----------------------------------------------- USER:NORTHERN ENG SERVICES INC-FT COLLINS COLORADO ........................... ON DATA 10-06-1998 AT TIME 13:36:44 VERSION=03-26-1994 *** PROJECT TITLE :HARMONY SAFEWAY *** SUMMARY OF HYDRAULICS AT MANHOLES ------------------------------------------------------------------------------- MANHOLE CNTRBTING RAINFALL RAINFALL DESIGN GROUND WATER COMMENTS ID NUMBER AREA * C DURATION INTENSITY PEAK FLOW ELEVATION ELEVATION MINUTES INCH/HR CFS FEET FEET ------------------------------------------------------------------------------- 1.00 0.00 0.00 0.00 57.30 75.00 72.61 OK 2.00 11.69 5.32 4.90 57.30 74.50 73.26 OK 3.00 0.84 5.00 4.90 4.10 73.70 74.40 NO 4.00 0.84 5.00 4.90 4.10 73.70 74.50 NO 5.00 10.86 5.17 4.90 53.20 75.30 73.93 OK 6.00 10.86 5.02 4.90 53.20 76.00 74.85 OK 7.00 10.86 5.00 4.90 53.20 76.50 75.19 OK 8.00 10.86 5.00 4.90 53.20 76.50 76.07 OK 9.00 10.86 5.28 4.90 53.20 74.75 73.49 OK OK MEANS WATER ELEVATION IS LOWER THAN GROUND ELEVATION *** SUMMARY OF SEWER HYDRAULICS NOTE: THE GIVEN FLOW DEPTH -TO -SEWER SIZE RATIO= .8 ------------------------------------------------------------------------------- SEWER MANHOLE NUMBER SEWER REQUIRED SUGGESTED EXISTING ID NUMBER UPSTREAM DNSTREAM SHAPE DIA(RISE) DIA(RISE) DIA(RISE) WIDTH ID NO. ID NO. (IN) (FT) (IN) (FT) (IN) (FT) (FT) ------------------------------------------------------------------------------- 12.00 2.00 1.00 ROUND 41.19 42.00 36.00 0.00 23.00 3.00 2.00 ROUND 13.49 15.00 18.00 0.00 34.00 4.00 3.00 ROUND 14.20 15.00 18.00 0.00 56.00 6.00 5.00 ROUND 37.96 42.00 36.00 0.00 67.00 7.00 6.00 ROUND 31.18 33.00 36.00 0.00 78.00 8.00 7.00 ROUND 33.74 36.00 36.00 0.00 29.00 9.00 2.00 ROUND 42.90 48.00 3fi.00 0.00 95.00 5.00 9.00 ROUND 30.36 33.00 33.95 0.00 DIMENSION UNITS FOR ROUND AND ARCH SEWER ARE IN INCHES DIMENSION UNITS FOR BOX SEWER ARE IN FEET REQUIRED DIAMETER WAS DETERMINED BY SEWER HYDRAULIC CAPACITY. SUGGESTED DIAMETER WAS DETERMINED BY COMMERCIALLY AVAILABLE SIZE. FOR A NEW SEWER, FLOW WAS ANALYZED BY THE SUGGESTED SEWER SIZE; OTHERWISE, EXISTING SIZE WAS USED ------------------------------------------------------------------------------- SEWER DESIGN FLOW NORMAL NORMAL CRITIC CRITIC FULL FROUDE COMMENT ID FLOW Q FULL Q DEPTH VLCITY DEPTH VLCITY VLCITY NO. NUMBER CFS CFS FEET FPS FEET FPS FPS ------------------------------------------------------------------------------- 12.0 57.3 40.1 3.00 8.11 2.45 9.29 8.11 0.00 V-OK 23.0 4.1 8.9 0.72 4.92 0.79 4.38 2.32 1.16 V-OK 34.0 4.1 7.7 0.78 4.44 0.79 4.38 2.32 1.OQ V-OK 56.0 53.2 46.3 3.00 7.53 2.37 8.89 7.53 0.00 V-OK 67.0 53.2 78.3 1.81 11.91 2.37 8.89 7.53 1.70 V-OK 78.0 53.2 63.4 2.10 10.06 2.37 8.89 7.53 1.28 V-OK 29.0 53.2 33.4 3.00 7.53 2.37 8.89 7.53 0.00 V-OK 95.0 53.2 71.9 1.81 12.52 2.37 9.45 8.46 1.76 V-OK FROUDE NUMBER=0 INDICATES THAT A PRESSURED FLOW OCCURS ------------------ SEWER ------------- SLOPE --- --------- INVERT ELEVATION ------ ----------- BURIED ---- DEPTH ------- COMMENTS ID NUMBER UPSTREAM DNSTREAM UPSTREAM DNSTREAM 8 (FT) (FT) (FT) (FT) ---------------------------------------------------------------------- 12.00 0.36 70.16 70.07 1.34 1.93 OK 23.00 0.71 70.82 70.16 1.38 2.84 OK 34.00 0.54 70.82 70.82 1.38 1.38 OK 56.00 0.48 71.73 71.40 1:27 0.90 NO 67.00 1.37 71.93 71.73 1.57 1.27 OK 78.00 0.90 71.93 71.93 1.57 1.57 OK 29.00 0.25 70.18 70.16 1.57 1.34 OK 95.00 1.58 70.57 69.35 1.90 2.57 OK OK MEANS BURIED DEPTH IS GREATER THAN REQUIRED SOIL COVER OF 1 FEET *** SUMMARY OF HYDRAULIC GRADIENT LINE ALONG SEWERS ------------------------------------------------------------------------------- SEWER SEWER SURCHARGED CROWN ELEVATION WATER ELEVATION FLOW ID NUMBER LENGTH LENGTH UPSTREAM DNSTREAM UPSTREAM DNSTREAM CONDITION FEET FEET FEET FEET FEET FEET ------------------------------------------------------------------------------- 12.00 25.60 25.60 73.16 73.07 73.26 72.61 PRSS'ED 23.00 93.00 93.00 72.32 71.66 74.40 73.26 PRSS'ED 34.00 0.10 0.10 72.32 72.32 74.50 74.40 PRSS'ED 56.00 69.23 69.23 74.73 74.40 74.85 73.93 PRSS'ED 67.00 14.60 14.60 74.93 74.73 75.19 74.85 PRSS'ED 78.00 0.10 0.10 74.93 74.93 76.07 75.19 PRSS'ED 29.00 8.00 8.00 73.18 73.16 73.49 73.26 PRSS'ED 95.00 77.21 71.78 73.40_ 72.18 73.93 73.49 JUMP PRSS'ED=PRESSURED FLOW; JUMP=POSSIBLE HYDRAULIC JUMP; SUBCR=SUBCRITICAL FLOW *** SUMMARY OF ENERGY GRADIENT LINE ALONG SEWERS ------------------------------------------------------------------------------- UPST MANHOLE SEWER JUNCTURE LOSSES 'DOWNST MANHOLE SEWER MANHOLE ENERGY FACTION BEND BEND LATERAL LATERAL, MANHOLE ENERGY ID NO ID NO. ELEV FT FT K COEF LOSS FT K COEF LOSS FT ID FT ------------------------------------------------------------------------------- 12.0 2.00 74.28 1.67 0.25 0.00 0.00 0.00 1.00 72.61 23.0 3.00 74.48 0.14 0.78 0.07 0.00 0.00 .2.00 74.28 34.0 4.00 74.59 0.00 1.25 0.20 0.00 0.00 3.00 74.48 56.0 6.00 75.73 0.44 0.28, 0.25 0.00 0.00 5.00 75.05 67.0 7.00 76.07 0.09 0.28 0.25 0.00 O.DO 6.00 75.73 78.0 8.00 76.95 0.00 1.00 0.88 0.00 0.00 7.00 76.07 29.0 9.00 74.37 0.05 0.05 0.04 0.00 0.00 2.00 74.28 95.0 5.00 75.05 0.62 0.05 0.06 0.00 0.00 9.00 74.37 BEND LOSS =BEND K* FLOWING FULL VHEAD IN SEWER. LATERAL LOSS= OUTFLOW FULL VHEAD-JCT LOSS K*INFLOW FULL VHEAD FRICTION LOSS=O MEANS IT IS NEGLIGIBLE OR POSSIBLE ERROR DUE TO JUMP. FRICTION LOSS INCLUDES SEWER INVERT DROP AT MANHOLE NOTICE: VHEAD DENOTES THE VELOCITY HEAD OF FULL FLOW CONDITION. A MINIMUM JUNCTION LOSS OF 0.05 FT WOULD BE INTRODUCED UNLESS LATERAL K=O. FRICTION LOSS WAS ESTIMATED BY BACKWATER CURVE COMPUTATIONS.