HomeMy WebLinkAboutSanitary Sewer Study UpdateOctober 20, 2008
Carol Cotter, P .E.
Sr. Assistant City Engineer
City of College Station
1101 Texas Avenue South
College Station, TX 77842
RE: Creek Meadows -Section l C, Phase One
Sanitary Sewer Study Upate
RME No. 202-0363
Carol Cotter:
P.O. Box 9253, College Station, TX 77842
Off/Fax: (979) 690-0329
email: civil@rmengineer.com
The follow are the cumulative revisions/updates to the "Regional Lift Station Study'', prepared
by this office on November 6, 2006, for the master planned Creek Meadows subdivision. These
revisions/updates will incorporate :Section IC into the existing and proposed sanitary sewer
systems and are as follows.
A. Table #1 -"Creek Meadows Time Table" is updated to reflect the addition of Section IC
and modifications (i.e. phasing adjustments and lot densities) to the Creek Meadows -
Preliminary Plat that have made to-date since the issuance of the original report. A copy
of the most current preliminary plat is attached to this letter.
CDl-202-0363-Ll3 Page I of6
Year
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
Creek Meadows-Section lC
Revised Sanitary Sewer Study
October 20, 2008
TABLE #1 -CREEK MEADOWS -TIME TABLE
Single-
Development Area Family Multi-Family Commercial
Section 1 A, Ph 1 & 2
Section lB, Ph 1-4 126 94 5.65
Section 1 C.. Phase I A
Section 4. Phase I
Section 5. Phase 1 58 1.28
Section 1 A, Phase 3 & 4
Section 2, Phase 1 A
Section 4, Pt.ase 2A&2B 33 84
Section 1 C, Phase 1 B&2
Section 2, Phase 1 B
Section 3, Phase 1
Section 4, Phase 2C 87 28 0.36
Section 1 C, Phase 3
Section 2, Phase 2
Section 4. Phase 3
Section 5. Phase 2 100 44
Section 1 C, Phase 4
Section 2, Phase 3
Section 3, Phase 2
Section 4, Phase 4 87 40
Section 1 C, Phase 5
Section 3, Phase 3
Section 5, Phase 3 34 36 4.26
Section 6, Phase 1 61
Section 6, Phase 2 47
Section 7, Phase 1 58
Section 7, Phase 2 43
TOTALS= 734 326 11.55
B. Utilizing this revised development time table for Creek Meadows the average sanitary
sewer flow values were c:tlculated and Table #2 -"Sanitary Sewer Flows" was
appropriately updated. As illustrated below, the ultimate Average Daily Flow (ADF) for
the fully developed Creek Meadows subdivision is 375,536 gpd with a 2-Hour Peak Flow
(PF) at 2.32 cfs.
CD 1-202-0363-L 13 Page 2 of6
Creek Meadows -Section lC
Revised Sanitary Sewer Study
October 20, 2008
TABLE #:i -SANITARY SEWER FLOWS
Average Average :l-Hour CUMM.
Development Daily Flow Dwelling Daily Flow Peak Flow Peak Flow CUMM. Peak Flow
Year (gpd/cap) Units (gpd) (gph) (cfs) ADF (gpm) (gpm)
2007 100 390 103,997 17,333 0.64 72 289
2008 100 96 25,739 4,290 0.16 90 360
2009 100 117 31,239 5,207 0.19 112 447
2010 100 126 33,589 5,598 0.21 135 540
2011 100 144 38,448 6,408 0.24 162 647
2012 100 127 33,909 5,652 0.21 185 741
2013 100 198 52,813 8,802 0.33 222 888
2014 100 61 16,287 2,715 0.10 233 933
2015 100 47 12,549 2,092 0.08 242 968
2016 100 58 15,486 2,581 0.10 253 1011
2017 100 43 11,481 1,914 0.07 260 1042
TOTAL EXPECTED FLOWS= 375,536 62,589 2.32
Flow Determination Notes:
1) Residential density is at 2.67 capita/Dwelling Unit;
2) Commercial uses were estim :ited at 30 capita/acre;
3) Average Daily flows, for t:ach use, were assigned per Table ill-"Average Wastewater
Generations" per the UTSDS;
4) Peaking factor of 4.0 was applied to the Average Daily Flows to determine the Peak Flow
which is used for line sizing;
C. In addition to updating the expected sanitary sewer flows with the revised development
time table also the project available line storage was appropriately modified. These
modifications also included the as-built conditions of constructed or under construction
collector lines that carry wa:;tewater to the two primary trunk lines "A" & "B''. These
revisions are reflected below in the updated Table #4-"Line Storage".
TABLE #4 -LINE STORAGE
Max.
Storage Available
Development Elevation Storage
Year Sanitary Sewer Line (ft) (gallons)
2007 Line A + Collectors 295.33' 7,132
2008 Line A & B +Collectors 295.33' 12,159
2009 Line A & B +Collectors 295.33' 12,159
2010 Line A & B +Collectors 295.33' 12,159
2011 Line A & B +Collectors 295.33' 13,575
2012 Line A & B + Collectors 295.33' 13,575
2013 Line A & B +Collectors 295.33' 14,964
2014 Line A & B +Collectors 295.33' 14,964
2015 Line A & B +Collectors 295.33' 14,964
2016 Line A & B +Collectors 295.33' 14,964
2017 Line A & B +Collectors 288.00' 14,500
CD 1-202-0363-L 13 Page 3 of6
Line Storage Note~;:
Creek Meadows -Section lC
Revised Sanitary Sewer Study
October 20, 2008
I) The maximum storage elevation is dictated by the top elevation of the wet well
less the freeboard. In this case, the maximum storage elevation is 295.33 ';
2) With the corn;truction of the portion of the sanitary sewer trunk line "B" that
extends into Section 7 of Phase Two, a minimum MH rim elevation of 290.00' is
anticipated. Therefore the line storage, in the entire system, will have a reduced
maximum sto;·age elevation of 288.00'. The wet well storage will be reduced
accordingly at this time, as iJlustrated in the follow subsections;
3) The line storage volume should be recalculated with each phase or phases of
construction tc1 reflect actual design conditions. Also, "collector'' lines that extend
off of the trunk line should be included, if applicable;
4) Volume that c1mld be gained from manholes were not considered;
D. Integrating the revised calculated wastewater flows and updated available line storage the
regional lift station limits could be quantified. The updated Regional Lift Station Sizing
Calculations are attached to 1his letter and provide further detailed information for the lift
station's requirements. Table #6 -"Lift Station Summary" was modified accordingly
and reports the regional lift station's storage and pump requirements for each yearly
development level.
As shown in the updated cak:ulations a second "overflow" wet well will need to be added
in the development year of 2012. As shown for the development year of 2015 the
required storage is not meet. It is anticipated that with the evaluation of all the existing
sewer lines, at that time, the required storage will be meet. If this is not the case then an
additional wet well will need to be added.
CD 1-202-0363-Ll 3 Page 4 of6
Creek Meadows -Section lC
Revised Sanitary Sewer Study
October 20, 2008
TABLE #6 -LIFT STATION SUMMARY
FLOW DATA WET WELL
l otal
Rftention Deff. Storage Wet Well Line Provided
~ ADF PF Storage Storage Req'd Storage Storage Storage
(gpm) (gpm) (gallons) (gallons) (gallons) (gallons) (gallons) (gallons)
2007 72 289 :),785 0 5,785 20,573 7,132 27,705
2008 90 360 '7,209 458 7,667 20,573 12,159 32,732
2009 112 448 a,945 3,127 12,072 20,573 12,159 32,732
2010 135 540 10,814 7,536 18,350 20,573 12,159 32,732
2011 162 648 12,950 13,658 26,608 20,573 13,575 34,148
2012 185 740 14,833 19,636 34,469 39,456 13,575 53,031
2013 222 888 17,770 29,615 47,385 39,456 14,964 54,420
2014 233 932 18,675 32,802 51,477 39,456 14,964 54,420
2015 242 968 19,372 35,285 54,657 39,456 14,964 54,420
2016 253 1012 20,233 38,377 58,610 39,456 14,964 54,420
2017 275 1100 21 ,998 44,808 66,806 39,456 14,500 53 ,956
PUMPS
Finn Average Daily Flow (ADF) Peak Flow (PF)
Pump Pump Pump Pump
~ Rate Time Off Purnp Time Cycle Pump Time Pump Time Cycle
~ (gpm) (min) On (min) (min) Off(min) On (min) (min)
2007 315 31.5 36.4 67.9 7.9 87.2 95.1
2008 315 29.9 61.6 91.5 7.5 97.l 104.6
2009 315 24.1 68.2 92.3 6.0 117.2 123.2
2010 315 19.9 77.0 96.9 5.0 148.6 153.6
2011 315 17.3 99.7 117.0 4.3 199.7 204.0
2012 315 15.1 117.8 132.9 3.8 264.5 268.3
2013 315 13.2 179.3 192.5 3.3 434.7 438.0
2014 315 12.5 :W4.2 216.7 3.1 51 8.7 521.8
2015 315 12.l :l28.6 240.7 3.0 601.4 604.4
2016 315 11.6 :~68.2 279.8 2.9 735.6 738.5
2017 315 11.2 ·t63 .2 474.4 2.8 1238 1240.8
Lift Station Notes:
I) Mr. Lee Betitt, with Bryan T·!xas Utilities (821-5824), researched their Greens Prairie Switch station
and reported that over the pas·: 24 months no power outages had occurred. Therefore, the minimum 20
· minute retention period was u ;ed to calculated required storage;
2) The wet well is calculated with a 12' diameter and a total depth of27.83'. The useable depth is 24.33 ',
thus the wet well storage ii. 20,573 gallons. This useable depth is reduced to 19.33' with the
construction of Section 7, Phase 2.
CDl-202-0363-Ll3 Page 5 of6
Please do not hesitate to call if you have any questions.
Sincerely,
CD 1-202-0363-L 13
Creek Meadows -Section lC
Revised Sanitary Sewer Study
October 20, 2008
Page 6 of6