R-00-04-27-12D5 - 4/27/2000RESOLUTION NO. R- 00- 04- 27 -12D5
WHEREAS, §8.610(4) and §8.611(10) Code of Ordinances (1995
Edition) provide for the reimbursement for the oversizing of water and
wastewater mains, and
WHEREAS, Continental Homes of Austin, L.P. has submitted a
reimbursement request for the oversizing of water and wastewater mains
associated with the Preserve at Stone Oaks Development, and
WHEREAS, the City Council wishes to approve said reimbursement,
Now Therefore
BE IT RESOLVED BY THE COUNCIL OF THE CITY OF ROUND ROCK, TEXAS,
That the City Council hereby approves of the reimbursement to
Continental Homes of Austin, L.P. of $57,927.45, which is the cost of
oversizing water and wastewater mains associated with the Preserve at
Stone Oaks Development.
The City Council hereby finds and declares that written notice of
the date, hour, place and subject of the meeting at which this
Resolution was adopted was posted and that such meeting was open to the
public as required by law at all times during which this Resolution and
the subject matter hereof were discussed, considered and formally acted
upon, all as required by the Open Meetings Act, Chapter 551, Texas
Government Code, as amended, and the Act.
RESOLVED this the 27th day of April, 2000.
E LAND, City Secretary
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ROBERT A. STLU JR., Mayor
City of Round Rock, Texas
INTRODUCTION
WASTEWATER SYSTEM
PRESERVE AT STONE OAK
WATER AND WASTEWATER LINE CAPACITY
The City of Round Rock Subdivision Ordinance provides for cost reimbursement for
developers who install oversized water and wastewater lines to serve off -site
development. The purpose of this report is to analyze the capacity of the water and
wastewater system that would have been designed to serve only the Preserve At Stone
Oak. The actual design will serve 360 single family lots and an Amenity Center within
the Preserve At Stone Oak, as well as off -site future development. This analysis will
demonstrate that the designed system is eligible for oversize reimbursement in
accordance with the City of Round Rock subdivision ordinance.
Construction of wastewater improvements in the Preserve At Stone Oak, Phase 1 Section
1, are complete. Two 12 -inch lines were constructed, and these tie into a 15 -inch line
segment, which in turn ties into an existing 15 -inch line serving Stone Oak at Round
Rock subdivision.
"FlowMaster" software by Haestad Methods was used to calculate line capacities for
given diameters and slopes. FlowMaster uses Manning's Equation to determine flow
characteristics.
The table below demonstrates that the 12 -inch and 15 -inch lines installed in Phase 1
Section 1 (and the continuation of a 12 -inch line in Phase 1 Section 3) are oversized and
therefore eligible for cost reimbursement. Please refer to the wastewater plan in
Appendix A.
Line Capacity Summary — Phase 1 Section 1
Line Dia. Min.
No. (in.) Slope(ft/ft)
A 15 .005
Req'd line size for on -site
B 12 .0115
Req'd line size for on -site
C 12 .005
Req'd line size for on - site
On -site Analysis
Peak' Inflow/ Total 75% Full
Lots* Flow(gom) Infiltration Flow Capacitv(gpm)
361.5 396 115 511 1,869
flows only: 12 - inch (capacity = 1,031 gpm @75% full)
312 342
flows only:
210 230
flows only:
73.2 386 1,031
8 - inch (capacity = 530 gpm @75% full)
51.4 282 1,563
8 -inch (capacity = 350 gpm @75% full)
Line Capacity Summary — Phase 1 Section 3
On -site Analysis
Line Dia. Min. Peak' Inflow/ Total 75% Full
2
No. (in.) Slope(ft/ft) Lots Flow(gpm) Infiltrat Flow Capacity(gpm)
B 12 .005 86 94 19 113 1,031
Req'd line size for on - site flows only: 8 - inch (capacity = 350 gpm @75% full)
*Includes an equivalent 1.5 lots for the Amenity Center.
'Peak flow calculated at 350 gpd/LUE, with a peaking factor of 4.5 applied.
2 lnflow /infiltration calculated as 1,500 gpd/acre of drainage basin served by the line.
Reimbursement amounts are calculated as follows:
Phase 1 Section 1
Reimbursement Total
Line No. Length(ft.) Ove i.ize in. Rate , Reimbursement
A 709.41/ 3 ✓ $ 7.80 $ 5,533.40V \ S 4-.
B 810.49 ✓ 4 ✓ $10.40 ✓ 3,241.96 €,411 • lo.
C 934.77/ 4 ✓ $10.40 91 -Crls` 1, t 1. :t 4 TOTAL: $1.972-7•0416:9_,`7
- 23,484 -t0,, 4 .,u,
Phase 1 Section 3
Reimbursement Total
Line No. Length(ft.) Oversize in. Rate Reimbursement
A 735.47✓ 4✓ $10.40 $ 7,648.89
TOTAL WASTEWATER SYSTEM REIMBURSEMENT:
WATER SYSTEM
$25;695:86
31, 332.99
Two 12 -inch water lines were designed to serve the 360 lots in Preserve At Stone Oak,
plus off -site future development. Attached as Appendix B are the results of a WaterCad
(Haestad Methods water modeling software) system analysis that demonstrates that two
8 -inch supply lines, instead of the two 12 -inch lines, would be sufficient to serve the on-
site water needs of the Preserve At Stone Oak.
The analysis was performed with the following assumptions:
Total on -site lots: 360
Peak Hour Demand: 2.2 gpm per house
Peak Hour System Requirement: Min. 35 psi throughout system
Peak Day Demand:
Fire Demand:
Peak Day + Fire - System Requirement:
1.3 gpm per house
1,000 gpm
Min. 20 psi residual throughout system
Peak -hour and Peak -day plus Fire Demand scenarios were analyzed. A fire demand was
placed at various locations throughout the site. As expected, the most critical locations
were at remote, elevated areas in the northwestern section of the site. The WaterCad
model indicates that the system, with 8 -inch lines serving the subdivision, is adequate to
serve the water demands of the on -site improvements. Since 12 -inch lines were installed,
oversizing for future off -site improvements are eligible for oversize reimbursement as
follows:
Phase 1 Section 1
Line Reimbursement Total
No. Length(ft.) Oversize Rate Reimbursement
A 93235— 4 inches ✓ $10.40. $ 9,696.44
//,960. �.S•�
Phase 2 Section 1
Line (sus Reimbursement Total
No. Lenath(ft.)n.S Oversize Rate Reimbursement
A 1276.311' 4inches. $10.40' $13,273.62 J-
A -7 130.85V 4 inches ' $10.40 1,360.84"
TOTAL WATER LINE REIMBURSEMENT: $
z6,54 4.44. d•g 4
SUMMARY
TOTAL OVERSIZE REIMBURSEMENT- WATER: $25;695786 z 6, 5 4 3 • if •
TOTAL OVERSIZE REIMBURSEMENT — WASTEWA'1'EK: 24:330790- 21 33Z.T1 . '$-
TOTAL OVERSIZE REIMBURSEMENT /CREDIT: $50 026;76• 57, 1 a7. 45
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DATE: April 21, 2000
SUBJECT: City Council Meeting — April 27, 2000
ITEM: 12.D.5. Consider a resolution authorizing a reimbursement to
Continental Homes of Austin, L.P. for oversize of water and
wastewater lines associated with the Preserve at Stone Oak
Development. Staff Resource Person: Jim Nuse, Public Works
Director.