O-81-902 - 6/11/1981ORDINANCE NO. go:90.12..,
AN ORDINANCE AUTHORIZING AN EMERGENCY APPROPRIATION
PURSUANT TO SECTION 8.05 OF THE HOME RULE CHARTER,
FOR CERTAIN STORM SEWER AND DRAINAGE IMPROVEMENTS
ALONG CREEKVIEW DRIVE.
WHEREAS, Section 8.05 of the Home Rule Charter for the
City of Round Rock, Texas, authorizes the Council to make
emergency appropriations to meet a pressing need for public
expenditure, to protect the public health, safety or welfare,
and
WHEREAS, the City Manager recommends an emergency appro-
priation for certain drainage improvements in and near Creek -
view Drive in the City, and
WHEREAS, the total amount of this emergency appropria-
tion does not exceed two and one-half per centum (21%) of the
tax levy for the current fiscal year, Now Therefore
BE IT ORDAINED BY THE COUNCIL OF THE CITY OF ROUND ROCK,
TEXAS
I.
That, pursuant to, and in accordance with, Section 8.05,
Home Rule Charter for the City of Round Rock, Texas, the
Council hereby authorizes an emergency appropriation to meet
a pressing need for public expenditure to protect the public
health, safety or welfare, to -wit: certain storm sewer and
drainage improvements for Creekview Drive as described in
Exhibit "A" attached hereto and incorporated herein for all
purposes.
II.
That, the total amount of the emergency appropriation
authorized herein shall not exceed Ten Thousand and No/100
Dollars ($10,000.00).
That the above amount, together with any other emergency
appropriation authorized this fiscal year shall not exceed
two and one-half per centum (21%) of the tax levy.
ROUND ROCK WEST
SECTION 6-A
STORM SEWER IMPROVEMENTS
This report on storm sewer improvements for Round Rock West, Sec-
tion 6-A has been prepared at the request of the City of Round Rock to
recommend modifications to the existing storm sewer system to solve a
recurring problem of rainfall flooding. On-site investigations were
made as well as review of construction plans and contact with City
officials and affected property owners. This report will outline
causes for the flooding and suggestions for correction.
CAUSES OF FLOODING
The original drainage plans indicated a predicted 25 year fre-
quency storm to produce a run-off of 28.85 cubic feet per second. This
run-off was to be intercepted by two l0 -foot inlets located in a low
point in Creekview Drive. Water from these inlets would have been car-
ried to Lake Creek. Had construction proceeded in accordance with the
plans, no significant flood would have occurred.
Field inspection of the problem area shows that neither the
streets or the drainage system were constructed as proposed. The
resultant drainage area produces a predicted rainfall run-off from a 25
year frequency storm of 37.0 cubic feet per second. The change in the
street grade of Creekview Drive changes one of the proposed inlets from
an inlet in a low point to an inlet on grade which significantly reduc-
es its capacity. In addition, the street grade tends to divert the
run-off away from this inlet. The other proposed inlet was moved ap-
proximately 100 feet and connected to its proposed location by an 18"
reinforced concrete pipe at a flat grade. This inlet cannot intercept
the major portion of the 37.0 cubic feet per second which would be
diverted to it in a 25 year frequency storm. In fact the inlet over-
flows into surrounding lots in minor storms.
SUGGESTED IMPROVEMENTS
Interception of the rainfall run-off can be most economically
effected by creating additional inlet capacity at the low point of
Creekview Drive. This would be accomplished by the construction of a
new l0 -foot curb inlet adjacent to or near the existing inlet. The
existing 18" reinforced concrete pipe does not have sufficient capacity
and a 24" reinforced concrete pipe should be constructed to augment the
existing system. This pipe would run along Lot 4 near the line of Lot
5 to discharge in Lake Creek. Contact with the property owner of Lot 4
indicates a willingness to grant a drainage easement provided the rout-
ing would not damage existing trees and soils and grasses were replac-
ed.
EXHIBIT "A", Page 1
Construction of the foregoing suggestions will eliminate overflow
of the existing inlet and pipe system during most rainfall events.
However, the capability of the street to carry a major storm run-off is
limited due to crossfall and spill over the curb, or down some drive-
ways, particularly Lots 5 and 6, may still occur. This problem may
have to be alleviated at some time in the future by re -crowning the
street, or by re -building the driveway at Lot 6 to make a higher ramp
and building a berm along the right-of-way to keep water from jumping
the curb.
ESTIMATED COST
The estimated cost of the suggested improvements are as follows:
1 - 10' curb inlet $1,200.00
260 L.F. of 24" RCP @ $24.00/L.F. 6,240.00
Replacing Soils and Grasses 250.00
Construction Cost $7,690.00
10% Contingency Fee 769.00
10% Engineering Fee 846.00
Total Improvements Cost $9,305.00
CONCLUSION
Damages by flooding of this area of Creekview Drive, have to this
point been minor; however, the rainfalls have not been as large as pre-
dicted design storms. In the event of a major storm, flooding could
cause considerable property damage. It is therefore recommended that
the City of Round Rock make the storm sewer improvements as suggested
herein as soon as is feasible.
EXHIBIT "A", Page 2
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EXHIBIT "A", Page 3
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MIPRoVEMEN T
Haynie & Kallman Inc.
St ' CONSULTING ENGINEERS
2115 North May3 ''? iwrl y
4-4715 E
F•iounc1 Rock , Texas 7136eA
ID- , (512) 255-4564 , 255-7861
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