HomeMy WebLinkAbout68 Development Permit 635 Lulac Walking Path and Pavillion..
Drainage Report
And
Development Permit Application Form
LULAC Walking Path and Pavilion
Prepared for:
Darrell Parker
Community Development Division
City of College Station
Prepared by:
Brett McCully, P.E.
Assistant City Engineer
January 13, 1999
Description
This project is generally located within the boundaries of Texas Avenue,
Holleman Drive, Anderson street and Pineridge Street.
Specifically, the project is located south of the Enclave Apartments, southeast of
the Bright Star development, northwest of the HEB/Target Detention Basin outlet
channel, and northeast of the LULAC Retirement Center.
This project includes the construction of concrete walking paths, rest shelters and
an outdoor pavilion in an area that is presently vacant land . The total impervious
area to be added is approximately 10,825 square feet or approximately 0.25
acres .
Drainage is anticipated to follow the existing drainage pattern for the site , which
is to the southeast through an existing inlet into the outlet channel below the
HEB/Target Detention basin.
Runoff Evaluation
According to the Drainage Design Report prepared by Urban Design Group for
the HEB/Target outlet channel dated June 1996, the subject area is part of a
2.46ac drainage sub-basin, which flows into the recently constructed concrete
channel through an existing inlet.
This report lists the design flows from the subject area as Q(25)=13 .3cfs and
Q(100)=17 .1cfs. The SCS curve 87 was used for this calculation, which would
effectively equal a rational runoff coefficient of 0.55, which in turn would fall into
the low density residential category within the COCS-DPDS Table 111-1 on page
23. This shows that some impervious cover is already accounted for in the
channel design.
In determining an actual weighted rational runoff coefficient for the subject area
in its proposed state, Table 111-1 suggests the use of a coefficient of 0 .35 for the
mowed grass and a coefficient of 0. 90 for the impervious areas as follows :
Surface
Mowed Grass
Impervious
Totals
Area
2.21ac
0.25ac
2.46ac
Coefficient
0.35
0.90
Resulting weighted C value equals 0.41
(A)(C)
0.77
0.23
1.00
..
r \.
:: .
Because the actual runoff coefficient for this development (0.41) will still be lower
than the coefficient used to design the receiving channel (0.55), this project will
not have an impact on the designed operation of the channel.
Detention Evaluation
Because of this project's close proximity to the downstream end of the
HEB!Target detention basin, the relative sizes of the drainage areas, and the fact
that the receiving channel is designed to receive this flow (and more), it is my
opinion that the flows from this development should be allowed to discharge into
the receiving channel without detention .
Erosion Control
The site presently drains through a shallow swale with fairly poor slope (0 .50%).
To prevent any silt from reaching the receiving channel, a hay bale barrier will be
constructed prior to clearing operations across the swale downstream of the
construction activities .
After construction, any soil areas left disturbed will be seeded or sodded to re-
establish a vegetative ground cover.
Summary
While this project will produce an increase in runoff due to the addition of
impervious cover, the receiv ing public structures are already designed to
accommodate the flows without detention effects.
Attachments:
1. Development Permit Application
2. Hay Bale Barrier Detail
3. Site Plan from Construction Drawings
4. UDG Drainage Map
..
Figure XU
Development Permit
City of College Station, Texas
Site Legal Description : 5. 41 AC. FbtJ.nDN t!>P 7/tAcr 147.I eJrC ~ -&~
Site Owner: LlJLAC. OAKHILL INC..
Architect/
Engineer: BRETT M= CIJL LY P. ~
Contractor: J"ACODY
Date Application Filed : __ l-_2_1_-_q_'1 __ _
Address : 1105 /-JNfJElt~O/\/ C.STX
Telephone: ~ </ 3 -C.~ ?Co
Address: CQC.S. eNt::.1/\/E€te/N6.
Telephone No : 7fo4 -~Bl~
Address: 240C FROST LOLL. Snt. TX.
Telephone No : ~'f U> -774S
Application is hereby made for the following development specific waterway alterations :
LOIV.£Tl2l/lTtON eJr 5/JJEWALJC~ A-/1/D .Sl-lt:LTE'IZ.S.
-B-Application Fee N/A
~ Signed Certifications /\//A
0 Drainage and erosion control plan, with supporting Drainage Report two (2) copies each .
0 Site and Construction Plans, with supporting Drainage Report two (2) copies each.
0 Other:
~-----------------------------
ACKNOWLEDGMENTS :
~" I, S~eT'r M~CULLY design engineer/o"'R~r. hereby acknowledge or affirm that :
The information and conclusions contained in the above plans and supporting documents comply
with the current requirements of the City of College Station, Texas City Code, Chapter 13 and its
associated Drainage Policy and Design Standards .
As a condition of approval of this permit application, I agree to construct the improvements
proposed in this application according to these documents and the requirements of Chapter 13 of
the College Station City Code .
Property Owner(s) Contractor
..
Flow
vertical face
EMBEDDING DETAIL
Angle first stake toward
previously laid bale ~;iE~i~~t!;1Z'Jl;iti.
Flow ~
the
contour
2 re-bars, steel pickets, or
2" x 2" stakes 1 1/2' to 2'
in ground
ANCHORING DETAIL
FIGURE X -I
TEMPORARY STRAW (OR HAY) BALE BARRIER
83