HomeMy WebLinkAboutLetter Regarding Access Driveway2 year
5 year
10 year
25 year
50 year
100 year
Existing Conditions
0.90
1.09
1.22
1.40
1.58
1.65
Proposed Conditions
2.08
2.53
2.84
3.24
3.66
3.83
Net Change (CFS)
1.18
1.44
1.62
1.84
2.08
2.18
• L;
December 13, 2011
Living Hope Baptist Church
4170 State Hwy 6 South
College Station, Texas 77845
Attn: M.D. Marshall (via email)
Re: Living Hope Baptist Church Driveway Extension
Mr. Marshall:
The referenced driveway connects the existing parking lot of the Church to Barron Road. The driveway
provides an additional entrance and exit from the Church campus. This letter summarizes the drainage
impacts of the proposed driveway.
The proposed driveway is approximately 0.346 acres, including a back of curb to the back of curb width
of 23' with two tumouts. The drainage flows along the driveway's north curb line to Barron Road. The
following table summarizes the change in flow due to the new driveway.
NOTE: Reference attachments for calculations of existing & proposed conditions.
Based on the area and minimal change in flows of the various storm events, it is our opinion storm
water detention is not needed.
John I. Rusk, P.E.
Regional Manager
Enclosures
•
GOODWIN • LASITER, INC.
ENGINEERS • ARCHITECTS • SURVEYORS
l � OF T > 1
r .. *
i JOHN RUSK
to% 87884
Ss
/2 / / / 3 / // I
EAST TEXAS OFFICE
(936] 637 -4900
FAX (936] 637 -6330
CENTRAL TEXAS OFFICE
(979] 696 -6767
FAX (979] 696 -2685
1609 S. CHESTNUT • SUITE 202 •LUFKIN, TEXAS • 75901 • adrnin@q, odwiniaeiter.corn TBPE #413
3600 ST. HIGHWAY 6 S. • SUITE 102 • COLLEGE STATION. TEXAS • 77845 • ctex @cagnuw■va^
WAS.981698040 Cones1698040.LTR.00t.doc
Peak Discharge
Q= C
2 -year
5 -year
10 -year
25 -year
50 -year
100 - year
C,,,
0.41
0.41
0.41
0.41
0.41
0.41
C
1.00
1.00
1.00
1.00
1.00
1.00
I (in /hr)
6.3
7.7
8.6
9.9
11.1
11.6
A (ac.)
0.346
0.346
0.346
0.346
0.346
0.346
Runoff Coefficient
Area Description
Acres Runoff Coefficient (C)
Structures
Unimproved
1 DL
1 Se,
Brewster
Briscoe
Brooks
Brown
Rainfall Intensity- Duration - Frequency Coefficients for Texas Counties
Coefficient
e (in)
d (mins) 7
Intensity (in /hr)
Intensity (mm /hr)"
* for time of Concentration =
Living Hope Baptist Church
Access Driveway
Existing Conditions
_12-year 5 -year 10 -year
0.806 0.785 0.763
65 761 80
8.0 8.5E 8.5
6.3 7.7 8.6
160.7 195.4 219.3
mins
Page 1 of 1
25 -year 50 -year 100 -year
0.754 0.745 0.730
89 98 96
8.5 8.5 8.0
9.9 11.1 11.6
GL No. 698040
December 13, 2011
Coefficient
e (mm)
b
d (mins)
2 -year
0.806
1651
8.0
5 -year
0.785
1930
8.5
10 -year 25 -year
0.763 0.754
2032 2261
8.5 8.5
50 -year 100 -year
0.745
2489
8.5
0.730
2438
8.0
250.5 283.2 295.6
Notes:
1. Runoff coeffiecient adjustment factor (CO is not utilized by the Design Guidelines and
therefore assumed to be 1.0 for all rain events.
Peak Discharge
Q= C
2 -year
5 -year
10 -year
25 -year
50 -year
100 -year
C
0.95
0.95
0.95
0.95
0.95
0.95
C,
1.00
1.00
1.00
1.00
1.00
1.00
I (in /hr)
6.3
7.7
8.6
9.9
11.1
11.6
A (ac.)
0.346
0.346
0.346
0.346
0.346
0.346
Runoff Coefficient
Area Description
Acres Runoff Coefficient (C)
Structures
Unimproved
Living Hope Baptist Church
Access Driveway
Proposed Conditions
Rainfall Intensity- Duration - Frequency Coefficients for Texas Counties
1. Select your county
County
Brazos
Bell
Bexar
Blanco
Borden
Bosque
Bowie
Brazoria
Brazos
Brewster
* for time of Concentration =
GL No. 698040
December 13, 2011
2 Fr,ter the IT to of ( ,r :E r t
Coefficient -7- 2 -year 5 -year 10-year 25- year 50 -year 100 -year
0.806 0.785 0.763 0.7540.745 0.730
65 76 80 89 98 96
8.0 8.5 8.5 8.5 8.5 87
6.3 7.7 8.6 9.9 11.1 11.6
e (in)
b
d (mins)
Intensity (in /hr)"
e (mm)
d (mins)
Intensity (mm /hr)"
2 -year 5 -year
0.806 0.785 0.763
1651- 1930 2032
8.08.5 8.5
160.7 195.4 219.3
mins
Page 1 of 1
100 -year
0.754 0.745 0.730
2261 2489 2438
8.5 8.5 8.0
250.5 283.2 295.6
Notes:
1. Runoff coeffiecient adjustment factor (CO is not utilized by the Design Guidelines and
therefore assumed to be 1.0 for all rain events.