The following minimum standards apply to drainage construction
within new subdivisions:
(1) Storm
sewers and culverts.
a. Minimum
diameter: 24 inches; 18 inches for pipe serving one inlet.
b. Minimum
slope: Storm sewers: 0.1 percent. Culverts shorter than 100 feet:
0.1 foot.
c. Material:
Class III reinforced concrete pipe, and Texas Highway Department standard
box culverts and headwalls.
d. Joints:
Ram-Nek asphaltic sealer.
(2) Open
channels.
a. Unlined
ditches.
1. Side
slopes: Three horizontal, one vertical.
2. Bottom
slope: 0.05 percent minimum.
3. Easement
width: Top width plus 16 feet on one side plus six feet on other side.
b. Lined
channels.
1. Bottom
slope: 0.05 percent minimum.
2. Lining
material: Five-inch-thick concrete with 43 bars at 18 inches.
3. Concrete
characteristics: Same as for street paving.
4. Easement
width: Top width plus 12 feet on one side and four feet on other side.
c. Junction
boxes and manholes.
1. Size:
Nominal pipe size plus 12 inches.
2. Material:
Reinforced concrete, designed for load. (Brick walls are permissible.)
3. Location:
At changes in pipe size or direction, and at 400 foot intervals.
4. Access:
22-inch diameter cast iron cover.
d. Inlets.
1. Minimum
thread size: Six inches high by five feet long.
2. Material:
Reinforced concrete, designed for load. (Brick walls are permissible.)
3. Wall
thickness: Six inches.
4. Access:
22-inch diameter cast iron cover.
e. Runoff
criteria.
2. Runoff
coefficient: Single-family area, 50 percent.
3. Multifamily
or commercial: 80 percent.
(3) Storm
water detention pond.
For all subdivisions, the developer
or property owner must obtain a letter from the Brookshire-Katy Drainage
District stating the proposed development meets or is exempt from
the district's storm water detention requirement. Such a letter is
not required if the proposed development meets all of the following
criteria:
a. Each
lot contains 20,000 square feet or more and is for a single family
residence;
b. The
area of the roof and paved surfaces, minus the area of landscape beds
containing at least six inches' thickness of mulch, is less than ten
percent of the total area of the lot;
c. The
lot grading and arrangement is such that all drainage from the roof
and paved surfaces leaves the lot as sheet flow (not in a pipe or
ditch);
d. The
above criteria in subsections (3)a, b and c of this section are included
as deed restrictions and also on the subdivision plat; and
e. Each
lot fronts on an existing paved public street.
(Ordinance 83-150-3, § 6(F),
adopted 7/26/1983; Ordinance
06-483-9, § 1, adopted 3/2/2006)