Chapter 15.50
STORM DRAINS
Sections:
15.50.010 General.
15.50.020 Pipe.
15.50.030 Minimum slopes.
15.50.040 Cleaning and testing.
15.50.050 Sumps.
15.50.060 Retention/detention basins.
15.50.010 General.
The installation specifications for storm drain systems shall conform to the APWA Standard Specifications unless noted otherwise in this chapter.
All residential developments will be responsible to provide a storm drain system on-site in the development that will contain a 100-year storm event. The maximum allowable storm water discharge from any commercial and industrial development will be limited to 0.2 cfs/acre of development. All storm drain pipes shall have a minimum cover of two feet. Minimum size of storm drains is 12-inch diameter for tie-ins and 15-inch diameter for main lines.
No person shall discharge or cause to be discharged any storm water, surface water, ground water, roof runoff, subsurface drainage, cooling water, or unpolluted industrial process waters to any sanitary sewer. Storm water and all other unpolluted drainage shall be discharged to such sewers as are specifically designated as combined sewers or storm sewers, or to a natural outlet approved by the director. Industrial cooling water or unpolluted process waters may be discharged, on approval of the director, to a storm sewer, combined sewer or natural outlet.
Storm drain manholes and sumps shall meet confined space requirements, and shall be equipped with ladder rungs and other such devices as required to ensure public safety. [Ord. O-12-2008 § 1 (Exh. A § 10.010)].
15.50.020 Pipe.
Piping used for storm water conveyance includes concrete and high density polyethylene (HDPE) piping. All pipe shall conform to the material and installation specifications included in this chapter. [Ord. O-12-2008 § 1 (Exh. A § 10.020)].
15.50.030 Minimum slopes.
Minimum slopes for different size pipes are as follows:
|
Pipe Diameter |
Minimum Slope |
|
12 inches |
0.194% |
|
14 inches |
0.158% |
|
15 inches |
0.144% |
|
16 inches |
0.132% |
|
18 inches |
0.113% |
|
21 inches |
0.092% |
|
24 inches |
0.077% |
|
27 inches |
0.066% |
|
30 inches |
0.057% |
|
36 inches |
0.045% |
[Ord. O-12-2008 § 1 (Exh. A § 10.030)].
15.50.040 Cleaning and testing.
After the storm drain lines have been laid and the trench backfilled, they shall be thoroughly cleaned and tested for leakage and alignment in the presence of the city engineer or his/her designee before acceptance by the owner. Cleaning shall be done using a high pressure jet cleaning machine, producing a minimum of 800 psi. Wastewater and debris shall not be permitted to enter storm drain lines in service, but shall be removed at the lowest manhole of the extension. Such cleaning shall be done by private crews at the expense of the owner.
Storm drain lines may be required to have a mandrel test prior to acceptance and prior to the release of the warranty bond. [Ord. O-12-2008 § 1 (Exh. A § 10.040)].
15.50.050 Sumps.
Sumps shall not be used in Eagle Mountain City unless approved by the city engineer. If approved, all sumps must be constructed with a grease trap.
Additionally, sumps shall only be located as staked in the field and indicated on the plans. They shall be to the grade indicated by the cutsheets and as staked in the field. Excavation and backfill shall conform to Chapter 15.30 EMMC. If the sump is located in an area where the earth is stratified with gravel layers, care shall be taken during backfill to be sure that these layers are not sealed off from the sump beginning three feet below the bottom of the sump up to the top of the subgrade. One- to three-inch diameter drain rock shall be used. The original material shall be removed and the total backfill done with imported drain rock. After backfilling is completed, the entire excavation shall be thoroughly flooded to ensure that settlement is complete. Grates shall be set in place and adjusted for final elevation and alignment. The city requires a fabric barrier between the drain rock and road base (or other backfill).
Sumps may only be constructed of reinforced concrete, precast sections, and shall meet the requirements of ASTM C478-73 in accordance with standard detail drawings S-15, S-16, and S-17. Sumps shall have eccentric lids to ensure adjustments in alignment. [Ord. O-12-2008 § 1 (Exh. A § 10.050)].
15.50.060 Retention/detention basins.
A. Retention Basins. All retention basins shall be constructed with a maximum water depth of four feet. All retention basins shall have a series of interconnected sumps connected to curb inlet boxes or storm drain main lines. All retention basins shall be landscaped in accordance with city standards. All retention basins shall be constructed with a minimum slope of 5:1.
All retention basins shall be constructed for drainage areas designated in the general plan. Basins for smaller areas may be allowed only with prior written approval of the city engineer or his/her designee.
B. Detention Basins. All detention basins shall be constructed with a maximum water depth of 18 inches, with that depth remaining for no longer than a six-hour period. Detention basins must be landscaped and they may be located in park and recreational areas. Each detention basin shall have a manually controlled outlet to a storm drain main line. Detention ponds greater than 18 inches must have a minimum side slope of 5:1. Fencing around detention ponds may be required as determined by the city engineer or his/her designee.
Ponds must be constructed as they are required for the detention of the proposed improvements. If the ultimate design of a subdivision has located the detention basin in a future phase of the subdivision, either a temporary detention basin must be constructed, or an easement for the approved detention must be given to the city and the detention basin must be constructed with the required phase. [Ord. O-12-2008 § 1 (Exh. A § 10.060)].