§ 14-4. Storm sewers.

(a)

Submittal procedure. For village approval of storm sewer systems, the applicant shall furnish to the village a detailed estimate of cost and three sets of storm sewer plans and specifications. Detailed storm sewer design computations and the drainage area map indicating the various areas going into the points of inlet shall be provided. The village engineer shall review the estimate and the plans for conformity to standards set forth in this section, and certify that they are consistent with the overall utility plans of the village, after which they will return one of the three sets with appropriate comments. The applicant, after making any changes requested on the set of plans returned to him, shall then submit four sets of revised plans to the village for final approval. The village engineer shall then review these revised plans for conformity to the comments mentioned heretofore and, if they have been properly made, will retain three copies for the village's records, and return one approved copy to the applicant.

(b)

Design standards.

(1)

Storm drainage systems shall be designed for a ten-year storm. The rational method for arriving at stormwater runoff shall be used. The formula for rainfall intensity in inches per hour shall be equivalent to I equals 175/T+25, in which T is the time of concentration. The consulting engineer shall use judgement in arriving at proper impervious factors. The consulting engineer shall submit a map outlining the various areas, including off-site upstream areas, which drain to the points of inlet used for design together with the storm sewer design computations. In general, sufficient capacity shall be provided in the storm sewer system to take fully developed (fully paved and sewered) upstream drainage into the system.

(2)

Where the hydraulic gradient is above the top of the sewer pipe, the design elevation of the hydraulic gradient shall be indicated.

(3)

Manhole spacing for storm sewers shall be as follows:

Diameter of Sewer	Absolute Maximum Manhole Spacing
12 inches to 15 inches	330 feet
18 to 30 inches	350 feet
36 inches and 42 inches	400 feet
48 inches	450 feet
54 inches and 60 inches	500 feet
66 inches and larger	600 feet

 

Note: Height of Lo-Hed pipe shall be used as the criteria for manhole spacing. Catchbasins shall not be constructed over a sewer line to replace manholes.

(4)

The following information shall be indicated on the storm sewer profile:

a.

Length of run between manholes;

b.

Size and slope of sewer between manholes;

c.

Class of bedding where concrete is required;

d.

Top elevation of all manholes.

Where possible, the slope of the sewers shall provide a minimum velocity of 2.5 feet per second velocity.

(5)

A note or detail shall show the type of bedding upon which the sewer pipe shall be installed.

(6)

Where possible, provide a minimum of three feet of cover from the top of curb (or road centerline) to the top of any storm sewer. If the depth of cover to the top of the pipe is less than one foot, C-76-C1. 4 pipe shall be used. If the cover is between one foot and three feet from the top of the curb to the top of the pipe, use C-76-C1. 3 pipe. All catchbasin leads within a street shall be C-76-C1. 3 pipe, including the leads to the manholes.

(7)

In general, catchbasins shall be located as follows:

a.

At the radius return of street intersections: 150 feet maximum distance along the street between a high point and a corner catchbasin is allowed when drainage is required to go around the corner.

b.

At all low points in streets.

c.

At intermediate points along the street such that there is a maximum of 600 feet of drainage draining from a high point to a catchbasin or from a previous intercepting catchbasin to this catchbasin.

d.

A maximum of 900 feet of drainage is allowed from two directions.

(8)

Field catchbasins shall be provided at all low points in easements. Intercepting field catchbasins shall be located so that not more than 600 feet of drainage runs into any one catchbasin other than a low point catchbasin, 1,200 feet of drainage is allowed to run into a low point catchbasin. Field catchbasins shall be located in rear lot easement swales when such swale changes direction by more than 45 degrees.

(9)

Finished easement grades shall be indicated on the plans.

(10)

Improved open drains may be permitted upon special circumstances in accordance with section 14-11.

(11)

Headwalls and inlet structures shall be placed as required.

(12)

Allowable types of sewer pipe and joints shall be current village standards and shall be covered on the plan by note or on the profile, where applicable.

(Ord. No. 81, art. IV, 5-15-1973)