§ 18-138. Preventing increased damages.

(a)

Generally. No development in the SFHA, where a floodway has not been determined, shall create a damaging or potentially damaging increase in flood heights or velocity or a threat to public health or safety.

(b)

Development standards. Within all riverine SFHA's where the floodway has not been determined, the following standards shall apply:

(1)

The developer shall have a registered professional engineer state in writing and show through supporting plans, calculations and data that the project meets the engineering requirements of section 18-107(a)(1) through (10) for the entire floodplain as calculated under the provision of section 18-21(e). As an alternative, the developer should have an engineering study performed to determine a floodway and submit that engineering study to the DWR for acceptance as a regulatory floodway. Upon acceptance of their floodway by the department, the developer shall then demonstrate that the project meets the requirements of division 4 of this article for the regulatory floodway.

(2)

A development permit shall not be issued unless the applicant first obtains a permit from the DWR or written documentation that a permit is not required from the DWR.

(3)

No permit from the DWR shall be required if the division has delegated permit responsibility to the village per 92 Ill. Adm. Code, part 708 for regulatory floodways, per the DWR statewide permit, entitled "Construction in Floodplains with No Designated Floodways in Northeastern Illinois."

(4)

Dam safety permits. Any work involving the construction, modification or removal of a dam or an on-stream structure to impound water shall obtain a state division of water resources dam safety permit or letter indicating a permit is not required prior to the start of construction of a dam. If the village engineer finds a dam that does not have a DWR permit, the village engineer shall immediately notify the dam safety section of the division of water resources. If the village engineer finds a dam which is believed to be in unsafe condition, the village engineer shall immediately notify the owner of the dam and the state emergency services and disaster agency (ESDA) and the DWR, dam safety section, in Springfield.

(5)

The following activities may be permitted without a registered professional engineer's review or calculation of a base flood elevation and regulatory floodway. Such activities shall still meet the other requirements of this article:

a.

Underground and overhead utilities that:

1.

Do not result in any increase in existing ground elevations;

2.

Do not require the placement of aboveground structures in the floodway; or

3.

In the case of underground stream crossings, the top of the pipe or encasement is buried a minimum of three feet below the existing streambed; and

4.

In the case of overhead utilities, no supporting towers are placed in the watercourse and are designed in such a fashion as not to catch debris.

b.

Storm and sanitary sewer outfalls that:

1.

Do not extend riverward or lakeward of the existing adjacent natural bank slope;

2.

Do not result in an increase in ground elevation; and

3.

Are designed so as not to cause stream bank erosion at the outfall location.

c.

Construction of shoreline and streambed protection that:

1.

Does not exceed 1,000 feet in length or two cubic yards per linear foot of streambed.

2.

Materials are not placed higher than the existing top of bank.

3.

Materials are placed so as not to reduce the cross sectional area of the stream channel by more than ten percent.

d.

Temporary stream crossings in which:

1.

The approach roads will be 0.5 feet or less above the natural grade.

2.

The crossing will allow stream flow to pass without backing up the water above the stream bank vegetation line or above any drainage tile or outfall invert.

3.

The top of the roadway fill in the channel will be at least two feet below the top of the lowest bank.

4.

All disturbed stream banks will be seeded or otherwise stabilized as soon as possible upon installation and again upon removal of construction.

5.

The access road and temporary crossings will be removed within one year after authorization.

e.

The construction of lightpoles, signposts and similar structures.

f.

The construction of sidewalks, driveways, athletic fields (excluding fences), patios and similar surfaces which are built at grade.

g.

The construction of properly anchored, unwalled, open structures, such as playground equipment, pavilions and carports built at or below existing grade that would not obstruct the flow of floodwaters.

h.

The placement of properly anchored buildings not exceeding 70 square feet in size, nor ten feet in any one dimension (e.g., animal shelters and tool sheds).

i.

The construction of additions to existing buildings which do not increase the first floor area by more than 20 percent, which are located on the upstream or downstream side of the existing building and which do not extend beyond the sides of the existing building that are parallel to the flow of floodwaters.

j.

Minor maintenance dredging of a stream channel where:

1.

The affected length of the stream is less than 1,000 feet.

2.

The work is confined to reestablishing flows in natural stream channels.

3.

The cross sectional area of the dredged channel conforms to that of the natural channel upstream and downstream of the site.

(6)

The flood-carrying capacity within any altered or relocated watercourse shall be maintained.

(c)

Compensatory storage. All placement of fill, structures or other materials above grade in the floodplain shall require compensatory storage equal to at least 1.0 times the volume of floodplain storage displaced. The storage shall be provided incrementally between the zero- to ten-year and the ten- to 100-year flood recurrence intervals at a minimum 1:1 ratio, respectively.

(Code 1997, § 34-128; Ord. No. 91-11-17, §§ 902.0—902.2, 11-5-1991; Ord. No. 08-06-13, § 1(34-128), 6-17-2008)