(A) General requirements.
(1) Agency jurisdictions and recommendations. At minimum, the following agencies or entities shall make recommendations to the Plan Commission pertaining to the adequacy of drainage and storm sewers in the proposed subdivision:
(a) Plan Commission staff;
(b) Lake County Superintendent of Highways;
(c) Lake County Surveyor;
(d) Lake County Soil and Water Conservation District; and
(e) Any other applicable participating jurisdiction, agency, or unit as deemed necessary by the Plat Officer.
(2) Plan submission. As part of the approved construction plans, the subdivider shall submit plans for the approval of the Commission for an adequate stormwater drainage system, which may include sewers, channels, and basins. The stormwater drainage system shall be separate and independent of any sanitary sewer system. The subdivider shall use existing drainage channels whenever possible. Storm sewers where required shall be designed according to accepted engineering practice and consistent with any ordinance regulating storm drainage in Lake County, and a copy of design computations shall be submitted along with construction plans. Inlets shall be provided so that surface water is not carried across any intersection, nor for a distance in the gutter greater than indicated by the design computations submitted with the construction plans. When calculations indicate that curb capacities are exceeded at a point, no further allowance shall be made for flow beyond that point. Surface water drainage patterns shall be shown for each and every lot and block.
(B) Nature of stormwater facilities.
(1) Location. The subdivider may be required by the Commission to carry away, by pipe or open ditch, any spring or surface water that may exist either previously to, or as a result of the subdivision. The drainage facilities shall be located in the road right-of-way where feasible, or in unobstructed easements of appropriate width, and shall be constructed in accordance with the approved construction plans.
(2) Accessibility to public storm sewers. Where a public storm sewer is accessible, the subdivider shall install storm sewer facilities, or if no outlets are within a reasonable distance, adequate provision shall be made for the disposal of stormwaters as shown on the approved construction plans. Inspection of facilities shall be conducted by the participating jurisdiction.
(3) Upstream and downstream drainage areas. The County Surveyor shall determine the effect of each proposed subdivision on existing drainage facilities outside the area of the subdivision downstream. The impact on the subdivision from upstream drainage shall also be determined. County drainage studies, together with such other studies as may be available and appropriate, shall serve as a guide to needed improvements. Where it is anticipated that the additional runoff incident to the development of the subdivision will overload an existing downstream drainage facility, the Commission may withhold secondary approval of the subdivision until provision (such as a storage facility) has been made for the improvement of the potential condition in such sum as the Commission shall determine. No subdivision shall be approved unless adequate drainage from it will be provided to an adequate drainage water course or facility.
(C) Design standards.
(1) The design of the drainage system shall be based on the following considerations:
(a) The drainage area as a whole: storm drainage upstream, downstream, and within the drainage area of which the subdivision is a part;
(b) Calculations as to volume and frequency of water to be accommodated;
(c) Design of culverts and storm sewer pipe sufficient in size to eliminate unreasonable flooding or ponding of water;
(d) Establishment of finished land grades throughout the subdivision so that there is no ponding of water on the land and that surface runoff will not be such as to cause serious erosion;
(e) Existing water courses; and
(f) Such other factors as are outlined in any duly adopted stormwater erosion control ordinance.
(2) Where ditches and swales are used to drain street construction, the following requirements shall be met.
(a) With grades to 4%, ditches shall have sod bottoms and banks.
(b) With grades from 4% to 8%, ditches shall have concrete ditch checks spaced not more than 100 feet apart.
(3) With greater than 8% grades, ditches shall be rip-rapped or paved.
(4) Culverts shall be provided at all street intersections sized to eliminate flooding or ponding of water, and with a minimum cover of 12 inches. Culverts shall be constructed with flared end sections.
(5) All water inlet and outlet structures will provide for erosion control protection.
(Prior Code, § 153.055) (Ord. 1670, passed 6-11-1996)