15.20.01.05

.05 Construction or Reconstruction Design Criteria.

The design of a project shall conform to the following criteria:

A. Channel Design.

(1) An outlet shall be designated for each channel to permit the discharge of water by gravity flow or pumping.

(2) All channels shall be sloped and aligned to produce stable channels.

(3) Water Control Structures.

(a) The channel design shall include necessary water control structures for the efficient functioning of the channels. These structures include:

(i) Water control devices and weirs;

(ii) Flood gates;

(iii) Pumping bays; and

(iv) Other structures affecting the functioning of the channel.

(b) Water control structures shall be designed, where applicable, according to the provisions in Natural Resources Article, §4-501 et seq., Annotated Code of Maryland.

B. Flood Control.

(1) A project shall be designed to minimize upstream and downstream flooding.

(2) An association shall submit an analysis of a project's hydrological impact when downstream flooding exists or may result from a project and populated areas may be affected.

(3) Hydrological analysis shall include hydrological models and hydraulic calculations necessary to determine the changes to a 100-year frequency flood including modifications to:

(a) Water surface elevations;

(b) Water velocities; and

(c) Hydrograph timing.

(4) Formulae, models, and analysis methods for the hydrological analysis shall be subject to approval by the Secretary.

C. Erosion Control.

(1) A project shall be designed to minimize erosion and sediment deposition.

(2) Sediment traps shall be installed in key locations along channel reaches.

(3) Water control structures shall be designed for the entry of concentrated flow of water into a channel without significant deposition or degradation.

(4) A channel shall be designed to minimize overbank wash of channel spoil by:

(a) Diverting surface water around spoil banks;

(b) Protecting channel bank stability by properly placing spoil; or

(c) Sloping the finished surface of the spoil away from a channel.

D. Vegetated Strips.

(1) The following definitions describe the meaning of the terms used in §D:

(a) "Main channel" means the primary water course constructed or maintained by an association that drains water from a subwatershed or watershed area and lateral channels.

(b) "Lateral channel" means any watercourse constructed or maintained by an association that transports water from segments of a subwatershed or watershed to the main channel.

(2) Vegetated strips shall be designed, established, and maintained to stabilize the soil and to minimize the movement of sediment into a channel during operation.

(3) Measurements for a vegetated strip shall be made from the top of a channel bank.

(4) A minimum 10-foot wide vegetated strip shall be established and maintained along each cleared side of a main channel.

(5) A minimum 4-foot wide vegetated strip shall be established and maintained along each cleared side of a lateral channel only if acceptable BMPs submitted to the Secretary for approval are implemented on adjoining cropland. The following apply:

(a) Acceptable BMPs may include:

(i) Minimum tillage;

(ii) Seasonal cover crops;

(iii) Reverse berms;

(iv) Permanent sediment traps in on-farm channels; and

(v) Other methods to achieve a level of water quality protection equivalent to a 10-foot wide vegetated strip.

(b) In the absence of BMPs approved by the Secretary, a minimum 10-foot wide vegetated strip shall be established and maintained along each cleared side of a lateral channel.

(6) Vegetation shall be established and maintained to stabilize the soil on the sides of both channel banks.

E. Water Temperature Controls.

(1) One-sided or off-sided construction or reconstruction of a channel in woodland shall be used if practical.

(2) Both-sided construction of a channel in woodland shall be allowed by the Secretary only when it is the only practical construction method.

(3) Both-sided reconstruction of a channel in woodland shall be allowed by the Secretary when:

(a) It is the only practical reconstruction method; or

(b) Both-sided construction or reconstruction was previously used and both right-of-ways are clear of woody growth.

(4) Areas of trees, shrubs, and herbaceous growth that shade a channel shall be retained, replanted, or allowed to reestablish naturally, unless it can be demonstrated to the Secretary that the:

(a) Presence of trees and shrubs will prevent adequate access to a channel for maintenance; or

(b) Absence of these areas of trees and shrubs will not elevate water temperature to levels that will adversely impact fish or other aquatic life.

F. Wetlands Replacement. An association shall replace drained or filled, non-tidal wetlands as required by this section. The following are included:

(1) Land areas that are required to be replaced by an association under this section are those areas that:

(a) Support a predominance of plants that grow in water or in periodically water saturated soils;

(b) Have remained natural and uncultivated for at least 3 successive years; and

(c) When drained or filled, will cause water pollution by significantly:

(i) Increasing erosion and siltation, or

(ii) Reducing the area's ability to filter water pollutants.

(2) Land areas required to be replaced under this section shall be replaced as follows:

(a) One acre of land with equal soil-water conditions shall be created to replace each acre of drained or filled land when the:

(i) Water table is near the soil surface for extended periods during the frost-free growing season of most years; or

(ii) Soil is water-saturated, or surface water is present for extended periods during the frost-free growing season of most years.

(b) In all other cases, 1 acre of temporarily to permanently flooded land shall be created to replace every 4 acres of drained or filled land.

(3) The Secretary shall consult with the Secretaries of the Departments of Natural Resources and the Environment to determine if an association's construction or reconstruction plan adequately meets the requirement of this section.