§ 17.10.080. Stormwater management criteria.

A.

The minimum control requirements established in this section and the Design Manual are as follows:

1.

The Department of Public Works requires that the planning techniques, nonstructural practices, and design methods specified in the Design Manual are to be used to implement ESD to the MEP. The use of ESD planning techniques and treatment practices must be exhausted before any structural BMP is implemented. Stormwater management plans for development projects subject to this Ordinance shall be designed using ESD sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the Design Manual. The MEP standard is met when channel stability is maintained, predevelopment groundwater recharge is replicated, nonpoint source pollution is minimized, and structural stormwater management practices are used only if determined to be absolutely necessary.

2.

Control of the two and ten-year frequency storm event shall be required according to the design manual if the Department of Public Works determines that historical flooding problems exist and impact existing downstream floodplain development.

3.

The Director of the Department of Public Works may require more than the minimum control requirements specified in this section if hydrologic or topographic conditions warrant or if flooding, stream channel erosion, or water quality problems exist downstream from a proposed project.

4.

Alternative minimum control requirements may be adopted subject to Administration approval. The Administration shall require a demonstration that alternative requirements will implement ESD to the MEP and control flood damages, accelerated stream erosion, water quality, and sedimentation. Comprehensive watershed studies may also be required.

5.

Stormwater management and development plans where applicable, shall be consistent with adopted and approved watershed management plans or flood management plans as approved by the Maryland Department of the Environment in accordance with the Flood Hazard Management Act of 1976.

B.

In the case of redevelopment, every stormwater management plan shall satisfy the following requirements.

1.

The stormwater management plan shall be consistent with the Design Manual.

2.

The stormwater management plan shall reduce existing site impervious areas by at least fifty percent. Where site conditions prevent the reduction of impervious area by fifty percent, the stormwater management plan shall provide qualitative control for at least fifty percent of the site's existing impervious area. When a combination of impervious area reduction and stormwater practice implementation is used, the combined area shall equal or exceed fifty percent of the site's impervious area. Any permit application legally submitted prior to April 9, 2007, shall meet the requirements of the unamended regulation.

3.

Upon application by the owner or his or her agent, the Director of Public Works may waive the requirements of the preceding paragraph if hydrologic and hydraulic design conditions prevent impervious area reduction or on-site stormwater management. Waivers shall be consistent with Section 17.10.120 of this Code. In granting such a waiver, the Director shall direct the applicant to the following practical alternatives:

a.

Off-site BMP implementation for a drainage area at least one and one-half times the size and percent imperviousness to that of the project;

b.

Watershed or stream restoration;

c.

Retrofitting; and/or

d.

Other practices to reduce impervious surfaces or the impact of stormwater runoff not inconsistent with the purposes of this chapter.

4.

The Department of Public Works may develop separate policies for providing water quality treatment for redevelopment projects. Any separate redevelopment policy shall be reviewed and approved by the Administration and may include, but not be limited to:

a.

A combination of ESD and an on-site or off-site structural BMP;

b.

Retrofitting including existing BMP upgrades, filtering practices, and off-site ESD implementation;

c.

Participation in a stream restoration project;

d.

Pollution trading with another entity;

e.

Payment of a fee-in-lieu; or

f.

A partial waiver of the treatment requirements if ESD is not practicable.

5.

The determination of what alternatives will be available may be made by the Department of Public Works at the appropriate point in the development review process. The Department shall consideration the prioritization of alternatives in Section 17.10.08[0].B.4. of this Code after it has been determined that it is not practicable to meet the 2009 regulatory requirements using ESD. In deciding what alternatives may be required, the Department may consider factors including, but not limited to:

a.

Whether the project is in an area targeted for development incentives such as a Priority Funding Area, a designated Transit Oriented Development area, or a designated Base Realignment and Closure Revitalization and Incentive Zone;

b.

Whether the project is necessary to accommodate growth consistent with comprehensive plans; or

c.

Whether bonding and financing have already been secured based on an approved development plan.

(Ord. O-30-08 Amended § 1 (part), 2009: Ord. O-25-07 Amended § 1 (part), 2007: Ord. O-50-06 § 1 (part), 2007: Ord. O-26-03 § 1 (part): Ord. O-10-02 § 1 (part))

(Ord. No. O-59-09, § I, 12-21-2009; Ord. No. O-26-10, § I, 9-13-2010)