No person shall develop any land for residential, commercial, industrial, or institutional uses without providing stormwater management measures that control or manage runoff from such developments, except as provided within this chapter. Stormwater management measures must be designed consistent with the Design Manual and constructed according to an approved plan for new development or the policies stated in § 465-8 of this chapter for redevelopment.
The following development activities are exempt from the provisions of this chapter and the requirements of providing stormwater management:
A. 
Agricultural land management practices;
B. 
Additions or modifications to existing single-family detached residential structures if they comply with Subsection C of this section;
C. 
Any developments that do not disturb over 5,000 square feet of land area; and
D. 
Land development activities that the Administration determines will be regulated under specific state laws which provide for managing stormwater runoff.
A. 
Except as provided in Subsections B and D of this section, the Department of Public Works shall grant stormwater management quantitative control waivers only to those projects within areas where watershed management plans have been developed consistent with Subsection G of this section. Written requests for quantitative stormwater management waivers shall be submitted that contain sufficient descriptions, drawings, and any other information that is necessary to demonstrate that ESD has been implemented to the MEP. A separate written waiver request shall be required in accordance with the provisions of this section if there are subsequent additions, extensions, or modifications to a development receiving a waiver.
B. 
Except as provided in Subsection D of this section, if watershed management plans consistent with Subsection G of this section have not been developed, stormwater management quantitative control waivers may be granted to the following projects, provided that it has been demonstrated that ESD has been implemented to the MEP:
(1) 
Projects that have direct discharges to tidally influenced receiving waters;
(2) 
Projects that are in-fill development located in a priority funding area where the economic feasibility of the project is tied to the planned density and where implementation of the 2009 regulatory requirements would result in a loss of the planned development density, provided that:
(a) 
Public water and sewer and stormwater conveyance exist;
(b) 
The quantitative waiver is applied to the project for the impervious cover that previously existed on the site only;
(c) 
ESD to the MEP is used to meet the full water quality treatment requirements for the entire development; and
(d) 
ESD to the MEP is used to provide full quantity control for all new impervious surfaces; or
(3) 
When the approving agency determines that circumstances exist that prevent the reasonable implementation of quantity control practices.
C. 
Except as provided in Subsection D of this section, stormwater management qualitative control waivers apply only to:
(1) 
In-fill development projects where ESD has been implemented to the MEP and it has been demonstrated that other BMPs are not feasible;
(2) 
Redevelopment projects if the requirements of § 465-8 of this chapter are satisfied; or
(3) 
Sites where the approving agency determines that circumstances exist that prevent the reasonable implementation of ESD to the MEP.
D. 
Stormwater management quantitative and qualitative control waivers may be granted for phased development projects if a system designed to meet the 2000 regulatory requirements and the Department of Public Works ordinance for multiple phases has been constructed by May 4, 2010. If the 2009 regulatory requirements cannot be met for future phases constructed after May 4, 2010, all reasonable efforts to incorporate ESD in future phases must be demonstrated.
E. 
Waivers shall only be granted when it has been demonstrated that ESD has been implemented to the MEP and must:
(1) 
Be on a case-by-case basis;
(2) 
Consider the cumulative effects of the Department of Public Works waiver policy; and
(3) 
Reasonably ensure the development will not adversely impact stream quality.
F. 
If the Department of Public Works has established an overall watershed management plan for a specific watershed, then the Department of Public Works may develop quantitative waiver and redevelopment provisions that differ from Subsection B of this section and § 465-8 of this chapter.
G. 
A watershed management plan developed for the purpose of implementing different stormwater management policies for waivers and redevelopment shall:
(1) 
Include detailed hydrologic and hydraulic analyses to determine hydrograph timing;
(2) 
Evaluate both quantity and quality management and opportunities for ESD implementation;
(3) 
Include a cumulative impact assessment of current and proposed watershed development;
(4) 
Identify existing flooding and receiving stream channel conditions;
(5) 
Be conducted at a reasonable scale;
(6) 
Specify where on-site or off-site quantitative and qualitative stormwater management practices are to be implemented;
(7) 
Be consistent with the General Performance Standards for Stormwater Management in Maryland found in the Design Manual; and
(8) 
Be approved by the Administration.
A. 
Stormwater management plans are required by the Department of Public Works for all redevelopment, unless otherwise specified by watershed management plans developed according to § 465-7G of this chapter. Stormwater management measures must be consistent with the Design Manual.
B. 
All redevelopment designs shall:
(1) 
Reduce impervious area within the limit of disturbance (LOD) by at least 50% according to the Design Manual;
(2) 
Implement ESD to the MEP to provide water quality treatment for at least 50% of the existing impervious area within the LOD; or
(3) 
Use a combination of Subsection B(1) and (2) of this section for at least 50% of the existing site impervious area.
C. 
Alternative stormwater management measures may be used to meet the requirements in section Subsection B of this section if the owner/developer satisfactorily demonstrates to the Department of Public Works that impervious area reduction has been maximized and ESD has been implemented to the MEP. Alternative stormwater management measures include, but are not limited to:
(1) 
An on-site structural BMP;
(2) 
An off-site structural BMP to provide water quality treatment for an area equal to or greater than 50% of the existing impervious area; or
(3) 
A combination of impervious area reduction, ESD implementation, and an on-site or off-site structural BMP for an area equal to or greater than 50% of the existing site impervious area within the LOD.
D. 
The Department of Public Works may develop separate policies for providing water quality treatment for redevelopment projects if the requirements of Subsections B and C of this section cannot be met. Any separate redevelopment policy shall be reviewed and approved by the Administration and may include, but not be limited to:
(1) 
A combination of ESD and an on-site or off-site structural BMP;
(2) 
Retrofitting, including existing BMP upgrades, filtering practices, and off-site ESD implementation;
(3) 
Participation in a stream restoration project;
(4) 
Pollution trading with another entity;
(5) 
Payment of a fee in lieu; or
(6) 
A partial waiver of the treatment requirements if ESD is not practicable.
E. 
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 of Public Works shall consider the prioritization of alternatives in Subsection D of this section 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 of Public Works may consider factors including, but not limited to:
(1) 
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;
(2) 
Whether the project is necessary to accommodate growth consistent with comprehensive plans; or
(3) 
Whether bonding and financing have already been secured based on an approved development plan.
F. 
Stormwater management shall be addressed according to the new development requirements in the Design Manual for any net increase in impervious area.
The Department of Public Works may grant a written variance from any requirement of Article IV, Stormwater Management Criteria, if there are exceptional circumstances applicable to the site such that strict adherence will result in unnecessary hardship and not fulfill the intent of this chapter. A written request for variance shall be provided to the Department of Public Works and shall state the specific variances sought and reasons for their granting. The Department of Public Works shall not grant a variance unless and until sufficient justification is provided by the person developing land that the implementation of ESD to the MEP has been investigated thoroughly.