Drainage On Private Property

The DPS Land Development Division reviews plans for conformance of drainage management in accordance with Bill 25-05 Stormwater - Drainage and Runoff. Building permit applications are checked to ensure compliance with Bill 25-05 though on-site drainage control as outlined in the Guidelines for Control of Water Runoff on Small Lots. The review determines whether plans are in compliance or if additional measures are needed resulting in further permitting needs such as a Public Right of Way Permit or Sediment Control Permit to meet the drainage needs.

Chapter 8, Section 8-29B of the Montgomery County Code establishes requirements to manage water runoff from new construction of single family dwellings and additions to single family dwellings on residential lots of less than 15,000 square feet.  Any application for a building permit for a new house that increases the existing lot coverage and/or changes the existing drain pattern must include provisions for the control or safe conveyance of any increase in runoff.  New houses that are built on lots covered by an approved on-site storm water management concept with on-site controls are exempted from the requirements of this legislation.  However, any application for a new house replacing a house built on a lot covered by an approved on-site storm water management concept with on-site controls must include provisions for the control or safe conveyance of the runoff.  Any application for a building permit for an addition that increases the building lot coverage by more than 400 square feet must include provisions for the control or safe conveyance of any increase in runoff.

If the discharges from the proposed impervious areas are managed on-site through the use of various types of approved methodologies as referenced in the Guidelines for Control of Water Runoff on Small Lots, no additional discharge conveyance review will be needed by the Land Development Right of Way staff.  Where the discharge pipe cannot be connected to an enclosed storm drainage system; extended through the curb; constructed to outfall into a drainage ditch; the potential creation of a drainage problem; or because of impracticality or economic infeasibility, an on-site investigation may be necessary to address and resolve, if possible, such situations on a case-by-case basis.

DPS review staff will assist customers in determining if plans as proposed meet the drainage criteria.