531 STORM WATER MANAGEMENT: PLAN

531.1 Every applicant shall submit to the Department a storm water management plan which meets the requirements of §§526 through 535 of this chapter.

531.2 The plan shall contain the following information:

1. (a) Supporting computations, drawings, and information sufficient to evaluate the environmental composition of the affected areas;
2. (b) The potential impacts of the proposed land development on water resources;
3. (c) The effectiveness and acceptability of measures for managing storm water runoff; and
4. (d) Maintenance and construction schedules.

531.3 The applicant shall certify on each drawing that all clearing, grading, drainage construction, and development shall be accomplished in strict accordance with the approved plan. Each plan submitted shall be signed by a professional engineer, licensed in the District of Columbia.

531.4 Each plan shall include, without limitation, the following information:

1. (a) Site characteristics:
2. (1) Topography survey showing existing and proposed contours, including area necessary to determine downstream analysis for proposed storm water management facility;
3. (2) Soils investigation including borings for construction of small ponds and infiltration practices (where applicable);
4. (3) Description of all water courses, impoundments and wetlands on, or adjacent to the site, or into which storm water flows;
5. (4) Delineation of one-hundred (100) year floodplain, (if applicable); and
6. (5) Structure classification (U.S. Department of Agriculture Soil Conservation Service (SCS) Pond Standard 378).
7. (b) Computations:
8. (1) Hydrological;
9. (2) Hydraulic; and
10. (3) Structural;
11. (c) Other items:
12. (1) Vicinity maps;
13. (2) Drainage area map showing the watershed boundaries, drainage area, and storm water flow paths;

(3) Proposed improvements including location of buildings or other structures, impervious surfaces, and storm drainage facilities, (if applicable);

(4) Location of utilities;

(5) Structural details for all components of the proposed drainage systems and storm water management facilities;

(6) Timing schedules and sequence of development clearing, including stripping, rough grading, construction, final grading, and vegetative stabilization;

(7) Maintenance responsibility and schedule;

(8) Notes on drawings specifying materials to be used;

(9) Construction materials and specifications as specified by the SCS or American Society for Testing and Materials (ASTM);

(10) Location of easements;

(11) Estimate of storm water management construction cost; and

(12) All storm water management plans shall be prepared utilizing a standard drawing size of 24 in. x 36 in. Unless otherwise approved, one of the following scales shall be used for the detailed storm water management plan; 1 in. equals 20 ft., 1 in. equals 30 ft., 1 in. equals 40 ft., 1 in. equals 50 ft. or 1 in. equals 80 ft. The drafting media used to prepare all plans shall yield first or second generation reproducible drawings with a minimum letter size of No. 4 (1/8 in.).

531.5 Following the receipt of an applicant's plan, the Department shall have ten (10) working days to approve or disapprove the plan. If a decision cannot be rendered within the ten (10) working days, the applicant shall be so notified in writing. The Department then shall have five (5) additional working days in which to render a final decision.

531.6 The approved plan shall serve as the basis for all outlined construction requiring storm water management.

SOURCE: Final Rulemaking published at 35 DCR 21, 24 (January 1, 1988).