SW7091208_COMPLIANCE_20091223

STORMWATER DIVISION CODING SHEET
POST -CONSTRUCTION PERMITS
PERMIT NO.
DOC TYPE
❑ CURRENT PERMIT
❑ APPROVED PLANS
❑ HISTORICAL FILE
COMPLIANCE EVALUATION INSPECTION
DOC DATE���
YYYYMMDD

•� STORMWATER SUBMITTAL REQUIREMENTS
INFILTRATION/EXFILTRATION SYSTEMS
Basins and Trench
Objective
A. Collect all runoff from all BUA (proposed and/or existing and/or offsite) as the case may be,
by any means including piping or swales, and direct it to the infiltration system.
B. Check the proposed basin/ trench design to make sure it meets or exceeds the minimum
design criteria for design storm, volume and drawdown. '•
II. What makes up a complete infiltration basin / trench application package?
A. Two sets of sealed, signed & dated layout & grading plans with appropriate details.
B. Completed application with supplement(s), SWU-101, SW401-Infiltration Trench, SW401-
Infiltration Basin, and inspection and maintenance agreements.
C. Deed restriction document, if applicable. (subdivisions & projects with out parcels)
D. Sealed, signed & dated calculations.
E. A soils report containing information in regard to the soil type, boring locations, seasonal high
water table elevation and expected infiltration rate.
F. Chlorides test results must be provided if the project is within'/Z mile of SR waters (Phase II):
(This, is only required to test out of SR water treatment requirements)
III. BIMS entry (for DWQ use only)
Enter & track application acknowledged date, review date, add info requested/received dates, permit
issue dates, and drainage area info. Best done after the add info letter is written and before sending
permit up for signature.
IV. Shell documents (for DWQ use'only)
Permit shells: s:\wqs\stormwater\shell\shighcominbasin
S:\wqs\stormwater\shells\highcomintrench
s:\wqs\stormwater\shells\highsubinbasin
s:\wqs\stormwater\shells\highsubintrench
Calculations: s:\wqs\stormwater\excel spreadsheets\inbasin
s:\wqs\stormwater\excel spreads heets\intrench
V. Review Procedure- look for consistency between the various elements of the package- application,
plan and calculations.
A. APPLICATION
1. Original signatures are required. Photocopied signatures cannot be accepted.
2. ✓A completed infiltration basin or infiltration trench supplement, one for each proposed
system. A signed, dated and notarized Inspection and Maintenance Agreement for
/each proposed system with an original signature.
3. V The elevations, areas and volumes reported on the supplement match up to the
Numbers used in the calculations and shown on the plan details.
4.v//Built-upon areas are reported in square feet in Section 111.6.
5.V Receiving stream name and classification.
6. Section 111.6 is filled in -cannot be left blank. One column must be filled in for each
/proposed infiltration basin or trench.
7. � If the applicant is a corporation, partnership or LLC, look it up on the Secretary of State
Corporations Database. Make sure corporation is spelled correctly (capitalization and
punctuation matter) and that the person signing the application is at least a vice-
president in the corporation, a General Partner in the partnership, a member in a
member -managed LLC, or the manager of a manager -managed LLC. Need
documentation to support if the Articles of Incorporation do not list the members or
managers of the LLC. If an agent signs, then a letter of authorization is needed from the
president, vice president, general partner, member or manager.
8. For subdivided projects, a signed and notarized deed restriction statement must be
rovided.
9. Soils report with the SHWT, Soil type and expected infiltration rate.

Infiltration Basin & Trench, cont.
B. CALCULATIONS
1. VThe basin ortrench must draw down within 5 days. Spray irrigation is not acceptable as
the sole means of drawdown.
2. I /The design storm is 1.5' if the project is,subject to Phase II or is sited within'/2 mile of
V and draining to SA waters. The design storm for projects subject to Phase II sited
within '% mile of and draining to SR waters must treat the difference between the pre
and post development conditions for the 1-yr 24-hr storm. Otherwise, use 1" design
storm.
3. Report the bottom surface area.
4. Report the surface area at the overflow elevation.
5./Show the calculation for the minimum required volume.
6. V Provide a table of elevations, areas, incremental volumes and accumulated volumes to
/demonstrate that the minimum required volume has been provided.
7. Calculations are signed, sealed & dated.
N'Report the Drainage Area and Built -upon area for each basin or trench.
The seasonal high water table must be at least 24" below'the proposed bottom
elevation of the system. For Phase 11 projects, at least 12" of this must be in naturally
occurring soils.
10 All runoff in excess of the design storm must bypass to a vegetated filter prior to
entering the basin or trench. If the system is designed to store a larger design storm
(generally 2-3 times the minimum), the requirement for an offline bypass can be waived.
Please contact the Division to determine what design storm 'is appropriate for the
project.

,f
Infiltration Basin & Trench, cont.
C. PLANS - Plan sheets should be kept to a minimum. For small commercial, single basin
projects, the plan set could consist of only 2 or 3 sheets, layout, grading and details. For
larger projects, show as much information as possible on as few sheets as possible, without
cluttering them up.
1. Development/Project Name
2. ngineer name and firm.
3. Legend
4.�// North Arrow
5. Location Map with nearest intersection of two major roads shown. Major road is any 1,
2, or 3 digit NC, US or interstate highway.
6. /Scale- standard engineering scale, no off-the-wall stuff.
7. Date
8.M:vision number and date, if applicable.
9. Original contours, proposed contours, spot elevations, finished floor elevations, pipe
1Winverts, swale inverts, etc.
Existing drainage (piping, swales, ditches, ponds, etc.), including off -site. Include a map
delineating the offsite drainage areas.
11 Property/Project boundary lines, bearing &distances.
12. Mean High Water Line or Normal High Water Line, if applicable.
13.1/ rainage easement locations shown on the plans along with their width.
14�Wetlands delineated, or a note on the plans that none exist. Provide a copy of the
wetlands delineation map signed by the Corps of Engineers, or have the applicant
include a copy of the unsigned delineation map submitted to the Corps. Infiltration
systems may not be located in wetlands unless a permit to fill those wetlands has been
dbtained and the soils meet the SHWT and hydraulic, conductivity requirements.
15.VDetails for the roads, parking, cul-de-sacs, including sidewalk width, radii, dimensions &
slopes.
14)/*'Apartment / Condo development- provide a typical building footprint with dimensions,
,and note all concrete and wood deck areas.
17 V The drainage area for each basin or trench is clearly delineated and numbered to match
up to the calculations and supplement. Drainage area delineation is best done as a
separate plan sheet.
18.I�A basin section detail showing bottom and storage elevations, 3:1 side slopes. The side
slopes of an infiltration basin are not restricted to vegetation. They may be hardened
with rock, timber, concrete, decorative brick, etc.
19V trench section detail with the perforated pipe diameter, filter fabric wrapped around
he pipe and around the trench, trench height and width, rock fill type.
2 fusing a pre-fab chamber structure, provide details of the chamber, including model #,
length, width, chamber volume and number of chambers being used.
21.V A,bypass structure detail is provided showing a trash rack with <_6" square openings,
and the necessary bypass weir or pipe elevation. Several types of bypass structure
✓designs are acceptable.
22. Dimensions for each line and arc formed by the bottom contour of an infiltration basin.
23V All runoff in excess of the design storm must pass through a vegetated filter prior to
being discharged into the receiving stream. The filter must be 50' long for SA waters
(v and 30' long for non -SA waters.
24YAII infiltration systems must be located at least 50' from the MHW line of surface waters.
25V Vegetation is specified for basin slopes not being hardened. Weeping Love Grass is not
/suitable as a permanent vegetated cover for side slopes.
20, All roof drainage must be directed to the system. Show the roof drain collection piping
on the plans. This is especially necessary for projects where the buildings back up the
property lines where roof drainage may leave the site prior to going through the system.
27✓Monitoring wells may be required on a case -by -case basis.