06_Dry Weather Flow Screening Program

Appendix G to Stormwater Management Program (SWMP)
Dry Weather Flow Screening Program
11 January 2013
1. Dry Weather Definition
Dry weather is no rainfall greater than .1 (one tenth) inch in the past 72 hours.
2. Screening Method
The City has identified and located approximately 168 outfalls to the various streams that
run through and around the city. The City will conduct routine dry weather flow
screening of these outfalls in accordance with this appendix, which acts as a supplement
to Section 3.3 Mapping and Field Screening in High Priority Areas.
Once an outfall has been selected for screening in accordance with Section 5 below, the
City will inspect the outfall twice over a two day period during dry weather. In
commercial or industrial areas, screening should take place between the hours of 9:00 am
and 5:00 pm during the work week. In residential areas, field screening should be
scheduled either before 9:00 am or after 5:00 pm when citizens are most likely to be
home and illegal discharges are more likely to be evident. The City Inspector will
complete the Outfall Reconnaissance Inventory Field Sheet for each outfall being
screened. The City Inspector will make a determination based on the screening as to the
potential for an illicit discharge based on the criteria below.
If an outfall has the potential for an illicit discharge, the inspector will conduct an
additional two day dry weather screening. After this additional two day screening, the
City Inspector make a determination if an illicit discharge is suspected or unlikely.
If the Inspector determines that the outfall has a suspected illicit discharge, he will then
attempt to track the suspected illicit discharge to its source (see Section 3.3 Mapping and
Field Screening in High Priority Areas). This can include sampling the Stormwater for
certain constituents over time, opening up and following the pipe or open conveyance
upstream, and other methods.
If the Inspector has reason to believe that a particular activity or location is the source of
an illicit discharge, he will take action as detailed in the Illegal Discharge Control
Ordinance (Section 6.6 of the Unified Development Ordinance).
The Inspector will document all activities under this appendix and cause to have the data
entered into the City's GIS.
3. Criteria for Determining a Suspected Illicit Discharge
Any non-stormwater discharge not expressly allowed in permit is an illicit discharge. A
potential illicit discharge is indicated by a flowing outfall during dry weather. The basic

criteria for the determination are when two or more observations of flow, odor, color,
turbidity, or floatables coincide with one or more observations at least moderately sever
(mildly, moderately, or strongly). A suspected illicit discharge must be confirmed by
identifying the source
4. Method for Tracking Outfall Information
The City Inspector will complete the Outfall Reconnaissance Inventory Field Sheet for
each outfall being screened. This information can be recorded on the paper copy or the
electronic copy of the Field Sheet. Selected information from the Field Sheet will be then
be placed into an excel spreadsheet and provided to the City's GIS Management Team
for placement into the City's GIS.
5. Measurable Goals for Dry Weather Screening
The City will conduct dry weather screening on four (4) outfalls a quarter; three (3)
outfalls should be located in priority areas BDW (Big Ditch Watershed) or SCW (Stoney
Creek West).
6. Equipment, Communications, and Safety
Basic equipment for the City Inspector will include a measuring tape or stick, water proof
boots, reflective vest, clip board or notebook, Field Sheets, and writing instrument. The
City Inspector may also have a hand held GPS system to confirm the location of the
outfall.
The City Inspector will have a means of communication to City departments such as a
two-way radio, cell phone, or wireless tablet.
The following safety measures will be followed.
• No confined space entry will be conducted by City Inspectors during dry weather
field screening..
• Any remote location screening will be conducted by two persons; the Director of
Engineering will make this determination prior to assigning locations for screening.
• The City Inspector will use the appropriate preventive measures during hot weather to
avoid heat injury or bug bites (hat, sun screen, bug repellant, carry water).
• The City Inspector will use the appropriate preventive measures during cold weather
to prevent cold weather injury (warm dress, layered, attention to falling
temperatures). Inspection of outfalls should not be attempted during periods of
freezing weather.

Outfall Reconnaissance Inventory Field Sheet
Section 1: Background Data
Sub -watershed:
Outfall ID:
Today's date:
Time (Military):
Investigator:
Feature:
Temperature (°F):
Rainfall (in.) in Last 72 hours:
Latitude:
Longitude:
Nearest Intersection:
Stain if Present:
Debris if present:
Sketch:
Notes (e.g.., damaged, vegetation, blockage, ):
Section 2: Outfall Description
LOCATION
MATERIAL
SHAPE
DIMENSIONS (IN.)
SUBMERGED
❑ RCP ❑
❑ Circular
❑ Single
Diameter/Dimensions:
In Water:
CUP
❑ No
❑ Elliptical
❑ Double
❑ Partially
❑ PVC ❑
❑ Fully
❑ Closed Pipe
HDPE
❑ Box
❑ Triple
With Sediment:
❑ Steel
❑ Other:
❑ Other:
❑ No
❑ Partially
❑ Other:
❑ Fully
❑ Concrete
❑ Trapezoid
Depth:
❑ Earthen
❑ Open drainage
❑ Parabolic
Top Width:
❑ rip -rap
❑ Other:
Bottom Width:
El Other:
Section 3: Characterization
FIELD OBSERVATION FOR FLOWING OUTFALLS
PARAMETER
FIRST OBSERVATION
SECOND OBSERVATION
COMMENTS
Date
Time
Flow (yes/no)
Standing Water (yes/no)
Direction of Flow
Flow (trickle, medium, heavy)
Odor (faint, noticeable, strong)
Color (faint, noticeable, clearly visible)
Turbidity (slight, cloudy, opaque)
Floatables (few, some, obvious source)
Potential for Illicit Discharge
(Unlikely, Potential, Suspected, Obvious)

Notes