HomeMy WebLinkAboutAppendix 4-SOBO Lofts-Storm Water Management Permit Application PROJECT VICINITY MAP Project SiteBozeman Creek
SHEETDESIGNED BY:QUALITY CHECK:JOB NO.FIELDBOOKDRAWN BY:DATE:B16-070171/21, 176/83-8712/20/16SOBO LOFTS MIXED USE BUILDING
BOZEMAN, MONTANA
MONTANAWASHINGTONIDAHO
GREAT FALLS-BOZEMAN-KALISPELL-SHELBY
REV DATELEWISTONSPOKANE
Engineering
tdhengineering.com
NORTH DAKOTAWATFORD CITY REVISIONKLSMMN1MMN1BABCOCK STREET7TH AVENUEB16-070 SWPPPSTORM WATER PERMIT APPLICATION
EXHIBIT.DWG1 of 1J:\2016\B16-070 718 West Babcock\CADD\CIVIL\DWG\B16-070 SWPPP.dwg, 12/19/2016 3:54:30 PM, MMN1
Stormwater Management Permit - Narratives
Project Name: SOBO Lofts Mixed Use Building
718 West Babcock Street, Bozeman, Montana
P a g e 1 | 4
Best Management Practices (BMP) Narrative –
This Storm Water Management plan shall cover the demolitions to existing buildings and
construction of a new mixed-use building and associated parking lot at 718 West Babcock Street
in Bozeman, Montana. The contractor shall be responsible for the installation, inspection and
maintenance of all required BMPs on this project.
The contractor shall install silt fencing along the perimeter of the property, inlet protection at the
inlets at the intersection of 8th Avenue and Babcock Street and at the intersection of 7th Avenue
and Babcock Street, and a vehicle track pad prior to beginning any construction activities, and
shall maintain these BMPs for the entirety of the project. These BMPs shall be the exterior
sediment and erosion controls at the construction site. Within these exterior controls, the contractor
shall utilize proper BMPs for all aspects of construction and site management including but not
limited to utilizing catch pans, vacuuming pollutants from construction activities, and good
housekeeping of the construction site. The contractor shall properly collect and dispose of any
contaminated water so that it does not enter the storm drain system and shall have spill kits readily
available on site to mitigate chemical spills, if such chemicals are used onsite.
The contractor shall inspect all BMPs weekly and after a storm event, and shall repair/replace any
BMPs which are found to be inadequate or damaged. If one method does not provide sufficient
containment, the contractor shall immediately implement a more appropriate BMP. The contractor
shall be solely responsible for the implementation of the storm water management plan and shall
take all responsibility for any violations to the plan.
(3) Project Information –
The proposed work for this project is the demolition of the existing buildings and
construction of a new multi-use building and associated parking lot at 718 West Babcock
Street. The six phases of the construction process along with major construction activities
are outlined below:
1. Initial Site Protection: All BMPs shall be installed at the work site, construction
access shall be established, equipment shall be mobilized to the site, and
material storage areas shall be established.
2. Demolition: Existing site features shall be demolished per the demolition plan,
including existing buildings, asphalt, concrete, utilities and any vegetation.
3. Site Grading & Excavation: Excavations shall be performed as required per the
project plans, and the site will be graded to finished grade.
4. Installation of Utilities: New utilities shall be installed into trenches and
backfilled.
5. Vertical Construction: The construction of the new building shall be completed.
6. Final Stabilization: New sidewalk, curbs, concrete and asphalt shall be poured.
Landscaping shall be established. All equipment, BMPs and excess materials
shall be removed off-site.
Stormwater Management Permit - Narratives
Project Name: SOBO Lofts Mixed Use Building
718 West Babcock Street, Bozeman, Montana
P a g e 2 | 4
Stormwater Management Checklist –
(1) Silt fencing shall be installed around the perimeter of the project to prevent silt, dirt
and topsoil from washing off the site and into the streets, alleys, etc. Inlet protection
shall be installed around the storm drain inlets to prevent sediment from entering the
storm drain system. Vacuuming shall be utilized during any concrete and asphalt
sawcutting operations to collect all dust and slurry. A cattle guard-type vehicle tracking
pad will be established at the entrance to the site to prevent vehicles from tracking mud
onto adjacent streets. Street sweeping shall be used on an as-needed basis, especially
after a large storm, if any mud is tracked onto the street by construction vehicles. These
BPMs shall be established at the beginning of the project and shall be maintained
throughout all six phases to protect the entire site for the duration of the project.
(2) The contractor shall be responsible for the installation, inspection and maintenance of
all BMPs on the project. All erosion control BMPs shall be established at the initial site
protection phase prior to beginning any construction work. Silt fencing, inlet protection
and the vehicle tracking pad shall be inspected once a week and after a large storm
event, and shall be replaced if damaged or worn.
(3) The locations for spoil areas and staging areas within the construction site shall be
determined by the Contractor for each phase of the project. Utilizing perimeter silt
fencing allows for flexibility of spoil and staging area locations for each project phase
as long as these are located within the silt fence. Each spoil and staging area shall be
surrounded by a secondary silt fence or other appropriate BMP and covered by a tarp
or other means of stabilization.
(4) Permanent erosion and sediment control shall include the new hardscaping and
landscaping per the project plans. Hardscaping shall include new concrete sidewalks
and asphalt areas constructed with proper drainage per the project plans. Landscaping
areas shall be graded to drain away from the new structure. These post-construction
BMPs shall be installed during the final stabilization phase upon completion of all
building renovation. All initial site protection BMPs shall be sufficient for erosion and
sediment control for the previous phases of the project, but additional BMPs may be
utilized as needed.
(5) The US Environmental Protection Agency (EPA) website has links to all the
specifications for all erosion and sediment control BMPs and may be found online at
http://water.epa.gov/polwaste/npdes/swbmp/Construction-Site-Stormwater-Run-Off-
Control.cfm. The BMPs specific to all phases of this project include:
- Silt fence
- Curb inlet protection
- Vehicle tracking pad
- Street sweeping and vacuuming
- Concrete Washout
- Curb Rock Socks
Stormwater Management Permit - Narratives
Project Name: SOBO Lofts Mixed Use Building
718 West Babcock Street, Bozeman, Montana
P a g e 3 | 4
(6) The existing vegetation at the site will need to be removed to make room for the
proposed building and parking lot. Since the project site is so small, it will not be
feasible to protect any portion of the vegetation within the property boundary.
Protecting the existing city-maintained boulevard will act as a vegetated buffer to help
protect existing drainage patterns in the areas surrounding the project site. Storm water
generated from the site will pass through the established initial site protection BMPs to
prevent sediment and soil from leaving the construction site.
(7) Inactivity upon clearing is not expected because the proposed structure covers the
majority of the property and construction will utilize the entire site. Erosion control
blankets or other approved BMPs shall be used if construction is placed on hold or is
inactive for a period of 14-days or longer.
(8) The contractor shall cover any stockpiles at the end of each work day with a plastic tarp
or other impervious covering. The tarp shall be secured in place by gravel bags. The
contractor shall position any stockpiles within the silt fence in an area out of the way
for each construction phase.
(9) On days when wind is anticipated or encountered, the contractor shall wet any exposed
earth within the work area with a water hose to prevent wind erosion. If water is
ineffective, weighted down tarps shall be used to cover the area until the wind ceases
from lifting soil particles.
(10) Any upland runoff will follow the existing drainage patterns to the storm drain inlets
on 7th and 8th Avenues. If upland runoff enters the disturbed areas of the site, the
Contractor will be responsible for diverting the runoff around the project site and into
the existing storm drain inlet using curb socks. Maintenance of the inlet protection shall
need to be increased during this time.
(11) Silt fencing shall be installed around the disturbed area as a perimeter control to prevent
the run-off of sediment and soil. In addition, inlet protection shall be installed around
the storm drain inlets to catch small amounts of run-off which make it through the silt
fence.
(12) Silt fencing around the construction site and vacuuming up concrete dust and slurry
will protect adjacent properties from construction run-off.
(13) The contractor shall provide dumpsters for construction and other waste collection
within the construction site boundaries and shall coordinate for regular emptying of the
dumpsters. A proper hazardous waste area shall also be provided, if required. The
contractor shall determine the location of these waste collection areas within the work
site for each phase of the work.
(14) Chemicals shall be stored either in the contractor’s trailer on catch pans or outside in a
secure covered area on catch pans. Any outdoor chemical storage areas shall be located
within the construction site and out of the way of the work, shall be covered by a tarp,
and all chemicals shall be stored in their proper sealed and labeled containers in
secondary spill pans. Pollutants generated from construction activities shall be
Stormwater Management Permit - Narratives
Project Name: SOBO Lofts Mixed Use Building
718 West Babcock Street, Bozeman, Montana
P a g e 4 | 4
collected as close to the activity as possible. Slurry and dust from concrete sawcutting
shall be vacuumed and properly disposed during the sawcutting process, chlorinated
water from water line flushing shall be collected at the end of the line and disposed of
properly, excess concrete and concrete equipment shall be rinsed in proper concrete
washout areas, and various types of construction dust shall be vacuumed as created.
Water shall not be used to mitigate construction dust (other than for wind erosion) to
prevent pollutants from entering the storm drains. Proper spill kits shall be readily
available.
(15) Chemicals shall be disposed of per the manufacturer’s instructions.
(16) Hazardous waste shall be disposed of per the manufacturer’s instructions.
(17) The contractor shall perform daily cleanup of the construction site at the end of each
work shift. Waste shall be collected and disposed of into on-site dumpsters, excess
materials shall be properly stored, chemical or fuel spills shall be cleaned-up as they
occur, and dumpsters shall be emptied regularly so they do not over-flow.
(18) All applicable materials shall be recycled.
(19) The contractor shall provide an eco-pan or similar on site to use for concrete washout.
The contractor shall coordinate to have the washout material properly disposed when
the eco-pan becomes full. The eco-pan shall come with a cover to prevent rain-water
from filling the eco-pan and spilling washout material. The contractor shall determine
the location for the concrete washout area within the work site and away from any
work.
(20) All waste wash shall be contained to the washout basin/pit.
(21) The sanitary facilities shall be located within the project site which shall be surrounded
by a perimeter silt fence. The facilities shall be installed on level ground in a low-traffic
area and tied down on all sides to prevent them from falling over.
(22) There are no designated flood plains near the project site.
(23) There are no waterbodies within 200 feet of the project site.
(24) The following stormwater conveyance systems are present within 100 feet of the
project site:
Curb and gutter along Babcock Street to the north of the project site.
Two curb inlets to the storm drain system at the intersection of 8th Avenue
and Babcock Street.
Four curb inlets to the storm drain system at the intersection of 7th Avenue
and Babcock Street.
Silt Fence (SF) SC-1
November 2010 Urban Drainage and Flood Control District SF-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph SF-1. Silt fence creates a sediment barrier, forcing sheet flow runoff to evaporate or infiltrate.
Description
A silt fence is a woven geotextile fabric
attached to wooden posts and trenched into the ground. It is designed as a sediment barrier to intercept sheet flow
runoff from disturbed areas.
Appropriate Uses
A silt fence can be used where runoff is conveyed from a disturbed area as sheet flow. Silt fence is not designed to
receive concentrated flow or to be used as a filter fabric. Typical uses include:
Down slope of a disturbed area to
accept sheet flow.
Along the perimeter of a receiving
water such as a stream, pond or
wetland.
At the perimeter of a construction site.
Design and Installation
Silt fence should be installed along the contour of slopes so that it intercepts sheet flow. The maximum
recommended tributary drainage area per 100 lineal feet of silt fence, installed along the contour, is
approximately 0.25 acres with a disturbed slope length of up to 150 feet and a tributary slope gradient no steeper than 3:1. Longer and steeper slopes require additional measures. This recommendation only
applies to silt fence installed along the contour. Silt fence installed for other uses, such as perimeter
control, should be installed in a way that will not produce concentrated flows. For example, a "J-hook" installation may be appropriate to force runoff to pond and evaporate or infiltrate in multiple areas rather
than concentrate and cause erosive conditions parallel to the silt fence.
See Detail SF-1 for proper silt fence installation, which involves proper trenching, staking, securing the fabric to the stakes, and backfilling the silt fence. Properly installed silt fence should not be easily pulled
out by hand and there should be no gaps between the ground and the fabric.
Silt fence must meet the minimum allowable strength requirements, depth of installation requirement, and other specifications in the design details. Improper installation
of silt fence is a common reason for silt fence failure; however, when properly installed and used for the appropriate purposes, it can be highly effective.
Silt Fence
Functions
Erosion Control No
Sediment Control Yes
Site/Material Management No
SC-1 Silt Fence (SF)
SF-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Photograph SF-2. When silt fence is not installed along
the contour, a "J-hook" installation may be appropriate to ensure that the BMP does not create concentrated flow parallel to the silt fence. Photo courtesy of Tom Gore.
Maintenance and Removal
Inspection of silt fence includes observing the
material for tears or holes and checking for slumping fence and undercut areas bypassing flows. Repair of silt fence typically involves replacing the damaged
section with a new section. Sediment accumulated behind silt fence should be removed, as needed to
maintain BMP effectiveness, typically before it
reaches a depth of 6 inches.
Silt fence may be removed when the upstream area
has reached final stabilization.
Silt Fence (SF) SC-1
November 2010 Urban Drainage and Flood Control District SF-3
Urban Storm Drainage Criteria Manual Volume 3
SC-1 Silt Fence (SF)
SF-4 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Inlet Protection (IP) SC-6
August 2013 Urban Drainage and Flood Control District IP-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph IP-1. Inlet protection for a curb opening inlet.
Description
Inlet protection consists of permeable
barriers installed around an inlet to filter runoff and remove sediment prior to entering a storm drain inlet. Inlet
protection can be constructed from rock socks, sediment control logs, silt fence,
block and rock socks, or other materials
approved by the local jurisdiction. Area inlets can also be protected by
over-excavating around the inlet to
form a sediment trap.
Appropriate Uses
Install protection at storm sewer inlets that are operable during construction.
Consider the potential for tracked-out
sediment or temporary stockpile areas to contribute sediment to inlets when determining which inlets must be protected. This may include inlets in the general proximity of the construction area, not limited
to downgradient inlets. Inlet protection is not a stand-alone BMP and should be used in conjunction with
other upgradient BMPs.
Design and Installation
To function effectively, inlet protection measures must be installed to ensure that flows do not bypass the inlet protection and enter the storm drain without treatment. However, designs must also enable the inlet
to function without completely blocking flows into the inlet in a manner that causes localized flooding.
When selecting the type of inlet protection, consider factors such as type of inlet (e.g., curb or area, sump or on-grade conditions), traffic, anticipated flows, ability to secure the BMP properly, safety and other
site-specific conditions. For example, block and rock socks will be better suited to a curb and gutter along a roadway, as opposed to silt fence or sediment control logs, which cannot be properly secured in a curb and gutter setting, but are effective area inlet protection measures.
Several inlet protection designs are provided in the Design Details. Additionally, a variety of proprietary products are available for inlet protection that may be approved for use by local governments. If proprietary products are used, design details and installation procedures from the manufacturer must be
followed. Regardless of the type of inlet protection selected, inlet protection is most effective when combined with other BMPs such as curb socks and check dams. Inlet protection is often the last barrier
before runoff enters the storm sewer or receiving water.
Design details with notes are provided for these forms of inlet protection:
IP-1. Block and Rock Sock Inlet Protection for Sump or On-grade
Inlets
IP-2. Curb (Rock) Socks Upstream of Inlet Protection, On-grade
Inlets
Inlet Protection
(various forms)
Functions
Erosion Control No
Sediment Control Yes
Site/Material Management No
SC-6 Inlet Protection (IP)
IP-2 Urban Drainage and Flood Control District August 2013
Urban Storm Drainage Criteria Manual Volume 3
IP-3. Rock Sock Inlet Protection for Sump/Area Inlet
IP-4. Silt Fence Inlet Protection for Sump/Area Inlet
IP-5. Over-excavation Inlet Protection
IP-6. Straw Bale Inlet Protection for Sump/Area Inlet
CIP-1. Culvert Inlet Protection
Propriety inlet protection devices should be installed in accordance with manufacturer specifications.
More information is provided below on selecting inlet protection for sump and on-grade locations.
Inlets Located in a Sump
When applying inlet protection in sump conditions, it is important that the inlet continue to function
during larger runoff events. For curb inlets, the maximum height of the protective barrier should be lower than the top of the curb opening to allow overflow into the inlet during larger storms without excessive
localized flooding. If the inlet protection height is greater than the curb elevation, particularly if the filter
becomes clogged with sediment, runoff will not enter the inlet and may bypass it, possibly causing localized flooding, public safety issues, and downstream erosion and damage from bypassed flows.
Area inlets located in a sump setting can be protected through the use of silt fence, concrete block and
rock socks (on paved surfaces), sediment control logs/straw wattles embedded in the adjacent soil and stacked around the area inlet (on pervious surfaces), over-excavation around the inlet, and proprietary
products providing equivalent functions.
Inlets Located on a Slope
For curb and gutter inlets on paved sloping streets, block and rock sock inlet protection is recommended
in conjunction with curb socks in the gutter leading to the inlet. For inlets located along unpaved roads,
also see the Check Dam Fact Sheet.
Maintenance and Removal
Inspect inlet protection frequently. Inspection and maintenance guidance includes:
Inspect for tears that can result in sediment directly entering the inlet, as well as result in the contents of the BMP (e.g., gravel) washing into the inlet.
Check for improper installation resulting in untreated flows bypassing the BMP and directly entering the inlet or bypassing to an unprotected downstream inlet. For example, silt fence that has not been
properly trenched around the inlet can result in flows under the silt fence and directly into the inlet.
Look for displaced BMPs that are no longer protecting the inlet. Displacement may occur following larger storm events that wash away or reposition the inlet protection. Traffic or equipment may also
crush or displace the BMP.
Monitor sediment accumulation upgradient of the inlet protection.
Inlet Protection (IP) SC-6
August 2013 Urban Drainage and Flood Control District IP-3
Urban Storm Drainage Criteria Manual Volume 3
Remove sediment accumulation from the area upstream of the inlet protection, as needed to maintain BMP effectiveness, typically when it reaches no more than half the storage capacity of the inlet
protection. For silt fence, remove sediment when it accumulates to a depth of no more than 6 inches.
Remove sediment accumulation from the area upstream of the inlet protection as needed to maintain the functionality of the BMP.
Propriety inlet protection devices should be inspected and maintained in accordance with
manufacturer specifications. If proprietary inlet insert devices are used, sediment should be removed in a timely manner to prevent devices from breaking and spilling sediment into the storm drain.
Inlet protection must be removed and properly disposed of when the drainage area for the inlet has
reached final stabilization.
SC-6 Inlet Protection (IP)
IP-4 Urban Drainage and Flood Control District August 2013
Urban Storm Drainage Criteria Manual Volume 3
Inlet Protection (IP) SC-6
August 2013 Urban Drainage and Flood Control District IP-5
Urban Storm Drainage Criteria Manual Volume 3
SC-6 Inlet Protection (IP)
IP-6 Urban Drainage and Flood Control District August 2013
Urban Storm Drainage Criteria Manual Volume 3
Inlet Protection (IP) SC-6
August 2013 Urban Drainage and Flood Control District IP-7
Urban Storm Drainage Criteria Manual Volume 3
SC-6 Inlet Protection (IP)
IP-8 Urban Drainage and Flood Control District August 2013
Urban Storm Drainage Criteria Manual Volume 3
Vehicle Tracking Control (VTC) SM-4
November 2010 Urban Drainage and Flood Control District VTC-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph VTC-1. A vehicle tracking control pad constructed with properly sized rock reduces off-site sediment tracking.
Description
Vehicle tracking controls provide
stabilized construction site access where vehicles exit the site onto paved public roads. An effective vehicle tracking
control helps remove sediment (mud or dirt) from vehicles, reducing tracking onto
the paved surface.
Appropriate Uses
Implement a stabilized construction
entrance or vehicle tracking control where frequent heavy vehicle traffic exits the
construction site onto a paved roadway. An
effective vehicle tracking control is particularly important during the following conditions:
Wet weather periods when mud is easily tracked off site.
During dry weather periods where dust is a concern.
When poorly drained, clayey soils are present on site.
Although wheel washes are not required in designs of vehicle tracking controls, they may be needed at
particularly muddy sites.
Design and Installation
Construct the vehicle tracking control on a level surface. Where feasible, grade the tracking control towards the construction site to reduce off-site runoff. Place signage, as needed, to direct construction
vehicles to the designated exit through the vehicle tracking control. There are several different types of stabilized construction entrances including:
VTC-1. Aggregate Vehicle Tracking Control. This is a coarse-aggregate surfaced pad underlain by a
geotextile. This is the most common vehicle tracking control, and when properly maintained can be effective at removing sediment from vehicle tires.
VTC-2. Vehicle Tracking Control with Construction Mat or Turf Reinforcement Mat. This type of
control may be appropriate for site access at very small construction sites with low traffic volume over vegetated areas. Although this application does not typically remove sediment from vehicles, it helps protect existing vegetation and provides a stabilized entrance.
Vehicle Tracking Control
Functions
Erosion Control Moderate
Sediment Control Yes
Site/Material Management Yes
SM-4 Vehicle Tracking Control (VTC)
VTC-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Photograph VTC-2. A vehicle tracking control pad with wheel wash facility. Photo courtesy of Tom Gore.
VTC-3. Stabilized Construction Entrance/Exit with Wheel Wash. This is an aggregate pad, similar to VTC-1, but includes equipment for tire washing. The wheel wash equipment may be as simple as
hand-held power washing equipment to more advance proprietary systems. When a wheel wash is
provided, it is important to direct wash water to a sediment trap prior to discharge from the site.
Vehicle tracking controls are sometimes installed in combination with a sediment trap to treat runoff.
Maintenance and Removal
Inspect the area for degradation and replace aggregate or material used for a
stabilized entrance/exit as needed. If the area becomes clogged and ponds water,
remove and dispose of excess sediment
or replace material with a fresh layer of aggregate as necessary.
With aggregate vehicle tracking controls, ensure rock and debris from this area do not enter the public right-of-way.
Remove sediment that is tracked onto the public right of way daily or more frequently as needed. Excess sediment
in the roadway indicates that the stabilized construction entrance needs maintenance.
Ensure that drainage ditches at the entrance/exit area remain clear.
A stabilized entrance should be removed only when there is no longer the potential for vehicle tracking to
occur. This is typically after the site has been stabilized.
When wheel wash equipment is used, be sure that the wash water is discharged to a sediment trap prior to
discharge. Also inspect channels conveying the water from the wash area to the sediment trap and
stabilize areas that may be eroding.
When a construction entrance/exit is removed, excess sediment from the aggregate should be removed
and disposed of appropriately. The entrance should be promptly stabilized with a permanent surface
following removal, typically by paving.
Vehicle Tracking Control (VTC) SM-4
November 2010 Urban Drainage and Flood Control District VTC-3
Urban Storm Drainage Criteria Manual Volume 3
SM-4 Vehicle Tracking Control (VTC)
VTC-4 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Vehicle Tracking Control (VTC) SM-4
November 2010 Urban Drainage and Flood Control District VTC-5
Urban Storm Drainage Criteria Manual Volume 3
SM-4 Vehicle Tracking Control (VTC)
VTC-6 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Street Sweeping and Cleaning S-11
November 2010 Urban Drainage and Flood Control District SWC-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph SSC-1. Monthly street sweeping from April through November removed nearly 40,690 cubic yards of sediment/debris from Denver streets in 2009. Photo courtesy of Denver Public Works.
Description
Street sweeping uses mechanical pavement
cleaning practices to reduce sediment, litter and other debris washed into storm sewers by runoff. This can reduce
pollutant loading to receiving waters and in some cases reduce clogging of storm
sewers and prolong the life of infiltration
oriented BMPs and reduce clogging of outlet structures in detention BMPs.
Different designs are available with typical
sweepers categorized as a broom and conveyor belt sweeper, wet or dry
vacuum-assisted sweepers, and
regenerative-air sweepers. The effectiveness of street sweeping is
dependent upon particle loadings in the
area being swept, street texture, moisture conditions, parked car management,
equipment operating conditions and frequency of cleaning (Pitt et al. 2004).
Appropriate Uses
Street sweeping is an appropriate technique in urban areas where sediment and litter accumulation on streets is of concern for aesthetic, sanitary, water quality, and air quality reasons. From a pollutant
loading perspective, street cleaning equipment can be most effective in areas where the surface to be cleaned is the major source of contaminants. These areas include freeways, large commercial parking lots, and paved storage areas (Pitt et al. 2004). Where significant sediment accumulation occurs on
pervious surfaces tributary to infiltration BMPs, street sweeping may help to reduce clogging of infiltration media. In areas where construction activity is occurring, street sweeping should occur as part of construction site stormwater management plans. Vacuuming of permeable pavement systems is also
considered a basic routine maintenance practice to maintain the BMP in effective operating condition. See the maintenance chapter for more information on permeable pavement systems. Not all sweepers are
appropriate for this application.
Practice Guidelines1
1. Post street sweeping schedules with signs and on local government websites so that cars are not
parked on the street during designated sweeping days.
2. Sweeping frequency is dependent on local government budget, staffing, and equipment availability,
but monthly sweeping during non-winter months is a common approach in the metro Denver urban
1 Practice guidelines adapted from CASQA (2003) California Stormwater BMP Handbook, Practice SC-70 Road and Street
Maintenance.
S-11 Street Sweeping and Cleaning
SWC-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Changes in Street Sweeper Technology (Source: Center for Watershed Protection 2002)
At one time, street sweepers were thought to have great potential to remove stormwater pollutants from
urban street surfaces and were widely touted as a stormwater treatment practice in many communities. Street sweeping gradually fell out of favor, largely as a result of performance monitoring conducted as
part of the National Urban Runoff Program (NURP). These studies generally concluded that street
sweepers were not very effective in reducing pollutant loads (USEPA, 1983). The primary reason for the mediocre performance was that mechanical sweepers of that era were unable to pick up fine-grained
sediment particles that carry a substantial portion of the stormwater pollutant load. In addition, the performance of sweepers is constrained by that portion of a street’s stormwater pollutant load delivered from outside street pavements (e.g., pollutants that wash onto the street from adjacent areas or are
directly deposited on the street by rainfall). Street sweeping technology, however, has evolved considerably since the days of the NURP testing. Today, communities have a choice in three basic
sweeping technologies to clean their urban streets: traditional mechanical sweepers that utilize a broom
and conveyor belt, vacuum-assisted sweepers, and regenerative-air sweepers (those that blast air onto the pavement to loosen sediment particles and vacuum them into a hopper).
For more information, see
http://www.cwp.org/Resource_Library/Center_Docs/PWP/ELC_PWP121.pdf
area. Consider increasing sweeping frequency based on factors such as traffic volume, land use, field observations of sediment and trash accumulation, proximity to watercourses, etc. For example:
Increase the sweeping frequency for streets with high pollutant loadings, especially in high traffic
and industrial areas.
Conduct street sweeping prior to wetter seasons to remove accumulated sediments.
Increase the sweeping frequency for streets in special problem areas such as special events, high
litter or erosion zones.
3. Perform street cleaning during dry weather if possible.
4. Avoid wet cleaning the street; instead, utilize dry methods where possible.
5. Maintain cleaning equipment in good working condition and purchase replacement equipment as needed. Old sweepers should be replaced with more technologically advanced sweepers (preferably
regenerative air sweepers) that maximize pollutant removal.
6. Operate sweepers at manufacturer recommended optimal speed levels to increase effectiveness.
7. Regularly inspect vehicles and equipment for leaks and repair promptly.
8. Keep accurate logs of the number of curb-miles swept and the amount of waste collected.
9. Dispose of street sweeping debris and dirt at a landfill.
10. Do not store swept material along the side of the street or near a storm drain inlet.
Concrete Washout Area (CWA) MM-1
November 2010 Urban Drainage and Flood Control District CWA-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph CWA-1. Example of concrete washout area. Note gravel tracking pad for access and sign.
Description
Concrete waste management involves
designating and properly managing a specific area of the construction site as a concrete washout area. A concrete
washout area can be created using one of several approaches designed to receive
wash water from washing of tools and
concrete mixer chutes, liquid concrete waste from dump trucks, mobile batch
mixers, or pump trucks. Three basic
approaches are available: excavation of a pit in the ground, use of an above ground
storage area, or use of prefabricated haul-
away concrete washout containers. Surface discharges of concrete washout
water from construction sites are prohibited.
Appropriate Uses
Concrete washout areas must be designated on all sites that will generate concrete wash water or liquid
concrete waste from onsite concrete mixing or concrete delivery.
Because pH is a pollutant of concern for washout activities, when unlined pits are used for concrete
washout, the soil must have adequate buffering capacity to result in protection of state groundwater standards; otherwise, a liner/containment must be used. The following management practices are recommended to prevent an impact from unlined pits to groundwater:
The use of the washout site should be temporary (less than 1 year), and
The washout site should be not be located in an area where shallow groundwater may be present, such as near natural drainages, springs, or wetlands.
Design and Installation
Concrete washout activities must be conducted in a manner that does not contribute pollutants to surface
waters or stormwater runoff. Concrete washout areas may be lined or unlined excavated pits in the ground, commercially manufactured prefabricated washout containers, or aboveground holding areas constructed of berms, sandbags or straw bales with a plastic liner.
Although unlined washout areas may be used, lined pits may be required to protect groundwater under certain conditions.
Do not locate an unlined washout area within 400 feet
of any natural drainage pathway or waterbody or within 1,000 feet of any wells or drinking water sources. Even for lined concrete washouts, it is
advisable to locate the facility away from waterbodies and drainage paths. If site constraints make these
Concrete Washout Area
Functions
Erosion Control No
Sediment Control No
Site/Material Management Yes
MM-1 Concrete Washout Area (CWA)
CWA-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
setbacks infeasible or if highly permeable soils exist in the area, then the pit must be installed with an impermeable liner (16 mil minimum thickness) or surface storage alternatives using prefabricated
concrete washout devices or a lined aboveground storage area should be used.
Design details with notes are provided in Detail CWA-1 for pits and CWA-2 for aboveground storage areas. Pre-fabricated concrete washout container information can be obtained from vendors.
Maintenance and Removal
A key consideration for concrete washout areas is to ensure that adequate signage is in place identifying the location of the washout area. Part of inspecting and maintaining washout areas is ensuring that
adequate signage is provided and in good repair and that the washout area is being used, as opposed to washout in non-designated areas of the site.
Remove concrete waste in the washout area, as needed to maintain BMP function (typically when filled to
about two-thirds of its capacity). Collect concrete waste and deliver offsite to a designated disposal location.
Upon termination of use of the washout site, accumulated solid waste, including concrete waste and any
contaminated soils, must be removed from the site to prevent on-site disposal of solid waste. If the wash water is allowed to evaporate and the concrete hardens, it may be recycled.
Photograph CWA-3. Earthen concrete washout. Photo courtesy of CDOT. Photograph CWA-2. Prefabricated concrete washout. Photo courtesy of CDOT.
Concrete Washout Area (CWA) MM-1
November 2010 Urban Drainage and Flood Control District CWA-3
Urban Storm Drainage Criteria Manual Volume 3
MM-1 Concrete Washout Area (CWA)
CWA-4 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Rock Sock (RS) SC-5
November 2010 Urban Drainage and Flood Control District RS-1
Urban Storm Drainage Criteria Manual Volume 3
Photograph RS-1. Rock socks placed at regular intervals in a curb line can help reduce sediment loading to storm sewer inlets. Rock socks can also be used as perimeter controls.
Description
A rock sock is constructed of gravel
that has been wrapped by wire mesh or a geotextile to form an elongated cylindrical filter. Rock socks are
typically used either as a perimeter control or as part of inlet protection.
When placed at angles in the curb line,
rock socks are typically referred to as curb socks. Rock socks are intended to
trap sediment from stormwater runoff
that flows onto roadways as a result of construction activities.
Appropriate Uses
Rock socks can be used at the perimeter
of a disturbed area to control localized
sediment loading. A benefit of rock socks as opposed to other perimeter controls is that they do not have to be trenched or staked into the
ground; therefore, they are often used on roadway construction projects where paved surfaces are present.
Use rock socks in inlet protection applications when the construction of a roadway is substantially complete and the roadway has been directly connected to a receiving storm system.
Design and Installation
When rock socks are used as perimeter controls, the maximum recommended tributary drainage area per
100 lineal feet of rock socks is approximately 0.25 acres with disturbed slope length of up to 150 feet and
a tributary slope gradient no steeper than 3:1. A rock sock design detail and notes are provided in Detail RS-1. Also see the Inlet Protection Fact Sheet for design and installation guidance when rock socks are
used for inlet protection and in the curb line.
When placed in the gutter adjacent to a curb, rock socks should protrude no more than two feet from the curb in order for traffic to pass safely. If located in a high traffic area, place construction markers to alert
drivers and street maintenance workers of their presence.
Maintenance and Removal
Rock socks are susceptible to displacement and breaking due to vehicle traffic. Inspect rock socks for damage and repair or replace as necessary. Remove sediment by sweeping or vacuuming as needed to maintain the functionality of the BMP, typically when sediment
has accumulated behind the rock sock to one-half of the sock's height.
Once upstream stabilization is complete, rock socks and
accumulated sediment should be removed and properly disposed.
Rock Sock
Functions
Erosion Control No
Sediment Control Yes
Site/Material Management No
SC-5 Rock Sock (RS)
RS-2 Urban Drainage and Flood Control District November 2010
Urban Storm Drainage Criteria Manual Volume 3
Rock Sock (RS) SC-5
November 2010 Urban Drainage and Flood Control District RS-3
Urban Storm Drainage Criteria Manual Volume 3