Journal of the NACAA
ISSN 2158-9429
Volume 8, Issue 1 - June, 2015


Greening the Department of Public Works Facility

Rector, P., County Environmental Resource Mgmt Agent, Rutgers Cooperative Extension
Christopher C. Obropta, Water Resources Specialist, Rutgers Cooperative Extension


There are a variety of stormwater Best Management Practices (BMPs) that have been utilized to address stormwater runoff in urban/suburban watersheds.  This paper examines the benefit of utilizing these well documented stormwater BMPs in a case study for one specific sector of local government, the municipal Department of Public Works.  By installing a variety of BMPs the implementation achieved an 89% disconnection of impervious surfaces and concomitant reduction in volume, total suspended solids, total phosphorus and total nitrogen.  This case study provides an example for others in this or similar sectors.


Many successful Extension efforts package well-accepted practices into a comprehensive program so that a particular group, organization or sector can easily integrate these practices into their particular domain to solve their problems.  Department of Public Works (DPW) facilities have been identified as one sector that is a potential source of stormwater pollution to streams and rivers under the New Jersey Department of Environmental Protection’s (NJDEP’s) Stormwater Municipal Separate Storm Sewer System (MS4) regulations.  The General MS4 permit requires DPW facilities to be regularly inspected and for standard operating procedures (SOPs) to be established to ensure that stormwater runoff from the site has minimal negative impacts on local waterways.

As part of a watershed restoration implementation program, the Rutgers Cooperative Extension (RCE) installed various stormwater best management practices (BMPs) at the DPW facilities in the Troy Brook watershed, Morris County, New Jersey.  One goal of this program was to serve as a model for others in the same sector, who are, or will need to, implement stormwater management practices to address similar problems.  The BMPs allow DPW yards to achieve compliance with their permit in the most cost-effective and environmentally conscious manner. The BMPs that were installed are all accepted practice methods known to infiltrate stormwate runoff and provide varying levels of pollutant removal (Barr Engineering,2006; Dietz, 2005; New Jersey Department of Environmental Protection (NJDEP),2004; Passeport, Hunt, Line & Brown, 2009;  USGS, 2005). 


Site description

A typical DPW facility may have large amounts of impervious surfaces.  The case study we present is the Parsippany-Troy Hills (PTH) Department of Public Works (DPW) facility in Morris County, N.J. with an additional example from the Mountain Lakes (ML) DPW, Morris County, N.J.  Both DPWs are located within the Troy Brook watershed.   The Troy Brook has been identified by the N.J. Department of Environmental Protection (NJDEP) as impaired for biological life based upon macroinvertebrate sampling conducted by NJDEP and RCE (NJDEP, 2014).  The RCE Water Resources Program developed a regional stormwater management plan for the Troy Brook watershed in 2006 that identified sites where stormwater management practices could be installed to reduce stormwater runoff from entering the Troy Brook.  As with many urban/suburban sites, there were many inputs into the Troy Brook; The Parsippany-Troy Hills DPW facility was one of these sites and was listed as a high priority due to its proximity to the stream and the potential impacts from the activities at the site.

The PTH DPW facility is three acres, of which approximately 2.1 acres are impervious cover (Fig. 1).  New Jersey’s stormwater management rules underwent major changes between the time the Troy Brook regional stormwater management plan was initiated and the installation of the stormwater BMPs at the DPW.  Over the lifetime of this program the DPW has gone above and beyond the New Jersey Stormwater Rules.  For the New Jersey water quality design storm (1.25 inches of rain over two hours), an estimate of the runoff volume from the impervious cover on the PTH DPW site is 9,529 cubic feet (71,275 gallons).  Therefore the task was to install practices that would reduce the runoff from the impervious surfaces while not detracting from the ability of the facility to conduct its tasks.  Through the implementation of these stormwater BMPs the PTH DPW achieves theoretical complete stormwater disconnection during the 1.25 inch/two-hour storm.

BMP prioritization

The process for reducing the impact of stormwater runoff from impervious surfaces is to first try to eliminate impervious surfaces through depaving, which is the removal of asphalt or concrete and replacing these surfaces with permeable surfaces such as turfgrass.  Depaving was not thought to be feasible at this site.  The constant movement of heavy trucks in and out of the site would compact the area, leading to a surface that functioned to some extent as impermeable.  A second option is to try to replace impervious surfaces with pervious surfaces.  Since the DPW facility needed hard surfaces for vehicle traffic, replacing traditional asphalt surfaces with permeable pavement systems was not a good option except for the fire access lane located behind the DPW garage/office.  A third option is to intercept the stormwater runoff from impervious surfaces prior to it entering a receiving waterbody or running off the property.  This final option is often referred to as “disconnecting” the impervious surface.  Typically bioretention systems or bioswales are used to disconnect an impervious surface.  These systems capture, treat and infiltrate stormwater runoff, dramatically reducing the stormwater runoff volume leaving the site.  At times rainwater harvesting systems are also used to disconnect impervious surfaces and the harvested rainwater can be used to satisfy non-potable water needs at the facility.

The stormwater BMPs that were installed at the two DPW facilities are shown in Table 1 and discussed below.  While costs for each BMP are provided, some of the BMPs were installed by the DPW staff so construction costs were not included.  The drainage area for each BMP is provided in Table 1.  The locations on the PTH of  the BMPs are shown in Figure 1.


Figure 1.  Parsippany Troy-Hills Department of Public Works.  Troy Brook is outlined in blue and locations of stormwater Best Management Practices are identified.


Table 1. Stormwater Best Management Practice (BMP).

Stormwater Best

Management Practice (BMP)

Impervious Area

Disconnected (ft2 )

Total Cost (design,

materials and


Grassed Pavers (Permeable


9,000 $39,500

Sedimentation Chambers

(pretreatment for the vegetated



$13,693 (materials

and design only)

Vegetated Swale 66,320

$7,000 (materials and

design only)

Cistern 5,500 $10,000
Rain Garden 1,800

$4,000 (materials and

design only)

















Permeable Pavement

There are several different types of permeable pavement that can be utilized for the reduction and treatment of stormwater runoff from small storm events.  These stormwater BMPs are: interlocking pavers; pervious concrete; and porous asphalt.  Pervious concrete and porous asphalt have both been shown by research to perform better than conventional pavement with issues such as black ice since the runoff/snowmelt will drain quickly alleviating the potential to freeze.  This also reduces the freeze/thaw action that takes a toll on many roads and parking lots in the colder climates.  The downside of porous asphalt is its inability to handle heavy traffic loads.  It is often more appropriate for installation in the stalls of parking lots.

Grass pavers and interlocking paving block systems have void spaces that allow water to pass through the surface into an underlying stone reservoir for storage and slow release to the soil below.  These systems are often placed on roads or parking areas that do not receive heavy traffic.  At the PTH DPW, Turfstone® grass pavers were installed on an emergency access road behind the main office building (Fig. 2) and DPW garage (Turfstone, Unilock, Hengestone Holdings, Toronto, ON).  The pavers allow grass to grow between them, decreasing the amount of runoff from the area and allowing infiltration.  The pavers have reduced stormwater runoff from the road, and the rooftop of the DPW garage where the staff offices are located.  Previously, drainage from the rooftop of the DPW garage had caused flooding in the offices.  The rooftop runoff originally discharged onto the emergency access road where it accumulated and eventually seeped into the building, causing physical symptoms such as headaches and health concerns due to mold issues.  Now the roof runoff from the DPW garage completely infiltrates into the grass pavers.  During Hurricane Irene, Parsippany-Troy Hills received more than 7-inches of rain; the building remained dry.


Figure 2.  Interlocking grass pavers installed at the Parsippany-Troy Hills Department of Public Works.

The area utilized to install the pavers was approximately 180 ft. x 12 ft. (2,160 ft2).  The treatment area is estimated at 2,000 ft2 for the access road and 7,160 ft2 for the roof top drainage.  The estimated gallons of rainwater captured and treated each year is 105,862 gallons/yr through the installation of the pervious pavers.  Although this was not installed by the DPW staff, this type of installation would be within the abilities of most DPW to install with in-house resources.

Maintenance includes mowing, irrigation as necessary especially in the first year and fertilization if needed.  Irrigation and fertilization were not required at this site.  Replacement seeding may be necessary if bare areas become apparent.  If erosion becomes apparent, the flow should be slowed perhaps with a few stones to break the velocity.  Deicing salts should not be used as this would negatively impact the grasses.  A standard plow may be used to clear the surface of snow.

The cost to install the Turfstone® grass pavers was $36,000 for labor and materials.  Design costs were $3,500.

Vegetated swale

A vegetated swale is a channel to move stormwater between locations while providing filtering and allowing for settling and infiltration.  The channel installed at the PTH DPW was 1,200 linear feet.  The entire eastern half of the DPW site drained to a ditch along the north western side of the property, carrying all the stormwater runoff directly to the Troy Brook.  This drainage ditch was converted into a vegetated swale with check dams to promote settling of sediment.  The drainage area for the vegetated swale is 66,300 square feet, which is approximately 72% of the impervious surface of the DPW site.  On an annual basis this runoff that the vegetated swale is treating is approximately 1.6 million gallons.

Pollutant removal for swales is estimated at 81% for total suspended solids, 38% for nitrate, 9% total phosphorus and 62% for hydrocarbons (US EPA 1999).  Reductions for some metals such as cadmium (42%), copper (51%), lead (67%) and zinc (71%) are also shown for vegetated swales (US EPA 1999).  As the swale receives runoff from a parking lot with a fueling station, the swale was vegetated with plants that are known for their ability to remove hydrocarbons such as switchgrass, ryegrass and big bluestem (Frick, 1999).  Grasses and sedges were planted in the channel to help reduce the velocity of the flow and allow for settling of solids.  Check dams were also installed to create a semi-permeable barrier to promote the slowing of the flow and the settling of sediments.

The excavation of the swale was conducted by the DPW staff.  The design was completed by the RCE Water Resources Program for approximately $4,750.  Plant costs were $2,250 and planting was completed by RCE of Morris County faculty, RCE Water Resources Program faculty, staff, and students.

Unfortunately, a complication due to natural disaster led to a communication breakdown and two fuel deliveries during Hurricane Sandy with an additional automatic shutoff valve failure.  A fuel delivery spill occurred, and 500 hundred of gallons of diesel fuel were discharged to the vegetated swale.  Fortunately, the swale performed admirably; a significant amount of the diesel fuel was captured and held by the swale, as determined by visual observation of the swale and the clean-up of the stream.  The swale was rebuilt by the DPW staff, faculty and staff from the RCE Water Resource Program, and RCE of Morris County along with volunteers from the Morris County Master Gardener program.

Maintenance of the swale includes watering and weeding during the first year, especially on the berm.  Regular inspections also occur to ensure there is no erosion in the swale and there is no standing water that could become breeding ground for mosquitoes.

Rainwater Harvesting System

One of the most cost-effective stormwater BMPs is a cistern.  Cisterns enable harvesting of rain water for irrigation, truck washing and other non-potable uses.  In the case of the PTH DPW a 5,000 gallon cistern disconnected more than 5,500 square feet of rooftop via six downspouts.  For effective stormwater quality and quantity stormwater management cisterns should be emptied prior to the next storm.  Combined with the pervious pavers in the back of the building, the entire roof was disconnected.  The recycled water is used to wash the DPW trucks and for filling the street sweeper.  The system cost approximately $10,000 to purchase and install.  It includes a first flush diverter so that the grit from the rooftop does not clog the system.  Drain and winterize the system in the colder months.  Inspect annually for sediment, debris and cracks.  Inspect gutters to prevent clogging.  Flush to remove sediment.  

Sedimentation Chambers

The vegetated swale at the DPW site was receiving an excessive amount of sediment from the DPW parking lot.  Due to this excessive sediment, the vegetative swale was not performing at optimum levels.  Therefore, sedimentation chambers were installed at the upstream end of the vegetated swale to capture the larger suspended sediment particles.  Originally these sedimentation chambers were going to be a three stage sand filter.  The intent was to have the first chamber of the sand filter for the settling of larger particles and debris.  The sand in the second chamber would filter pollutants such as total suspended solids and fecal coliform bacteria.  The third chamber is the holding chamber where the treated filtrate is slowly discharged to the vegetated swale.

After constructing the sand filter, the system almost immediately clogged.  The system was then modified into sedimentation chambers to accommodate stormwater runoff at a DPW yard.  These are basically sand filters without the sand.  Large particles settle in these sedimentation chambers which are much easier for the DPW staff to clean.  On a monthly basis, they simply lift off the grate and vacuum out the chambers.

The DPW facility had leftover inlets and grates from a roadway construction project.  These concrete pre-cast inlets were adapted to serve as the sedimentation chambers and the DPW staff installed the system.  The use of existing materials and the installation by the DPW staff helped increase the cost-effectiveness of this project.

Rain Garden

As a result of the RCE outreach and educational programming, the Borough of Mountain Lakes, located directly upstream from Parsippany-Troy Hills on the Troy Brook, became interested in implementing stormwater management practices at their DPW facility.  A site inspection yielded an opportunity to install a bioretention system (also known as a rain garden) to disconnect the rooftop of the main building at the DPW facility.  Rain gardens are shallow landscaped depressions that capture runoff from impervious surfaces such as rooftops, driveways and parking lots.  The rain garden captures, treats and infiltrates the runoff during smaller storm events.  In New Jersey, rain gardens are typically designed to capture the entire runoff volume of the water quality design storm (1.25 inches of rain over two hours).  To account for the increasing frequency in the 2-inch storm event (Northeast Regional Climate Center and Natural Resources Conservation Service, 2015), the RCE Water Resources Program has been overdesigning rain gardens to capture the two-year design storm (3.3 inches of rain over 24-hours).  

The Mountain Lakes DPW facility is situated so that a majority of the runoff from the yard will drain to a wooded area.  The roof for the main building is 1,800 square feet and drains to the roadway.  A rain garden was designed by the RCE Water Resources Program to capture runoff from the two-year design storm from the entire rooftop.  The project was excavated by the Mountain Lakes DPW staff this past fall and stabilized.  It will be planted with native plants this spring by the Mountain Lakes Garden Club.

Maintenance includes watering and weeding, especially during the first year.  Keeping inflows, outflows, and ponding area in the rain garden clear of leaves and debris that will interfere with drainage along with checking the gutters and drain pipes to assure they are clear of leaves or other debris.  Maintenance also will require the removal of excess sediment and conversely checking the garden for erosional spots.  Sediment should be removed if it is excessive and if there are spots that are showing signs of erosion these should have rocks or additional plants placed to slow the water force at that spot.

Costs were minimal for this project.  The DPW staff excavated the site, the cost of RCE Water Resources Program for the engineering design was $1,500 and the cost of plants is estimated to be $2,500.  As mentioned there is no real cost of planting as the Mountain Lakes Garden Club will be responsible for the planting in the spring.


One of the main goals for greening DPW facilities is to reduce pollutant loading to local waterways in a cost effective manner.  Approximately 89% of the impervious surfaces on the PTH DPW site have been disconnected using various stormwater BMPs.  For the New Jersey water quality design storm (1.25 inches of rain over two-hours), these BMPs capture and treat 8,440 cubic feet (63,129 gallons) of stormwater runoff.  To determine pollutant load reductions, aerial loading coefficients were used to determine existing pollutant loads from PTH DPW site (total nitrogen = 16 pounds/acre/year, total phosphorus = 1.5 pounds/acre/year, total suspended solids = 200 pounds/acre/year) (NJDEP BMP Manual, 2004).  These aerial loading coefficients correspond to NJDEP’s methodology for the calculating total maximum daily loads (TMDLs).  The existing pollutant loads and the reduction in pollutant loads for each BMP is shown in Table 2.  These pollutant reductions were based upon literature values (NJDEP BMP Manual, 2004).  The BMPs at the PTH DPW site reduce the total suspended solids loading from the site by 82% and total phosphorus and total nitrogen by 69% for the impervious areas being treated.  Since only1.9 of the 2.1 acres of impervious area are being treated, the total suspended solids reduction for the entire 2.1 acres is 74% and 63% for the total phosphorus.


Table 2.  Reduction in Pollutant Loads from PTH DPW BMPs.


Drainage area



Loading Coefficients


Existing Load


Load Reduction



Removal (%)



























Grassed Pavers

Permeable Pavement

9,000 16 1.5 200 3.31 0.31 41.32 2.98 0.28 37.19 90 90 90
Sedimentation chambers/Vegetated swale 69,070 16 1.5 200 25.37 2.38 317.13 16.49 1.55 253.70 65 65 80
Cistern 2,750 16 1.5 200 1.01 0.09 12.63 0.91 0.09 11.36 90 90 90
Rain garden 1,800 16 1.5 200 0.66 0.06 8.26 0.60 0.06 7.44 90 90 90
Untreated area 8,712 16 1.5 200 3.20 0.30 40.00 0.00 0.00 0.00 0 0 0
Total Impervious Area (2.1 acres)     33.55 3.15 419.34 20.97 1.97 309.69 63 63 74
Total Treated Impervious Area (1.9 acres)     30.35 2.85 379.34 20.97 1.97 309.69 69 69 82





















The mission of the Cooperative Extension System is to extend the knowledge of the university to help improve the quality of life of all the state’s residents.  An urban Extension program was created to help municipal Department of Public Works facilities minimize their impact on local waterways.  A combination of well-accepted stormwater management practices have been packaged into this urban Extension program.  As part of this program, Rutgers Cooperative Extension has worked with two municipal Departments of Public Works to identify opportunities for installing stormwater best management practices, design these practices, and help install the practices.  The DPW staff were also educated on how to maintain the practices to ensure that these practices are always operating optimally.

The New Jersey Department of Environnmental Protection (NJDEP) requires both structural and non-structural stormwater BMPs to be designed using the New Jersey-specific stormwater quality design storm runoff (1.25 inches/2 hours), called the Stormwater Quality Design Storm.  The hands-on application of stormwater BMPs at the Parsippany-Troy Hills Department of Public Works facility led to an approximate 100% reduction in stormwater runoff from this site. usinng the Stormwater Quality Design Storm as the standard.  The types of BMPs that were installed were BMPs that the DPW staff could be involved with in a hands-on way, could take responsibility for and perform maintenance and repair on.  As the installers they had intimate knowledge and became stewards of the stormwater BMPs.


This program was made possible through funding from the New Jersey Department of Environmental Protection, 319(h) funding, from the Bureau of Environmental Analysis, Restoration and Standards.  The authors thank the Township of Parsippany-Troy Hills, especially the Township Department of Public Works, Greg Schneider and Karl Kuber.  The authors extend their thanks to Sal Mangiafico for help reviewing this manuscript.

Literature cited

Barr Engineering Company. (2006).  Burnsville Stormwater Retrofit Study.  Prepared for the City of Burnsville.  Minneapolis, MN.

Bean, E.Z.,  Hunt,W.F., D.A. Bidelspack, D.A., and R.J. Burak.RlJ  (2004).  First Water and Environment Specialty Conference of the Canadian Society for Civil Engineering.  Saskatoon, Saskatchewan, Canada.  June 2-4, 2004.

Dietz, M.E., and J.C. Clausen  (2005).  A field evaluation of rain garden flow and pollutant treatment.  Water, Air and Soil Pollution.  167:.123-138

Frick, C.M., R.E. Farrell and J.J. Germida (1999).  Assessment of phytoremediation as an in-situ technique for cleaning oil-contaminated sites.  Petroleum Technology Alliance of Canada (PTAC), Calgary, AB.

New Jersey Department of Environmental Protection (NJDEP) (2004).  New Jersey Best Management Practices Manual. Chapter 5, p5-5.  Available at 

New Jersey Department of Environmental Protection (NJDEP) (2014).  New Jersey Integrated Report Appendix B: Final 2014 303(d) List of Water Quality Limited Waters July 2014.

Northeast Regional Climate Center and Natural Resources Conservation Service (2015).  Extreme precipitation in New York and New England, an interactive tool for extreme precipitation analysis.  Available at 

Passeport,E., W.F. Hunt, D.E.Line, and R.A.Brown (2009).  Field study of ability of two grassed bioretention cells to reduce storm-water runoff pollution.  Journal of Irrigation and Drainage Engineering.  135(4):505-510.

Rusciano,G.M., and Obropta, C.C. (2007).  Bioretention column study: fecal coliform and total suspended solids reduction.  American Society of Agricultural and Biological Engineers.  50(4): 1261-1269.

U.S. Environmental Protection Agency, US EPA (1999).  Storm water technology fact sheet vegetated swales.  Fact sheet 832-F-99-006.  U.S. Environmental Protection Agency, Office of Water, Washington, D.C.

U.S. Geological Survey, USGS (2005).  Effects of Rain Gardens on the quality of water in the Minneapolis-St. Paul Metropolitan area of Minnesota 2002-04.  Scientific Innvestigations Report 2005-5189.  U.S. Department of the Interior, U.S. Geological Survey.  Mounds View, MN.