Evaluation and Demonstration of the Performance …unix.eng.ua.edu/~rpitt/Presentations/Urban_water...Evaluation and Demonstration of the Performance of Stormwater Dry Wells and Cisterns

Evaluation and Demonstration of the Performance of Stormwater Dry Wells and Cisterns in Millburn

Township, New Jersey

Leila Talebi1 and Dr. Robert Pitt2

February, 2013

1 PhD Candidate, Department of Civil, Construction and Environmental Engineering, The University of Alabama, Tuscaloosa, Alabama. Email: [email protected]

2 Cudworth Professor of Urban Water Systems, Department of Civil, Construction and

Environmental Engineering, The University of Alabama, Tuscaloosa, Alabama Email: [email protected]

• B.S., Civil Engineering, Polytechnic University of Tehran, Iran, 2004

• M.S., Civil Engineering, Khajeh Nasir Toosi University of Technology, Iran, 2007

• Ph.D. Student, Civil Engineering, University of Alabama, 2010-present

Education

Description of the Township of Millburn, NJ

• Population: 20,149 (2010 US census)

• 5,900 detached homes

• 1,500 dry wells

http://upload.wikimedia.org/wikipedia/commons/5/58/Millburn_twp_nj_013.png

Presenter

Presentation Notes

The Township of Millburn, Essex County, NJ, is located near New York City, and less than 10 miles from Newark International Airport. The 2010 US census indicated the township had a population of 20,149. Housing costs are very high (According to Wikipedia, Millburn had the highest annual property tax bills in New Jersey in 2009 at an average of more than $19,000 per year, compared to the statewide average property tax that was $7,300 which was the highest statewide average in the country). There are about 5,900 detached homes in the township and about 1,500 have dry wells.

http://upload.wikimedia.org/wikipedia/commons/5/58/Millburn_twp_nj_013.png

Dry Wells in Millburn, NJ

Presenter

Presentation Notes

Backyard dry well showing lawn area also as a source. Backyard dry well showing driveway runoff also as a source. Many of the dry wells are located in landscaped areas and have open covers, allowing surface runoff from the lawns to enter the dry wells, as well as the subsurface piped roof runoff Typical dry wells in Millburn, NJ are 4 ft diameter and 6 ft tall perforated concrete chambers surrounded by 2 feet of gravel on all sides, including below the chamber. The bottom of the dry well device (including the lower rock layer) is therefore about 10 ft below the ground surface

To investigate the effectiveness of Millburn’s stormwater management practices that rely on the use of dry wells limiting stormwater discharges into the local drainage system.

Objectives

Presenter

Presentation Notes

to investigate the hydraulic performance of the dry wells along with water quality changes associated with the dry well operation

Monitored dry wells (blue icons), cistern (green icon), and newly constructed dry wells outfitted for water quality monitoring (red icons)

Presenter

Presentation Notes

Fifteen dry wells were monitored for water levels during periods ranging from 2 months to one year, or by controlled tests using township water from fire hydrants. Four systems (three dry wells and one cistern) were also monitored for water quality during 10 storms to indicate any differences in water quality directly below the dry well (or at the cistern inlet) compared to deeper depths at least 0.6 m (2 ft) below the bottom of the crushed stone layer, or at least 1.2 m below the bottom of the dry well itself (or in the cistern). Four rain gages were also installed near the dry wells.

Rain Gauges

Residential rooftop rain gage Roof of Township’s maintenance garage

Municipal Par 3 Golf Course Old tennis court at Greenwood Gardens

Presenter

Presentation Notes

Four rain gages were installed in the study area for this project.

• A or B soils needed with associated minimum 5 to 12 mm/hr (0.2 to 0.5 in./hr) infiltration rates

• Depth to the seasonal water table or bedrock: at least 2 ft below the infiltration system

• Restrict the source waters for infiltration to be roof runoff only.

New Jersey State Dry Well Regulations

Hydrologic Soil Group Index of the Township of Millburn for Surface Soils

Hydrologic Soil Group Index of the Township of Millburn for Shallow Subsurface Soils 2 ft Deep

Infiltration Data Analysis

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7-Fox Hill Lane - 10/01/2010

Observed Data Fitted Horton Equation Water stage in drywell

f = fc + (fo - fc)e-kt

Horton’s Equation f is the infiltration rate at time t (in./hr), fo is the initial infiltration rate (in./hr), fc is the final (constant) infiltration rate (in./hr), and k is first-order rate constant (hr-1 or min-1)

Presenter

Presentation Notes

Purple line shows Water level in every 10 mins, the water level dropped down about 12 inches in about 20 hrs, we have so much scatters in the beginning of the infiltration and finally if you look at the tail of the graph we have kinda constant rate of 0.5 in/hr for fc


Green-Ampt Equation ft is infiltration rate, in./hr; y is the initial matric potential of the soil (in.); DQ is the difference of soil water content after infiltration with initial water content (in.3/ in.3); K is hydraulic conductivity (in./hr); and Ft is the cumulative infiltration at time t (in.).

)1( +∆

=t

t FKf θψ

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./hr

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383 Wyoming Ave. 8-02-2009

Observed

Horton

Green Ampt

f=0.928+4.522exp(-0.003t)

Presenter

Presentation Notes

As it is shown in Figure, the Horton equation usually had a better fit to the data compared to the Green-Ampt equation for the Millburn data. However, for some sites, the Green-Ampt equation was a better fit.


Statistical Groupings of Site Data for Horton Coefficients

All Sites vs, 258 Main St Site

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Fc (i

n/hr

)

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P=0.004

Presenter

Presentation Notes

The Horton equation usually had a better fit to the data compared to the Green-Ampt equation for the Millburn data Statistical Groupings of Site Data for Horton Coefficients Multiple iterations of grouped box and whisker plots and ANOVA tests were used to identify data groupings. The data were not normally distributed so ANOVA based on ranks and Mann-Whitney Rank Sum nonparametric tests were used to calculate the significance that the data did not originate from the same populations. ; there is a statistically significant difference, with P = 0.004 Same patterns for fo and k

Standing Water Conditions in Dry Wells

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11 Woodfield Dr water stagerain eventHydrant test

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87/89 Tennyson water stage rain event

No standing water after all events

High water conditions after all events

Standing Water Conditions in Dry Wells

No standing water after some events

Same site: Possible mounding of water

table conditions after some events (very

wet period)

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142 Fairfield water stage rain event

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142 Fairfield water stage rain event

Water Table Conditions in Dry Wells

Presenter

Presentation Notes

• Sites having no standing water after the events (completely drained with no apparent high water table conditions): 11 Woodfield Dr, 15 Marion, 258 Main St, 1 Sinclair Terrace (only one observation), 8 South Beechcroft Rd, 11 Fox Hill Lane (only one observation), 36 Farley Place • Sites having a few standing water conditions after the events (standing water of several inches, or more, indicating possible seasonal high water table conditions): 2 Undercliff Rd, 383 Wyoming Ave., 142 Fairfield Dr. • Sites with all or most events having high water conditions: 260 Hartshorn Dr , 87/89 Tennyson Dr, 7 Fox Hill Lane, 9 Fox Hill Lane Doesn’t seem to be reflected by the topography, there is no strong pattern

Observed Infiltration Coefficient Values Compared to Literature Values

fo (in./hr) fc (in./hr) K (1/min) Surface A and B soils well drained A subsurface soils (average and COV)

44.6 (0.53)

5.6 (0.2) 0.06 (0.22)

Surface C and D soils well drained A and B subsurface soils (average and COV)

4.3 (0.64) 0.45 (0.85) 0.01 (0.63)

UDFCD (2001) A soils (average) 5.0 1.0 0.04 UDFCD (2001) B soils (average) 4.5 0.6 0.11 UDFCD (2001) C and D soils (average) 3.0 0.5 0.11 Pitt, et al. (1999) Clayey, dry and non-compacted (median) 11 3 0.16 Pitt, et al. (1999) Clayey, other (median) 2 0.25 0.06 Pitt, et al. (1999) Sandy, compacted (median) 5 0.5 0.1 Pitt, et al. (1999) Sandy, non-compacted (median) 34 15 0.08 Akan (1993) Sandy soils with little to no vegetation 5 Akan (1993) Dry loam soils with little to no vegetation 3 Akan (1993) Dry clay soils with little to no vegetation 1 Akan (1993) Moist sandy soils with little to no vegetation 1.7 Akan (1993) Moist loam soils with little to no vegetation 1 Akan (1993) Moist clay soils with little to no vegetation 0.3

Presenter

Presentation Notes

The very large observed fo value (45 in./hr) for the A and B surface soil sites that are well drained is greater than any of the reported literature values, and only approaches the observations for the non-compacted sandy soil conditions (34 in./hr) observed by Pitt, et al. (1999). The subsurface soil conditions affecting the dry well infiltration rates are likely natural with little compaction. Also, the subsurface soils at that location are noted as being sandy loam (A) and stratified gravelly sand to sand to loamy sand (A). The other sites having smaller fo rates (4.3 in./hr) are described as gravelly sandy loam (A) and fine sandy loam (B) and are similar to many of the reported literature values for sandy soils, with some compaction. The largest fc value (5.6 in./hr) observed for the well-drained A and B surface soil location is bracketed by the non-compacted clayey and sandy soil conditions (3 and 15 in./hr) reported by Pitt, et al. (1999), but is substantially larger than the other reported values. The fc value observed for the well-drained C and D surface soil site (0.45 in./hr) is similar to the other reported values (0.5 to 1.0 in./hr). The k first-order rate values (0.01 and 0.06 1/min) are similar, but on the low side, of the reported values (0.04 to 0.11 1/min).

Three dry wells: a shallow monitoring well and a deep monitoring well

A new water storage cistern: sampled at the inlet and from the outlet.

8 to 10 storms were sampled (all samples were analyzed in duplicate.)

Water Quality

Presenter

Presentation Notes

Three dry wells during new construction had both a shallow monitoring well placed directly beneath the concrete chamber (sampling water similar to the water in the dry well tank), along with a deep monitoring well located at least 60 cm (2 ft) beneath the deepest depth of the seepage pit gravel.

• The samples were analyzed in laboratories of the University of Alabama for bacteria: (total coliform and E. coli screening analyses), total nitrogen (TN), nitrate plus nitrite (NO3 plus NO2), total phosphorus (TP), and chemical oxygen demand (COD).

• Lead, copper, and zinc were analyzed at a commercial laboratory (Stillbrook Environmental Testing Laboratory in Fairfield, AL).

• Selected samples were also analyzed for pesticides by the EPA (not reported here).

Water Quality – Methods and Materials

Presenter

Presentation Notes

Therefore, seven to ten water quality samples were available from each sampling location for the study. Statistical analyses and plotting of the data were conducted using MINITAB, and MS-Excel software.

Date Rain Depth 10/20/2010 0.10 in.* 7/29/2011 0.15 in.* 8/5/2011 0.14 in.* 08/10/2011 0.12 in.* 08/16/2011 0.15 in. 08/17/2011 0.20 in. 08/18/2011 0.10 in. 08/22/2011 0.50 in. 08/25/2011 0.25 in. 08/28/2011** 9 in.

*The data from these rains was obtained from http://www.wunderground.com/ while the other rains were obtained from the on-site rain gages.

**Hurricane Irene rain began about 3:00 pm on 08/27/2011 and finished at about 10:00 am on 08/28/2011, producing record rainfall for the area. (1 in. = 25.4 mm)

Rain Depths for Monitored Events (all relatively small during this dry period, except for the record rainfall during Hurricane Irene)

Water Quality – Methods and Materials

http://www.wunderground.com/

IDEXX method within 24 hr of sampling (undiluted UDL: 2,419 MPN/100 mL, or 24,192 with 10X dilutions and 48,384 with 20X dilutions)

139 Deep139 Shallow18 Deep18 Shallow135 Deep135 Shallow79 Cistern79 Inflow

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Tota

l col

iform

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PN)

Total coliform

p=0.03 p=0.40 p=0.16 p=0.72

Bacteria

Presenter

Presentation Notes

The cistern related sample bacteria levels (especially the outlet samples) were generally lower than for the dry well samples. Total coliform levels are higher in the cistern than the inflow and generally the deep locations at each of the dry well sites had higher levels of total coliforms, possibly indicating some re-growth in the systems. I will discuss the stat methods later in the presentation, but it is important to show with the figures. Also, I previously added bacteria "screening" analyses as the samples were about a day old before analyses (but still high).�


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Total Nitrogen as N (mg/L)

p=0.86 p=0.50 p=0.42 p=0.64

Nutrients

Presenter

Presentation Notes

The total nitrogen concentrations (HACH total nitrogen) (reported as N) ranged from <1 to 16.5 mg/L. The NO3 plus NO2 concentrations (HACH Accu-Vac method) ranged from 0.2 to 3.2 mg/L. The total phosphorus concentrations (HACH test-n-tube) ranged from 0.02 to 1.36 mg/L. The median values for most of the locations were very similar for both the shallow and the deeper monitoring well samples and for the inflow and cistern samples, except for one of the sites in which the deeper samples have higher TN median values than for the shallow samples. However, as shown later, these differences were not significantly different, based on the number of samples available.


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NO3 - N

p=0.14 p=0.24 p=0.15 p=0.77

Nutrients

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Presentation Notes



1.4

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Total Phosphorus (mg/L)

p=0.77 p=0.94 p=0.10 p=0.27

Nutrients

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Presentation Notes



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COD

(m

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COD (mg/L)

p=0.04 p=0.14 p=0.40 p=0.83

Chemical Oxygen Demand (COD)

Presenter

Presentation Notes

The COD concentration in different locations and for various storm events ranged from 5.0 to 148 mg/L. Also, as shown later, the statistical analyses did not indicate any significant differences between the shallow and deep samples for any location (or inflow or cistern samples), for the number of samples available.

• Many were below the method detection limit (BDL).

• The maximum observed concentration for lead (380 µg/L) occurred in a deep monitoring well sample under a dry well.

• The maximum observed concentration of copper (1,100 µg/L) occurred in a cistern influent sample (possibly due to copper roof gutters on the home).

• The concentrations of zinc in all samples ranged from BDL to 140 µg/L.

Metals

Presenter

Presentation Notes

Too many of the heavy metals results were not detected and could not be effectively plotted.

Metal

79 Inflow vs. 79 Cistern

135 Shallow vs.

135 Deep

18 Shallow vs. 18 Deep

139 Shallow vs. 139 Deep

Lead > 0.06 > 0.06 0.18 > 0.06

Copper 0.125 * >0.06 *

Zinc 0.45 0.45 >0.06 >0.06

* All the results are below the detection limit (BDL), therefore it is not possible to do a statistical comparison test

Summary of Paired Sign Test for Metal analysis

Presenter

Presentation Notes

Due to large amounts of non-detected metal results, the Mann Whitney test could not be used. However, the sign test can be used if at least one value of a pair had a detectable result, allowing the identification of the larger value of the pair. The null hypothesis: the population medians are similar. In each pair of observations, a comparison was made to determine if there is an increase from the shallow sample to the deep sample or if there was a decrease. If the calculated p value is less than 0.05, then the null hypothesis will be rejected and the data are assumed to originate from different sample populations. No statistically significant differences are seen between the sample sets for these heavy metals for the numbers of samples available.

Constituent Groundwater Quality Criterion

Observed Range Fraction of samples that exceed the criteria

Microbiological criteria

Standards promulgated in the Safe Drinking Water Act Regulations (N.J.A.C. 7:10-1 et seq.): 50 MPN/100 mL

Total coliform: 1 to 36,294 MPN/100 mL E. coli: 1 to 8,469 MPN/100 mL

Total coliform: 63 of 71 samples exceeded the criterion for total coliforms E. coli: 45 of 71 samples exceeded the criterion for E. coli

Nitrate and Nitrite 10 0.0 to 16.5 (one sample had a concentration of 16.5 mg/L)

1of 71 samples exceeded the criterion for nitrates plus nitrites

Nitrate 10 0.1 to 4.7 0 Phosphorus 0.02 to 1.36 COD 5.0 to 148 Lead 0.005 BDL to 0.38 33 of 71 samples exceeded the

criterion for lead

Copper 1.3 BDL to 1.1 0 Zinc 2.0 BDL to 0.14 0

Groundwater Quality Criteria for the State of New Jersey Compared to Observed Water Quality from Dry Wells (mg/L)

Presenter

Presentation Notes

Clearly, the microbiological and lead concentrations frequently exceeded the groundwater criteria.

• The Horton equation usually had a better fit to the data compared to the Green-Ampt equation for the Millburn dry well infiltration data.

• The infiltration rate characteristics were separated into three conditions:

• A and B surface soils having well drained HSG A subsurface soils • C and D surface soils having well drained A and B subsurface soils • C and D surface soils having poorly drained subsurface soils with long-term standing water

Conclusion

• No significant differences in water quality between the deep samples and shallow samples in dry wells (p values were > 0.05).

• If the influent water quality is of good quality, the dry wells can be a safe disposal method for stormwater quality.

• However, the bacteria and lead concentrations exceeded the groundwater disposal criteria for New Jersey

• Significant differences (p< 0.05) between the quality of inflow samples and cistern samples for total coliform and E. coli (increased values possibly indicating re-growth), and COD (reduced values).

Conclusion

• The deep monitoring well samples were located at least 1.3 m (4 ft) below the bottom of the dry well (at least 2 ft in the soil). This distance was not sufficient to result in observed significant reductions in the stormwater constituents.

• Rain gardens or biofilters as alternatives: – Provide better groundwater protection – Receive runoff from several of the source areas

Conclusion

Documents

Evaluation and Demonstration of the Performance …unix.eng.ua.edu/~rpitt/Presentations/Urban_water...Evaluation and Demonstration of the Performance of Stormwater Dry Wells and Cisterns