1. Introduction 5 Case Studies Impervious Cover (%) for Various Land Uses [2] [2] Low Density Residential 10 Medium Density Residential 30 High Density Residential 40 Multifamily60 Industrial75 Roadway80 Commercial85 “impervious surfaces are responsible for more stormwater runoff than any other type of land use” [1] … [1] [1] EPA, 2000: Low Impact Development (LID) - A Literature Review. EPA-841-B-00-005, Office of Water, Washington, D.C. [2] http://www.stormwatercenter.net/monitoring%20and%20assessment/simple%20meth/simple%20imp%20table%205.htm [2]

2. Stormwater Quality Three paving materials 0.30-0.70 0.18- 0.29 0.03 Interlocking pavers Porous asphalt Porous concrete Manning’s nRunoff Coefficient Stormwater Quantity Four Sites 1%

3. Objective: evaluate various surface materials in urban parking areas to reduce stormwater runoff and annual pollutant loads Pennsylvania Stormwater Management Manual Definition: “Porous pavement is a permeable asphalt or concrete surface that allows stormwater to quickly infiltrate to an underlying stone reservoir”

4. Peak Flow As Tt=Tc increases peak runoff decreases Q = CiA Rational Method widely used for small urban drainage area required limited data Peak Flow (cfs)

5. Travel Time T c = T t for only one segment Ferguson, B. 2005. Porous Pavements. CRC Press http://www.dep.state.fl.us/water/nonpoint/docs/erosion/chapter3.pdf “Travel time ( Tt ) is the time it takes water to travel from one location to another in a watershed”. Length of Flow Path 434.73 ft 695.10 ft 632.33 ft 509.67 ft S Congress E 7th Street Burnet Road E. Riverside Dr 695.10 ft 632.33 ft 509.67 ft 632.33 ft Depth of precipitation (in) Time of Travel (hr) Recurrence interval 2yr

6. Annual load (L) TNTPTSSZnCu (lbs) S Congress54.4910.324704.941.590.25 Burnet Rd63.8312.085511.532.160.30 E. Riverside Dr38.277.253304.651.020.16 E 7th St70.7013.386104.582.120.34 Annual Pollutant Loads Pollutant concentration: STORMWATER RUNOFF QUALITY AND QUANTITY FROM SMALL WATERSHEDS IN AUSTIN, TX, City Of Austin, Watershed Protection Department, Environmental Resources Management Division, Water Quality Report Series, COA-ERM/WQM 2006-1, November 1, 2006 L = 0.226 * R * C * A Simple Method “No significant relationship was found for total suspended sediment based on impervious cover or development condition” TP and TN: impervious cover ranges: 0-1% and 5-100%

7. Water Quality Volume Area 632,397.80 ft 2 621,467.95 ft 2 667,667.02 ft 2 658,754.68 ft 2 S Congress 93,5788.57 ft2 E 7th Street 1,706,624.16 ft2 Burnet Road 1,051,130.49 ft2 E. Riverside Dr 902,001.86 ft2 Water Quality Volume WQv ProposalActual (ft3) S Congress5,777.336,441.34 Burnet Rd6,582.747,235.28 E. Riverside Dr5,517.096,208.78 E 7th St6,711.287,412.33 Average 10% reduction in WQv with decrease impervious surfaces Depth of gravel bed/reservoir S Congress Burnet Rd E. Riverside Dr E 7th St (in)(feet)(ft3) 60.5126,479.56124,293.59131,750.94133,533.40 121252,959.12248,587.17263,501.87267066.81 An average increase of 21% of WQv New York State Stormwater Management Design Manual

8. Porous ConcreteDense AsphaltPorous AsphaltInterlocking Pavers $ 4.00 $ 0.75 $ 1.00 $ 3.50 S Congress $2,529,591.20 $ 474,298.35 $ 632,397.80 $2,213,392.30 Burnet Rd $2,485,871.79 $ 466,100.96 $ 621,467.95 $2,175,137.82 E. Riverside Dr $2,635,018.70 $ 494,066.01 $ 658,754.68 $2,305,641.37 E 7th St $2,670,668.08 $ 500,750.27 $ 667,667.02 $2,336,834.57 note: Average price per ft2 from EPA, Dr. Barrett, City of Seattle Department of Planning and Development and City of New York ;base/storage bed not included in cost estimate. http://www.ci.austin.tx.us/watershed/rsmp_fee_com-mf.htm on average a 33% increase Regional Stormwater Management Participation Fees “the number of impervious acres…based on the maximum allowable impervious cover” BMP’s Land Costs! / Incentives?

9. Maintaining flow path lengths Regulation Reduce stormrunoff and increase water quality Disconnecting impervious surfaces Porous surfaces END Preliminary Conclusions

10. L = 0.226 * R * C * A L= Annual load (lbs) P= Pollutant Concentration A= Area (acres) R= Annual Runoff (inches) Annual rainfall P (in) 199028.44 199152.21 199246.05 199326.05 199441.16 199533.98 199629.56 199747.04 199839.11 199923.93 200037.96 200142.9 200235.98 200321.43 200452.27 200522.33 200634.6 200746.95 36.775 *NOAA:National Weather Service R = P * Pj * Rv P= Annual Rainfall (in) Pj= Fraction of year rainfall events that produce runoff 0.9 Rv= Runoff Coefficient Rv=0.05+0.9Ia Ia= Fraction of impervious cover Simple Method

11. Rv=0.05+0.9Ia Ia= Fraction of impervious cover WQv=Water Quality Volume (ft3) A= Total Area (ft2) P= 90% Rainfall event (inches) 1.4 in for Austin Ap= Porous Pavement Surface (ft2) n=Porosity of bed gravel (0.4) dt=Depth of gravel bed/reservoir (ft) WQv=Water Quality Volume (ft3) New York State Stormwater Management Design Manual