residential stormwater quality evaluation...avg. property value (just value 2014) $170,137 $109,831...

RESIDENTIAL STORMWATER QUALITY EVALUATION

RESIDENTIAL STORMWATER QUALITY EVALUATION

TAMPA BAY ESTUARY PROGRAM

December 11, 2014

Water Quality Results & RecommendationsWater Quality Results & Recommendations

OVERVIEW

• Study Goal• Brief Review Methods• Nutrient Inputs: Social Data and Soil Results

(review)• Nutrient Outputs: Environmental Data• Conclusions• Recommendations

Fertilizer Ordinance is passed with seasonal sales restriction in one County (Pinellas)

Is there a difference in ordinance awareness among residents living in sales-restricted County?

Is there a difference in fertilizing practices among residents living in sales-restricted County?

Is there a difference in N pollutant loads among residents living in sales-restricted County?

STUDY OBJECTIVES

1. Measure and compare average inputs of N in lbs/area

2. Measure and compare residential landscape management practices and knowledge

3. Estimate residential fertilizer inputs to the community nutrient budget

4. Measure nutrient concentrations in stormwater runoff and pond water throughout the year

WHICH COMMUNITIES?

• Landscape management practices (Mixed)

• Biological, geographic, and geological features

• Drainage areas and general hydrology

• HOA presence • Housing demographics

(house age, lot size, density)• Absence of golf course• No reuse water used for

irrigation• No septic onsite

Control Variables

COMMUNITY CHARACTERISTICSJurisdiction Hillsborough Manatee Pinellas Pinellas

Location Code H101 M101 P201 P202

Total acreage 58.70 45.73 17.65 102.90

Have HOA Y Y Y Y

Year Built (mean age) 2002 2003 2003 1984

Avg. Property Value (Just Value 2014)

$170,137 $109,831 $313,259 $176,0721

Total Pervious (aerials) 41.96 33.02 8.66 53.52

Golf course presence No No No No

HOA self-maintained No No No No

Average lot size 0.37 0.23 0.18 0.25

Average built area 2596 1738 2566 2228

Irrigation SourceCommunity

Well City City City

SOCIAL DATA COLLECTION

1. Representative Countywide Telephone Survey (n=835)

2. Community Level Homeowner Interviews (n=81)

3. Community Level Professional Interviews (n=6 of 31 attempted)

ENVIRONMENTAL SAMPLING

1. 10 soil samples from each community (total 40)2. 3 irrigation samples from each community (total

12)3. 9-11 storm events collected from each comunity

(total 40)4. 18 surface water sampling events within

community stormwater ponds or retention areas(total 72)

5. Standard Laboratory Analysis of pond/stormwater and soil extracts

6. Isotope Analysis (15N and 18O) of soil extracts and selected pond/stormwater samples (15N and 18O)

FERTILIZER USE FREQUENCY

County-wide Telephone SurveyCommunity Homeowner

InterviewsCounty n Mean Site n Mean

Hillsborough* 253 2.46 H101* 23 5.96Manatee 252 2.17 M101* 12 2.17

Pinellas* 223 1.73P201 11 3.82

P202* 15 3.67Total 728 2.14 Total 61 4.26

* ANOVA with Tukey post-hoc significant difference at p < .05

MONTHS FERTILIZER USED (%)

Important to note that we didn’t investigate WHAT was being applied

County n Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Hillsborough 167 20 22 33 27 20 19 16 16 22 26 19 17

Pinellas 133 11 13 29 20 17 15 13 11 21 22 11 13

Manatee 179 14 14 26 21 15 15 15 11 17 19 20 13

ORDINANCE AWARENESSHillsborough Pinellas Manatee

Do the ordinances…Restrict the use of lawn fertilizer during the rainy season? 75% 75% 66%Restrict the sale of lawn fertilizer during certain months?* 62% 79% 51%Reduce the amount of phosphorous (“P”) allowed in lawn fertilizer? 65% 77% 69%Reduce the amount of nitrogen (“N”) allowed in lawn fertilizer? 58% 62% 66%Require training for professional landscaping companies? 57% 52% 45%N = 188 * p < .001

Pinellas County residents were significantly more likely (43%, p < .0001) to respond that they had heard about government regulations concerning residential fertilizer use than either Hillsborough or Manatee (both 26%).

NITROGEN INPUTS FROM LANDSCAPE MANAGEMENT - ESTIMATES

Community

ProfessionalFertilized

(Acres)

Owner Fertilized

(Acres)

Not Fertilized

(Acres)

Pervious Area

(Acres)N Input

(Lbs)N Inputs

(Lbs/acre)H101 28.53 13.43 0.00 41.96 5496.3 93.6M101 5.45 11.06 16.51 33.02 1775.2 38.8P201 2.25 3.90 2.51 8.66 676.0 38.3P202 16.06 24.08 13.38 53.52 4504.4 43.8

SOILS BY LOCATIONAnalyte H101 P201 P202 M101

NOx-N Mean (mg/kg)

9.1 (2.6) 11.9 (5.8) 6.2 (2.9) 5.9 (2.4)

NH4 Mean (mg/kg)

2.4 (1.4) 2.8 (0.9) 2.1 (0.7) 2.5 (1.4)

*Org. Matter (%) 4.5 (1.12) 6.5 (2.2) 4.3 (0.9) 2.6 (0.6)

*TKN Mean (mg/kg)

1296.2 (356) 1657.3 (499.9) 1395.7 (251.8) 793.6 (181.7)

**P Mean (mg/kg)

49.6 (14.3) 55.9(22.1) 54.5 (30.3)325.900 (514.87)

*EC Mean (ds/m)

0.1 (<0.1) 0.2 (<0.1) 0.1 (<0.1) 0.1 (<0.1)

*pH Mean 6.5 (0.5) 7.4 (0.3) 6.3 (0.6) 6.7 (0.6)

House Age Mean (yrs)

12 11 30 11

MONTHLY RAINFALL TOTALS AT H101

Dry Season (Oct-May): 18.91”Wet Season (Jun-Sep): 37.46”Modified Wet Season (Jul-Oct): 39.61”

H101 TOTAL NITROGEN CONCENTRATIONS

MONTHLY RAINFALL TOTALS AT M101


M101 TOTAL NITROGEN CONCENTRATIONS

MONTHLY RAINFALL TOTALS AT P201


P201 TOTAL NITROGEN CONCENTRATIONS

MONTHLY RAINFALL TOTALS AT P202


P202 TOTAL NITROGEN CONCENTRATIONS

ANNUAL LOAD ESTIMATES

Load Estimate = runoff volume * EMC (concentration)* conversion factor *treatment reduction

CommunityMean TN

(mg/l)

Runoff Volume

(1000 m3/yr)

TN Load

(lbs/yr)

TN Load by Area

(lbs/acre)

H101 1.76 72.60 196.99 4.89

M101 1.39 67.05 143.41 4.22

P201 1.45 28.48 63.64 3.48

P202 1.76 17.79 48.34 3.66

SOIL ISOTOPESSoil Samples

Awareness is significantly higher in Pinellas County

Fertilizer ordinance is effectively changing behavior: residents use less fertilizer in Pinellas County

Caveat: no pre-ordinance behavior data available

Water quality concentrations in stormwater do not yet show a clear improvement due to intervention

Estimated TN loads appear to be highest in communities with highest use of fertilizer and lower in areas with seasonal sales restriction

Lag time between social Intervention to change behavior to visible water quality improvements

Nitrogen can be retained in soils for decades and released slowly over time (Sebilo et al. 2013)

CONCLUSIONS

• Evidence of fertilizer use: peaks TN, isotopic signatures of stormwater, soil isotopes

• N input estimates highest for H101 lawns (93.6 Lbs/acre)• Coincides with highest: fertilizer frequency, % professionals &

estimated TN output loads (4.9 lbs/acre)• Professionals might be applying same N annually, just not in

summer – limited data• Professionals travel to multiple jurisdictions – City of Tampa

and Hillsborough same application?• Limited timeframe of the study, difficult to confidently

establish the final link between a change in behavior and the long-term environmental benefit

STUDY DESIGN RECOMMENDATIONS

• Further in situ research is needed at the landscape scale• In situ experiments to evaluate before/after interventions• Intervention study controlling application timing/amount• Use an enriched fertilizer and trace it through a subdivision• Measure isotopic signatures of the rainfall for comparison

with stormwater signature• Obtain N and O isotopic information• Need for community-level socio-demographics and

behaviors studies to compare differences in behaviors over time in treatment vs control groups.

• Trend testing required multiple years of data, preferentially >10 yrs.

ParameterH101 M101 P201 P202

Pond Storm Pond Storm Pond Storm Pond Storm

Total Nitrogen 23 64 32 54 28 85 22 56

Total Inorganic Nitrogen 35 26 102 74 61 31 139 54

Total Phosphorus 42 54 243 167 139 143 38 139

POWER TESTING RESULTS

Note: Minimum Sample Size Required to Detect a 20% Reduction in Mean Parameter for Pond and Stormwater in the Four Communities. Estimates based on a one-sample T-test and not a seasonal trend test.

residential stormwater quality evaluation...avg. property value (just value 2014) $170,137 $109,831...

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