Nutrient Management Strategy for Falls Lake

Ariel AtkinsonJames Kribs

James Mattice

Outline• Background• Costs and Benefits– New development– Existing development– Point Sources– Agriculture– Drinking Water– Recreational and Other Benefits

• Cost/Benefit Analysis Results• Sensitivity Analysis• Conclusions

Goals of the NMS• Decrease Nitrogen levels by 40% and

Phosphorus by 77%.• Improve Water Quality Designation (Impaired

to Normal)• Protect recreational and ecological value;

reduce drinking water treatment costs

Background• Other nutrient management project have

been started successfully in the area• Rules consist of two rule amendments and

nine new rules• Rules apply to six counties and eight

municipalities• Rules were adopted on November 19th, 2010

Background• Rules focus on sources of nutrient pollution

including: new development, existing development, agriculture, and point sources

Analysis• Assess Costs – Planning and Water Quality Monitoring– New development– Existing Development– Point Sources– Agriculture

• Assess Benefits– Reduced/Avoided Drinking Water Treatment Costs– Recreational– Other Benefits

New Development• As part of the Falls Lake

Nutrient Management Strategy, new development must: – Institute nutrient control

on-site – Purchase credits to offset

their production– Only applicable to

properties larger than 5000 sq. ft.

New DevelopmentTN (lbs/year)

Cost of removal of TN per year TP (lbs/year)

Cost of removal of TP per year Total cost per year

For the Eight Municipalites 20337 $150,410 1419 $141,024 $142,442

For 3 Rural Counties (Person,

Franklin, Granville) 134197 $992,523 9523 $946,732 $956,255

For 3 Urban Counties (Wake,

Durham, Orange) 415548 $3,073,395 29505 $2,933,233 $2,962,738

Total 570082 40447 $4,061,435

Amt of reduction 342049 24268

Goal Level 228033 16179Total Cost of TN and TP removal $121,843,062

Existing Development• Each county or municipality must institute a plan for

regulating nitrogen and phosphorus in stormwater runoff– Also, they must monitor their pollutant levels

• Any existing plan must attempt to reach the recommended levels according to what is “economically and technically feasible”

Existing DevelopmentTN (lbs/yr) TP(lbs/yr)

Current level 1141667 152174

Percentage from Development 13% 5%

Current load from Development 148417 7609

Percentage Reduction Goal 40% 77%

Reduction Amount 59367 5859

TN TP Total

Cost of Reduction per year $1,097,690 $832,052 $1,929,742

Cost of Reduction for 30 year plan $29,637,621 $22,465,403 $52,103,024

Point SourcesDischargers TN allocation(lbs/yr) TP allocation (lbs/yr)

Large 95858 5228

Small 1052 175

Total 96910 5403

Total Reduction per year 64607 18088

Cost of Reduction per year $1,194,577 $2,568,901

Total Cost of Reduction $35,837,318 $77,067,030

Total Cost of TN and TP Reduction $112,904,348

Agriculture• Fertilizers and animal waste contribute

heavily to a farms total pollution.• Runoff leads to streams and rivers which

lead into the lake.• A riparian buffer 10 meters wide will filter

much of this waste before it reaches water.

AgricultureRemoval Efficiency(lbs/acre/yr)

Stage 1 Reduction (lbs/yr)

Amt of Buffers Needed to Reach Stage 1 Reduction(acres)

TN 21 66217 3153

TP 4 28000 7000

Stage 2 Reduction (lbs/yr)

Amt of Buffer Needed to Reach Stage 2 Reduction(acres)

TN 21 132433 6306

TP 4 53900 13475

Stage 1 Stage 2 Both StagesCost of Buffer Construction $2,555,000 $2,363,375 $4,918,375

Maintenance Cost $766,500 $472,675 $1,239,175Opportunity Cost of Land $28,672,000 $26,521,600 $55,193,600

Total Cost $31,993,500 $29,357,650 $61,351,150

Drinking Water Benefits

• The levels of nitrogen and phosphorus in Raleigh’s drinking water will not change as a result of this study, but will reduce cost of treatment

• The amount of treatment required to achieve the 1mg/l of N and 1µg/l (1/1000 mg) of P

Drinking Water BenefitsYear of the Program

Consumption (gallons)

Cost of Removing TN and TP w/NMS

Cost of Removing TN and TP @ Current Levels of Pollution Benefit of NMS

Discounted Benefit of NMS

0 17646008160 $277,384 $3,673,336 $3,395,952 $3,395,952

1 18950606928 $277,362 $3,673,313 $3,395,952 $3,173,787

2 20255205696 $277,340 $3,673,291 $3,395,952 $2,966,156

3 21559804464 $277,317 $3,673,269 $3,395,952 $2,772,108

⁞ ⁞ ⁞ ⁞ ⁞ ⁞

28 54174773664 $276,763 $3,672,714 $3,395,952 $510,759

29 55479372432 $276,741 $3,672,692 $3,395,952 $477,345

30 56783971200 $276,718 $3,672,670 $3,395,952 $446,116

Total Benefit over 30 yrs $105,274,499 $45,536,455

Recreational Benefits

• Travel Cost Study done

• Evaluate how changes in water quality correlated with changes in the amount of trips made and the WTP per trip to Falls Lake for recreation

Other Benefits• Decrease in Other

Types of Pollution• Improved Aesthetics• Impact on Public

Health• Ecological Benefits• Increased Property

Values

Results of Cost/Benefit AnalysisCosts of NMS Cost

Planning and Monitoring $854,700

New Dev'p Stormwater Management $293,131,625

Existing Dev'p Stormwater Management $52,103,024

Point Source Loading Reductions $112,904,348

Agricultural Loading Reductions $61,351,150

Total Cost $520,344,847

Benefits of NMS Benefit

Recreational Benefits $241,000,000

Reduced Drinking Water Treatment $45,536,455

Avoided Upgrade in Treatment (only avoided construction costs) $120,000,000

Others(Aesthetic, Ecological, Property Values, Public Health) ---

Total Benefit $406,536,455

Net Benefit -$113,808,392

Sensitivity Analysis

• Changing the discount rate effects the results, but never results in the costs outweighing the benefits

• All population growth was assumed to be linear• Property values were assumed to be constant• Cost of reducing nutrient pollution was

assumed to be at a constant rate ($/lb) for development and point sources

• Technological Advances

Conclusions

• While the costs exceed the benefits, due to uncertainty and sensitivity of the analysis, it is not recommended to accept or reject these rule changes– Economic Analysis of other Nutrient Management

Plans have shown benefits outweigh costs– Future efforts should focus on detailing the

methodology and timeframe

References• Army Corps of Engineers- Wilmington District. (2008, January 18). Falls Lake. Retrieved from Army Corps of Engineers- Wilmington District:

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http://www.ncparks.gov/Visit/parks/fala/main.php• NC Divison of Water Quality, Planning Section. (2010, June 14). Fiscal Analysis for Proposed Nutrient Management Strategy. Retrieved November 5, 2010, from

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