NHDOT TMDL Implementation Plan Development Considerations o - - PowerPoint PPT Presentation

NHDOT TMDL Implementation Plan Development Considerations

• Flexibility
• Adaptability
• Measurable
• Safety & Socio-Economic Benefits
• Practical and Cost Effective and therefore

Achievable

NHDOT TMDL Issues

• Salt Usage (Load) Based Allocations do not

account for:

– the weather – planned expansion of I-93 – different vehicle usage levels – Level of Service and Level of Safety

Season to Season Variation

• Salt Usage Predictions were based on a mild

winter season therefore the percent reduction is actually greater than reported

• Winter Severity Index (WSI) can be used to

remove the variance caused by weather (i.e. mild vs. harsh winters)

• 10 year average is almost identical to the

WSI predicted salt usage

Planned I-93 Expansion

• Current TMDL Allocations do not address

future salt needs, Public or Private

• I-93 Travel Lanes are mostly doubled from

4 to 8 lanes along the corridor

• NH Route 111 is relocated with 4 new

travel lanes at Exit 3

• Target date for 4-lane operation is 2013

On-Board GPS Tracking

Vehicle Usage vs. Salt Usage

Watershed Vehicle Usage Salt Usage Beaver Brook 45% 11% Dinsmore Brook 95% 50% Policy Brook 48% 11%

Load Based Allocation

• Does not address vehicle usage ranging from

parked vehicles to vehicles traveling at the highway speed

• A single application of salt on I-93 may provide

service up to 1,800 vehicles per hour

• The same application could provide service to a

single vehicle per day in a parking lot or a few vehicles per day on a cul-de-sac

Vehicle Usage Based Allocation

• Total watershed allocation remains unchanged
• Distributes the salt allocation based on intensity of

vehicle usage

• Based on traffic volumes and travel lane distance

(Vehicle Lane Miles)

• Is a measure of how efficient and effective salt is

used

• Existing Load Based Allocations penalizes

previous efficient and effective salt use and rewards previous wasteful and inefficient salt use

Beaver Brook

518 518 906 906 393 77 814 3,593 2966 1,758 3472 2,217 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 TMDL Load Based Allocation Vehicle Usage Based Allocation Tons of Salt

Parking Lots Municipal Roads State Roads Private Roads Margin of Safety Other

NHDOT Salt Reduction

• Ground Orientation
• Pre-Wetting
• Brine
• Underbelly Plows
• RWIS/MDSS
• Training

NHDOT Salt Reduction

• Compared to conventional winter

maintenance practices, we can produce a 15%-20% reduction in salt use by fully deploying the previously mentioned BMPs

• BMPs do not change the Level of Service or

Level of Safety on the Highways, it just increases the efficiency and effectiveness

Beaver Brook

669 949 759 1,158 814 3,593 500 1000 1500 2000 2500 3000 3500 4000 Beaver Brook Tons of Salt TMDL 04/05 Load Existing Estimated Annual Average (tons/yr) Existing Est. Annual Average w/ BMPs(tons/yr) Estimated Future Average Annual w/ I-93 Expansion and BMPs (tons/yr) TMDL Load Based Allocation Vehicle Usage Based Allocation

Dinsmore Brook

3 3 26 2 62 116 3 2 33 6 20 40 60 80 100 120 140 TMDL Load Based Allocation Vehicle Usage Based Allocation Tons of Salt Parking Lots Municipal Roads State Roads Private Roads Other

Dinsmore Brook

82 139 111 125 62 116 20 40 60 80 100 120 140 160 Dinsmore Brook Tons of Salt TMDL 06/07 Load Existing Estimated Annual Average (tons/yr) Existing Est. Annual Average w/ BMPs(tons/yr) Estimated Future Average Annual w/ I-93 Expansion and BMPs (tons/yr) TMDL Load Based Allocation Vehicle Usage Based Allocation

Policy Brook

456 676 545 1,002 365 1,650 200 400 600 800 1000 1200 1400 1600 1800 Policy Brook Tons of Salt TMDL 06/07 Load Existing Estimated Annual Average (tons/yr) Existing Est. Annual Average w/ BMPs(tons/yr) Estimated Future Average Annual w/ I-93 Expansion and BMPs (tons/yr) TMDL Load Based Allocation Vehicle Usage Based Allocation

Proposed NHDOT Allocations

(Averaged over 10 year verified with WSI)

• Beaver Brook – 1,158 tons / year out of

9,069 tons / year total watershed allocation

• Dinsmore Brook – 125 tons / year out of

126 tons / year total watershed allocation

• Policy Brook – 1,002 tons / year out of

3,635 ton / year total watershed allocation

Plan Development Considerations

• Flexibility – Accounts for weather
• Adaptability – Accounts for the I-93 expansion

and does not prevent other BMPs from being deployed

• Measurable – Shed data, GPS and WSI
• Safety & Socio-Economic Benefits – No

reductions proposed

• Practical and Cost Effective – Continued use of

rock salt and brine and therefore achievable

Questions