NHDOT TMDL Implementation Plan Development Considerations o Flexibility o Adaptability o Measurable o Safety & Socio-Economic Benefits o 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 Parking Lots 10000 Municipal Roads 9000 State Roads 8000 Private Roads 2,217 3472 Margin of Safety 7000 Other Tons of Salt 6000 1,758 5000 2966 4000 3,593 3000 814 2000 393 77 1000 906 906 518 518 0 TMDL Load Based Vehicle Usage Based Allocation Allocation
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 TMDL 04/05 Load 4000 3,593 3500 Existing Estimated Annual Average (tons/yr) 3000 Existing Est. Annual 2500 Tons of Salt Average w/ BMPs(tons/yr) 2000 Estimated Future Average Annual w/ I-93 Expansion 1500 and BMPs (tons/yr) 1,158 949 TMDL Load Based 814 1000 759 669 Allocation 500 Vehicle Usage Based Allocation 0 Beaver Brook
Dinsmore Brook Parking Lots 140 Municipal Roads 6 2 120 State Roads 33 Private Roads 100 Other 3 Tons of Salt 80 116 60 62 40 20 26 2 3 3 0 TMDL Load Based Vehicle Usage Based Allocation Allocation
Dinsmore Brook TMDL 06/07 Load 160 139 140 Existing Estimated Annual 125 Average (tons/yr) 116 120 111 Existing Est. Annual Tons of Salt 100 Average w/ BMPs(tons/yr) 82 80 62 Estimated Future Average 60 Annual w/ I-93 Expansion and BMPs (tons/yr) 40 TMDL Load Based Allocation 20 Vehicle Usage Based 0 Allocation Dinsmore Brook
TMDL 06/07 Load Policy Brook 1800 1,650 Existing Estimated 1600 Annual Average (tons/yr) 1400 Existing Est. Annual 1200 Average w/ Tons of Salt 1,002 BMPs(tons/yr) 1000 800 Estimated Future 676 Average Annual w/ I-93 545 600 Expansion and BMPs 456 (tons/yr) 365 400 TMDL Load Based Allocation 200 0 Vehicle Usage Based Policy Brook 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 o Flexibility – Accounts for weather o Adaptability – Accounts for the I-93 expansion and does not prevent other BMPs from being deployed o Measurable – Shed data, GPS and WSI o Safety & Socio-Economic Benefits – No reductions proposed o Practical and Cost Effective – Continued use of rock salt and brine and therefore achievable
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