Snow Plan--ANC: winter in Alaska presents challenges that would test even the most efficient snow clearing teams. Airports International talked to Anchorage about the airport's 2004/5 winter planning.
During the Northern Hemisphere winter, snow can be expected at ANC from October through to April, with November to January usually experiencing the greatest accumulations. Surrounded on two sides by the warm water of Cook Inlet, ANC is also susceptible to freezing rain, dense fog and freezing fog, which rolls in from Cook Inlet. These conditions are quite common and obviously cause considerable concern to those responsible for airport ground operations.
The Snow Plan
The airport authorities produce an annual Snow Plan, which is put into practice whenever snow or ice threatens operational capabilities or the safety of the travelling public. It lays out detailed operating procedures for the staff to follow during periods of snow or Ice, as well as the post-storm clean-up. The men and women of the Field Maintenance, Operations, and Safety departments form a proud ANC team that works long hours on a 24/7 basis throughout the winter. They are multiple winners of the prestigious US Bernt Balchen Post Award for snow and ice control at large airports, and they are one of the few teams able to boast that their airport has never yet been closed by snow.
ANC--the largest airport in Alaska--is owned and operated by the State authorities. It is divided into two separate and distinct segments, the International Airport and the Lake Hood Complex. The airport consists of three paved runways, each 10,500ft (3,200m) or longer, as well as three major taxiways, numerous small taxiways and parking aprons. The Lake Hood Complex comprises a seaplane base, a 2,000ft (610m) gravel runway, and taxiways that provide services for general aviation aircraft. The Hood and Spenard lakes are used for ski operations during winter months when the ice thickness exceeds 12 inches.
Numerous roads and state-maintained car parks fall within the airport boundaries, and snow-clearing operations for these facilities are also carried out by ANC Airfield Maintenance personnel.
As you would expect, airfield snow/ice removal from aircraft movement areas takes priority over all the other airport service areas.
When snow or ice control operations begin the airport utilises the US NOTAM system for reporting airport condition information to all concerned, while Airport Information Advisories--transmitted via ARI NC--are used to offer carriers additional details on almost anything that is not related to flight activities and, therefore, not appropriate for NOTAMs.
The Airport Operations Officers and the Airfield Maintenance Shift Supervisor are kept constantly aware of how work is progressing, what equipment is being used and what its status is, as well as which personnel are available. Consequently, the supervisors are tasked with diverting snow removal personnel and equipment from one assignment to another as and when required. Volume, types of precipitation, wind direction and velocity, drifting snow, obstructions and runway/NAVAID availability must all be considered in the decision-making process.
Procedures and Priorities
When snow accumulation and intensity increases, the snow teams then effectively 'change-gear' into a high-speed snow removal mode and a Continuous Snow Removal NOTAM will be issued in order to keep ANC open and functional.
Snow removal priorities are essentially divided into four major categories. Category 1 (otherwise know as Priority Red) is primarily concerned with instrument runways, taxiways with direct access to the main runways in use, emergency response avenues for crash/rescue vehicles, and limited access to operations areas. Added to this is secondary or 'Priority IA' (Orange) ramp cleaning, which begins with the main lead-in lines and taxi lines to the North and South Terminals, plus their refuelling areas. Priority II (Blue) includes other access taxiways, refuelling areas, aircraft parking gates and Runway 14/32, unless a priority change is directed by weather conditions or the Runway 06R/6L ILS is inoperative or unavailable. Priority III (Green) includes Runway 24R, Runway 06L (Localizer), ramps, ground support equipment access roads, and all other runways and taxiways not included in Priorities I and II, while Priority IV (Yellow) covers public access roads and terminal access areas. Priority IV operations also involve the removal of snow from ramp areas, which has been piled in specific locations on the north ramp to expedite cleaning.
Sand and Chemicals
The application of sand and chemicals is normally conducted simultaneously with snow removal, dependent on pavement surface conditions, to maintain safe braking and taxying friction for aircraft.
Snow removal procedures for runways and taxiways will normally begin with sweeping operations using runway jet brooms towed by Fifth-wheel type trucks equipped with rubber blades. Rubber-edged or poly-edged blades are used to remove the majority of the snow from paved surfaces because they are less likely to damage lighting systems or paving surfaces.
The jet brooms are followed by snow-blowers, which should cast any remaining snow beyond the runway and taxiway edge lights. If friction tests taken by the Airfield Foremen record 'slick' pavement surface conditions; sand and/or deicing chemicals are applied to improve the braking action. Snow removal on the ramp areas begins with cleaning the ramp taxi lanes and nose lines leading to aircraft parking gates. Often, sand is then applied to improve braking and turning capabilities.
The majority of snow is pushed to a designated storage area before a final ramp cleaning is conducted using graders equipped with steel blades to completely remove compacted snow and ice. The ramp is then sanded and/or treated as necessary.
Service access and perimeter roads are also cleaned by using steel-bladed graders, before being sanded as required. When clearing roads, particular emphasis is placed on sanding stop signs as well as curves and hills--places where vehicles are more likely to lose control.
Snow, which contains de-icing chemicals (i.e. urea, potassium acetate, calcium chloride or glycol), is classified as 'dirty snow' by the airport and must be removed to those storage areas furthest from the Lake Hood and Spenard floatplane base, as well as other sensitive environments. Snow within airport operations areas is considered 'dirty' and must be disposed of in dedicated snow storage areas within the airport. Snow that is free of chemicals is usually considered 'clean' and can, therefore, be disposed of in approved storage locations. Airport tenants are asked to ensure that no solid waste is contained within the snow they may be responsible for moving, and leaseholders who push snow from their lease lots are charged for its removal.
Communication is a critical safety factor during all snow removal operations conducted on active runways, taxiways and in other controlled areas, so all snow removal vehicles operating in aircraft movement areas are equipped with two-way radios. Each state vehicle has an established call sign that remains with it. Whenever possible, where there are multiple vehicles operating on a given controlled airfield area, one vehicle will be the focal point for communications with the tower while all the other operators will monitor the appropriate frequency.
Temporary runway closures are a common occurrence during the winter. While every effort is made to optimise safety, during periods of snowfall, freezing rain and low visibility, busy flight operations may limit the maintenance team's access to the runways, resulting in a build-up of snow and slush on the runway surface, necessitating a temporary closure until it can be removed. Runway closures are also necessary during the removal of large accumulations of snow due to the hazard presented by large snow berms on runway surfaces during cleaning operations.
When the primary instrument runway (06R/24L) has to be closed for snow removal, careful co-ordination is maintained between Airport Operations, Airfield Maintenance and ATC. Except in the case of emergencies, prior to the closure of Runway 6R, Runway 14/32 must be cleaned, sanded and made ready for aircraft landings, as this allows aircraft to coordinate a Runway 14 approach should they elect not to use the CAT I approach to Runway 6L.
Obviously, ice build-up on runway surfaces presents a severe hazard to landing aircraft, so when a 'nil braking' pilot report is received from a landing aircraft, action must be taken immediately to ensure the safety of subsequent arrivals. ATC will immediately stop all operations on the affected area and notify Airport Operations of the report and the location of the affected area, which in turn alerts Airfield Maintenance supervisory personnel by radio or telephone. The runway is then 'NOTAM closed' for inspection and, if required, corrective action completed. If the runway inspection indicates a braking friction in excess of .20, the runway is reopened, if not it remains dosed. As a follow-up action, friction readings on the runway in question are recorded on a Runway Condition Report, and transmitted through the AIRINC/US NOTAM System. Taxiways are also deemed opened or closed using the same method.
Friction tests are taken at the beginning of each shift and as often as required using either a Bowmonk or Tapley meter. However, this winter the Field Maintenance team is experimenting with a continuous 'tow-behind' friction tester. Friction tests are also routinely carried out when there is a significant change in the weather, and each time a runway is cleared of snow or swept following anti-icing or de-icing. Tests may additionally be carried out at the request of ATE, or whenever the Airfield Maintenance shift supervisor estimates braking action to be .40 or below.
It is standard procedure that all braking tests are performed at 20mph (32km2/h) and that the testing vehicle's brakes will be applied in a manner that avoids wheel lockup. On runway surfaces, the test is carried out approximately 20ft (6m) either side of the centreline, with readings taken in each third (touchdown, middle and stop end) of the runway and averaged out. Taxiway surfaces are tested approximately 10 to 15ft (3m to 4.5m) either side of the centreline and a second friction test needs to be carried after sand or de-icing chemicals have been applied to remedy 'slick' areas.
As every Boy Scout knows, the key to success is to be prepared. So, prior to the start of each winter season, calculations are made to ensure there will be sufficient sand, urea, liquid de-icer and other related snow and ice control assets before the Snow Plan becomes operational on October 1 each year. Approximate figures include 4,000 tons of sand, 1,800 tons of urea, and 90,000 gallons of liquid de-icer.
Vehicle spares are also made ready, with 260 sets of cutting edges stockpiled, together with 36 sets of broom bristles, 86 sets of ice blades and 40 sets of rubber blades. A great effort is made to ensure that equipment is maintained in a state of readiness throughout the snow removal season--an obvious requirement but something so often overlooked at many airports--and it has been found that effective operating levels require four plough trucks for normal conditions, and five for high-speed operations.
All in all, it is a major task to prepare for the local winter conditions. But as we know, nature is all powerful--freak blizzard conditions led to the local Air National Guard being called in to assist with snow-clearing activities after a record-breaking 28.6 inches (72cm) fall in March 2002. Thankfully, such extremes are rare, leaving ANC operational throughout your 'average' winter.
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|Title Annotation:||winter services; Anchorage International Airport|
|Comment:||Snow Plan--ANC: winter in Alaska presents challenges that would test even the most efficient snow clearing teams.|
|Date:||Jan 1, 2005|
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