Chapter 4 Building Area Developm ent

(FBO) that provides maintenance, and a OVERVIEW general aviation terminal. The County of Mariposa operates and maintains the fuel facility as well as The building area of an encompasses all of the general aviation terminal. the airport property not devoted to runways, major taxiways, required clear areas, and other airfield- related functions. Typical facilities found at a DESIGN FACTORS general aviation airport area shown in the list to Many factors influence the planning and future the right. development decisions associated with Mariposa- This chapter examines the factors that affect the Yosemite’s building area. Most of these factors siting of future building area facilities at Mariposa- can be grouped under the five headings that Yosemite Airport and alternative ways of follow. accommodating projected demand. The focus is on providing direction for the appropriate Airport Property expansion and use of the core building areas of The current airport property consists of the airport. The various design issues associated approximately 150 acres. The runway and taxiway with Mariposa-Yosemite Airport are discussed in system occupies about 8 acres of this total, while the sections that follow. The two most critical some 9 acres consists of aviation-related buildings concerns are defining the most cost-effective (i.e., FBO, aircraft storage hangars). Although it is location for additional aircraft storage hangars and possible to expand an airport’s property (and will a site for a large parking position. The be recommended at this airport), the existing Building Area Plan enclosed with the Master Plan property boundary shapes the path of future report presents the recommended layout of development. facilities for these areas.

It should be recognized that there are two distinct Demand building areas on the airport. Currently most The demand for additional building area facilities development is located on the south side of the at Mariposa -Yosemite Airport is forecast to airport. However, there are some building area increase over the 20-year planning period. As facilities located on the north side. documented in Chapter 2, the The choice of which side of the Typical Building Area Functions and number of based aircraft is forecast airport to place facilities will be a Facilities Commonly Found at to increase from the current 32 reoccurring theme in this chapter. General Aviation : aircraft to 62 aircraft. The additional • Based aircraft tie downs and storage The existing building area contains hangars based aircraft at Mariposa- most of the uses expected at a • Transient aircraft parking Yosemite Airport translate directly • Administration building/office general aviation airport: aircraft • Pilots’ lounge/flight preparation area to building to building area facilities storage hangars, aircraft tiedowns, • Public restrooms and telephone needed there. • Fixed Base Operator (FBO) facilities a fueling facility, fixed base • Fuel storage and dispensing

operator equipment • Aircraft washing area • Perimeter fencing and access control • Access roads and automobile parking

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All but 1 of the aircraft currently based at Existing Facilities Mariposa-Yosemite Airport are single-engine, piston-powered aircraft; there is 1 piston twin. It is Generally, the facilities at Mariposa-Yosemite anticipated that most of the aircraft based at the Airport are expected to remain viable throughout airport will continue to be single-engine piston the 20-year planning period. The exception is the aircraft. Partially this is due to demand, but the aircraft storage hangars on the north side of the runway’s length is a limiting factor for larger airfield. These hangars are in poor condition and aircraft. will need to be replaced somewhere on the airport. As expected, periodic maintenance will be required Because Mariposa-Yosemite Airport is used as a to preserve the functionality of airfield pavement, means of accessing Yosemite National Park, other structures, and associated drainage and utilities. local tourist sites (e.g., historic towns), and second homes, transient parking is an important Accessibility component of this plan. The forecasts presented An important design consideration is the ease of in Chapter 2 anticipate that peak transient parking access to individual portions of the building areas demand will increase from 5 to 10 aircraft. from both the taxiway system and public roads. Demand for new fixed base operator (FBO) At Mariposa-Yosemite Airport, Taxiway A (the leaseholds is expected to be limited. The most parallel taxiway) provides adequate access to the likely source of demand is from the existing southern building area. The building area is maintenance FBO. There is the potential that this relatively shallow; most facilities are directly operator may wish to expand into a larger hangar accessible from Taxiway A. There is not sufficient or otherwise expand his business. There is also space for an apron edge taxiway. the potential that a specialized FBO may be developed during the life of this plan. However, There are two components to vehicular given the number of based aircraft and relatively accessibility: access to the airport; and access to remote location of the airport, demand for the airfield (e.g., hangars). The south side of the additional FBO site is uncertain. airport enjoys very convenient access from California State Highway 49. This highway passes Setback Distances immediately south of the airport. The north side of The interior boundary of the airport building areas the airfield is accessed from the Cya Road. is determined in large part by the necessary The airfield is accessible to the public from three setback distances from the nearest runway and points. On the south side, there is both a vehicle taxiways. Based upon FAA design standards gate and a pedestrian gate that provide access to discussed in the preceding chapter, the following the airfield from the public parking lot adjacent to design criteria are applied where appropriate: the General Aviation Terminal. A third gate • A minimum of 245 feet from the centerline of provides access to the north side from a road that Runway 8-26 to any future buildings. intersects Highway 49 immediately east of the • A minimum of 125 feet from the centerline of airport. All are controlled access points, as will be Runway 8-26 to any future aircraft parking described in more detail later in this chapter. positions.

• A minimum of 45 feet from center of a taxilane to fixed or movable object.

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At a general aviation airport, the system of fencing BASED AIRCRAFT STORAGE AND and gates is intended to provide three functions: PARKING

• Exclude stray domestic and wild animals (e.g., The forecasts prepared as part of this master plan cows and deer) update indicate that demand will exist for storage • Prevent inadvertent entry of people and facilities for up to 32 additional based aircraft by vehicles onto the airfield operations area the year 2026. Sites for at least 5 box hangars • Increase the difficulty of determined entry by currently exist, so 27 additional sites are needed. those with malicious intent (i.e., thieves). Meeting this forecast demand is contingent upon hangar availability. A need for additional tiedowns There are general Federal Aviation Administration to accommodate based aircraft is not anticipated. guidelines for fencing and gates. Hangars BUILDING RESTRICTION LINE Background The building restriction line (BRL) establishes the The demand for specific sizes of hangars cannot closest location that buildings can be placed be anticipated. The size of new hangars will be relative to a nearby runway or, in some cases, a determined by market forces (e.g., price), the primary taxiway. The FAA no longer defines a types of aircraft owned by prospective tenants, and specific BRL setback distance standard, but rather the personal preference of prospective tenants. provides guidance on factors to be considered in The best design will be one that permits determining the BRL location. construction of a variety of hangar sizes. An The purpose of a BRL is to ensure safe use of the optimum design would accommodate box hangars airport by providing: from 42’ x 36’ to 60’ x 50’ and standard T-hangars.

• Clearances necessary for visual and The FAA standards specify that the maximum instrument flight operations gradient for taxiways is 2%. Areas in front of • Clear visibility from the air traffic control tower, hangars and on aprons have a practical limit of when one exists 1%. With side slopes greater than 1 % fuel will • Clear visibility between runways, when drain from wing vents while parked. With multiple runways exist longitudinal slopes aircraft will be very hard to push in and out of hangars, and will roll if brakes are not At Mariposa-Yosemite Airport, the BRL for Runway set. These shallow gradient limitations narrows 8-26 is set at 245 feet on each side of the runway the range of possible sites and necessitates filling centerline. Effectively, the BRL is established to or cutting into slopes. create a visually uniform “flight line” facing the runway. At the established distance, a 17-foot tall building situated at the same elevation as the T-H angars runway would not penetrate the 7:1 transitional surface of FAR Part 77. The 17-foot standard is

appropriate because this airport is designed to accommodate small aircraft (i.e., those under 12,500 pound gross weight). Typical storage

hangars for small aircraft are less than 17 feet in T-hangars (definition): T-hangars are groups of hangars height. built in one unit. The placement of interior partitians gives each unit a “T” shape.

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Constraints on Possible Hangar Sites • East of the helicopter parking pads Both the south and north sides of the airport were • On the western tiedown apron. evaluated for possible hangar sites. The generally Within these three areas, a total of six alternative steep terrain significantly constrained the location layouts were evaluated. The six alternatives are: of potentially viable hangar sites. It was assumed 1. North Side Site: The sole alternative located that sites requiring retaining walls would not be on the north side of the airport. It is centered economically viable. near the existing hangars. The north side of the airport currently has several 2. Southeastern Site: The only alternative in the hangars that directly access the runway via a short southeastern corner of the airport (east of the taxiway. Due to safety concerns, it would be highly helicopter parking pads). desirable for any new hangars on the north side to 3. Southwestern Site – Box Hangars with north- be served by a parallel taxiway. At a minimum, a south orientation: one of three alternatives that partial parallel taxiway that connects to one of the would extend the existing hangar area further runway ends would be needed. A direct taxiway west. connection forces aircraft increases the potential 4. Southwestern Site – T-hangars with north- for a runway incursion. A midfield connection south orientation: similar to the previous forces the pilot to cross the runway to reach the alternative by includes two-sided T-hangars runway end. Pilots who are landing or taking off rather than single-sided box hangars. are also less likely to notice an aircraft entering the 5. Southwestern Site – Box Hangars with east- runway midfield than at a runway end. west orientation – would extend two rows of It would be physically possible to create a full- small, box hangars along an extension of an length parallel taxiway on the north side. However, existing taxilane. the earthwork volumes required to build this 6. West Tiedown Apron – Would convert two taxiway would make it very expensive. rows on the existing tiedown apron to T- Constructing a full-length parallel taxiway would hangars. only be justified if significant development were The six alternatives are shown in Figures 4A possible on the north side. Unfortunately, the only through 4F at the end of this chapter. Table 4A location with significant development potential is describes each alternative’s key features and the site with the existing hangars. Elsewhere summarizes its strengths and weaknesses. along the north side no potential building sites could be created without large retaining walls. Therefore, the only north-side hangar alternative that will be evaluated will consist of redevelopment of the existing hangar site. N ested T-H angars The south side of the airport property also has variations in slope, but there are less design restrictions. New hangar development on the south west side could capitalize on the existing taxiways and taxilanes. Three general areas could accommodate hangar sites: Stacked T-H angars • West of the existing hangar area

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Table 4A Storage H angar Alternatives

ALTERN ATIVE DESC RIPTIO N STREN G TH S WEAKN ESSES

Alternative 1: N orth Side Site

• Three lines of box hangars in an L-shaped layout. • W ould provide two-thirds of the forecast • Partial-parallel taxiway requires taxiing aircraft to • Cut slopes for northern section and fill for western dem and for hangars. cross runway for departures to the west, the m ost section. • W ould utilize the existing m idfield runway com m on direction. • Requires acquisition of private property or agreem ent exit. • Requires relocation or replacem ent of airport with owner because toe of fill slope would extend off • Partial-parallel taxiway would im prove m anager’s house. site. safety over current configuration. • Acquisition of adjacent private property has • W ould accom m odate 18 sm all box hangars. historically been a sensitive local issue. However, • A partial-parallel taxiway would be constructed. fee sim ple acquisition not essential, because only earth fill would be on private land. • M ost expensive alternative. Alternative 2: Southeastern Site

• Four short lines of box hangars. • W ould provide about 40% of forecast • Direct connection of hangar taxilanes to run-up • W ould provide space for 11 sm all box hangars. dem and for hangars. apron is a likely source of conflict between aircraft. • Center of site is relatively level. Fill would be required • Very convenient access to runway. • Connection of access road to Highway 49 is for sides of site. undesirable from a highway safety perspective. It • An access road would connect to Highway 49. m ay be difficult to obtain an encroachm ent perm it • W ould require acquisition of private property. from Caltrans. • Access road would interfere with existing cattle crossing easem ent. • Acquisition of adjacent private property has historically been a sensitive local issue. Alternative 3: Southw estern Site – Box H angars w ith North-south O rientation

• Three lines of box hangars. • W ould provide alm ost half of forecast • Acquisition of adjacent private property has • W ould provide space for 13 sm all box hangars. hangar dem and. historically been a sensitive local issue. However, • M inor property acquisition required or agreem ent with • Connects to existing hangar area taxilanes fee sim ple acquisition not essential, because only owner, because toe of fill slope will extend off airport earth fill would be on private land. property. Alternative 4: Southw estern Site – T-H angars w ith N orth-south O rientation

• Three banks of T-hangars. • W ould provide alm ost 90% of forecast • Acquisition of adjacent private property has • Could provide about 24 units if configured as nested T- hangar dem and. historically been a sensitive local issue. However, hangars. • Connects to existing hangar area taxilanes fee sim ple acquisition not essential, because only • M inor property acquisition required or agreem ent with earth fill would be on private land. owner, because toe of fill slope will extend off airport property. Alternative 5: Southw estern Site – Box H angars w ith East-w est O rientation

• Two long lines of hangars. • W ould provide about 93% of forecast • About 35 hangars will be served by one taxilane. • Could provide up to 25 sm all box hangars. hangar dem and. The m ost of any There is not sufficient room for aircraft to pass each alternative. other. The taxiway m ay be tem porarily blocked • Does not require acquisition of private when an aircraft is pulled out of a hangar. property. • Connects to existing hangar area taxilanes. • Least expensive on a per hangar basis of all alternatives that require fill. Alternative 6: W est Tiedow n Apron

• Two banks of T-hangars • W ould provide about half of the forecast • W ould reduce visibility of runway and parallel • Could provide 14 units in a stacked configuration. hangar dem and. taxiway from term inal. • Existing portable hangars would be relocated to • Least expensive alternative. • Construction of second bank of hangars should not existing rows with portable hangars. occur before parking pad for large helicopter is constructed. Otherwise it would reduce ability to m eet peak transient parking dem and. • The FAA would have to approve conversion of the apron to hangars.

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Analysis of Alternatives The need for the vehicle access to connect the Southeastern Site directly to State Highway 49 is None of the six alternatives are capable of also undesirable. It creates another direct access satisfying the forecast demand for hangars alone. to a highway with its associated turning Therefore, we are seeking the most efficient movements. It is expected that California’s combination of alternatives to meet the forecast Department of Transportation (Caltrans) would not hangar demand. Evaluation criteria include safety, favor this new access, but unknown whether the cost and complexity. additional encroachment permit would be granted. The North Side Site (Alternative 1, Figure 4A) Additionally, this access road would need to would provide space for about 18 small box include provision for a cattle crossing. A cattle- hangars. A partial parallel taxiway would be crossing easement currently exists around the created to connect this group of hangars to the east end of the runway. The cow path is fenced to western runway end. This alternative raises the exclude cows from the airfield. It connects grazing most significant safety concerns of any alternative. land that lies north and south of the airport.

Aircraft based in these hangars would have to The Southeastern Site has several minor safety cross the runway to depart to the west – the most concerns, and more substantial security problems. common direction. This significantly increases the It has a degree of complexity and uncertainty not likelihood of an accident with another aircraft that found in any other alternative. While none of is landing or taking off. A full-length parallel these problems makes this alternative infeasible, it taxiway would reduce this problem. However, certainly makes its less desirable. these aircraft can be expected to cross the runway The next three alternatives considered are all because fuel is only available on the south side. located in the southwestern corner of the airport. This would mean a runway crossing before or after They would connect to the taxilanes already every flight. Additionally, this alternative is already serving the hangars in this corner of the airport. the most expensive (on a per hangar basis) All three would require significant fill to provide a because of the partial-parallel taxiway. The relatively level area for the hangars and associated combination of safety concerns and high price pavement. make this alternative unacceptable. Alternative 3 (Figure 4C) would create space for The Southeastern Site, Alternative 2 (Figure 4B), 13 small box hangars in a north-south orientation could accommodate 11 small box hangars. Safety (i.e., the doors would face east and west). The concerns, albeit less significant ones, also exist use of box hangars requires access to only one with Alternative 2. This alternative would connect side of each group of hangars – unlike T-hangars the hangar taxilanes to the area used for run-ups. which require access to both sides. The fill slope The connection is unusual, and as such raises for this alternative would extend off of airport concerns over taxiing accidents. Providing property to the south. Therefore, either additional adequate security for the Southeastern Site will be land would need to be acquired or some form of difficult because it is not readily visible from the agreement with the landowner created to allow the general aviation terminal. This site’s isolation from fill. The north-south orientation of the hangars where most other aircraft are stored reduces the extends the fill platform further from the native informal security value provided by the presence of slope than an east-west orientation. This means other based aircraft owners.

What is a run-up? Immediately prior to takeoff, piston aircraft perform various engine checks. This requires that the engine be run at a specified RPM while oil pressure and other systems are checked. Aircraft with variable-pitch propellers “exercise” the propeller to verify that the variable pitch system is operational. These system checks are normally conducted at an apron adjacent to the runway end.

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that the fill platform is more extensive that it would The final alternative (Alternative 6, Figure 4F), be for an alternative with an east-west orientation. would utilize two rows on the West Tiedown Apron. This increases the cost per hangar. Alternative 3 It would replace 20 tiedowns with 14 units in two T- does not have any significant operational hangars. Site preparation would be minimized deficiencies. Its only complication is the need for because the site already has the very shallow permission from the adjacent land owner to extend slope require for a parking apron. The existing the fill slope into grazing land. However, being pavement would need to be removed and more expensive per hangar than the east-west redesigned to provide proper drainage away from alternative makes this alternative less attractive. the hangars. Because this tiedown apron was constructed with FAA grant funds, the FAA would Alternative 4 (Figure 4D) is very similar to have to approve of the conversion to hangars. Alternative 3 except that T-hangars are substituted Clear documentation that the loss of tiedown for small box hangars. This configuration results spaces would not constrain either based or in more hangars: 24 versus 13. Alternative 5 transient demand would be needed. would have lower costs per hangar than Alternative 3. However, its per hangar cost would Alternative 6 would fit two rows of hangars on the be higher than alternative 5. It has a functional apron without requiring any reconfiguration of the design with no significant operational deficiencies. balance of the apron. This will work only if the T- Its only complication is the need for permission hangars are configured in the “stacked” from the adjacent land owner to extend the fill configuration; a “nested” configuration would be slope into grazing land. It, too, is an acceptable too wide (see adjacent illustration). This alternative that is less desirable than a lower cost alternative would require relocating the portable alternative in this general area. hangars already located on these rows. As can be seen in Figure 4F, there is space in the adjacent The third, and final, alternative in the southwest rows to accommodate these portable hangars. corner of the airport (Alternative 5, Figure 4E) would develop two rows of box hangars with an While this would be the least cost alternative, it east-west alignment. The two rows of hangars has one limitation and a one timing complication. would face each other across an extension of the Alternative 6’s limitation is that it would restrict existing taxilane. This alternative would produce visibility of the runway and parallel taxiway from about the same number of hangars as Alternative within the general aviation terminal. Currently all 4 (25 versus 24), but its east-west orientation of the runway and most of the parallel taxiway can would require significantly smaller amounts of fill. be seen from within the terminal. This allows This gives it a lower cost per hangar. Of the viable airport staff to monitor the airfield when they are in alternatives examined so far, this has the lowest the terminal. These hangars would block the view per hangar cost. of the western third of the runway and parallel taxiway. While visibility of the airfield is not The only weakness of Alternative 5 is that it places essential (many general aviation airports do not about 35 hangars on one taxilane. An aircraft have it), it is desirable. A clear view of the entire parked in front of a hangar while being readied for airfield makes it easier for airport staff to identify departure would temporarily block the taxilane. potential problems (e.g., deer on the runway) or This minor complication could be overcome with respond to an emergency (e.g., a gear-up landing). courtesy and coordination among tenants in this row.

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The timing complication for Alternative 6 is linked least complicated means of providing additional to resolution with the large helicopter parking hangars. The Airport Layout Plan incorporates this issue. Currently, a large helicopter is often based selection. at the airport for several weeks each summer as part of wildland fire fighting operations. Typically Based Tiedowns the helicopter is either a Sikorsky S-64 Aircrane or Currently there are two based aircraft that utilize Boeing CH-47 Chinook. Due to the constrained tiedowns. It is anticipated that with new hangar airfield and steep terrain there are few choices of development there will be no additional demand where to park this helicopter. The optimum site for based tiedowns. If demand for based tiedowns has proven to be the southern tiedown apron. is higher than anticipated, there are sufficient However, these large utilize the entire existing tiedowns to accommodate a large number southern apron while they are stationed at the of based aircraft. airport. This leaves only the western apron available for based and transient aircraft. TRANSIENT AIRCRAFT PARKING Under most circumstances, there would be sufficient tiedown spaces for based and transient Fixed Wing Aircraft Parking aircraft even if Alternative 6 was implemented and a large helicopter was occupying the southern As noted in Chapter 2, peak transient fixed-wing apron. However, special events (e.g., organized aircraft parking demand is forecast to increase fly-ins) or unusual occurrences (e.g., several from 5 aircraft to 10 aircraft over the next 20 years. aircraft with large wingspans) could result in a During this period, the share of large aircraft shortage of tiedown spaces. Therefore, if this (mostly piston twins and turboprops) is expected to alternative is used, it is recommended that only the continue to increase. The main apron is large westernmost bank of T-hangars is constructed enough to accommodate this demand. However, prior to a large helicopter parking pad being specific parking areas for larger aircraft have not constructed. been designated. To better serve Mariposa- Yosemite airport, and the occasional large aircraft, Selection of Hangar Sites it is recommended that two large aircraft parking For the reasons presented above, Alternatives 1 positions be defined. This could be accomplished and 2 have been eliminated from further by converting five tiedowns on the northern end of consideration. The remaining four alternatives a row on the west apron. A painted rectangle were determined to be viable alternatives, would define the parking area. although none are without at lease minor deficiencies. As noted earlier in this chapter, no Helicopter Parking one alternative can satisfy the forecast 20-year During the summer, the Mariposa-Yosemite demand for hangars. The best combination is Airport serves as a base for helicopters involved in judged to be Alternatives 5 (Southwestern Site – wildland fire fighting operations. The airport also box hangar with an east-west orientation) and 6 sees use by helicopters on other missions, (West Tiedown Apron). Alternative 5 would be including: implemented first. Once this area is built out, • Flight training Alternative 6 would be implemented (assuming • Utility patrol FAA concurrence could be obtained). This • Law enforcement combination would provide the most cost-effective, • Military proficiency flights

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Three helicopter parking positions were During the weeks when a large helicopter is based constructed east of the fixed-wing tiedowns. The at Mariposa-Yosemite Airport, 18 fixed-wing helicopter parking pads connect directly to the tiedowns are rendered unusable. Rotor wash from parallel taxiway. Each parking position features a these large helicopters also produces operational 50’ x 50’ Portland cement concrete pad problems for those using the general aviation surrounded by an area stabilized with asphaltic terminal and fuel island. An alternative to using concrete. The design aircraft for these pads is the the eastern apron is needed to reduce the Bell 212. This helicopter has a rotor diameter of operational conflicts. 50 feet and a gross weight of 11,200 pounds. This need could be satisfied by either a helicopter These three helicopter parking positions are parking position or a helipad designed to adequate to meet typical demand by small accommodate these large helicopters. A helipad helicopters. would need to be sited at least 700 feet laterally from the runway for its operations to be independent of the runway. It is technically possible to site a helipad within 700 feet of a runway. However, this would mean that the operations on the runway and helipad were dependent; that is, the runway could not be used while a helicopter was landing or taking off from the helipad. As there is no way to ensure that this coordination will occur at a nontowered airport, locating a helipad within 700 feet of a runway is undesirable from a safety perspective. Therefore, It is important to understand that these are only helicopter parking positions will be considered helicopter parking positions, not helipads. A for sites within 700 feet of the runway. helipad is a landing facility equivalent to a runway. Whether designed as a helipad or helicopter The three pads are parking positions. Helicopters parking position, the pad would be 60 feet by 60 must make approaches to landings to the runway feet and constructed of Portland cement concrete. or other location before parking on these pads. If served by a taxiway, the taxiway would be 35 As a part of summer firefighting operations, the feet in width. Surrounding the taxiway and pad airport is also regularly used by larger helicopters would be an area stabilized to prevent blowing of such as the Sikorsky S-64 Aircrane or Boeing CH- dust and debris. Stabilization could be 47 Chinook. The Aircrane has a rotor diameter of accomplished with pavement or turf. The stabilized 72 feet and a gross weight of 42,000 to 47,000 area would have a width of 132 feet. pounds (depending upon model). The Chinook’s Most of the large helicopters using this pad are twin rotors each have a diameter of 60 feet; it has expected to be associated with wildland fire a gross weight of 54,000 pounds. Currently there suppression. Therefore, space needs to be are no facilities designed for parking this class of allocated for the supporting facilities that helicopter. Due to the constrained airfield and accompany this type of operation. A level site for steep terrain, the eastern tiedown apron is used the portable slurry mixing tank needs to be within for parking this class of helicopter. One helicopter about 75 feet of the pad. A level area nearby also of this type utilizes the entire eastern apron. need to be provided for a modular office and

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parking area for support vehicles. The support Sites 1 and 2 have two major problems in vehicles will include a fuel truck and service truck. common. First, neither would be readily visible to aircraft ready to depart from either end of the The range of possible sites for a large helicopter runway. This is a significant safety liability. parking position or helipad is limited by several Additionally, these two alternatives would be the constraints: least compatible with adjacent land uses. The pad • Steep terrain location would force the large helicopters to overfly • Existing development on the airport the community of Mount Bullion at low altitudes • Nearby roads during arrivals and departures. These two sites • Required setbacks from the runway and have, therefore, been eliminated from further taxiways. consideration. Only two areas on or adjacent to the airport could Site 3 has similar safety problems. A helicopter on meet the physical requirements for this parking the pad would be visible from the end of Runway pad or helipad: south of the existing building area 26, but not the end of Runway 8. More and north of the runway. Each alternative area is significantly, large helicopters arriving or departing examined in the paragraphs that follow. to the east would have to pass very low over With some additional property acquisition, a large Highway 49. This would be a very significant helicopter parking position or helipad could be safety hazard. Therefore, Site 3 has been constructed in the area south of the existing rejected. building area. The area is generally open, so a The three remaining sites are all located north of parking position or helipad could be developed the runway. Sites 4 and 5 are similar in that they almost anywhere along the south side. The only could be connected to the runway with a loop physical constraints are State Highway 49 and the taxiway. This is the source of important strengths airport entrance road. and weaknesses of these two sites. Unlike most Three sites were selected to represent the range smaller helicopters, the large helicopters that will of possible sites south of the airport building area use this pad have wheels. A landing helicopter (see Figure 4G). Site 1 (Southwest) is on the would make its approach down the runway, land western end, Site 2 is in the center (South-center), on the runway and then taxi to the parking pad. and Site 3 (Southeast) is located east of the airport This proximity to the runway makes Sites 4 and 5 entrance road. readily visible to fixed-wing aircraft, both from the Three additional sites have been evaluated in the ground and air. It also raises the potential that the area north of the runway. Site 4 (Northwest) rotor wash from these helicopters could interfere includes the area currently occupied by four with landing or departing aircraft. The FAA hangars and the airport manager’s residence. Site minimum separation between the parking pad and 5 (Northeast) is located further east, near midfield. runway centerline is 165 feet. In order to reduce Site 6 (Far North) is located uphill from Site 4. the potential for rotor wash to affect operations on Table 4B summarizes the strengths and the runway, increasing the pad setback to 300 feet weaknesses of each of the 6 alternative sites. In is proposed. Site 4 is superior to site 5 in that the the paragraphs that follow, the relative importance parking pad can be shifted further from the runway of the strengths and weaknesses are considered. without the need for retaining walls or property acquisition.

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Table 4B Large H elicopter Alternatives

ALTERN ATIVE STREN G TH S WEAKN ESSES SITE 1

Southwest • Can be sited so that operations are • This site lies within the com m on traffic pattern for fixed-wind aircraft. Arriving and departing independent of those on the runway. helicopters will have to cross the fixed-wing pattern. • The site is about 75 feet below the elevation of the west end of the runway. Helicopters operating from this location could not see or be seen by fixed-wing aircraft ready for departure. • Additional property would need to be acquired. In addition to the cost, property acquisition at this airport can be expected to be controversial. • An access road would need to be extended to this site. • Arrivals and departure paths would bring helicopters low over residences in the com m unity of M t. Bullion. SITE 2

South-central • Can be sited so that operations are • This site lies within the com m on traffic pattern for fixed-wind aircraft. Arriving and departing independent of those on the runway. helicopters will have to cross the fixed-wing pattern. • The site is about 75 feet below the elevation of the west end of the runway. Helicopters operating from this location could not see or be seen by fixed-wing aircraft ready for departure. • Additional property would need to be acquired. In addition to the cost, property acquisition at this airport can be expected to be controversial. • An access road would need to be extended to this site. • Arrivals and departure paths would bring helicopters low over residences in the com m unity of M t. Bullion. SITE 3

Southeast • Close to other helicopter parking positions. • Operations would not be independent of those of the runway. • Although the site is about 40 feet lower than • Aircraft departing from Runway 8 could not see or be seen by a helicopter at this site. the eastern end of the runway, helicopters • Helicopters arriving or departing to the east would pass low over State Highway 49. operating from this site could see and be • This site would elim inate the cow path easem ent that connects the grazing lands north and seen by fixed-wing aircraft at the run-up south of the airport. apron for Runway 26 (the m ost com m only • Additional property would need to be acquired. In addition to the cost, property acquisition at used end). this airport can be expected to be controversial. SITE 4

Northw est • Taxiway access from the runway can be • Operations would not be independent of those of the runway. provided. This is of value because the large • Depending upon the distance between the runway and helicopter parking position, rotor wash helicopters have wheels, not skids. could affect fixed-wing aircraft landing and taking off. • Helicopters operating from this location • Existing hangars and the airport m anager’s residence would need to be relocated. could see and be seen by fixed-wing aircraft ready for departure. • No property would need to be acquired. • Arrival-departure pattern overflies few residences in the airport’s vicinity. SITE 5

Northeast • Taxiway access from the runway can be • Operations would not be independent of those of the runway. provided. This is of value because the large • Depending upon the distance between the runway and helicopter parking position, rotor wash helicopters have wheels not skids. could affect fixed-wing aircraft landing and taking off. • Helicopters operating from this location • Additional property would need to be acquired. In addition to the cost, property acquisition at could see and be seen by fixed-wing aircraft this airport can be expected to be controversial. ready for departure at either runway end. • An access road would need to be extended to this site. • Arrival-departure pattern overflies few residences in the airport’s vicinity. SITE 6

Far North • Can be sited so that operations are • Terrain higher than the pad elevation underlies the approach from the east. Although the independent of those on the runway. terrain is likely below the helicopter approach surfaces (depending upon the actual design), it Arrivals and departures could be conducted would be a safety concern. outside of the fixed-wing pattern. • An avigation easem ent would need to be acquired to protect the approaches from • Helicopters operating from this location encroachm ent by structures or trees. could see and be seen by fixed-wing aircraft • The west side’s access road passes through the eastern approach. ready for departure at either runway end. • CYA Road underlies the approach from the east. Helicopters will pass low over the road, • Arrival-departure pattern overflies few which creates a safety concern. residences in the airport’s vicinity.

Mariposa-Yosemite Airport Master Plan (April 2008) 4–11 BUILDING AREA DEVELOPM ENT C H APTER 4

However, Site 4 has the disadvantage of requiring helicopter operations. Annual reminders could removal of four hangars and the airport manager’s also be given prior to fire season (when the pad is residence. This negative factor is somewhat most likely to be active) to the owners of aircraft reduced by the fact that three of the hangars lie based on the north side. This approach is similar within the building restriction line and two of these ones routinely used at commercial service airports. hangars are at the end of their useful life. Of these The second physical feature is less easily to work two alternatives, Site 4 is judged to be superior around: terrain closely underlies the approach because of the relative ease of placing the pad surface. The helipad would only be used during further from the runway; this is judged to be a key daylight and under VFR conditions. So this terrain safety criteria. Therefore, Site 5 will be removed would be clearly visible to helicopter pilots. from further consideration. However, the close proximity of terrain to the The final site, Site 6, is located uphill from site 4. approach path is undesirable. It would be Operationally, it differs from the other alternatives especially problematic during gusty wind north of the runway in two ways. First, the terrain conditions. However, the helipad would meet all makes it impractical to connect this site to the FAA helipad design standards, and must be runway with a taxiway. Second, this distance considered a viable alternative. enables the pad to be designed as a helipad. That Based upon the preceding analysis, all but Site 4 is, helicopters can fly directly to this pad. Their (Northwest) and Site 6 (Far North) have been arrival-departure pattern would remain north of the eliminated. Neither site is ideal, but both can meet pattern used by fixed-wing aircraft. This makes or exceed all FAA design standards. The these helicopter operations independent of those independence of Site 6 from other airfield on the runway. It also keeps these helicopter operations is an important asset. However, Site operations further from residential uses than the 6’s proximity to terrain and interaction with the on- other sites. airport access road, and Cya Road make it less Two physical features complicate approaches operationally acceptable than Site 4. Therefore, a from or departures to the east. First, the north helicopter parking position at Site 4 has been side’s access road runs immediately east of the incorporated into the Airport Layout Plan. pad. Although most vehicles would pass below

the eastern approach surface for the helipad, it FIXED BASE OPERATIONS would not be safe for the road to be in use during arrivals from or departures to the east. This road As was noted in Chapter 1, Mariposa-Yosemite is accessible only through an automatic gate Airport currently has one fixed base operation equipped with a card-reader. The volume of traffic (FBO). This FBO provides aircraft maintenance is also very low; it is limited to three aircraft owners services. The FBO is located in one bay at the and the airport manager. These two factors mean west end of the box hangars. The County provides that the potential for conflict between a helicopter several products, services, and facilities that are and vehicle is low. A reasonable means of often provided by FBOs. This include fuel from a reducing the potential for conflict below a level of fuel island, pilot supplies, a computer and significance is to place informational and stop telephone for pre-flight planning, as well as other signs on the access road. The signs would direct pilot support facilities in the general aviation those driving on the road to stop and check for terminal.

What is VFR? VFR stands for visual flight rules. Federal Aviation Administration has established regulations that apply to both visual and instrument flight conditions. In the airspace surrounding Mariposa-Yosemite Airport, the visual flight rules require that during daylight hours pilots have 1 mile of forward visibility and remain clear of clouds.

Mariposa-Yosemite Airport Master Plan (April 2008) 4-12 BUILDING AREA DEVELOPM ENT C H APTER 4

It is not expected that the volume of turbine- powered aircraft will support introduction of Jet A fuel service. Should the volume of turbine use be greater than anticipated, Jet A fuel service could be established either of two ways: fueling from a truck or from a fuel island. Turbine users prefer fueling from trucks because it avoids the necessity of an additional engine start. Turbine users count engine starts because they affect the longevity of the engine. If a truck were used, a fuel storage tank would need to be established. Given the limited available space, placing the Jet A tank next Interior of G eneral Aviation Term inal to the 100 low-lead tank is a possible choice. This There may be demand for leaseholds for FBOs location would also make it possible to fuel a during the 20-year life of this plan. The most likely turbine aircraft after hours using a credit card self- source of demand is for the existing FBO to fueling system. expand its facility. There is also potential demand for leaseholds for specialty FBOs (e.g., those SECURITY offering only a limited number of services). It is not anticipated that there would be sufficient Fencing and Gates activity to support a full-service FBO by the end of the planning period. The events of 9/11 dramatically increased public and agency concerns over aviation security. Given the small based aircraft population and Although most attention is focused on airports with relative remoteness of the airport, the demand for scheduled passenger service, all airports have FBO leaseholds is uncertain. Chapter 5 contains seen security concerns increased. At general a discussion of factors affecting FBO development aviation airports such as Mariposa-Yosemite and optimum means of attracting additional FBOs. Airport, the physical requirements for increased Should demand occur, it is expected to be for one security focus on controlling entry to the airfield. or two hangars and limited area for aircraft Macready Way is the only access point on the parking. Because the demand is expected to be south side. There are vehicle and pedestrian limited, and the airport has limited available space, gates located at the main parking area adjacent to a separate area for FBO leaseholds has not been shown. An FBO could be established in the area designated for larger box hangars.

AIRCRAFT FUEL STORAGE AND DISPENSING

Mariposa Airport provides 100 low-lead fuel. Dispensing is from self-serve pumps located north of the general aviation terminal. The location is expected to continue to be adequate throughout Fuel Island the 20-year planning period.

Mariposa-Yosemite Airport Master Plan (April 2008) 4-13 BUILDING AREA DEVELOPM ENT C H APTER 4

the general aviation terminal. The vehicle access point is secured with a card reader and the pedestrian gate with a key pad. The only vehicle access to airport property on the north side is via a gated access road off of Cya Road. This gate is secured with a card reader access system. The north access road provides entry to the Airport Manager’s house, hangars and future helicopter parking. The perimeter of the airport property is surrounded by cattle fencing which includes cattle gates at various locations. Chain link fencing is used in the terminal area. Currently, the existing airport fencing is adequate. The terrain surrounding the airport makes inadvertent entry unlikely. Unless mandated by the FAA, this master plan does not recommend fencing changes throughout the 20 year planning period.

Vehicle Access and Parking

Vehicle access to the general aviation terminal is obtained from Macready Way. Macready Way connects Mariposa-Yosemite Airport with State Highway 49. Public parking is available in front of the terminal. With the exception of special meetings or large events the parking facilities has sufficient capacity for current operations and long- term growth. Additional parking could be created by relocating the vehicle access gate farther west and utilizing the space between Macready Way and the hangar area.

Mariposa-Yosemite Airport Master Plan (April 2008) 4-14

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