T

PLANNING & DEVELOPMENT _

Developing Underground Space In Louisville, Kentucky

C. Robert Ullrich D.

Joseph Hagerty

University of Louisville

Joseph C. Corradino

Schimpeler-Corradino Associates

he Louisville Crushed Stone Company's underground quarry operation supplies crushed

limestone and dolomite to the Louis­ ville and Jefferson County construc­ tion market. The quarry is located north of the 1-264 Watterson Expressway and east of Poplar Level Road in south-cen­ tral Louisville. Although active quar­ rying stopped in 1970, the operators of the quarry continue to sell from the large stockpiles of crushed stone on the property. The large underground cav­ ern created by the quarry operation as bee': the subject of ecfnt feasibil­ Ity studtes of commercial( and indus­

trial development. In 1982 the City of Louisville con­

tracted with a team of geotechnical en­ gineers from the University of Louis­ ville to study whether the cavern was safe for development. Although var­ ious issues of concern were identified by the study, none was deemed un­ solvable within reasonable limits of cost. Thus, a second study was undertaken in 1982-83, again under City of Louis­ ville sponsorship, to examine the land­ use, economic, engineering, environ­ mental, and implementation issues in­ herent in developing the quarry. This second study was done by the Metro Consulting Group, a consortium of ar­ chitectural, legal, and marketing firms,

C. Robert Ullrich is Associate Professor of Civil Engineering and D.Joseph Hagerty is Professor of Civil Engineering, University of Louisville, Louisville, Kentucky. Joseph C. Corradino is Principal, Schimpeler-Cor­ radino Associates, Louisville, Kentucky.

196

including representatives of the Uni­ versity of Louisville.

This paper describes the results of the two studies mentioned above, with emphasis on the description of the cav­ ern, its physical features, and its struc­ tural and drainage problems. Recom­ mendations presented to the City of Louisville for development of the cav­ ern are also described. Geology of the Quarry Area

Louisville is situated at the falls of the Ohio River, a series of rapids de­ veloped on the Devonian jeffersonville lim estone. The Jeffersonville lime­ stone and underlying Silurian lime­ stone and shale formations are essen­ tially flat-lying sediments which underlie most of eastern and central Louisville. Western Louisville is underlain by al­ luvial sediments contained in a deep valley incised into bedrock.

In the vicinity of the Louisville Crushed Stone Company quarry, up­ lands are capped by the Jeffersonville limestone and a clayey, red residual soil developed from it. Underlying the jef­ fersonville limestone are, in sequence, the Louisville limestone (approxi­ mately 60ft thick); the Waldron shale (10 ft thick); the Laurel dolomite (40 ft thick); and the Osgood formation, which consists of thinly-bedded lime­ stones and shales (Fig. 1). At the quarry site, mining has been done from mid­ depth of the Louisville limestone down to the upper few feet of the Osgood Formation.

Undtrground Spaet, Vol. 8. pp. 196-205, 1984.

Printed in the U.S.A. All rights reserved.

Site Characteristics

Active quarrying at the Louisville

Crushed Stone Company site began in the 1930's as an open-pit operation, and work moved underground in the late 1940's. In the early stages of quarrying only the lower 20-25 ft of the Louis­ ville limestone overlying the Waldron shale was mined. Quarrying was re­ stricted to the outlines shown in Figure 2 because of property ownership, legal considerations, and public concerns re­ garding quarry operations in an urban area. Subsequent mining was done by stripping the Waldron shale first and stockpiling it in various parts of the quarry; then the Laurel dolomite was mined for its val ue as crushed stone.

The Osgood Formation, which un­ derlies the Laurel dolomite, is not a construction-quality material. Thus, quarrying operations ceased when most parts of the mine had been excavated to the base of the Laurel dolomite. The cavern created by this excavation se­ quence contains approximately 96 acres of space, and the ceiling of the mine is supported by 223 pillars whose loca­ tions are shown in Figure 2.

A short section of the Watterson Ex­ pressway, built in the 1950's, crosses the southern extremity of the mine; surface areas occupied by the express­ way are federally owned. Also, surface development rights to property over­ lying the northern one-half of the mine are held by the City of Louisville. The Louisville Zoological Gardens were constructed on this property in the

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1960's and now overlie northern parts of the mine.

The topography of surface areas overlying the quarry dips toward Bear-

grass Creek, which is located east of the quarry site (Fig. 2). The ceiling of the underground quarry was developed to

an essentially constant elevation and

corresponds to a natural, relativel y smooth bedding plane near mid-depth of the Louisville limestone. The shal­ lowest depth of cover is about 20 ft and occurs along western boundaries of the mine. Not coincidentally, most leakage

0' Beechwood I+I of water into the mine is found in these

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areas. (The locations of all water-bear­ c .00

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cover, approximately 60 ft, is found along western boundaries of the quarry.

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consist of Louisville limestone and Jef­ fersonville limestone, as well as resid­ ual soil cover.

Two joint sets are exposed in the ceiling of the quarry. The major (best­ developed) joint set strikes basically

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ing a vertical orientation. Joints in this set are spaced about 10-20 ft apart and are generally infilled with calcite. A mi­ nor east-west striking joint set consists

of joints which are vertical in attitude

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and generally more closely spaced than joints in the major set. (East-west strik­ ing joints are frequently water-bear­ ing, especially along the eastern perim­ eter of the quarry.)

The floor of the quarry is situated basically at two levels. An upper floor elevation about 4 ft above the contact between the Louisville limestone and the Waldron shale is typical of areas near the mine entrance (Subarea D in Fig. 2) and the northern portion of the southern extension of the mine (Sub­ area A). Floor-to-ceiling distances on the upper level range from 20 to 25 ft. In these areas the pillars and sidewalls contain very little loose rock. Condi­ tions in Subarea A are shown in Figure

3. (Note the seepage throughjoints in the ceiling and along sidewall areas.)

Lower levels of the quarry encom­

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pass all the quarry extending under the Louisville Zoo (Subareas F, G, and H), that portion of the quarry extending

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westward to Poplar Level Road (Sub­ area E), and the portion of the quarry extending under the Watterson Ex­ pressway (Subareas B and C). On the lower bench, pillar and sidewall heights vary from 65 ft to as much as 80 ft. Louisville limestone, Waldron shale, and Laurel dolomite are exposed in the pil­ lars and on the sidewalls.

Conditions on the lower levels of the quarry are shown in Figures 4 through 6. Figure 4 shows Subarea B of the quarry, located west of Subarea A. Two bench levels are visible, with Subarea A, on the upper level, in the back­ ground. Pillars in the foreground are 65 ft high. The first bench is developed at the base of the Waldron shale.

Subarea C is an area of old workings, Figure I. Geologic column for the vicinity of the Louisville Crushed Stone Company quarry.

Vol ume 8, Number 3, 1984

which extends under the Watterson

UNDERGROUND SPACE 197

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Figure 3. Conditions in Subarea A-little loose rock, but ceiling and sidewall seepage.

Figure 4. Conditions in Subarea B-two bench levels, with 65ft-high pillars.

bench, is deteriorating from cyclic wet­ ting and drying attributable to seasonal variations in humidity. Deterioration and falling chunks of Waldron shale have led to the formation of large over­ hangs (some as large as 6 ft) in the overlying Louisville limestone. Figure 7 shows an overhang developed above the Waldron shale in a pillar located near the base of the shale pile in Sub­ area G.

In addition to the problem of shale deterioration, many tall pillars on the lower bench are quite ragged in ap­ pearance, i.e., contain an abundance of loose, small rock. One such pillar, lo­ cated in Subarea C, is shown in Figure 8. Also, in many locations on the lower level, pillars have been left connected at their bases by unmined Laurel do­ lomite.

Site Evaluation and Remedial Measures

The University of Louisville study of the Louisville Crushed Stone Com­ pany quarr y included the following tasks: complete photographic coverage of all pillars, sidewalls, and ceiling areas; structural evaluation of each pillar and sidewall area; complete mapping of ceiling areas, noting all joint orienta­ tions, locations of seepage, and other features; reconnaissance of surface areas, noting possible avenues of seep­ age into the mine; evaluations of pillar and ceiling stability; and recommen­ dations for remedial work. The follow­ ing sections describe features which University of Louisville investigators identified as areas of concern. The sug­ gested remedial measures are also de­ scribed.

Ceiling Overhang The presence of a dangerous over­

hang in the ceiling rock between two pillars in Subarea A was noted. The overhang consists of a layer of rock about 12 in. thick which has separated

Expressway. Pillars in this area average 65 ft in height and are also very large in area. For example, the pillar shown in Figure 5 measures 80 ft by 80 ft (note the car for scale).

A photograph of Subarea E is shown in Figure 6. Pillars in this area are as high as 80 ft and extend several feet into the Osgood Formation.

Subarea F is located along the east­ ern boundary of the northern exten­ sion of the mine, which underlies the Louisville Zoological Gardens. This area includes significant portions of mine sidewall and a number of alcoves and extensions which project eastward into the sidewall. Subarea F contains rela-

Volume 8, Number 3, 1984

tively tall pillars (60-65 ft) with the Waldron shale located virtually in the middle of each pillar. Significant seep­ age of water into the mine is occurring in Subarea F, as noted in Figure 2.

Subareas G and H are located east of Subarea F. Pillars in Subarea H are 60-65 ft in height, as in Subarea F. Significant stockpiles of Waldron shale, stripped during the mining operation, are located in Subarea G, in the north­ west corner of the mine. The shale stockpile occupies an area of about 12 acres and is about 60 ft high at its high­ est level.

The Waldron shale, exposed at mid­ height or above on pillars on the lower

along a bedding plane from overlying rock. At the time of the University of Louisville study active seepage was oc­ curring along the overhang and ap­ peared to be related to a surface drain­ age feature. Removal of the overhang is feasible, since it is thin enough to break into slabs by prying. (A discus­ sion of the related seepage problem is included in a following section.)

Loose Rock A problem common to all areas of

the quarry is man y small (and some very large) pieces of rock hanging from pillars and sidewalls (Figure 8). In or­ der to develop the quarry safely for industrial use, loose rock must be re-

UKDERGROUND SPACE 199

Volume 8, N umber 3, 1984 200 UNDERGROUND SPACE

Figure 5. Conditions in Subarea C- tall pillars, some 80ft by 80ft at the base.

·

Figure 6.Conditions in Subarea £-pillars extending downward into the Osgood Formation.

lated to moisture changes, methods of stopping the deterioration must in­ volve some means of sealing the shale from moisture. Several methods are feasible, including spraying the shale with an impervious material such as epoxy resin; but this would do little to stop the falling of loose rock (wh1ch would break the impervious seal).

Another method of sealing the Waldron shale is to spray each pillar with shotcrete. Before sealing, loose fragments should be removed by scal­ ing; then wire mesh or a similar rein­ forcing material should be wrapped around the shale band. The wire mesh would serve as a structural contain­ ment for the shale and would prevent the falling of rock fragments, and the shotcrete would seal the shale from moisture. Seepage

Water enters the quarry from three sources: minor inflow at the portal area, seepage from surface sinkholes, and seepage through the joint structure in the ceiling and sidewalls. The locations of sinkholes and sidewall and ceiling seepage are shown in Figure 2.

The ceiling and sidewall seepage de­ scribed herein and shown in Figure 2 can be controlled, to some extent, by improving the ground surface features above the underground quarry-fill­ ing and capping sinkholes; lining ponds on the zoo property with im­ pervious materials; and injecting ce­ ment grout into the ground in an at­ tempt to reduce the water movement through the joints. While any of these techniques would help curtail the water intrusions, it is uncertain to what ex­ tent the amount of seepage would be reduced; thus, additional seepage con­ trol measures should be considered, in­ cluding the installation of gutter troughs to collect water coming through the ceiling, and surface ditches or piping to collect water reaching the quarry floor. Other Concerns

moved from pillars and sidewalls or prevented from falling. Scaling is the easiest method for removing loose rock: potentially loose pieces of rock are tested with prybars and wedges; then loose fragments of rock are removed and tightly-held fragments are left in place. Generally, the highest pillars in the quarry are also the most ragged in ap­ pearance. Thus, scaling of tall pillars would be most time-consuming and ex­ pensive, whereas scaling of short pil­ lars would be relatively easy.

Shale Deterioration

Deterioration of the Waldron shale

is a particular problem in lower levels of the quarry where the shale appears at mid-height or above on most pillars. The deterioration can be attributed to volume changes in the shale associated with seasonal variations in the humid­ ity. The shale cracks into loaf-sized fragments which fall from the pillars and litter the surrounding quarry floor. On many pillars so much shale has de­ teriorated and fallen that these pillars show a marked reduction in diameter (Fig. 7). This "necking" of the pillars has. led to the formation of large over­ hangs in the Louisville limestone.

Because shale deterioration is re-

Several other, less important con­ cerns were also identifed. For example, the presence of connectors between adjacent pillars and the irregular na­ ture of the quarry floor (many benches and steep ramps) might impede free movement through the quarry.

The structural and drainage con­ cerns mentioned in preceding para­ graphs are summarized in Table l, as are the engineering measures sug­ gested for their correction. Stability Analyses

In the University of Louisville study, existing structural conditions in the

Vol ume 8, Number 3, 1984 UND£RGROU!'<D SPACE 201

Figure 7 Overhang created by shale deterioration in Subarea G.

120ft are allowable. This range of spans is typical of those observed in Subarea A.

The factors of safety against ceiling failure for other parts of the quarry were assumed to be greater than that for Subarea A.

Recommendations for Development

The University of Louisville srudy of the quarry site indicated that, although several structural and drainage con­ cerns existed, no "fatal flaw" was pres­ em which would preclude quarry de­ velopment. In late 1982, the City of Louisville sponsored a second study of the quarry site, with the goal of iden­ tifying a workable plan for develop­ ment of the property. The second study was performed by the Metro Consult­ ing Group; their recommendations were made to the City of Louisville in early 1983.

The plan for development recom­ mended by the Metro Consulting Group was based on several considerations. In light of the economic recession m Louisville and the fact that almost 2,800 acres of available but unused land ex­ ists in jefferson County. it was decided to pursue a plan in which under­ ground development would be staged as unused surface areas are utilized. A multi-use development concept was endorsed. Also, approximately 55 acres of surface area, located south of the Louisville Zoological Gardens prop­ erty, is available for development in conjunction with development of the underlying quarry area. The neigh­ borhood surrounding the quarry property contains some of the most de­ sirable single-family locations in Louis­ ville, and the availability of developable single-family lots is tight in the quarry area. Thus, surface area directly above the quarry was identified as a prime area for single-family housing. It was decided to limit industrial develop­

quarry were analyzed with respect Lo pillar stability and ceiling stability. These analyses were performed so that the effects of changes in the quarry struc­ ture (for example, removal of selected pillars) could be assessed in planning studies, such as the Metro Consulting Group study.

Calculations of pillar stability were made for Pillar 22, which is the slen­ derest pillar in the quarry. The load on this pillar was purposely overesti­ mated by assuming worst-case values for the overburden thickness (60ft) and the distance to adjacent pillars (120 ft). The calculated factor of safety against crushing, based on a compressive strength value of 5,500 psi for the Waldron shale, was 3.5. Factors of safety

against crushing for other pillars in the quarry were assumed to be gr·eater than that for Pillar 22.

Calculations of ceiling stability were made for Subarea A, portions of which are overlain by as little as 20 ft of over­ burden. Spans between pillars and si­ dewalls in Subarea A are the greatest in the quarry (120 ft). Also, the layer of Louisville limestone which forms the immediate ceiling in Subareas A, D, and E is 4.5-6.0 ft thick, which is the min­ imum ceiling beam thickness in the quarry. Calculations of maximum safe spans were made using a flat arch anal­ ysis developed by Wright (1974). Using a factor of safety of 2.0 against crush­ ing of ceiling rock at the pillars, it was calculated that spans ranging from I05-

ment in this surface area to office space directly related to subsurface indus­ trial activity. Retail uses of the property were purposely de-emphasized.

Based on the market information described above and on other analyses, a plan for development of the Louis­ ville Crushed Stone Company quarry was prepared. The development plan described below integrates surface and subsurface space use in a physically feasible and economically sound man­ ner.

Swface Development Plan

The plan for development of the surface area overlying the quarry in­ tegrates several land uses-residential, open and recreational space, commer­ cial-office, commercial-retail, and

Volume 8, Number 3, 1984

Structural or Drainage Concern

Engineering Measure to Correct

Ceiling overhang

Loose rock on sidewalls and pillars

Deterioration of shale layer on pillars and

sidewalls

Deterioration of shale layer on pillars and

sidewalls accompanied by severe notching and development of overhangs

Heave of shale layer in quarry floor

Irregular floor elevations

Connectors between pillars

Sinkholes

Seepage through joints in ceiling and

sidewalls

Remove by prying, splitting, or using wedges; if necessary, use light explosives

Scaling; or isolate (e.g., behind walls of

buildings)

Scale, install steel reinforcement and spray with shotcrete; or isolate pillars and sidewalls

Scale, install steel reinforcement and pour concrete ring around shale band; or scale, install steel reinforcement and spray with shotcrete; or isolate pillars and sidewalls

Spray shale with impervious material, install roadbed, shotcrete around edges

Regrade and fill as necessary with waste material from quarry

Remove with explosives

Fill sinkholes with concrete, grout joints,

and seal surface with clay blanket

Install surface drainage corrective measures, seal joints by pressure grouting; or seal joints by pressure grouting, seal surface with clay blanket; or install guttering and downspout system inside quarry

Figure 8. Loose rock on a pillar in Subarea C.

Table 1. Possible solutions to structural and drainage concerns in the Louisville Crushed Stone Company u"Uierground quarry.

Maintenance of the common areas will be an integral part of ownership. Dur­ ing the first stage of construction (the first few years of the project) an esti­ mated 30-40 units would be con­ structed. In total, up to 129 individual units are contemplated.

The office park is conceived as a spe­ cial-purpose complex in which build­ ings will be built to suit tenants. Be­ cause of market conditions in the region, speculative office space is not consid­ ered feasible. It is estimated that the first stage of the project would include the construction of 48,000 to 64,000 sq ft of special-purpose office space on the western portion of the site adjacent to Illinois Avenue. Ultimate develop­ ment would include 192,000 to 256,000 sq ft of office development.

In order to accommodate the con­ sumer needs of the workers at the de­ velopment and the local residents, a small retail complex would be devel­ oped in conjunction with the first stage of office development on the western portion of the surface site adjacent to Illinois Avenue. The retail complex has been restricted deliberately to a sup­ portive function to avoid the deleteri­ ous neighborhood effects of shops with larger geographic markets.

Subsurface Development Plan The subsurface development plan

would incorporate surface access and vertical connections with office space on the surface for operations with higher needs for office staff. This con­ cept is based on the desire to use the prime space in the quarry first, to at­ tract immediately the best use for the excavated area. The first, 10-year stage of development involves filling and lev­ eling three subareas of the quarry, ap­ proximately one-third of the total space, to produce a uniform floor-to-ceiling height of approximately 30ft. This stage of underground space use would co­ incide with the surface development. Vertical connections to office devel­ opment areas on the surface would be created during Stage I (Fig. 10).

Beyond Stage I, development of the quarry would proceed in three stages over 15 years. Because the ceiling heights in the Stage II-IV areas would be 60 ft or more, the intensity of use would be lower than in the Stage I de­ velopment. Stages II-IV would be ori­ ented to warehousing and bulk stor­ age, and would involve development of

parking for Derby City Field. Access to the site is from Poplar Level Road through Taylor Avenue. Figure 9 shows the plan for surface development, which, very roughly, encompasses the­ land above Subarea A and the property to the west of it, Subarea B, the lower

half of Subarea C, Subarea D, and the property between Subarea A and D.

The residential area is envisioned as a high-quality condominum type of de­ velopment. This will ensure the per­ manence of occupants and the protec­ tion of the values of nearby properties.

subsurface space below the Louisville Zoological Gardens (Stages II and III) and Subareas B and C (Stage IV). As development proceeds beyond Stage I, the primary circulation corridor would be extended to allow access to all parts of the underground. Utility services

Figure 9. Surface concept plan for the proposed development above the Louisville quarry.

Key: 0 = office, R = Commercial/retail, T, = Townhouse (21 units), T, = Townh e (8 units), T, = Townhouse (10 units), C = Condominium (90 units), V = Verttcal

circulation, A = Air shaft (covered), U = Utility distribution center, W = Water storage,

E = Vertical emergency access.

widths and fire-rated classifications to correspond with the activities in the spaces created. Concrete block walls have been selected for general use be­ cause they are economical; the blocks are easy to use and are readily available in various sizes and colors. Because of the solid natural rock floor in the quarry, the structural requirements for wall foundations will be eliminated (except in places where fill materials are used), thereby reducing significantly the cost of creating enclosed space.

Because of the great floor-to-ceiling heights in the quarry, each tenant space will be roofed . In areas where a floor­ to-ceiling height of 24-30 ft is built through backfilling, a roof may not be required. However, roofs will be nec­ essary in other areas to protect people and property from the danger of fall­ ing rock. Although all the loose rock will be scaled from the pillars and ceil­ ing during development, and contin­ uous inspection and maintenace of the rock surfaces will be integral to the op­ erating activities of the developer, there can be no guarantee that rock will not fall. To support the roofs of the build­ ings, reinforced concrete masonry piers will be required in all load-bearing walls.

Rock surfaces in the quarry will be coated with a mixture of whitewash and concrete to achieve acceptable air qual­ ity within the quarry. (Painting reduces the generation of dust from exposed rock.) Light levels in the quarry will be improved by the painting, as the effects of artificial lighting will be enhanced. The primary circulation corridor and parking and docking areas will be lighted; appropriate signage and strip­ ing will be used to control vehicular movements.

Costs for underground develop­ ment were estimated for industrial and other uses. It is expected that it will cost an average of about $3.00 per square foot to prepare the en tire under­ ground quarry for development. A major component of this cost (36%)

would follow the primary circulation corridor.

The underground development concept provides for residential rec­ reation, service, and storage areas lo­ cated in the north portion of Subarea A (Fig. 10). Residential facilities within the underground would provide for activities such as tennis, swimming, and exercise; restaurants and storage space could also be provided. This area would have a separate entrance (new open­ ing) from Taylor Avenue and would be segregated from areas designated for commercial and industrial uses.

Development of the underground would be controlled by a single entity responsible for construction, utility

Volume 8, Number 3, 1984

service, maintenance, and marketing, with all space utilized on a lease basis. Areas ranging from as little as I 0,000 sq ft to greater than 100,000 sq ft could be developed according to the needs of tenants. All required parking would be provided underground in areas which would have marginal utility for industrial uses and warehousing be­ cause of the configuration of the space.

Standard concrete slab floors with a minimal amount of reinforcement will be suitable for most uses within the un­ derground because of the rock base. These floors will be poured in spaces created principally by wall enclosures between the rock pillars. Walls will be of concrete masonry units of various

stems from providing the under­ ground development with a fire detec­ tion system and vertical access with evacuation systems.

Underground light manufacturing and assembly space is expected to cost about $14.50 per square foot, while warehousing space is estimated at about $12.20 per square foot. (Similar con­ struction on the ground surface ranges from $26-32 per square foot.) Recre­ ational space for athletic activities is ex­ pected to cost about $22.90 per square foot underground, compared to $48- 52 per square foot aboveground.

Conclusions

Studies of underground space de-

UNOERGROt::-10 SPACE 203

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velopment at the Louisville Crushed Stone Company quarry which were performed by the University of Louis­ ville and the Metro Consulting Group have determined that development of the quarry space and overlying surface areas is feasible under certain condi­ tions.

First, it is feasible to develop the quarry from a physical standpoint. There are no major impediments that would prohibit development. How­ ever, it must be recognized that anum­ ber of difficu l ties do exist which de­ mand attention to make the quarry usable for underground industrial use and related purposes. Specifically, ground water seepage into the quarry must be controlled; shale deterioration on the pillars supporting the quarry ceiling must be remedied; and loose rock must be scaled from pillars and sidewalls. All of these problems, how­ ever, are solvable with proper engi­ neering solutions and the expenditure of funds. This issue of funds is impor­ tant to recognize because repair of the

Volume 8, Number 3, 1984

quarry (site preparation) will be more expensive than preparing space above ground for development. Likewise, special requirements such as fire pro­ tection (mainly evacuation corridors, ventilation, and fire-rated construction materials) will consume more funds for underground space than above.

Second, the project is feasible envi­ ronmentally. The only significant con­ cerns are traffic and noise intrusion on the Louisville Zoological Gardens. Traffic access to both the surface and underground portions of the quarry must be accommodated adequately; widening Taylor Avenue (Fig. 9) will help ameliorate the traffic problem. The noise problem can be remedied through the proper design and construction of noise barriers along the common prop­ erty boundary with the zoo.

Third, the quarry project is feasible from a social viewpoint. The conver­ sion of the abandoned property to an active economic and social center com­ patible with its surroundings will make it a more pleasant neighbor for the ad-

jacentcommunity. Over 1,200 jobs (ex­ cluding construction jobs) will be cre­ ated over 20-25 years.

Finally the project as planned ap­ pears to be feasible financially. How­ ever, dealing with solutions to the above­ mentioned issues will increase the pr-oj­ ect cost. It will cost $66.2 million (1983 dollars) to purchase the land, improve the site, and construct all the buildings for the development. Surface devel­ opment accounts for 44% (29.2 mil­ lion) of this figure, while subsurface development represents the remain­ der ($37.0 million).

At present, the City of Louisville has an option to acquire the underground quarry and accompanying surface areas. However, firm development commit­ ments are being sought before exer­ cising this option. 0

Reference Wright, F. D. 1974. Designofroofbolt patterns

for jointed rock. U.S. Bureau of Mines. Open File Report No. 61-75.

UNDERGROUND SPACE 205