But no one foresaw the explosive growth that took place in and around Denver in the decades that followed. New suburbs blossomed in the surrounding plains and foothills, and the old ones spread riotously: Englewood and Littleton to the south; Lakewood and Wheat Ridge to the west; Arvada to the northwest; Thornton, Northglenn, and Westminster to the north; Aurora to the east. Vast unincorporated areas of Arapahoe, Adams, J efferson, and Douglas Counties changed practically overnight from open range into dense subdivisions. It's the familiar Los Angeles pattern; slowly merging with Fort Collins to the north and Colorado Springs to the south, greater Denver is in the process of becoming a sprawling megalopolis-one vast strip city along the Front Range, the eastern flank of the Rockies. A number of factors have helped make Denver the seventh-fastestgrowing metropolitan region in America. Only Washington has more federal agencies; the defense industry is a particularly big presence. Then, there are numerous defense-related industries, like Martin Marietta, an aerospace outfit, which put Littleton on the map. A lot of microchip and other high-tech companies have started up in Denver. After Interstate 70 was completed through Denver, in the early sixties, Denver became the hubthe marketing and distribution and banking center-of the High Plains and the Rocky Mountain region. People flocked to Denver because there was work and because the mountains, with their year-round recreational possibilities, were so close.

       But the plains and foothills around Denver are dry-they get only fifteen inches of rain a year-and all these new places needed water. Englewood, having arranged its own supply of transmountain water back in the fifties, was set. (Englewood acquired water rights in the Winter Park area, on the West Slope, and has an exchange arrangement with the Denver Water Department whereby it can draw South Platte water in return for delivering an equal volume of Winter Park water through the Moffat Tunnel.) Aurora cornered a piece of the South Platte action in 1981 by building its own onstream reservoir, the Spinney Mountain Reservoir (capacity fifty-three thousand eight hundred acre-feet). But the other suburbs were mainly dependent on pump water, as ground water is referred to in the West, and the more they pumped the lower the water table got and the more expensive the pump water became. Some wells had contamination problems, too. Trichloroethylene, a common degreasing agent and suspected carcinogen, turned up in the water in Commerce City, a northern suburb. The first source to be identified was the Rocky Mountain Arsenal, just out of town. The Army had to give the Environmental Protection Agency seven million dollars to build carbonfiltration plants for the South Adams County water district, which includes Commerce City. East of Aurora-the fastest-growing part of greater Denver, where new subdivisions are springing up almost by the hour-the pump water is in danger of being tainted by the Lowry landfill, where industrial wastes were dumped for a period of fifteen years. Parents of prospective students at a high school that is being built near the landfill have taken to calling the school Toxic High.

       Although the Denver Water Department had a number of long-standing suburban contracts, its initial reaction to the rampaging growth outside the city limits was to have nothing to do with it. "Even before Dillon Reservoir came on line, the Board of Water Commissioners, our executive arm, drew a blue line around our hundredand-fifteen-square-mile service area and told everybody that's it," Edward Ruetz, the board's manager of community affairs, recalled not long ago. "But the growth rolled on merrily over the landscape-or, rather, it hopscotched. Anywhere some developer could sink a well big enough, a subdivision popped up. Our blue line didn't put one dent in the growth of the suburbs, whether we were in a position to help them or not." In any event, as the new independent suburban water districts began to have problems with their water sources they turned to the Denver Water Department, and gradually the department relented and entered the business of selling water. Today, it has water contracts with almost a hundred suburban agencies. It has total-service contracts with several water districts, under which it assumes complete responsibility for their water needs, at roughly double the insidecity rate. It has a raw-water contract with Arvada, a northern suburb, which takes care of about a hundred thousand people.
 

      RELENTLESS growth appears to be in store for greater Denver. According to the best study, there may be two million four hundred thousand people by 2010 and more than three million by 2035. In the late seventies, the Water Department began to worry again about an impending shortage.  "The nightmare of every utility is that one day your customers are going to turn their faucets on and nothing will come out," Ruetz told me. The direst prediction had a "tap gap" developing by 1987.

       The department had been aware of the potential of the Two Forks site for decades. (Some people call the main stem of the South Platte above the North Fork the South Fork; hence the name Two Forks.) Its predecessors had filed for water-storage rights in that section of the canyon in the late nineteenth century, and the department itself had filed for a right-of-way with the Forest Service, which owns most of the land there, in 1931. As a place to put up a dam, the Two Forks site has a lot going for it. Ruetz describes it enthusiastically as "the best remaining site in Colorado." The Front Range is riddled with faults, but there are no active ones at Two Forks.  A mile and a half below the meeting of the two rivers, the gap between the walls at the bottom of the narrow, Vshaped canyon is only a hundred feet. From a dam builder's viewpoint, it's just asking to be plugged with concrete. The geology of the rocks that would hold up the two abutmentsthe anchorage-is absolutely sound. Furthermore, the site is close to Denver, so there would be easy access for the construction force. On top of this, very little of the eleven thousand-plus acres to be flooded is privately owned, and not many people live there. Only a few weekend cabins are perched on the
steep walls. In 1942, the Water Department began buying up what private land there was, and it now owns about two-thirds of it, so the dispossession problem is minimal.

       And, best of all, Two Forks "would give us operational control over our system that we don't have now," Robert Taylor, the environmental coordinator in the department's planning division, told me. "When there's a good water year on the West Slope, we can't capitalize on it, because of lack of storage. During 1983 and 1984-years of heavy snowfall on the East SlopeDenver lost about a million acre-feet of spring runoff, because there was nowhere to store it. Two Forks would enable us to collect high flows wherever they occur, including West Slope water released through Roberts Tunnel into the North Fork." This time, the department wanted something really big-a deep, narrow lake backing up the South Platte twenty-nine miles and the North Fork maybe seven, with a total capacity of eleven hundred thousand acre-feet. But that didn't mean that all those acre-feet would be available. The storage capacity and the annual safe yield of a water system are two different things. Two Forks would increase the Denver system's yield by only ninety-eight thousand acre-feet. The 1980 yield was three hundred and seventy-nine thousand acre-feet-uncomfortably close to the total annual metropolitan consumption.of three hundred and fourteen thousand. By 2010, consumption is projected to be around five hundred and ninety-nine thousand, but the yield of the existing system will have increased (because wells for which permits have already been issued will have been sunk, among other things) to only four hundred and fourteen thousand, so there won't be enough water for Denver even with Two Forks on line.  The balance will have to be made up by recycling and conservation.

       But not everybody was as keen on the dam as the Water Department was. Few words, in fact, are likely to start a fight faster in the West these days than "dam." The seventies were not only years of sprawling growth around Denver but also the time when the environmental movement was spreading. Its messages hit home with many Coloradans, and strong antigrowth sentiment developed in the state. Some environmentalists felt that the only way to stop the development was to shut off the water. 

       Early in the decade, with greater Denver's population approaching a million and a half, the Water Department became concerned about its treatment capacity. There was enough raw water for the city but not enough treated water for peak summer demands. On July 6, 1973, the temperature went up to a hundred and three degrees, and five hundred and six million gallons of treated water-an all-time record-was consumed. The combined output of the treatment plants at the time was only four hundred and sixty million gallons a day; fortunately, there was three hundred million gallons more in underground storage. But that was too
close for comfort. So the department proposed the construction of a diversion dam on the South Platte at a place called Strontia Springs, a few miles below the Two Forks site. The dam would divert some of the river into a tunnel through the southern wall of the canyon to a treatment plant in the foothills on the other side. A waterbond issue to pay for, among other things, the Strontia Springs-Foothills project was defeated in 1972 but was approved the second time around, a year later; a barrage of lawsuits involving environmental groups, including the Colorado Open Space Council, Trout Unlimited, and the Water Users Alliance, created a terrible legal tangle, however, and froze the project for five years, hanging up the rightsof-way that the department needed from the Forest Service and the Bureau of Land Management, and the dredge-and-fill permit that it needed from the Army Corps of Engineers. Finally, in 1978, Colorado Representative Timothy Wirth brought the disputants together, and in two intensive weekend negotiating sessions in Denver they reached what became known as the Foothills Accord. One stipulation of the accord was that the federal agencies involved would not approve expansion of the Denver water system until a review of the system-a system-wide environmental-impact statement-was made. The Foothills Treatment Plant came on line in June of 1983; it now contributes a hundred and sixty million gallons a day to the system's treatment capacity, and fifty million gallons of storage.

      IN 1977, Ray Stanford heard that the Two Forks project was next on the department's agenda, and he began to worry about the effect that the lake would have on the Pawnee montane skipper. He called an old friend, Paul Opler, in Washington, and filled him in on the situation. He and Opler had caught butterflies together in California in the fifties; now Opler was in charge of listing invertebrate endangered species for the Fish and Wildlife Service. Opler decided that the skipper was a good candidate for the list. The bureaucratic definition of a species is different from the scientific one. According to the Endangered Species Act of 1973, a subspecies can also be considered as a species, so montana qualified. For a species to be "endangered," it has to be "in danger of extinction throughout all or a significant part of its range." Its habitat can be designated as "critical habitat," whereupon it becomes illegal for federal agencies to destroy or adversely modify it, or to take any action that would "jeopardize the [species'] continued existence." The status of an endangered species whose habitat is in private hands is less certain; it is easier to get protection for the habitats of animals, including insects, than for the habitats of plants. A "threatened" species is a step down the ladder: it is in danger of becoming endangered. 

       After a species has been proposed for the list, its name is published in the Federal Register. Then there is a ninety-day "comment period," during which people can send in written opinions on whether the species is really endangered (the same sort of public review process, also ninety days long, that the Two Forks dam proposal will be going through, probably early next year). The difficulty with montana was that nobody except Scott and Stanford was familiar with its true identity and distribution, for at the time montana was proposed for the endangered list-in July of 1978the two of them hadn't published their paper. Even the eminent F. Martin Brown confused montana with pawnee; he didn't realize that there was a smaller, darker form in the mountains, different from the common one on the Plains, which ranges all the way up into Saskatchewan, and he argued that montana wasn't endangered. Other lepidopterists, who weren't familiar with the butterfly and so were unqualified to voice an opinion-among them, Stanford recalled, were conservative amateurs who oppose the federal government's sticking its nose into what specimens they can or can't collectwrote in against listing it, so the proposal more or less died. Montana wasn't listed, but it wasn't removed from the list of proposed endangered species, either.

            
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