【黑鹰水坝】
Translating|:en:Black Eagle Dam
time=2018-01-19T06:58:18+00:00
黑鹰水坝 (Black Eagle Dam)正确来说是黑鹫水坝(eagle不能译作鹰，只可译作鹫或雕)，位于蒙大拿州，大瀑布城，座落于密苏里河，是一座用于水力发电的重力坝 。第一大坝在1890年建成并开放，是一座土石坝 。黑鹰水坝是蒙大拿州第一座使用此结构的水力发电坝，也是第一座建造在密苏里河的水坝。水坝使大瀑布城获得了电力城的封号。第二大坝于1926年开工，1927年启用，使用混凝土建成。第二大坝在不拆除第一大坝的情况下淹没并取代它。自1926年以来，水坝为lk=in长，m高，几乎没有改变，其发电厂有三台涡轮机，每台能产生7兆瓦的能量。最大输出达18兆瓦。第二大坝为蒙大拿电力公司建造，宾州电力（PPL）公司在1997年买下并在2014年卖给西北公司。水库没有正式的名字，多年来被称作长池（Long Pool）。水库大约km 长，蓄水量从lk=in到lk=in。黑鹰水坝的发电方式是川流式发电 ，也就是它不刻意储存水源来产生电力。
== 黑鹰瀑布 ==
黑鹰瀑布是美国蒙大拿州密苏里河大瀑布群中的第一个瀑布。在盖水坝之前，此瀑布高低差就有m。
黑鹰瀑布形成于大瀑布构造区中，一条不平稳的下降沿上。密苏里河在此流经古代沉积在河流、冰川与湖泊下，大部分为非海砂岩组成的库图纳哈组，少部分是从浅海堆积而成。河流侵蚀较软的砂岩，剩下的硬岩便自然形成了瀑布。
曼丹族和南派岗黑脚族等美国原住民都知道黑鹰瀑布。1805年6月13日，路易斯和克拉克远征队的梅里韦瑟·路易斯成为了第一位看到大瀑布的白人（五个瀑布中最大的）。第二天，探险队在瀑布群附近露营时， 梅里韦瑟·路易斯发现了黑鹰瀑布。
探险队中某个成员称瀑布为高音（Upper Pitch）。路易斯看到后称其为黑鹰。1872年，一位设计北太平洋铁路的定线工程师，托马斯‧P‧罗伯茨，在得知记录在路易斯日志的事件后，正式命名此瀑布为《黑鹰瀑布》。
=== 1890年的大坝 ===
约1907年，从黑鹰水坝上向东北方向看。南边发电厂在图片的底部，坝在左边。
大瀑布城水电公司（GFWPTC）成立于1887年，目标是发展大瀑布城，提供电力、自来水与污水的处理，以吸引工商业进入城市。铁路巨头詹姆士·希尔集合大北铁路的主要股东，5百万美元资本。 希尔把股票卖给他的朋友，菲利普·丹福斯·阿莫尔，查尔斯·亚瑟·布罗德沃特，马歇尔·菲尔德，约翰·穆雷·福布斯，丹尼尔·威利斯·詹姆斯，约翰·斯图尔特·肯尼迪，伦纳德·刘易斯和查尔斯·埃利奥特·珀金斯。巴黎‧吉布森是希尔的朋友，大瀑布城水电公司的股东之一，也是大瀑布城成立的推手。吉布森意识到，密苏里河的大瀑布可以为工业提供丰富，便宜的电力，并在此基础上推动城镇发展。但吉布森的计划意味着实际上要建设一个或更多水坝来提供想像中的电力。公司立刻开始购买密苏里河沿岸的土地和水利权，从黑鹰瀑布一路买到绵羊溪，约mi。到最后，公司几乎拥有了大瀑布城的所有土地，加上河岸边的ha地产。公司雇佣一位水利工程师J.T. Fanning，在1887年夏天调查黑鹰瀑布，以确定瀑布的适宜性和大坝的最佳位置。当时计划已完成，但没有采取任何行动。
黑鹰水坝当时是为了供电给铜冶炼厂。在1887年7月22日，波士顿与蒙大拿铜银综合矿业公司创立，它是由伦纳德‧路易森的路易森兄弟（一间铜贸易公司），蒙大拿公司（一间矿业控股公司）与C. X. Larrabee （拥有高产量的矿场，Larrabee和有名的山中矿）合并而成。 1889年9月12日，波士顿和蒙大拿州与GFWPTC签署了一项协议，其中电力公司同意在1890年9月1日之前建造一座能够为该矿业公司提供至少lk=on电力的水坝，并在1891年1月1日前达到hph。作为交换，波士顿与蒙大拿铜银综合矿业公司同意在大坝附近建立一个30万美元的铜冶炼厂。
1890年黑鹰水坝开始施工，GFWPTC的工程师设计一个由厚重木材定型，里面充满岩石的溢流坝。这个坝并不大，目的是在其后面建造一个蓄水池，以产生足够的水压（扬程）推动涡轮机发电。这水坝建造在上游边缘（尽可能创造最深的水库），花费约515,000美元（通货膨胀至2010年约12,335,000美元）。1890年2月5日工程开始投标，标案要求工程要在1890年12月1日前完成。所有投标都被拒绝，机械工程师莫里斯‧帕克被雇来设计与建造大坝，为了把河流从工作区域转移开，1890年4月15日开始建造了围堰坝。在工地北边的岸上盖了名叫河岸（River Bank）的棚户区，提供给帮助建造大坝的克罗地亚人、斯堪地那维亚人、斯洛伐克人与威尔士人（其中绝大多数人帮助找到了黑鹰镇，还能看到当时土制的棚户地基）。红砂岩的河床尽可能弄平整，大块的木材用螺栓固定到岩石上，与河流垂直。每两块木材间距m，中间有六块小木材，组成m深的水坝，水坝的下游面间隔为1.05块／公尺， 顶部间隔1.08块／公尺，延伸了m。水坝南端建立一个m 的石墙以保护发电厂，防止水坝向厂房的压力。水坝顶部每m 建造一个m宽的混凝土疏洪道，共八条。在坝顶加装一条m高的档板以增加蓄水量。水坝m高，m宽。
水坝在1890年12月开始发电。1891年1月6日，水可流过水坝的顶部，1891年3月15日，宣布水坝完工。
河的南边建了一栋占地ft, 砖瓦盖的发电厂。内部有三台双组横流维克托式水轮机，每台能够产生1.27兆瓦的能量。南岸和离岸一段距离的石墙间产生一个供给钢管河水的调整池，水流入钢管的量一部分由调整池上游的闸门控制。主要的钢管长m，直径m，提供发电机水源（另有其他三条钢管建成，但没有立即投入使用）。
黑鹰水坝北岸发电厂的内部。图中为绳索与滑轮系统，将机械能转换给冶炼厂。
河的北边是另一座在1892年建成的发电厂，里面有七八组维克托水轮机，共产生1.940兆瓦的能量，从河北岸底部切割出来的石块堆积在附近形成一座小岛：水渠岛（Tailrace Island），而发电厂就盖在这座人造岛上。岛屿与密苏里河的北岸间形成了黑鹰水坝的水渠（也是发电厂的水渠）。水渠岛由电力公司与波士顿蒙大拿矿业公司共同拥有。电厂与冶炼厂由一座木制天桥连接起来。北岸与石强形成笔直的调整池供应北边的发电厂（最宽的部分有m） 水的流量与南边一样，由闸门控制。三条钢管供给北边发电厂水源。然而，此发电厂产生的机械能大部分并没有转成电能，而是透过绳索与滑轮系统直接转移到冶炼厂。
两间电厂产生的部分机械能，透过汤姆逊-休斯顿发电机转换成电力，单一员工在电厂里工作八小时。次要的发电厂盖在南边发电厂隔壁，里面装载一台Armington & Sims蒸汽发电机，在主发电机关闭时，供应客户电力。adj=长的缆索铁道（倾斜的铁路）接通悬崖上面与南边发电厂。悬崖上有多条m长， m宽的吊桥跨越河上连接各个发电厂。水坝预估可用50年。
==== 1890年水坝运作历史 ====
1890年春天，冶炼厂开始动工；1891年3月，选矿机启用；1892年4月，Brückner cylinders与反射炉启用；1892年8月，蒸馏转换器启用；1893年1月，精炼炉启用；1893年2月，电解精炼炉启用；1893年4月，高炉启用。冶炼厂起初预算为200万美元，在1892年员工数已达1000位。1908年4月7日，大烟囱（Big Stack）开始建造，底部内径m，顶部m，将废气排到m的高空。由纽约的Alphonse Custodis建筑公司于1908年10月23日完工，成为当时最高的烟囱。
1893-1894年，GFWPTC在现有的南岸发电厂下游，建造了第二个发电厂，将电力输送至悬崖上的皇家研磨公司的面粉研磨厂。1897年，又在北岸旁建造另一个发电厂以提供冶炼厂更多电力。
1908年4月14日，炸毁黑鹰水坝。炸毁水坝使得从Hauser水坝来的洪水能迅速通过。
1908年4月14日，下午2:30左右，大瀑布上游90英里处的豪瑟水坝溃堤，高ft到ft的浪潮袭卷下游。大北铁路指派一台火车头沿路警告住在通往大瀑布城的铁路周边居民。矿业公司的工人简易地搭建了一个翼坝，以从冶炼厂转移洪水，并炸开了一部分的黑鹰水坝以利洪水迅速流向下游。但当河水到城市时，密苏里河只涨潮了ft。有两名员工在爆破时身亡：一位在移除水坝的插板时溺死，另一位死于船只翻覆。
同年的6月6日，黑鹰水坝遭受另一波洪水的攻势。一天之内地区降雨量达7.6公分，密苏里河在八小时内涨潮将近41公分。河水比洪水位高出m（密苏里河的平均水位为m），5位居民被淹死。冶炼厂试图在黑鹰水坝北边利用4辆满载的火车车厢阻挡朝向发电厂的洪水 。许多建筑被冲走，在当时是大瀑布城最严重的水灾。一些建筑撞上了黑鹰水坝，一些超过水坝的部分掉到瀑布下，大坝上的行人吊桥也被冲毁（今日，可以在第六街地下道看到一个牌子标示高水位的范围。）大坝本身也有些受损，之后便修复完成，通往水渠岛的旧木桥也用沃伦桁架桥取代，可行驶汽车。现在岛上甚至有停车场供员工停车。
20世纪前期，黑鹰水坝的所有权改变了两次。1908年，约翰‧D‧莱恩（比尤特的达利信托与阿纳康达铜矿公司总裁，之后成为助理国务卿） 购买了GFWPTC绝大部分的股份。1910年，GFWPTC组织其子公司大瀑布电力公司，接管了黑鹰水坝及其他水力发电项目（当时正在建设）的所有权与经营权。1912年发生了第二次所有权变更。霍尔特水坝的成本超支，投资者对水坝建设的热情减弱，以及与豪瑟水坝溃堤的责任使联合密苏里河电力公司的最大股东塞缪尔‧托马斯‧豪瑟几乎破产，使他必须售出联合密苏里河电力公司给约翰‧D‧莱恩。1912年10月25日，约翰‧D‧莱恩把两间公司合并成比尤特电力公司、比灵斯与东蒙大拿电力公司与麦迪逊河电力公司，三间公司组成了蒙大拿电力公司。同年，黑鹰水坝产生的功率（3.9兆瓦至5.7兆瓦）输往新的冶炼厂，而仅有 0.7兆瓦的电力输送到附近城市。另外有300马力的机械能来自水车，并透过绳索与滑轮输送往皇家面粉厂。
1913年，蒙大拿电力公司升级了黑鹰水坝的产电能力（而不是机械能）。公司放弃了原先规划的南岸第二座发电厂，改装载两台法兰西斯水轮机。第一座发电厂的旧发电机汰换成两台可产生1.5兆瓦的新发电机。厂内又造了两座调压舱，并连接压力管。翻新后的南方发电厂现在直接提供电力给冶炼厂和磨坊而不是机械能了。
===1926年的水坝===
1909年，大瀑布电力公司的工程师提议在三个地点盖水坝：彩虹瀑布（彩红水坝，Rainbow Dam）、大瀑布（瑞安水坝，Ryan Dam）、密苏里河的峡谷（科克伦水坝，Cochrane Dam，位于前两个水坝中间）。1914年，蒙大拿电力公司打算加高黑鹰水坝来增加发电能力。1916年，大部分的波士顿与蒙大拿冶炼厂被现代铜矿与锌矿的冶炼厂取代，同时加设电线跟电缆的制造厂。虽然黑鹰水坝更新了涡轮机与发电机，它当时仍然只能产生3兆瓦的电力，而电力需求则一直提升。在1920年早期，黑鹰水坝已不足以提供大瀑布城的用电所需，再加上新的锌冶炼厂需要10兆瓦的电力。1925年，北边发电厂被认为严重的过时。
1925年末，蒙大拿电力公司计划建设新的水坝与发电厂。查尔斯‧T‧马恩（Charles T. Main）的公司负责监督水坝的重建，蒙大拿的顾问工程师亨利‧柯克伦（Harry Cochrane）负责重新设计水坝，因此此水坝称作科克伦水坝（Cochrane Dam）。1926年4月1日，蒙大拿电力公司宣布要花费100万美元在黑鹰水坝建造新的发电厂。但随著工作的进展，他们意识到水坝及其四座发电厂太旧，无法满足发电需求。他们调整计划，决定在水坝下游m处新建一个水坝。南边的调整池被放弃，并保留北边的调整池且好好地维修一番。1897年盖的北岸发电厂被拆除，在同一地点盖了混凝土的新发电厂。他们记取1908年的教训，厂房设计与位置皆有以此作为考量。
拆除南岸发电厂的同年夏天，开始了新建水坝的工程。工人替新水坝浇灌混凝土时，旧水坝用来当作围堰。新水坝于1927年8月1日完工，完全淹没了旧水坝，在9月开始发电。新水坝长m，高m，溢洪道长m。它的高度受到上游城市的淡水和污水设施限制，如果水坝更高，会淹没设施。水坝顶部呈现O形，可以改善水流。新大坝有八个水闸，与一条带栏杆的人行道，让维护人员能够到达闸门和水坝。1996年，位于黑鹰水坝北岸发电厂的涡轮机。
新发电厂由混凝土建成，不过公司曾计划要建造成砖瓦屋，但当地砖匠要求获得城市规定的工资，而不是蒙大拿州政府的，因后者薪资较低。厂房南边和北边的混凝土和石砌墙用于防止水流侵蚀调整池和水渠道。调整池m长，m宽，延伸至较下游的新动力室，旧动力室的砖拱门结合到了调整池的墙壁中。新发电厂搭载三台由S.摩根史密斯公司提供的垂直卡布兰式水轮机，能够产生18兆瓦能量，成为蒙大拿电力公司在大瀑布地区五座水坝中最大产能的一座。史密斯公司在涡轮机上加装油压调速器（调节每个涡轮机的速度）与导流管（在水离开涡轮机后速度被降下来，并使得从上快速落下的水持续向涡轮机的螺旋桨传递能量）。涡轮机螺旋状入口和导叶门固定在发电厂的地下室，每台涡轮机都安装在自己的坑槽内。每台涡轮机通过一楼的屋顶连接到额定功率为7000伏安的阿里斯－查尔默斯（Allis-Chalmers）发电机。直流发电机作为阿里斯－查尔默斯发电机的激励器。六台6,600 / 2,200伏变压器降低了电压供使用。
1926年重建后，黑鹰水坝遭遇了四次洪水，但都没有造成损害。第一次发生在1953年6月4日，春雨和融雪导致密苏里河高于洪水位m，没有大坝损毁的报告。第二次在1964年6月10日，洛矶山脉的大雨导致密苏里河高于洪水位m，比1908年的洪水高出m。位于桦树溪的Swift Dam溃堤，造成19人死亡，下双麦迪逊湖水坝（Lower Two Medicine Lake Dam）也溃堤，造成9人死亡。尽管因大洪水造成3000人被迫离开家园，此次黑鹰大坝仍未受损。 （Mel Ruder因洪水报导而被授予突发新闻报导普利策奖）。1975年6月21日发生第三次洪水，洛矶山脉24小时内降雨超过cm。在太阳河升至m（高于洪水位m）后，超过5000人从大瀑布城撤离。损失超过1700万美元，ha的土地被淹没。洪水几乎淹没了黑鹰大坝，但没有对结构造成伤害。第四次大洪水在1997年6月17日，又多又快的融雪导致密苏里河高于洪水位m。黑鹰水坝还配备了一个紧急“trip face”可以解除水坝上所有插板，让河水能够以每秒钟m3的水量流过。
== 长池水库 ==
黑鹰水坝在它后面创建了一个长约km的水库。紧邻第一大坝的水库大约m深，容量lk=in。目前水坝的蓄水量为m3到m3。
这水库没有正式名称，但由于水流缓慢犹如静止，以及从上游的喀斯喀特到黑鹰瀑布的坡度低（沿著蜿蜒的密苏里河约km长），这个水体一直被称为「长池」。在1872年，命名黑鹰瀑布的托马斯P‧罗伯茨，正式命名这个水体。美国陆军工兵部队于1883年和1910年使用过这名称。在1891年至1917年就已经广为流行，蒙大拿州议会也已在此时使用这名称。因此现代历史学家也用这名称提及它，1949年后被电力业出版物使用。现在，从第一林道北桥到密苏里河与太阳河交汇处（距离约km）为知名的布罗德沃特湾（知名人士如：查尔斯‧阿瑟‧布罗德沃特、蒙大拿铁路执行长、房地产投资者和银行家）。
== 水坝开发 ==
1926年大坝重建后，工人和居民可以穿越大坝顶部上班或上学。出于安全原因，蒙大拿电力公司在二战时期关闭了道路，并封闭到现今。
1950年，根据《联邦电力法》，蒙大拿电力公司被迫授权黑鹰水坝等大部分发电用水坝。联邦电力法案于1935年通过，在1937年12月，联邦电力委员会（FPC）开始执行一项程序（FPC Docket IT-5840），赋予1935年之前建造的所有水坝许可证。该法案赋予联邦电力委员会在美国可航行水域中，所有水坝的控制权。经过长时间的研究、数据收集以及谈判之后，1946年11月18日开始举行听证会，以确定蒙大拿电力公司在1935年之前修建水坝前，河流是否可通航以致水坝属法律生效范围 。1947年9月30日发布的第170号意见书中，审判员认为此河流可以通航，并且含黑鹰水坝等水坝应该获得许可。 蒙大拿电力公司在联邦电力委员会于1948年2月16日举行听证会时诉愿。当联邦电力委员会驳回时，蒙大拿电力公司转向哥伦比亚特区联邦上诉法院上诉。1950年10月4日，David L. Bazelon法官以2比1多数决判决「蒙大拿电力公司诉联邦电力委员会案」，指出「密苏里河从本顿堡到斯里福克斯长达263英里，属美国通航水域，符合《联邦电力法》的许可要求」。法院认为黑鹰、莫罗尼、彩虹、瑞安水坝都在通航水域，无权侵占公有地。豪瑟水坝在通航水域，并持有无效许可证占用公共土地。霍尔特水坝拥有有效许可证，但该许可证没有延伸到它使用的通航水域。赫布根和麦迪逊水坝在不通航水域，但没有有效许可证而占用公有地。上诉法院将Canyon Ferry水坝的问题退还给地方法院，因为该水坝已被出售给联邦政府。蒙大纳州电力公司向美国最高法院提出上诉， 美国最高法院于1951年3月否决了特许权（拒绝审理此案）。 蒙大拿电力公司随后于2000年9月27日由联邦能源管理委员会（FPC的继承机构）重新授权并赢得了黑鹰水坝营运许可，许可证编号为P-2188。另外还有7座需要法院裁决。
1978年，修复三台阿里斯－查尔默斯发电机，1982年，再修复一次。1997年，蒙大拿电力公司修复并重新粉刷了通往水渠岛的桥。
1999年11月2日，蒙大拿电力公司宣布以16亿美元的价格卖给宾州电力公司（PPL）所有水坝和发电厂。这笔包含黑鹰水坝的买卖估计会给蒙大拿州带来3000万美元的税收（但蒙大拿电力公司表示税金会比3000万少）。2001年11月，因电价上涨而不满的民众提出一项倡议：要求州政府收购PPL所有用来发电的水坝（包含黑鹰水坝）。在2002年11月，这项倡议被否决了。
在蒙大拿电力公司将黑鹰水坝卖给PPL的时候，蒙大拿电力公司正在安装控制装置，使黑鹰水坝能够从彩虹水坝远程操作。当时，PPL表示他没有计划扩大黑鹰水坝的发电能力。同样在1999年，蒙大拿电力公司将大部分的水渠岛转移到大瀑布市作为娱乐区。此外，蒙大拿电力公司和ARCO（波士顿和蒙大拿州的后继公司）在该岛上铺设了cm（46公分）的表土，花费了50万美元用于景观设计，并增强了动力厂附近的安全边界，并同意资助一部分小岛的定期保养费用。
1990年代后期，历史学家史蒂芬·安布罗斯建议拆除黑鹰水坝，将瀑布恢复原状。
2010年，黑鹰水坝的发电与输电系统开始翻新。同年6月，PPL蒙大拿州分公司花费5500万美元用高压电线取代该地区电力网路。新的电线取代了80多年前的设备，电线间隔更大，使得大型鸟类可以安全地通过或栖息在电线上。PPL也计划更新电厂旁的变电所，两项工程都预期会在2012年完工。
=== 沉积物、水流量、残骸、紧急状况 ===
密苏里河与支流夹带的沉积物是黑鹰水坝的一大问题。太阳河（Sun river）在黑鹰大坝上游几英里处与密苏里河相连，夹带著污泥，养份与藻类，因此还被讽刺成“浮渣河（Scum river）”。 太阳河水呈现如巧克力牛奶的颜色，流入相对清澈的密苏里河后使其变得污浊。污泥降低水库容量，充满调整池，也会对发电机组造成损害。1988年，由于密苏里河从太阳河到彩虹水坝一段的沉积物和悬浮物，蒙大拿州环境质量部（Montana Department of Environmental Quality, MDEQ）根据1972年清净水法第303（d）节，将其水质状态列入受损。黑鹰水坝因为减缓水流流速，被列为问题来源之一。为了解决这个问题，1994年，7个联邦机构，8个州政府机构，10个蒙大拿州政府机构，4个环境组织和几个蒙大拿州地主共同努力减少进入太阳河及其主要支流（Muddy Creek与Careless Creek）的营养物和沉积物。约623,500美元的清洁水法基金、200万美元的联邦基金以及250万美元的州与地方基金用于恢复河岸植被、改善河边放牧、复原河床斜度和改善灌溉方法。到2010年，Muddy Creek减少75%沉积物，Careless Creek减少25%。
黑鹰瀑布是否流通，取决于黑鹰水坝。每年5月，理论上密苏里河的中位水流量为每秒m3。2000年10月，水坝水位下降，瀑布停止流水四周，PPL蒙大拿在这段时间修整了调整池，闸门和钢管滤网。PPL蒙大拿的工作许可证要求水坝在周末与亡兵纪念日至劳动节期间的上午9点至下午8点流出至少每秒m3的水量。如果水位或发电需求允许，水量可能更多。2001年5月，PPL蒙大拿表示因为水流量只有平时的40%，他们要在7月4日后截断瀑布。2004年9月，水库水位再次降低，以修复档板，河流缺水使巨人泉附近的密苏里河天然通道暴露出来。2008年6-7月，水库水位又过低以致瀑布再次停流，而在一次大雨后移除了档板使水流快速通过。当水流通过并把档板归位后，水库内剩没多少水，而瀑布再次流通也是几天后的事了。
一台Alvis Stalwart，用来在黑鹰水坝进行两栖维修。
因为黑鹰水坝属于溢流坝，所以漂流的残骸很容易阻塞进水口。常见的阻塞物有浮木与原木，但有时连船坞、保龄球、划艇、浴缸、木棚与钢棚也会卡在水坝上。 Removing hollow items can be dangerous, because the water pressure against them can cause them to implode. In addition to large amounts of driftwood, about 100 animal carcasses (cattle, deer, dogs, and various small animals) become lodged against the dam or the penstock intake screens each year. Floating screens at the entrance to the forebay catch many items, as do the penstock intake screens. Workers use a crane to remove items from these screens, and bury the items retrieved at a landfill. Dam operators also use a yellow civilian version of the Alvis Stalwart amphibious vehicle to remove objects, and to maintain the dam. (This vehicle caused a stir in Great Falls in June 2006, when local residents driving on a nearby road mistook the vehicle for a sport utility vehicle which had fallen into the water.) Ice is another form of dangerous debris for the dam. In December 2010, blocks of floating ice overwhelmed the top of the dam, tearing the handrails off the maintenance walkway.
For many years, Black Eagle Dam's owners were required to hold simulations every five years to plan for various kinds of emergencies (flood, sabotage, mechanical breakdown, etc.) which might affect the dam and public safety. After the September 11 attacks, these exercises were required to happen every year. PPL Montana works with local and state government and law enforcement, other companies, and the news media to plan for various contingencies and improve how it might respond in a disaster or emergency.
=== Tax dispute and Supreme Court riverbed case ===
Taxation of the dam has been an issue of contention since 2000.  During the 2002 ballot initiative fight, PPL Montana said its dams were worth at least $767 million. But in 2003, PPL argued that the dams were worth much less. PPL Montana challenged the amount of property taxes assessed on Black Eagle and its four other dams in the area, protesting 10.87 percent of the $4.48 million 2000 tax assessment, 6.5 percent of the $4.8 million 2001 tax assessment, and 85.65 percent of the $4.96 million tax assessment. This amounted to 30 percent of its total property tax assessment in the state of Montana—with one-third of amount owed payable solely in Cascade County. In February 2005, the Montana State Tax Appeal Board gave the state a partial victory, reducing the state's assessments by 10 percent but otherwise upholding the assessment method. However, the tax board did not address PPL Montana's primary claim that the state was assessing its plants differently solely because they were unregulated. PPL Montana appealed the ruling to the Montana Supreme Court in 2007. On December 4, 2007, the Montana Supreme Court unanimously ruled in State Dept. of Revenue v. PPL Montana that the tax appeal board had properly assessed PPL Montana's dams. However, PPL Montana had continued to dispute its tax assessments from 2003 to 2007, and the ruling did not directly address those challenges. But on December 14, 2007, PPL Montana offered to pay its 2003-to-2007 tax assessments at the slightly lower rate established by the tax appeal board.
Another tax issue arose in 2007. The parents of several Montana schoolchildren filed suit in the United States District Court for the District of Montana against PPL Montana. The parents argued that all riverbeds in Montana are owned by the state, are held in trust for the benefit of all the people, and that such riverbeds constitute a portion of state lands which must be taxed or leased to provide support for public schools. The plaintiffs argued that PPL Montana and its predecessor, Montana Power, only leased these riverbeds from the state and did not own them. The parents sued to force PPL to pay rent due. (At no time in the past had the state sought rental income from Montana Power, and no payments by Montana Power or PPL Montana had ever been made.) Although the federal suit was dismissed for lack of a federal issue, PPL Montana filed suit in Montana's First Judicial District Court seeking a declaratory judgment in its favor, arguing that the Federal Power Act preempts the parents' suit and denies states the power to make companies pay for the use of riverbeds. The state district court held against PPL's request for summary judgment on all counts. The two parties then went to trial, which lasted from October 22 to October 30, 2007. On June 13, 2008, the state district court ruled in favor of the state (although it denied the state's request for interest on the rent due). PPL Montana appealed to the Montana State Supreme Court.  On March 30, 2010, the Montana State Supreme Court held (5-to-2) that the state district court had not erred in its rulings on various issues of summary judgment, that riverbeds were state public trust lands (but not school trust lands) under the Montana Constitution, and that the district court's calculation of payments due was appropriate. PPL Montana, appealed to the Supreme Court of the United States, and in November 2010 the Supreme Court asked the United States Solicitor General for the views of the federal government. Finally, on February 22, 2012, the U.S. Supreme Court held in PPL Montana v. Montana (No. 10–218, dec. February 22, 2012) that the Montana Supreme Court had erred in finding all of the riverbeds beneath all PPL Montana dams navigable.  The unanimous U.S. Supreme Court held that the correct test is whether the portion of the riverbed under each specific dam (not the entire river, nor even a large or small portion of a river) was navigable at the time of statehood.  If it was, then the riverbed is "navigable" and may be taxed.  The case was remanded back to the state supreme court for further hearings.
Flashboards on the dam were slightly damaged during flooding in the spring and early summer of 2011.  Water behind the dam was lowered until it barely crested the dam so repair crews could replace the flashboards.
== Recreational aspects and fishery management ==
=== Fishing and water quality issues ===
Walleye, a popular sport fish caught at Black Eagle Dam.
The river above and below Black Eagle Dam is used for fishing. Westslope cutthroat trout were first identified at Black Eagle Falls by Lewis and Clark in 1805, and the fish still are plentiful in the area. Rainbow trout are also plentiful upstream from the dam. The area below Black Eagle Falls has been rated by one guide as a good area for fly fishing smallmouth bass and walleye. For many years, the state of Montana managed the Long Pool reservoir as part of one fishing management area, and the river below the dam as part of another. This was changed in 1999, so that the two are now managed together. The change also instituted a new limit on trout caught and killed below the dam of five fish per day (only one of which could be over cm). Limits on the number of walleye caught per day were lifted in 2010 to protect the rainbow and brown trout populations (they had been five daily and 10 in possession). According to dam officials, there are no screens to prevent fish from going over the dam or through the penstocks and turbines. Fish "go right through the turbines, it doesn't seem to bother them," dam operators say.
Since 1988, the Long Pool and the Missouri River in and around the city of Great Falls have been listed as an "impaired" waterway under the 1972 Clean Water Act. This area was first listed as impaired due to sedimentation, siltation, and suspended solids in 1988. High levels of chromium, mercury, and selenium were listed as impairing factors in 1992. High turbidity (haziness of water due to suspended particles) was added as an impairing factor in 2000. Sources of these impairments include Black Eagle Dam, upstream abandoned mines, irrigation runoff, industrial sources, and stormwater runoff. The MDEQ has given the area a quality ranking of B-2 (fourth out of 18), declaring it suitable for human consumption and recreation (after treatment) but only marginal for salmonid fish, other aquatic animals, waterfowl and fur-bearing animals. MDEQ has scheduled the Long Pool and Missouri River watershed in this area for future improvement.
In 2011, the former smelter next to Black Eagle Dam was listed by the United States Environmental Protection Agency (EPA) as a Superfund hazardous and toxic waste site. The EPA also said it would begin sampling for the riverbed above and below Black Eagle Dam, as well as residential areas in the town of Black Eagle, for heavy metals contamination. Historic records show that plant wastes were routinely dumped into the Missouri River below Black Eagle dam. MDEQ estimated in 2002 that between m3 and m3 of waste were dumped into the river between 1892 and 1915. EPA samples indicated that the contamination could extend as far downstream as Fort Benton, km away. Toxins present in the water and riverbed, according to the EPA, include antimony, arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, silver, sodium, and zinc.
=== Wildlife and hunting ===
The area around the falls, despite its urban setting, is a habitat for many animal and bird species. Among the birds commonly found in the area are bald eagles, California gulls, Canada geese, cliff swallows, eared grebes, egrets, golden eagles, American goldfinches, gray catbirds, house wrens, ibises, ospreys, red-necked grebes, sandhill cranes, snow geese, tundra swans, turkey vultures, western grebes, western meadowlarks, white pelicans, and numerous species of duck, owl, and warbler. Common animal species in the area include beavers, mule deer, muskrats, river otters, and white-tailed deer. Beavers are so common in the area that officials consider them pests, and trees in city parks have had to be protected against them. (At one point, beavers were chewing down two trees nightly on Black Eagle Memorial Island. These included two red oak trees found growing on the hill above the dam—the only two red oak trees in northcentral Montana). As of 2006, most of the north shore of the Missouri River below Black Eagle Dam was undeveloped as far down a Sulphur Spring (a distance of about km). Known as the Lewis and Clark Greenway, this area is under a permanent conservation easement.
Although the area below Black Eagle Dam is open for bird hunting, the reservoir and river upstream from Black Eagle Dam to Sand Coulee Creek is a no-hunting area.
Wildlife hunting is also available on the north shore of the Missouri River from below Black Eagle Dam to Morony Dam. Most of this land is owned by PPL Montana, but there is some private land here which is not open to hunting. The PPL Montana lands are open to hunting due to a conservation easement, but the Montana Department of Fish, Wildlife and Parks requires hunters to obtain a map of these lands before using them for hunting. There are also restrictions on the type of weapons which may be used in this area, and where hunters may park.
=== Recreation area improvements ===
Lewis & Clark National Historic Trail Interpretative Center, located just downstream of Black Eage Dam.
Black Eagle Dam is also utilized as a recreation area. The whitewater just below the falls is a good place for canoeing, inner-tube floating, and kayaking. Hiking and bicycling also occur in the area. Beginning in 2006, the Black Eagle Dam Run (a adj=on run/walk and adj=on run) has been held at Black Eagle Dam in mid-July. The annual Lewis and Clark Festival, celebrated in late June (the anniversary of the discovery of the Great Falls), focuses on events held around Black Eagle and other dams on the Great Falls of the Missouri. In mid-July, the River's Edge Trail Luminaria Walk occurs around Black Eagle Dam and the falls, and are illuminated with colored spotlights during the event. On May 5, 1998, the United States Forest Service opened the adj=on Lewis and Clark Interpretive Center, a $6 million museum and education center (which includes an exhibit hall, theater, store, and classrooms) which tells the story of Lewis and Clark's passage through central Montana and their discovery of the Great Falls of the Missouri.
Much work has been done in the past two decades to create public access to and public viewing areas of the dam and falls. For decades, two gravel spaces existed on River Drive North near the Bob Speck Municipal Golf Course where drivers could stop, get out, and view Black Eagle Falls and the dam. In 1991, the River's Edge Trail, a paved and gravel pedestrian recreational trail, opened along tracks of the former Burlington Northern Railroad on the south bank of the Missouri River at Black Eagle Dam. In 2001, Tailrace Island was renamed Black Eagle Memorial Island (in honor of those workers who lost their lives while working on or at the dam) and turned over to the River's Edge Trail. A new adj=mid section of the trail linking the existing adj=mid trail was also opened that year. The same year, a public boathouse was constructed on Black Eagle Memorial Island for use by canoeists, kayakers, and other watercraft; observation decks; public restrooms; and parking lot. The boat landing was completed in October 2001. Construction also began on a adj=mid section of trail designed to link Art Higgins Memorial Park (on the north bank of the Missouri River just behind the dam) with the island. Most of the construction costs were paid for by PPL Montana. In 2001, another segment of the trail was added, leading from the Black Eagle Memorial Island spur up Smelter Hill. The adj=mid trail was paid for by a Community Transportation Enhancement Project grant. There is no fee to enter Black Eagle Memorial Island, which is open daily to the public from 9 A.M. to 8 P.M. and is maintained by the Montana Department of Fish, Wildlife and Parks. In 2004, the River's Edge Trail was extended along the north bank of the Missouri River from the Black Eagle Dam powerhouse westward about km to the 15th Street Bridge. About $175,000 of the $204,500 cost of the extension was paid for by the Community Transportation Enhancement Program, and the remainder by the Montana Air Congestion Initiative (a state program), the American Public Land Exchange (a nonprofit organization), and Recreational Trails (a nonprofit which manages the trail). Black Eagle Memorial Island opened to the public on June 2, 2005.
The development of the River's Edge Trail and the growing importance of riverside parks and attractions around Black Eagle Dam and along the banks of the Missouri River led the city of Great Falls to develop its first Missouri River Urban Corridor Plan in 2003. The master plan, which covered both banks of the Missouri River from White Bear Island to Black Eagle Dam, inventoried the entire shoreline and assessed the riverbanks for condition, rehabilitation and refurbishment, and improvement opportunities. The plan laid out a number of options above and below Black Eagle Dam for improvements to public access, recreation, and beautification.
Black Eagle Dam has changed very little between its construction in 1926 and 2010. The ruins of the powerhouses from the 1890 dam and the 1913 reconstruction were still visible as of 2005. The large cast-iron sheets which formed the south bank penstocks can also still be seen.
== 脚注 ==