黑鷹水壩

1890年的大壩

大瀑布城水電公司（GFWPTC）成立於1887年，目標是發展大瀑布城，提供電力、自來水與汙水的處理，以吸引工商業進入城市。鐵路巨頭詹姆士·希爾集合大北鐵路的主要股東，5百萬美元資本。 希爾把股票賣給他的朋友，菲利普·丹福斯·阿莫爾，查爾斯·亞瑟·布羅德沃特，馬歇爾·菲爾德，約翰·穆雷·福布斯，丹尼爾·威利斯·詹姆斯，約翰·斯圖爾特·甘迺迪，倫納德·劉易斯和查爾斯·埃利奧特·珀金斯。巴黎‧吉布森是希爾的朋友，大瀑布城水電公司的股東之一，也是大瀑布城成立的推手。吉布森意識到，密蘇里河的大瀑布可以為工業提供豐富，便宜的電力，並在此基礎上推動城鎮發展。但吉布森的計劃意味著實際上要建設一個或更多水壩來提供想像中的電力。公司立刻開始購買密蘇里河沿岸的土地和水利權，從黑鷹瀑布一路買到綿羊溪，約12英里（19公里）。到最後，公司幾乎擁有了大瀑布城的所有土地，加上河岸邊的5,000英畝（2,000公頃）地產。公司僱傭一位水利工程師J.T. Fanning，在1887年夏天調查黑鷹瀑布，以確定瀑布的適宜性和大壩的最佳位置。當時計劃已完成，但沒有採取任何行動。
黑鷹水壩當時是為了供電給銅冶煉廠。在1887年7月22日，波士頓與蒙大拿銅銀綜合礦業公司創立，它是由倫納德‧路易森的路易森兄弟（一間銅貿易公司），蒙大拿公司（一間礦業控股公司）與C. X. Larrabee （擁有高產量的礦場，Larrabee和有名的山中礦）合併而成。 1889年9月12日，波士頓和蒙大拿州與GFWPTC簽署了一項協議，其中電力公司同意在1890年9月1日之前建造一座能夠為該礦業公司提供至少1,000匹馬力小時（750千瓦·小時）電力的水壩，並在1891年1月1日前達到5,000匹馬力小時（3,700千瓦·小時）。作為交換，波士頓與蒙大拿銅銀綜合礦業公司同意在大壩附近建立一個30萬美元的銅冶煉廠。
1890年黑鷹水壩開始施工，GFWPTC的工程師設計一個由厚重木材定型，裡面充滿岩石的溢流壩。這個壩並不大，目的是在其後面建造一個蓄水池，以產生足夠的水壓（揚程）推動渦輪機發電。這水壩建造在上游邊緣（盡可能創造最深的水庫），花費約515,000美元（通貨膨脹至2010年約12,335,000美元）。1890年2月5日工程開始投標，標案要求工程要在1890年12月1日前完成。所有投標都被拒絕，機械工程師莫里斯‧帕克被雇來設計與建造大壩，為了把河流從工作區域轉移開，1890年4月15日開始建造了圍堰壩。在工地北邊的岸上蓋了名叫河岸（River Bank）的棚戶區，提供給幫助建造大壩的克羅埃西亞人、斯堪地那維亞人、斯洛伐克人與威爾斯人（其中絕大多數人幫助找到了黑鷹鎮，還能看到當時土製的棚戶地基）。紅砂岩的河床盡可能弄平整，大塊的木材用螺栓固定到岩石上，與河流垂直。每兩塊木材間距8英尺（2.4公尺），中間有六塊小木材，組成56.66英尺（17.27公尺）深的水壩，水壩的下游面間隔為1.05塊／公尺， 頂部間隔1.08塊／公尺，延伸了8英尺（2.4公尺）。水壩南端建立一個30英尺（9.1公尺） 的石牆以保護發電廠，防止水壩向廠房的壓力。水壩頂部每48英尺（15公尺） 建造一個14英尺（4.3公尺）寬的混凝土疏洪道，共八條。在壩頂加裝一條1英尺（0.30公尺）高的檔板以增加蓄水量。水壩15英尺（4.6公尺）高，1,100英尺（340公尺）寬。
水壩在1890年12月開始發電。1891年1月6日，水可流過水壩的頂部，1891年3月15日，宣布水壩完工。
河的南邊建了一棟佔地40乘165英尺（12乘50公尺）, 磚瓦蓋的發電廠。內部有三台雙組橫流維克托式水輪機，每台能夠產生1.27百萬瓦的能量。南岸和離岸一段距離的石牆間產生一個供給鋼管河水的調整池，水流入鋼管的量一部分由調整池上游的閘門控制。主要的鋼管長400英尺（120公尺），直徑9英尺（2.7公尺），提供發電機水源（另有其他三條鋼管建成，但沒有立即投入使用）。
河的北邊是另一座在1892年建成的發電廠，裡面有七八組維克托水輪機，共產生1.940百萬瓦的能量，從河北岸底部切割出來的石塊堆積在附近形成一座小島：水渠島（Tailrace Island），而發電廠就蓋在這座人造島上。島嶼與密蘇里河的北岸間形成了黑鷹水壩的水渠（也是發電廠的水渠）。水渠島由電力公司與波士頓蒙大拿礦業公司共同擁有。電廠與冶煉廠由一座木製天橋連接起來。北岸與石強形成筆直的調整池供應北邊的發電廠（最寬的部分有100英尺（30公尺）） 水的流量與南邊一樣，由閘門控制。三條鋼管供給北邊發電廠水源。然而，此發電廠產生的機械能大部分並沒有轉成電能，而是透過繩索與滑輪系統直接轉移到冶煉廠。
兩間電廠產生的部分機械能，透過湯姆遜-休斯頓發電機轉換成電力，單一員工在電廠裡工作八小時。次要的發電廠蓋在南邊發電廠隔壁，裡面裝載一台Armington & Sims蒸汽發電機，在主發電機關閉時，供應客戶電力。200英尺（61公尺）長的纜索鐵道（傾斜的鐵路）接通懸崖上面與南邊發電廠。懸崖上有多條200英尺（61公尺）長， 10英尺（3.0公尺）寬的吊橋跨越河上連接各個發電廠。水壩預估可用50年。

1890年水壩運作歷史

1890年春天，冶煉廠開始動工；1891年3月，選礦機啟用；1892年4月，Brückner cylinders與反射爐啟用；1892年8月，蒸餾轉換器啟用；1893年1月，精煉爐啟用；1893年2月，電解精煉爐啟用；1893年4月，高爐啟用。冶煉廠起初預算為200萬美元，在1892年員工數已達1000位。1908年4月7日，大煙囪（Big Stack）開始建造，底部內徑78.5英尺（23.9公尺），頂部50英尺（15公尺），將廢氣排到506英尺（154公尺）的高空。由紐約的Alphonse Custodis建築公司於1908年10月23日完工，成為當時最高的煙囪。
1893-1894年，GFWPTC在現有的南岸發電廠下游，建造了第二個發電廠，將電力輸送至懸崖上的皇家研磨公司的麵粉研磨廠。1897年，又在北岸旁建造另一個發電廠以提供冶煉廠更多電力。
1908年4月14日，下午2:30左右，大瀑布上游90英里處的豪瑟水壩潰堤，高25英尺（7.6公尺）到30英尺（9.1公尺）的浪潮襲捲下游。大北鐵路指派一台火車頭沿路警告住在通往大瀑布城的鐵路周邊居民。礦業公司的工人簡易地搭建了一個翼壩，以從冶煉廠轉移洪水，並炸開了一部分的黑鷹水壩以利洪水迅速流向下游。但當河水到城市時，密蘇里河只漲潮了7英尺（2.1公尺）。有兩名員工在爆破時身亡：一位在移除水壩的插板時溺死，另一位死於船隻翻覆。
同年的6月6日，黑鷹水壩遭受另一波洪水的攻勢。一天之內地區降雨量達7.6公分，密蘇里河在八小時內漲潮將近41公分。河水比洪水位高出8.1英尺（2.5公尺）（密蘇里河的平均水位為15英尺（4.6公尺）），5位居民被淹死。冶煉廠試圖在黑鷹水壩北邊利用4輛滿載的火車車廂阻擋朝向發電廠的洪水 。許多建築被沖走，在當時是大瀑布城最嚴重的水災。一些建築撞上了黑鷹水壩，一些超過水壩的部分掉到瀑布下，大壩上的行人吊橋也被沖毀（今日，可以在第六街地下道看到一個牌子標示高水位的範圍。）大壩本身也有些受損，之後便修復完成，通往水渠島的舊木橋也用沃倫桁架橋取代，可行駛汽車。現在島上甚至有停車場供員工停車。
20世紀前期，黑鷹水壩的所有權改變了兩次。1908年，約翰‧D‧萊恩（比尤特的達利信託與阿納康達銅礦公司總裁，之後成為助理國務卿） 購買了GFWPTC絕大部分的股份。1910年，GFWPTC組織其子公司大瀑布電力公司，接管了黑鷹水壩及其他水力發電項目（當時正在建設）的所有權與經營權。1912年發生了第二次所有權變更。霍爾特水壩的成本超支，投資者對水壩建設的熱情減弱，以及與豪瑟水壩潰堤的責任使聯合密蘇里河電力公司的最大股東塞繆爾‧托馬斯‧豪瑟幾乎破產，使他必須售出聯合密蘇里河電力公司給約翰‧D‧萊恩。1912年10月25日，約翰‧D‧萊恩把兩間公司合併成比尤特電力公司、比靈斯與東蒙大拿電力公司與麥迪遜河電力公司，三間公司組成了蒙大拿電力公司。同年，黑鷹水壩產生的功率（3.9百萬瓦至5.7百萬瓦）輸往新的冶煉廠，而僅有 0.7百萬瓦的電力輸送到附近城市。另外有300馬力的機械能來自水車，並透過繩索與滑輪輸送往皇家麵粉廠。
1913年，蒙大拿電力公司升級了黑鷹水壩的產電能力（而不是機械能）。公司放棄了原先規劃的南岸第二座發電廠，改裝載兩台法蘭西斯水輪機。第一座發電廠的舊發電機汰換成兩台可產生1.5百萬瓦的新發電機。廠內又造了兩座調壓艙，並連接壓力管。翻新後的南方發電廠現在直接提供電力給冶煉廠和磨坊而不是機械能了。

1926年的水壩

1909年，大瀑布電力公司的工程師提議在三個地點蓋水壩：彩虹瀑布（彩紅水壩，Rainbow Dam）、大瀑布（瑞安水壩，Ryan Dam）、密蘇里河的峽谷（科克倫水壩，Cochrane Dam，位於前兩個水壩中間）。1914年，蒙大拿電力公司打算加高黑鷹水壩來增加發電能力。1916年，大部分的波士頓與蒙大拿冶煉廠被現代銅礦與鋅礦的冶煉廠取代，同時加設電線跟電纜的製造廠。雖然黑鷹水壩更新了渦輪機與發電機，它當時仍然只能產生3百萬瓦的電力，而電力需求則一直提升。在1920年早期，黑鷹水壩已不足以提供大瀑布城的用電所需，再加上新的鋅冶煉廠需要10百萬瓦的電力。1925年，北邊發電廠被認為嚴重的過時。
1925年末，蒙大拿電力公司計畫建設新的水壩與發電廠。查爾斯‧T‧馬恩（Charles T. Main）的公司負責監督水壩的重建，蒙大拿的顧問工程師亨利‧柯克倫（Harry Cochrane）負責重新設計水壩，因此此水壩稱作科克倫水壩（Cochrane Dam）。1926年4月1日，蒙大拿電力公司宣布要花費100萬美元在黑鷹水壩建造新的發電廠。但隨著工作的進展，他們意識到水壩及其四座發電廠太舊，無法滿足發電需求。他們調整計畫，決定在水壩下游50英尺（15公尺）處新建一個水壩。南邊的調整池被放棄，並保留北邊的調整池且好好地維修一番。1897年蓋的北岸發電廠被拆除，在同一地點蓋了混凝土的新發電廠。他們記取1908年的教訓，廠房設計與位置皆有以此作為考量。

拆除南岸發電廠的同年夏天，開始了新建水壩的工程。工人替新水壩澆灌混凝土時，舊水壩用來當作圍堰。新水壩於1927年8月1日完工，完全淹沒了舊水壩，在9月開始發電。新水壩長782英尺（238公尺），高34.5英尺（10.5公尺），溢洪道長646英尺（197公尺）。它的高度受到上游城市的淡水和污水設施限制，如果水壩更高，會淹沒設施。水壩頂部呈現O形，可以改善水流。新大壩有八個水閘，與一條帶欄杆的人行道，讓維護人員能夠到達閘門和水壩。
新發電廠由混凝土建成，不過公司曾計劃要建造成磚瓦屋，但當地磚匠要求獲得城市規定的工資，而不是蒙大拿州政府的，因後者薪資較低。廠房南邊和北邊的混凝土和石砌牆用於防止水流侵蝕調整池和水渠道。調整池421英尺（128公尺）長，96英尺（29公尺）寬，延伸至較下游的新動力室，舊動力室的磚拱門結合到了調整池的牆壁中。新發電廠搭載三台由S.摩根史密斯公司提供的垂直卡布蘭式水輪機，能夠產生18百萬瓦能量，成為蒙大拿電力公司在大瀑布地區五座水壩中最大產能的一座。史密斯公司在渦輪機上加裝油壓調速器（調節每個渦輪機的速度）與導流管（在水離開渦輪機後速度被降下來，並使得從上快速落下的水持續向渦輪機的螺旋槳傳遞能量）。渦輪機螺旋狀入口和導葉門固定在發電廠的地下室，每台渦輪機都安裝在自己的坑槽內。每台渦輪機通過一樓的屋頂連接到額定功率為7000伏安的阿里斯－查爾默斯（Allis-Chalmers）發電機。直流發電機作為阿里斯－查爾默斯發電機的激勵器。六台6,600 / 2,200伏變壓器降低了電壓供使用。
1926年重建後，黑鷹水壩遭遇了四次洪水，但都沒有造成損害。第一次發生在1953年6月4日，春雨和融雪導緻密蘇里河高於洪水位4.1英尺（1.2公尺），沒有大壩損毀的報告。第二次在1964年6月10日，洛磯山脈的大雨導緻密蘇里河高於洪水位9.6英尺（2.9公尺），比1908年的洪水高出1.5英尺（0.46公尺）。位於樺樹溪的Swift Dam潰堤，造成19人死亡，下雙麥迪遜湖水壩（Lower Two Medicine Lake Dam）也潰堤，造成9人死亡。儘管因大洪水造成3000人被迫離開家園，此次黑鷹大壩仍未受損。 （Mel Ruder因洪水報導而被授予突發新聞報導普利茲獎）。1975年6月21日發生第三次洪水，洛磯山脈24小時內降雨超過2英寸（5.1公分）。在太陽河升至21英尺（6.4公尺）（高於洪水位6英尺（1.8公尺））後，超過5000人從大瀑布城撤離。損失超過1700萬美元，21,000英畝（8,500公頃）的土地被淹沒。洪水幾乎淹沒了黑鷹大壩，但沒有對結構造成傷害。第四次大洪水在1997年6月17日，又多又快的融雪導緻密蘇里河高於洪水位3英尺（0.91公尺）。黑鷹水壩還配備了一個緊急「trip face」可以解除水壩上所有插板，讓河水能夠以每秒鐘100,000立方英尺（2,800立方公尺）的水量流過。

長池水庫

黑鷹水壩在它後面創建了一個長約2英里（3.2公里）的水庫。緊鄰第一大壩的水庫大約17英尺（5.2公尺）深，容量459.1英畝·英尺（566,300立方公尺）。目前水壩的蓄水量為1,710英畝·英尺（2,110,000立方公尺）到1,820英畝·英尺（2,240,000立方公尺）。
這水庫沒有正式名稱，但由於水流緩慢猶如靜止，以及從上游的喀斯喀特到黑鷹瀑布的坡度低（沿著蜿蜒的密蘇里河約55英里（89公里）長），這個水體一直被稱為「長池」。在1872年，命名黑鷹瀑布的托馬斯P‧羅伯茨，正式命名這個水體。美國陸軍工兵部隊於1883年和1910年使用過這名稱。在1891年至1917年就已經廣為流行，蒙大拿州議會也已在此時使用這名稱。因此現代歷史學家也用這名稱提及它，1949年後被電力業出版物使用。現在，從第一林道北橋到密蘇里河與太陽河交匯處（距離約1英里（1.6公里））為知名的布羅德沃特灣（知名人士如：查爾斯‧阿瑟‧布羅德沃特、蒙大拿鐵路執行長、房地產投資者和銀行家）。

水壩開發

1926年大壩重建後，工人和居民可以穿越大壩頂部上班或上學。出於安全原因，蒙大拿電力公司在二戰時期關閉了道路，並封閉到現今。
1950年，根據《聯邦電力法》，蒙大拿電力公司被迫授權黑鷹水壩等大部分發電用水壩。聯邦電力法案於1935年通過，在1937年12月，聯邦電力委員會（FPC）開始執行一項程序（FPC Docket IT-5840），賦予1935年之前建造的所有水壩許可證。該法案賦予聯邦電力委員會在美國可航行水域中，所有水壩的控制權。經過長時間的研究、數據收集以及談判之後，1946年11月18日開始舉行聽證會，以確定蒙大拿電力公司在1935年之前修建水壩前，河流是否可通航以致水壩屬法律生效範圍 。1947年9月30日發布的第170號意見書中，審判員認為此河流可以通航，並且含黑鷹水壩等水壩應該獲得許可。 蒙大拿電力公司在聯邦電力委員會於1948年2月16日舉行聽證會時訴願。當聯邦電力委員會駁回時，蒙大拿電力公司轉向哥倫比亞特區聯邦上訴法院上訴。1950年10月4日，David L. Bazelon法官以2比1多數決判決「蒙大拿電力公司訴聯邦電力委員會案」，指出「密蘇里河從本頓堡到斯里福克斯長達263英里，屬美國通航水域，符合《聯邦電力法》的許可要求」。法院認為黑鷹、莫羅尼、彩虹、瑞安水壩都在通航水域，無權侵佔公有地。豪瑟水壩在通航水域，並持有無效許可證佔用公共土地。霍爾特水壩擁有有效許可證，但該許可證沒有延伸到它使用的通航水域。赫布根和麥迪遜水壩在不通航水域，但沒有有效許可證而佔用公有地。上訴法院將Canyon Ferry水壩的問題退還給地方法院，因為該水壩已被出售給聯邦政府。蒙大納州電力公司向美國最高法院提出上訴， 美國最高法院於1951年3月否決了特許權（拒絕審理此案）。 蒙大拿電力公司隨後於2000年9月27日由聯邦能源管理委員會（FPC的繼承機構）重新授權並贏得了黑鷹水壩營運許可，許可證編號為P-2188。另外還有7座需要法院裁決。
1978年，修復三台阿里斯－查爾默斯發電機，1982年，再修復一次。1997年，蒙大拿電力公司修復並重新粉刷了通往水渠島的橋。
1999年11月2日，蒙大拿電力公司宣布以16億美元的價格賣給賓州電力公司（PPL）所有水壩和發電廠。這筆包含黑鷹水壩的買賣估計會給蒙大拿州帶來3000萬美元的稅收（但蒙大拿電力公司表示稅金會比3000萬少）。2001年11月，因電價上漲而不滿的民眾提出一項倡議：要求州政府收購PPL所有用來發電的水壩（包含黑鷹水壩）。在2002年11月，這項倡議被否決了。
在蒙大拿電力公司將黑鷹水壩賣給PPL的時候，蒙大拿電力公司正在安裝控制裝置，使黑鷹水壩能夠從彩虹水壩遠程操作。當時，PPL表示他沒有計劃擴大黑鷹水壩的發電能力。同樣在1999年，蒙大拿電力公司將大部分的水渠島轉移到大瀑布市作為娛樂區。此外，蒙大拿電力公司和ARCO（波士頓和蒙大拿州的後繼公司）在該島上鋪設了18英寸（46公分）（46公分）的表土，花費了50萬美元用於景觀設計，並增強了動力廠附近的安全邊界，並同意資助一部分小島的定期保養費用。
1990年代後期，歷史學家史蒂芬·安布羅斯建議拆除黑鷹水壩，將瀑布恢復原狀。
2010年，黑鷹水壩的發電與輸電系統開始翻新。同年6月，PPL蒙大拿州分公司花費5500萬美元用高壓電線取代該地區電力網路。新的電線取代了80多年前的設備，電線間隔更大，使得大型鳥類可以安全地通過或棲息在電線上。PPL也計畫更新電廠旁的變電所，兩項工程都預期會在2012年完工。

沉積物，水流量, debris issues, and emergencies

密蘇里河與支流夾帶的沉積物是黑鷹水壩的一大問題。太陽河（Sun river）在黑鷹大壩上游幾英里處與密蘇里河相連，夾帶著汙泥，養份與藻類，因此還被諷刺成「浮渣河（Scum river）」。 太陽河水呈現如巧克力牛奶的顏色，流入相對清澈的密蘇里河後使其變得汙濁。汙泥降低水庫容量，充滿調整池，也會對發電機組造成損害。1988年，由於密蘇里河從太陽河到彩虹水壩一段的沉積物和懸浮物，蒙大拿州環境質量部（Montana Department of Environmental Quality, MDEQ）根據1972年清淨水法第303（d）節，將其水質狀態列入受損。黑鷹水壩因為減緩水流流速，被列為問題來源之一。為了解決這個問題，1994年，7個聯邦機構，8個州政府機構，10個蒙大拿州政府機構，4個環境組織和幾個蒙大拿州地主共同努力減少進入太陽河及其主要支流（Muddy Creek與Careless Creek）的營養物和沉積物。約623,500美元的清潔水法基金、200萬美元的聯邦基金以及250萬美元的州與地方基金用於恢復河岸植被、改善河邊放牧、復原河床斜度和改善灌溉方法。到2010年，Muddy Creek減少75%沉積物，Careless Creek減少25%。
黑鷹瀑布是否流通，取決於黑鷹水壩。每年5月，理論上密蘇里河的中位水流量為每秒11,200立方英尺（320立方公尺）。2000年10月，水壩水位下降，瀑布停止流水四週，PPL蒙大拿在這段時間修整了調整池，閘門和鋼管濾網。PPL蒙大拿的工作許可證要求水壩在周末與亡兵紀念日至勞動節期間的上午9點至下午8點流出至少每秒200立方英尺（5.7立方公尺）的水量。如果水位或發電需求允許，水量可能更多。2001年5月，PPL蒙大拿表示因為水流量只有平時的40%，他們要在7月4日後截斷瀑布。2004年9月，水庫水位再次降低，以修復檔板，河流缺水使巨人泉附近的密蘇里河天然通道暴露出來。2008年6-7月，水庫水位又過低以致瀑布再次停流，而在一次大雨後移除了檔板使水流快速通過。當水流通過並把檔板歸位後，水庫內剩沒多少水，而瀑布再次流通也是幾天後的事了。
Because Black Eagle Dam is an overflow dam, it is common for debris to jam against the dam or obstruct the penstock intakes. Driftwood and logs are the most common forms of debris, but unusual objects such as boat docks, bowling balls, canoes, hot tubs, and small wooden and steel sheds and buildings also sometimes become lodged against the dam. 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.

Fishing and water quality issues

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 18英寸（46公分）). 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 27,500,000立方碼（21,000,000立方公尺） and 31,000,000立方碼（24,000,000立方公尺） 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, 34英里（55公里） 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 18公里（11英里）). 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

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 5-公里（3.1-英里） run/walk and 10-公里（6.2-英里） 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 25,000-平方英尺（2,300-平方公尺） 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 10-英里-long（16-公里） section of the trail linking the existing 14-英里-long（23-公里） 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 0.5-英里-long（0.80-公里） 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 2,950-英尺-long（900-公尺） 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 1.3英里（2.1公里） 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.