{ "bbox":null, "type":"Feature", "geometry":{ "bbox":null, "type":"Point", "coordinates":[ -121.78712, 47.27675 ] }, "properties":{ "provider":"NWS", "code":"HAH", "slug":"hah", "elevation":null, "horizontal_datum":"WGS84", "vertical_datum":"NGVD29", "state":"WA", "kind":"PROJECT", "nearest_city":"Palmer", "public_name":"HOWARD A HANSON DAM", "location_code":53847029, "nsid":null, "aliases":{ "NIDID":"WA00298" }, "timeseries":[ { "tsid":"HAH.Flow-In.Inst.1Hour.0.NWSRADIO-COMPUTED-REV", "label":"Inflow", "base_parameter":"Flow", "parameter":"Flow-In", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-04-14T21:00:00Z", "latest_value":1082.09, "delta24h":null, "sort_order":6, "results":null }, { "tsid":"HAH.Stor.Inst.1Hour.0.NWSRADIO-REV", "label":"Flood Storage", "base_parameter":"Stor", "parameter":"Stor", "unit":"ac-ft", "unit_long_name":"Acre-feet", "latest_time":"2026-04-14T22:00:00Z", "latest_value":37665.58, "delta24h":null, "sort_order":11, "results":null }, { "tsid":"HAHW.Flow.Inst.1Hour.0.IRIDIUM-REV", "label":"Outflow", "base_parameter":"Flow", "parameter":"Flow", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-04-14T22:00:00Z", "latest_value":1003.3, "delta24h":null, "sort_order":7, "results":null }, { "tsid":"HAH.Precip-Inc.Inst.1Hour.0.IRIDIUM-REV", "label":"Precipitation", "base_parameter":"Precip", "parameter":"Precip-Inc", "unit":"in", "unit_long_name":"Inches", "latest_time":"2026-04-14T22:00:00Z", "latest_value":0.08, "delta24h":null, "sort_order":16, "results":null }, { "tsid":"HAH.Elev-Forebay.Ave.1Hour.1Hour.IRIDIUM-REV", "label":"Elevation", "base_parameter":"Elev", "parameter":"Elev-Forebay", "unit":"ft", "unit_long_name":"Feet", "latest_time":"2026-04-14T22:00:00Z", "latest_value":1156.86, "delta24h":null, "sort_order":1, "results":null } ], "name":"HOWARD A HANSON DAM", "hasResopsAverages":"true", "nidId":"WA00298", "nidid":"", "levels":[ { "slug":"elev.bottom of normal", "label":"Bottom of 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"latest_value":59916, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.streambed", "label":"Streambed", "parameter":"Stor", "base_parameter":"Stor", "tsid":"HAH.Stor.Inst.0.Streambed", "latest_value":1, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of dam", "label":"Top of Dam", "parameter":"Stor", "base_parameter":"Stor", "tsid":"HAH.Stor.Inst.0.Top of Dam", "latest_value":147181, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of flood", "label":"Top of Flood", "parameter":"Stor", "base_parameter":"Stor", "tsid":"HAH.Stor.Inst.0.Top of Flood", "latest_value":104266, "units":"ac-ft", "units_long_name":"Acre-feet" }, { "slug":"stor.top of normal", "label":"Top of Normal", "parameter":"Stor", "base_parameter":"Stor", "tsid":"HAH.Stor.Inst.0.Top of Normal", "latest_value":422, "units":"ac-ft", "units_long_name":"Acre-feet" } ], "id":549896, "associatedStructuresCount":0, "conditionAssessDate":null, "conditionAssessDetail":null, "conditionAssessId":6, "damHeight":null, "damLength":500, "distance":26, "drainageArea":221, "eapId":1, "dsacAssignedDate":"2022-11-11T12:00:00.000Z", "eapMeetsGuidelinesId":1, "emergencyContactsUpdated":"2024-11-01T12:00:00.000Z", "eapLastRevDate":"2024-11-22T12:00:00.000Z", "enforcementAuthorityId":0, "federalId":"WA00298", "oldFederalId":"WA00298", "hazardId":4, "hydraulicHeight":220, "inspectionAuthorityId":0, "inspectionDate":"2021-10-07T12:00:00.000Z", "inspectionFrequency":5, "jurisdictionAuthorityId":0, "latitude":47.278206165, "lengthOfLocks":0, "secondaryLengthOfLocks":null, "longitude":-121.786547915, "maxDischarge":129000, "maxStorage":136700, "nidHeight":235, "nidStorage":136700, "normalStorage":26000, "numberOfLocks":0, "operationalStatusDate":"2022-11-11T12:00:00.000Z", "operationalStatusId":2, "originalDesignerName":null, "otherStructureId":null, "permittingAuthorityId":0, "politicalPartyId":null, "privateDamId":null, "projectDescription":"The U.S. Army Corps of Engineers (USACE) built Howard A Hanson Dam in 1962. The dam is located on the Green River, near Palmer, Washington, approximately 65 miles above the mouth of the Green/Duwamish River. Hanson Dam reduces downstream flood risk for Auburn, Kent, Renton, Tukwila, and Seattle by holding back water during flood events. Although flood risk management is the project\u2019s primary authorized purpose, the water held back by the dam forming Eagle Gorge Reservoir stores water for stream flow augmentation during the annual summer and early fall low flow period for fish and wildlife conservation benefits. The dam also supplies municipal and industrial water to the City of Tacoma and its partners. The dam structure is an earthen embankment with a concrete outlet tower and outlet tunnel through bedrock which is used to release water downstream to the Green River. A gated concrete spillway is also available to release large flows during rare flood events. In addition to the dam, the Green River levee system, which includes a series of federal and non-federal levees in the Kent-Auburn Valley, helps reduce downstream flood risks.", "riskCharSummary":"USACE completed a risk assessment for Hanson Dam in April 2022 to determine potential threats to the ability of USACE to meet the flood risk management goals of the dam. As a result, the project\u2019s risk is characterized as moderate, which is USACE\u2019s third highest risk category. One hypothesized failure scenario involves an extremely rare flood event overtopping the dam, resulting in erosion of the dam, breach, and an uncontrolled surge of water from the reservoir. This would result in potentially deadly flooding in Auburn, Kent, and other downstream communities. A second failure scenario involving erosion and collapse of the dam due to excessive seepage could lead to a similar, but even less likely result. Although these failure scenarios are considered extremely unlikely, USACE maintains a Hanson Dam Emergency Action Plan to lower the risk of life loss if any of these scenarios occurred.\n\nUSACE is confident that the dam is solidly built, well-maintained, and will continue to significantly reduce flood risks. However, the dam cannot eliminate flooding. Extreme rainfall events could require USACE to release water through the dam\u2019s outlet tunnel and/or the spillway to prevent overtopping and failure of the dam, resulting in downstream flooding that could resemble conditions experienced prior to the dam\u2019s construction.", "riskManagementMeasures":"USACE is continuously taking significant steps to reduce risks to life safety and property, including major dam repairs between 2009 and 2012. USACE intends further study of this dam to better characterize the recent risk assessment and will recommend and execute appropriate actions to reduce risks. \n\nUSACE conducts regular inspections and maintains a network of instruments to monitor the health of the dam. The frequency of inspections and instrumentation readings increases when the lake level rises to confirm whether the structure is performing as designed and to identify areas of potential concern. Regular maintenance and repairs are performed as needed to keep the dam functioning properly. Precipitation forecasts are continuously monitored to determine when high water events may occur to provide information for any necessary flood warnings. USACE also works closely with local emergency managers to annually update the Emergency Action Plan, conducts emergency exercises with state and local response teams, and annually hosts water control information stakeholder meetings.", "riverName":"GREEN", "separateStructuresCount":0, "sourceAgency":"US Army Corps of Engineers", "spillwayTypeId":1, "spillwayWidth":90, "stateFedId":"WA00298", "stateRegulatoryAgency":null, "stateRegulatedId":0, "structuralHeight":235, "submitDate":"2023-02-16T17:25:26.838Z", "surfaceArea":20000, "volume":1502000, "widthOfLocks":0, "secondaryWidthOfLocks":null, "yearCompleted":1962, "congDist":"Congressional District 08, Washington", "city":"AUBURN", "county":"King", "aiannh":null, "websiteUrl":"https://www.nws.usace.army.mil/Missions/Civil-Works/Locks-and-Dams/Howard-Hanson-Dam/", "coreTypeIds":null, "damTypeIds":"5;8", "fedConstructionIds":"1", "fedDesignIds":"1", "fedFundingIds":"1", "fedInspectionIds":"1", "fedOperationIds":"1", "fedOtherIds":"1", "fedOwnerIds":"1", "fedRegulatoryIds":"1", "formerNames":"Eagle Gorge Dam", "foundationTypeIds":null, "nonFederalDamOnFederalId":0, "designerNames":"CE", "otherNames":null, "ownerNames":"USACE - Seattle District", "ownerTypeIds":"3", "primaryDamTypeId":5, "primaryOwnerTypeId":3, "primaryPurposeId":9, "purposeIds":"9;4;8", "dsacId":3, "femaRegion":"10", "lastEapExcerDate":"2024-10-09T12:00:00.000Z", "dataUpdated":"2025-04-18T12:00:00.000Z", "usaceDistrict":"Seattle District", "noConsequencesId":0, "secretaryAgricultureBuiltId":null, "nrcsWatershedAuthorizationId":null, "isAssociatedStructureId":"No", "fedRegulatedId":"Yes", "inundationNidAddedId":1, "damStatusId":2, "huc06":"171100", "doi_region":"CPN", "doi_region_name":"Columbia-Pacific Northwest", "doi_region_number":9, "thirtyYearAverage":25.41, "tenthPercentile":4.0902, "ninetiethPercentile":40.1898 }, "id":53847029, "links":[ { "type":"application/json", "rel":"root", "title":"The landing page of this server as JSON", "href":"https://api.wwdh.internetofwater.app?f=json" }, { "type":"text/html", "rel":"root", "title":"The landing page of this server as HTML", "href":"https://api.wwdh.internetofwater.app?f=html" }, { "rel":"self", "type":"application/geo+json", "title":"This document as JSON", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/53847029?f=json" }, { "rel":"alternate", "type":"application/ld+json", "title":"This document as RDF (JSON-LD)", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/53847029?f=jsonld" }, { "rel":"alternate", "type":"text/html", "title":"This document as HTML", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/53847029?f=html" }, { "rel":"collection", "type":"application/json", "title":"USACE Access2Water API", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr" } ] }