{ "bbox":null, "type":"Feature", "geometry":{ "bbox":null, "type":"Point", "coordinates":[ -72.1817, 41.765 ] }, "properties":{ "provider":"NAE", "code":"MHD", "slug":"mhd", "elevation":195.01, "horizontal_datum":"", "vertical_datum":"", "state":"CT", "kind":"PROJECT", "nearest_city":"Willimantic", "public_name":"Mansfield Hollow Dam", "location_code":8112021, "nsid":null, "aliases":{ "NIDID":"CT00503", "CWMS Legacy Naming":"MHD", "CWMS Standard Naming":"MHD", "USGS Station Number":"01122000" }, "timeseries":[ { "tsid":"MHD.Temp-Air.Inst.15Minutes.0.DCP-rev", "label":"Air Temperature", "base_parameter":"Temp", "parameter":"Temp-Air", "unit":"F", "unit_long_name":"Fahrenheit", "latest_time":"2026-08-25T22:00:00Z", "latest_value":80.0, "delta24h":null, "sort_order":22, "results":null }, { "tsid":"MHD.Flow-Inflow.Total.15Minutes.6Hours.DCP-rev", "label":"Inflow", "base_parameter":"Flow", "parameter":"Flow-Inflow", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-08-25T21:30:00Z", "latest_value":93.94, "delta24h":null, "sort_order":6, "results":null }, { "tsid":"MHD.Precip.Inst.15Minutes.0.DCP-rev", "label":"Precipitation", "base_parameter":"Precip", "parameter":"Precip", "unit":"in", "unit_long_name":"Inches", "latest_time":"2026-08-25T22:00:00Z", "latest_value":38.84, "delta24h":null, "sort_order":16, "results":null }, { "tsid":"MHD.Stor.Inst.15Minutes.0.DCP-rev", "label":"Flood Storage", "base_parameter":"Stor", "parameter":"Stor", "unit":"ac-ft", "unit_long_name":"Acre-feet", "latest_time":"2026-08-25T22:00:00Z", "latest_value":3182.4, "delta24h":null, "sort_order":11, "results":null }, { "tsid":"MHD.Flow.Inst.15Minutes.0.DCP-rev", "label":"Outflow", "base_parameter":"Flow", "parameter":"Flow", "unit":"cfs", "unit_long_name":"Cubic feet per second", "latest_time":"2026-08-25T21:30:00Z", "latest_value":93.24, "delta24h":null, "sort_order":7, "results":null }, { "tsid":"MHD.Stage-TAILWATER.Inst.15Minutes.0.DCP-rev", "label":"Stage Tailwater", "base_parameter":"Stage", "parameter":"Stage-TAILWATER", "unit":"ft", "unit_long_name":"Feet", "latest_time":"2026-08-25T21:30:00Z", "latest_value":1.81, "delta24h":null, "sort_order":5, "results":null }, { "tsid":"MHD.Stage-Pool.Inst.15Minutes.0.DCP-rev", "label":"Stage", "base_parameter":"Stage", "parameter":"Stage-Pool", "unit":"ft", "unit_long_name":"Feet", "latest_time":"2026-08-25T22:00:00Z", "latest_value":17.38, "delta24h":null, "sort_order":4, "results":null } ], "name":"Mansfield Hollow Dam", "hasResopsAverages":"false", "nidId":"CT00503", "nidid":"", "levels":[ { "slug":"stage.bottom of normal", "label":"Bottom of Normal", "parameter":"Stage-Pool", "base_parameter":"Stage", "tsid":"MHD.Stage-Pool.Inst.0.Bottom of Normal", "latest_value":16.5, "units":"ft", "units_long_name":"Feet", "type":"REGULAR" }, { "slug":"stage.streambed", "label":"Streambed", "parameter":"Stage-Pool", "base_parameter":"Stage", "tsid":"MHD.Stage-Pool.Inst.0.Streambed", "latest_value":0, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"stage.top of dam", "label":"Top of Dam", "parameter":"Stage-Pool", "base_parameter":"Stage", "tsid":"MHD.Stage-Pool.Inst.0.Top of Dam", "latest_value":78, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"stage.top of flood", "label":"Top of Flood", "parameter":"Stage-Pool", "base_parameter":"Stage", "tsid":"MHD.Stage-Pool.Inst.0.Top of Flood", "latest_value":62, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"stage.top of normal", "label":"Top of Normal", "parameter":"Stage-Pool", "base_parameter":"Stage", "tsid":"MHD.Stage-Pool.Inst.0.Top of Normal", "latest_value":16.5, "units":"ft", "units_long_name":"Feet", "type":"CONSTANT" }, { "slug":"stor.bottom of normal", "label":"Bottom of Normal", "parameter":"Stor", "base_parameter":"Stor", "tsid":"MHD.Stor.Inst.0.Bottom of Normal", "latest_value":1715, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" }, { "slug":"stor.top of flood", "label":"Top of Flood", "parameter":"Stor", "base_parameter":"Stor", "tsid":"MHD.Stor.Inst.0.Top of Flood", "latest_value":52000, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" }, { "slug":"stor.top of normal", "label":"Top of Normal", "parameter":"Stor", "base_parameter":"Stor", "tsid":"MHD.Stor.Inst.0.Top of Normal", "latest_value":2800, "units":"ac-ft", "units_long_name":"Acre-feet", "type":"CONSTANT" } ], "id":549841, "associatedStructuresCount":4, "conditionAssessDate":null, "conditionAssessDetail":null, "conditionAssessId":6, "damHeight":78, "damLength":14050, "distance":null, "drainageArea":159, "eapId":1, "dsacAssignedDate":"2018-02-05T12:00:00.000Z", "eapMeetsGuidelinesId":1, "emergencyContactsUpdated":"2024-12-20T12:00:00.000Z", "eapLastRevDate":"2019-08-29T12:00:00.000Z", "enforcementAuthorityId":0, "federalId":"CT00503", "oldFederalId":"CT00503", "hazardId":4, "hydraulicHeight":74, "inspectionAuthorityId":0, "inspectionDate":"2020-06-01T12:00:00.000Z", "inspectionFrequency":5, "jurisdictionAuthorityId":0, "latitude":41.7557545430001, "lengthOfLocks":0, "secondaryLengthOfLocks":null, "longitude":-72.181452313, "maxDischarge":106500, "maxStorage":76000, "nidHeight":78, "nidStorage":76000, "normalStorage":2800, "numberOfLocks":0, "operationalStatusDate":"2018-02-05T12:00:00.000Z", "operationalStatusId":1, "originalDesignerName":null, "otherStructureId":null, "permittingAuthorityId":0, "politicalPartyId":null, "privateDamId":null, "projectDescription":"The U.S. Army Corps of Engineers (USACE) operates and maintains more than 700 dams across the United States. A dam is an earthen embankment and/or solid concrete structure that is built across a river, stream, or other waterway to temporarily hold back and store water that would otherwise flow downstream. More detail related to this specific dam will be added at a future time.", "riskCharSummary":"USACE completed a risk assessment of Mansfield Hollow Dam in 2011 and has classified the risks associated with the dam as Low. The dam significantly reduces the risk of flooding to surrounding communities. However, it does not entirely eliminate the risk. The most likely scenario that could result in downstream flooding from Mansfield Hollow Dam would be an uncontrolled high volume release of water from the dam's spillway during significant storm events. The amount of water being released could be great enough to cause flooding in downstream communities. Such higher releases from the spillway could create conditions similar to how the river might behave during a flood event if the dam did not exist. \n\nThere are also six unlikely, but far more devastating scenarios that would result in failure of the dam or dike B and downstream flooding: The most likely, but still \"moderate\" is the sliding failure of a spillway monolith. Overtopping of the dam, toe drains plugging or being damages are the other risk drivers at the dam, with low likelihoods of occurrence. At Dike B, the risk driving failure modes are foundation erosion and erosion along the conduit. Were any of these events to occur, an uncontrolled surge of water would flow out of the reservoir, flooding downstream communities. It should be noted that a new Periodic Assessment is currently being conducted, and will be based on current guidance and understanding of risk drivers. Mansfield, Windham, Scotland, Sprague, Norwich, Lisbon, and Preston, CT are the major areas in immediate danger in the event of the flood. Towns and cities further downstream would also be impacted, but less so. \n\nEven though very unlikely, if any of the scenarios described above were to occur, the downstream floodwater would be swift and deep, destroying buildings and key infrastructure, and those caught unaware and/or unable to evacuate could perish. In the less likely dam breach scenarios, the water depth, property damage, and lives lost would likely be far greater than flooding due to spillway discharges.", "riskManagementMeasures":"USACE manages dam-related flood risks by continually monitoring the condition and health of the dam, prioritizing activities that will most impact the risks, and engaging upstream and downstream emergency managers and members of the public to raise awareness of the dam and support actions to prepare and be ready to respond in the case of a dam-related emergency. USACE works closely with local emergency managers to share what is known about the dam and support the development of local emergency and evacuation plans. USACE regularly updates the emergency action plan for the dam. Regular maintenance and repairs are performed as needed to keep the dam functioning properly.", "riverName":"NACHAUG RIVER", "separateStructuresCount":4, "sourceAgency":"US Army Corps of Engineers", "spillwayTypeId":3, "spillwayWidth":690, "stateFedId":"CT00503", "stateRegulatoryAgency":null, "stateRegulatedId":0, "structuralHeight":78, "submitDate":"2023-02-16T17:25:22.975Z", "surfaceArea":450, "volume":1458000, "widthOfLocks":0, "secondaryWidthOfLocks":null, "yearCompleted":1952, "congDist":"Congressional District 02, Connecticut", "city":"WILLIMANTIC", "county":"Windham", "aiannh":null, "websiteUrl":"https://www.nae.usace.army.mil/Missions/Civil-Works/Flood-Risk-Management/Connecticut/Mansfield-Hollow/", "coreTypeIds":"3", "damTypeIds":"9;8", "fedConstructionIds":"1", "fedDesignIds":"1", "fedFundingIds":"1", "fedInspectionIds":"1", "fedOperationIds":"1", "fedOtherIds":"1", "fedOwnerIds":"1", "fedRegulatoryIds":"1", "formerNames":null, "foundationTypeIds":"1", "nonFederalDamOnFederalId":0, "designerNames":"CENAE", "otherNames":"Mansfield Hollow Lake", "ownerNames":"USACE - New England District", "ownerTypeIds":"3", "primaryDamTypeId":9, "primaryOwnerTypeId":3, "primaryPurposeId":9, "purposeIds":"9", "dsacId":4, "femaRegion":"1", "lastEapExcerDate":"2024-04-05T12:00:00.000Z", "dataUpdated":"2024-12-20T12:00:00.000Z", "usaceDistrict":"New England District", "noConsequencesId":0, "secretaryAgricultureBuiltId":null, "nrcsWatershedAuthorizationId":null, "isAssociatedStructureId":"No", "fedRegulatedId":"Yes", "inundationNidAddedId":1, "damStatusId":2, "huc06":"011000", "doi_region":null, "doi_region_name":"North Atlantic-Appalachian", "doi_region_number":1 }, "id":8112021, "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/8112021?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/8112021?f=jsonld" }, { "rel":"alternate", "type":"text/html", "title":"This document as HTML", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr/items/8112021?f=html" }, { "rel":"collection", "type":"application/json", "title":"USACE Access2Water API", "href":"https://api.wwdh.internetofwater.app/collections/usace-edr" } ] }