St Marys Pond
St Marys Pond is a rockfill dam located in Newport County, Rhode Island, built in 1878. It carries a High hazard potential classification and has a poor condition assessment.
About St Marys Pond
The primary purpose of St Marys Pond is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by Newport, City Of (local government). It impounds the Lawton Valley Brook near Portsmouth.
The dam stands 12 feet tall and stretches 2,288 feet across, creates a reservoir covering 117 acres, has a maximum storage capacity of 1,220 acre-feet, and collects water from a drainage area of 1 square miles. Completed in 1878, the structure is over a century old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. Notably, no emergency action plan is currently on file for this high-hazard dam.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Rhode Island dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Rhode Island |
| County | Newport |
| Nearest City | Portsmouth |
| River/Stream | Lawton Valley Brook |
| Coordinates | 41.55445, -71.27328 |
Physical Characteristics
| Dam Type | Rockfill |
| NID Height | 12 ft |
| Dam Height | 12 ft |
| Dam Length | 2,288 ft |
| Year Completed | 1878 (148 years old) |
Storage & Hydraulics
| NID Storage | 1,220 acre-ft |
| Max Storage | 1,220 acre-ft |
| Normal Storage | 1,040 acre-ft |
| Surface Area | 117 acres |
| Drainage Area | 1 sq mi |
| Max Discharge | 375 cfs |
Ownership & Safety
| Purpose | Water Supply |
| Owner | NEWPORT, CITY OF |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Emergency Action Plan | No |
Identifiers
| NID ID | RI02703 |
| Federal ID | RI02703 |
| More Info | State Dam Safety Program |