A sewer main, and what happened when it broke
Baldwin's row on the Nassau County Department of Health's list of public sewer collection districts assigns the community to the Nassau County Department of Public Works, 1194 Prospect Ave., Westbury, 516-571-6841. The Baldwin and Baldwin Harbor NY Rising reconstruction plan treats the two hamlets as one community, so its figures cover both. It records that in 2012 "A state of emergency was declared for portions of the community near Barnes Avenue to facilitate the cleaning out and decontamination of homes and other affected areas since the sewer main leading to the Bay Park Sewage Treatment Plant was breached and sewage backed up at manholes and basement drains into private residences" (plan). Sewer mains exist where there are sewers, so the passage corroborates the district row, though that reading is inference rather than a second authority. The plant association is a plan-era statement, not a county service-area map, and the county's Sewage Treatment Master Plan page publishes no community-by-community assignment. The point worth carrying into a basement: water can arrive through a floor drain, not only over a sill.
Two caveats ride with that row. The county prints no date on the table and its server returns no last-modified header, so the vintage of the list is anyone's guess. And what is listed is a community, not a house: a parcel within the district may never have been hooked up, or may have been hooked up over a cesspool left where it lay. The county's per-address lookup settles it for the property itself, and the seller should confirm it in writing.
Where the water goes, per the community's own plan
The plan gives the shape of the place: "Baldwin and Baldwin Harbor extend from Middle Bay and Baldwin Bay north to the Southern State Parkway, crossing over the Merrick Road and Sunrise Highway corridors", a combined "4.72 square miles, of which 0.6 square miles (approximately 13%) is bay water", and a population across the two of more than 32,000. On 2012 it is exact: "The two tributary systems of Parsonage Cove to the west and Baldwin Bay to the east overflowed and caused flooding that extended north beyond Atlantic Avenue as far as Merrick Road. Flooding from the storm exceeded many of the Federal Emergency Management Agency's (FEMA) 100-year flood zones."
The plan puts standing exposure at "almost 2,000 homes in high and extreme risk flooding areas, which represents approximately 20% of all housing units in the Community", and names an everyday mechanism too: "Parsonage Creek and Milburn Creek on the west and east edges of the Community carry flood water and storm surge deeper into the Community, as far north as Merrick Road to Silver Lake Park and Milburn Creek Park, causing more localized flood risk in those areas even during regular high tide and rainfall events." On damage it reports "More than 2,500 housing units were reported to be damaged", with "heavy damage to 1,270 housing units, which were damaged in excess of 50% or more of their value", and another 620 damaged to between 20 and 50 percent. Those are post-Sandy counts, not today's.
Insurance, and the map you still have to pull
Baldwin is unincorporated, so the NFIP community for an address here is the Town of Hempstead: CID 360467, current effective map date 09/11/2009, per FEMA's Community Status Book for New York. The town's row shows no Community Rating System entry and no class, so no CRS discount applies. Nothing above identifies the zone for any particular lot, and no part of the hamlet belongs outside the question; Zone X is a wide category that takes in the 500-year floodplain, so it settles nothing either. Get the zone, panel and effective date for the exact lot from the FEMA Map Service Center before making an offer.
Bulkheads, and who owns which
The plan proposed a project to "inspect and identify the bulkheads at street ends and canal ends that fall under the Town of Hempstead ownership which require raising or replacement", designing and constructing "up to 1,000 linear feet of bulkhead" at an estimated $2,700,000. Whether it was built is not established here. The division it implies matters to a canal-front buyer: street-end and canal-end structures are a town responsibility, the bulkhead across the back of a private lot generally is not. On a waterfront house that private bulkhead, its tiebacks and the fill behind it are the owner's cost, and a dip in the lawn behind the cap says more than the dock does. Permits for that work run through the Town of Hempstead, which also holds the certificate of occupancy: Baldwin has no village hall.
The stock
Baldwin CDP holds 11,190 housing units, 3,649 of them predating 1940 and 2,151 built in the 1940s (table B25034); roughly 8,368 date from 1959 or earlier. 9,598 are single-unit detached (table B25024). Of 10,870 occupied units, 9,414 are owner-occupied (table B25003), and 2,695 of those occupied units are heated with fuel oil or kerosene (table B25040); age figures count all units and the heating figure occupied ones. All are 2020 to 2024 five-year estimates. An older frame stock burning oil is what produces buried tanks: a house predating 1940 has had time for a tank to be installed, abandoned and forgotten. Look for fill and vent pipes, and for evidence of a tank cut open and filled rather than pulled.
Water and the train
The state health department's public water supply contact list for the county lists LIBERTY UTILITIES NEW YORK, LYNBROOK as PWS NY2902835, serving 220,000; that list enumerates systems, not the hamlets each covers, so verify the supplier from the bill. On the Babylon Branch, the state rail station dataset files Baldwin under code BWN in fare zone 7 with accessibility full, which is a data field rather than a walk down the platform.