SALEM – A Jamaica Plain construction worker about to go on trial on firearm and drug charges out of Lynn instead opted to plea-bargain his case and received 18 months in the House of Corrections.Nelson Joel Irizary-Alvarado, 34, formerly of 3118 Washington St., #7, Jamaica Plain, made his plea in Salem Superior Court to a reduced charge of possession of heroin with the intent to distribute as well as illegal possession of a firearm and illegal possession of ammunition before Judge Timothy Q. Feeley.The charges arise out of his arrest on Jan. 15 when police responded to a noise complaint at around 12:30 a.m. at 92 South Common St., #3.A strong odor was coming from inside the apartment as police knocked on the door and heard scuffling inside and someone saying “Oh (expletive), police.”A man identified as Jared Owens opened the door. Inside the apartment they found Irizary-Alvarado and his co-conspirator, Henry Ocasio, 24, standing nervously inside another room.Police officers Michael O?Connell and Paul Holey became suspicious because of their actions and began to check out the room that apparently reeked of marijuana, discovering a pot, blender and sifter with white residue on them.Underneath a bed, a large bag was found containing a substance and another bag was found under a mattress, containing a total of more than three ounces, approximately 87.70 grams of heroin. Also found was a .22 Ruger semi-automatic pistol and several live cartridges of ammunition.Also found was a prescription from Beth Israel Hospital in the name of Henry Rivera in the room. Police later learned Henry Rivera was actually Henry Ocasio.Police seized $425 in cash from Ocasio, believed to be profits from drug sales.Ocasio currently is in default on the case after being free on $3,000 cash bail out of Lynn District Court. A warrant has been issued for his arrest.As part of the plea agreement reached, the initial drug trafficking charge of heroin against Irizary-Alvarado was reduced to possession with the intent to distribute heroin. In addition a charge of a felon being in possession of a firearm and using a firearm while committing a crime was dropped.The judged credited Irizary-Alvarado the 318 days he has spent in jail in lieu of bail awaiting trial on the case.Assistant District Attorney Melissa Woodard prosecuted the case and Jayne Alice was the defense lawyer.