A small-scaled period ensemble piece about Long Island clam-diggers facing professional extinction in 1976 as the result of corporate intrusion while attempting to deal with their own personal problems, Katherine Dieckmann’s “Diggers” manages to create a fairly convincing sense of place but not a particularly compelling narrative. It boasts some good performances and occasional flashes of dramatic insight, but overall comes across as a picture that, apart from its salty language and a few sexually explicit shots, would be right at home on TV.

If one has to identify the central character in Ken Marino’s script, it’s Hunt (a scruffy Paul Rudd), a thirty-something digger who’s obviously dissatisfied with his life, more interested in taking still photographs than in going out every morning to scrape the bottom for clams in areas increasingly restricted by government agreements with private firms. He sleeps in one morning rather than joining his dad on the boat, and that turns out to be the day his father suffers a fatal heart attack.

Hunt has good reason to be even glummer than usual, but so has his sister Gina (Maura Tierney), a waitress whose marriage has recently broken up over her husband’s infidelity. One of Hunt’s drinking buddies, Jack (Ron Eldard), takes up with her, but that bothers Hunt because Jack’s the town womanizer. Hunt, on the other hand, himself strikes up a relationship with Zoey (Lauren Ambrose), a sophisticated visitor from the city, though he expects more of it than she proves willing to give.

Meanwhile another pal, Cons (Josh Hamilton)—a stoner philosopher—sells drugs to supplement his income while trying to keep peace in the group. And Lozo (Marino), a hot-tempered guy with an understanding wife (Sarah Paulson) and an ever-growing brood of kids, rages against the injustice of a system that threatens his livelihood and a traditional way of life in the service of heartless big business.

“Diggers” is about the interrelationships among all these figures, and it’s obviously intended to indicate how each of them is, in his own way, trying to scrape out a life for himself in an increasingly difficult environment—with a particular emphasis on Hunt, whose decision about what road to take is clearly at issue. And some may find the plot threads Marino has woven about them credible and insightful. But to this viewer, the web of interconnected stories comes across as contrived and slightly soapoperatic, and some of the characters—particularly Zoey and Cons—as overwritten literary devices rather than convincing human beings, though Ambrose and especially the amusingly laid-back Hamilton work hard to bring them to life.

More problematic are Rudd’s Hunt and Marino’s Lozo. These are the characters around whom the script really circulates, and both as written and as played neither really works. Hunt is the typical guy on the cusp of making a life-altering choice, but all Rudd manages to invest him with is a generalized malaise. And Marino nearly throws the whole picture out of whack in a part and performance that seem oversized in these surroundings: he gives himself too many “big” moments (like a destructive scene at a corporate personnel office) and plays them at a very high pitch, looking—and sounding—rather like Ray Romano on speed.

The point-making extends to the physical production, which lays on the period detail a bit thick, especially in the use of the 1976 presidential election to provide context and emphasis. A scene set against the backdrop of the Ford-Carter debate in which a microphone failure left the two men standing rigid and speechless before the cameras is entirely too blunt a reflection of the stasis in which the characters, particularly Hunt, are trapped. (It’s the sort of commentary more suitable to the stage than the screen.)

Otherwise the picture calls up the time and place more persuasively, with Michael McDonough’s HD camerawork capturing suitably gritty images. But ultimately this is a rather drab dramedy that, despite the title and some very real virtues, doesn’t really dig deep or true enough.