RipRap in New York: Heavy Stone for Banks, Outlets and Shorelines

Walk around a pile of riprap dropped beside a Lake Ontario bluff and the size range is obvious before you have touched anything. The small end is a piece you can lift with one hand. The large end takes both arms, or a machine. The material runs from 4 inches to 12 inches and up, and individual stones are rough, blocky and irregular rather than sorted to a tidy grade. That spread is deliberate: smaller pieces wedge into the gaps between the larger ones and the whole mass locks against itself.

New York yards and NYSDOT grade this kind of material as light, medium or heavy stone fill. If a plan sheet or a local ordinance specifies a class, that is the language it will use.

RipRap against #4 Crushed Stone, Railroad Ballast and Large River Rock

Four materials on this site look superficially similar in a pile, and the differences decide whether a bank holds.

The dividing line is shape and weight together. Rounded stone rolls when water pushes on it, which is why large river rock suits a dry creek that only runs after a storm but not a shoreline that takes waves and ice. Closely graded stone has uniform voids, which is good for drainage and poor for interlock. Riprap is the option that stays put because each piece is heavy enough to resist being moved and shaped to catch on its neighbors.

Wall backfill, a pond edge and a construction entrance

Behind a retaining wall, the drainage zone immediately against the wall stem is a clean washed stone such as #57, not riprap. Where riprap earns its place on a wall job is at the toe, in front of the wall where runoff lands, and in the rough backfill behind the drainage zone on a cut bank that would otherwise slump while the wall is being built.

A pond or shoreline edge is the classic job. Along Lake Erie, Lake Ontario, the St. Lawrence and Long Island Sound, waves, ice and high water wear at banks year after year, and on the tidal Hudson south of Troy tide and ice do the same. The stone goes on the face that takes the attack, carried below the low water line at the toe so the base cannot be undercut.

A construction entrance is the third. Riprap laid over fabric at a site access point breaks up the mud and keeps wheels from tracking soil onto the road. For that job the stone can be on the smaller end of the range, and #4 Crushed Stone is often the more workable choice.

A permit note worth taking seriously: work in or along a stream, a wetland or a regulated shoreline in New York frequently needs approval before stone is placed. Check with your local authority before you order.

Layer thickness on a bank, and why nothing here gets compacted

Riprap is never compacted. There are no fines to bind, and the strength of the layer comes from the weight of the individual stones and the way they interlock. Running a plate over it would only crack the faces that are doing the gripping.

Layer thickness is normally described as a multiple of the largest stone rather than a fixed number of inches. A single layer of stone is not a revetment; the rule of thumb is a thickness of at least one and a half times the largest piece, so a layer built from 12 inch stone is planned at 18 inches or more. Steeper faces and harder wave attack push that up.

What sits underneath matters as much as the stone. On soft or wet ground, a non-woven filter fabric or a graded bedding layer keeps the fines below from being pumped out through the gaps by wave action and freeze-thaw. Skip it on clay and the stone slowly sinks into the bank it was meant to protect. Set the toe of the run below the level that water scours to, and key the top and the sides into undisturbed ground so there is no edge for water to get behind.

Measuring 40 feet of pond edge and a culvert apron

Illustrations with invented dimensions.

Pond edge, 40 ft long, 6 ft of face measured up the slope, 12 in thick

• 40 x 6 = 240 sq ft of face
• 240 x 12 / 12 = 240 cu ft
• 240 / 27 = 8.9 cu yd

Culvert outlet apron, an irregular fan, 15 in thick

Split the fan into two rectangles you can actually measure:

• 8 x 10 = 80 sq ft
• 6 x 4 = 24 sq ft
• 80 + 24 = 104 sq ft
• 104 x 15 / 12 = 130 cu ft
• 130 / 27 = 4.8 cu yd

Measure slope faces along the slope, not across the map, because a 6 foot face on a steep bank is longer on the ground than it looks from above. Volumes here are the finished placed layer. The two come to 13.7 cubic yards together, and this site publishes rip rap at roughly 3,100 pounds per cubic yard, about 1.55 tons per yard, so 13.7 x 1.55 is approximately 21.2 tons on an approximate weight. To convert cubic yards into the tonnage the product page orders by, run the same numbers through the rip rap calculator.

Getting a heavy load close to the water

Riprap is handled once if you plan it and three times if you do not. Work out where the stone has to end up, then work backwards to a dump spot the truck can reach on firm ground. Tipping on soft spring ground on a lake plain, or on a lawn above a bank, tends to cost more in repair than the double handling saves.

Steep banks often mean the last stretch is done by hand or with a machine working from above, and hand-placed stone should be set with the flat face bedded down rather than dropped loose. Once you know the quantity, set it and a delivery date on the RipRap product page, and confirm the delivery ZIP at checkout. If the site is awkward, the contact page is the place to describe it before you book.