Why grading and drainage is needed in Hilmar
Hilmar's whole storm system drains to one irrigation lateral, split east and west by Lander Avenue. Highway 165 divides the community into east and west drainage areas, and both discharge into Turlock Irrigation District Lateral No. 7, which bounds the plan area on the east. A private lot reaches a point the district or the County accepts, and on flat ground the building code fall away from a wall, over a set distance with a swale where room is short, is what carries the water there.
The lateral stopped taking new discharge, so storm water is held on the ground instead. At the Community Plan's adoption TID was no longer accepting new discharges, and a non-operational private golf course on 1st Street east of Lander, with smaller sites around the community, serves as a drainage basin in peak storms; new development has to show a positive discharge before it is approved. On a private lot that means a basin, a swale or a dry well sized to hold what it sheds, and a site of an acre or more needs the owner's construction stormwater coverage before work starts.
West of Lander the ground is low and the water table high, which rules basins out. The community is relatively flat, and many areas, particularly west of Lander Avenue, sit low enough that sewage is pumped by force mains and lift stations, and the high groundwater table may keep a drainage basin from working there. A French drain or an excavation on that side meets water early, so a drain is sized and routed to a point that can take it rather than to ground that will not soak it away.
Digging is settled before the first bucket. Government Code 4216.2 has the dig area marked in white and the notification center told two working days ahead, with nothing opened until every operator answers. Irrigation canals and private laterals meander through the community and the water district's wells and mains run from Golf Link Road south to town, so grading, which counts as excavation under the same article, waits for the same positive response as a trench.
The old Irwin town site has no storm drain system, and the community is exposed to dam inundation. LAFCO records that Irwin, the southern area of Hilmar, has no drainage system and that existing facilities do not meet storm water demand, and the County's hazard plan puts about 1,450 improved parcels in the Hilmar sphere inside the Don Pedro Dam failure inundation area. Where there is no public system, a lot holds and sheds its own water, and fill in a mapped flood hazard area is placed and sloped against erosion.
At the Community Plan's adoption Turlock Irrigation District was no longer accepting new discharges, and a non-operational golf course on 1st Street east of Lander serves as the community's storm basin in peak storms. New development must show a positive discharge before it is approved.
Grading and drainage, as delivered in Hilmar
Hilmar is nineteen road miles from the Modesto base, by Highway 99 to Turlock and then Lander Avenue. Every job leaves the same record: levels before and after, photographs of each drain before backfill, and the water test.
The contractor assigned to the request walks the property, and a wet day shows where the water sits. Site visit scheduled at a time that suits you. Start date set in the written estimate. The fall at each wall, the inlets, any on-site basin and the point the site sheds to are all recorded.
The dig area is marked in white before the notification center is told, and no ground opens until every operator has answered for its line. A high priority installation within ten feet is met on site first, and the ticket is renewed by its 28th day.
The grading permit comes from the Merced County Building and Safety Division on M Street in Merced, since Hilmar is unincorporated, with the owner's approved plans and any soil report in hand before work starts.
A trench of five feet or more takes a protective system, spoil is held two feet back from the edge, and paving is supported before it is undercut, with any accumulating water inspected before anyone enters.
Unsuitable ground is stripped, fill is placed in lifts and compacted without organics or oversize rock, and the backfill at a foundation is set high for the settlement to come. The finished grade is cut so each run reaches its basin or inlet.
French drains are bedded in clean stone and wrapped, channels are set in concrete, and the discharge goes by gravity or pump to a point the district or the County accepts.
The finished falls are surveyed, water is run through the new drains, bare ground is stabilised, and the County building official signs the work off for the owner's file.
Where grading and drainage is needed in Hilmar
Hilmar is split by Lander Avenue into two drainage areas, both ending in one lateral, with low ground on the west side.
Downtown Hilmar, Lander Avenue from American Avenue to 1st Street
The traditional downtown, Mixed Use along Lander Avenue from American Avenue to 1st Street, with the water district building and the Covenant Church. Frontages to the walk drain through a threshold section, since there is no room for the full fall behind them.
Lander Avenue south of Bloss Avenue and the old Irwin town site
Larger-lot houses and converted offices along Lander south of Bloss, and the old Irwin town site. Irwin, the southern area, has no drainage system, so a lot there holds and sheds its own water to a point the County accepts.
West of Lander Avenue (Census Tract 4.04)
Mostly single-family ground west of Lander with commercial along the avenue and farmland beyond. This side has low ground, sewage pumped by force mains, and a high water table that may rule out a basin, so a drain is routed to a point that can take it.
East of Lander Avenue and the TID Lateral No. 7 edge
The census tract east of Highway 165, with commercial and light industrial near Lander and single-family beyond, where TID Lateral No. 7 bounds the plan area and both drainage areas empty. A drain near the lateral goes to a point the district or County accepts, not into it.
1st Street golf-course drainage basin
A non-operational private golf course on 1st Street east of Lander that doubles as the community's storm basin in peak storms. The Plan requires its basin portions to stay, or move to the district's satisfaction, if the site is redeveloped, so its grade and inlets are kept working.
Bloss Avenue industrial strip and Hilmar Lumber
Industrial parcels along Bloss Avenue, the collector to Highway 99 and Livingston, with Hilmar Lumber the model use. Yard storage sheds wide areas to few inlets, so the fall across it is surveyed and a trench drain set where the water collects.
Hilmar Cheese Company plant, north of the Plan area
The plant about a quarter mile north of the plan boundary. A large industrial site drains wide roofs and yard to few inlets, and the grade between them and their basins is the drainage design.
Schools, Community Center and Fire Station 95, Lander and Geer
Schools near Lander and Geer, the Community Center reached by Falke Street, and Fire Station 95 at Falke and Lander. Civic ground is graded to keep the fall away from the buildings and to a defined inlet.
Villa Cordoba and the mobile home parks
The area around Villa Cordoba and the mobile home parks north of them, served by a planned sewer trunk line. Coach rows drain along long, near-level aisles to few inlets, so one lost inlet leaves standing water under several coaches at once.
Camden Drive, American Avenue and Bloss Avenue housing sites
Farmland parcels zoned for housing at Camden Drive and American Avenue and along Bloss Avenue, planned for over a hundred units each. Farm ground graded to a plan needs a pad, a fall and a basin before anything is built on it.
Golf Link Road, Lana Lane and Country Club
North of town, where the water district's wells and pipelines near Golf Link Road carry groundwater south, and small subdivisions on Lana Lane run on private wells and drainage basins. A parcel on its own well is graded to hold and shed its own water.
Dairy and orchard fringe
Orchards east of the plan area, field crops south and numerous dairies to the west. Farm parcels turning into built sites need a pad, a fall and a basin, and their drainage is held on the ground rather than sent to a public line.
Grading and drainage sub-services available in Hilmar
Questions from Hilmar property owners and managers
Into one of two drainage areas split by Lander Avenue, both discharging to Turlock Irrigation District Lateral No. 7. But at the Community Plan's adoption TID was no longer accepting new discharges, and a non-operational golf course on 1st Street and smaller sites serve as storm basins in peak storms. A private site has to show a positive discharge to a point the district or the County accepts; no new connection to the lateral is promised in advance.
Irwin, the southern area of Hilmar, has no drainage system, and LAFCO records that the existing facilities do not meet storm water demand. Without a public line to reach, a lot there holds and sheds its own water: a fall that runs, a swale where the room is short, and a drain to a point the County accepts. A parcel is surveyed against the wall line first to find where the fall was lost.
It can. Many areas west of Lander Avenue sit low enough that sewage is pumped by force mains and lift stations, and the high groundwater table may keep a drainage basin from working there. A French drain or an excavation meets water early, so the answer is often a shallow regrade to a swale and a drain routed to a point that can take the water, rather than a basin that would sit in the water table.
Hilmar is unincorporated, so the grading permit comes from the Merced County Building and Safety Division on M Street in Merced, which inspects all construction in the unincorporated county. The County decides whether a grading plan or a soil report is needed, both are the owner's, and the work is built to those approved plans and to what the building official requires. County permits are valid for six months, and each inspection extends them.
The building code requires the ground next to a foundation to fall away from it over a set distance, with lower minimums for a swale and for paving inside that band, and it allows a reduced slope where soil conditions warrant. Where a lot line or an obstruction leaves no room for the full fall, a swale or another approved way of carrying the water off is accepted. On Hilmar's flat ground that measured fall to a swale and an outlet is what keeps water off a wall; the walk or apron laid on it is concrete flatwork.
A French drain is a gravel trench around a perforated pipe, wrapped so soil does not clog the stone, that collects water in the ground and carries it to a discharge point. The building code describes that detail as the foundation drain used at basements and below-grade floors. West of Lander, where the water table sits high, a French drain can meet groundwater rather than draining the yard, so a shallow regrade to a surface outlet is often the better answer there.
Grading and drainage near Hilmar
