The U.S. Environmental Protection Agency has urged the U.S. Army Corps of Engineers to withhold a wetlands permit for Helis Oil & Gas Co.’s proposed St. Tammany Parish well until the company can prove that drilling a well at that location will have the smallest possible environmental impact, according to an email from an EPA official to the Corps.

Helis needs to demonstrate “the need for the project and its location within a wetland area, and provide a full evaluation of less environmentally damaging alternatives,” says the email from the EPA’s Raul Gutierrez.

Helis has proposed putting a drilling pad on a 3.2-acre site, of which approximately 91 percent is wetlands, near the southeast corner of a wooded 960-acre tract northeast of Mandeville. It needs a permit from the Corps to drill in wetlands.

The company originally applied for a wetlands permit for a 10-acre drilling pad but revised the application after geologists expressed skepticism about whether such a large pad was needed.

The Nov. 13 email from Gutierrez was attached to a letter sent by the Corps to Helis on Dec. 4, restating the EPA’s concerns and adding another: whether adequate contingency plans are in place to deal with a major storm that causes widespread flooding, such as Hurricane Isaac in 2012.

“The Corps presumes that there may be other available sites in this geographical area that would accommodate the applicant’s desired goals,” the Corps’ letter says. Those other locations, it contends, might be less damaging.

The Dec. 4 letter was the second sent by the Corps to Helis last week. A Dec. 2 letter asked the company to respond to several concerns that were brought up in public comments on the wetlands permit application. The 30-day public comment period ended Nov. 13.

That letter asked Helis about truck traffic to the site, water sources, potential pollution and a lawsuit claiming the parish’s zoning law should prevent the well from being drilled.

In past statements, Helis has promised to restrict truck traffic to off-peak traffic hours so as to prevent conflicts with the traffic going in and out of nearby Lakeshore High School. The proposed well location is on Log Cabin Road, a private road. Log Cabin Road and La. 1088 intersect within 1,500 feet of the two entrances to Lakeshore High School, and some people have expressed worries about well traffic exacerbating traffic issues there in the mornings and evenings.

Helis also has promised to use water from private ponds and not to take it from the parish’s aquifer or from streams or rivers. The Corps asked Helis whether those ponds are “in the vicinity of the proposed site” or whether the water would be trucked in from other areas. If the ponds are in the vicinity, the Corps asked Helis to explain how it would get water from them to the drill site — by hose, pipeline or truck.

The Corps also questioned how much water would be used in drilling the vertical test well Helis plans. According to the letter, Helis’ permit application says 800,000 gallons will be required, but the Corps asks if that is a total or daily amount.

Finally, the Corps asks Helis to address the lawsuit filed in state court in Baton Rouge by St. Tammany Parish government that alleges the parish’s zoning designation of the drill site as suburban residential would preclude a well from being drilled there. In late October, Judge William Morvant refused to dismiss the case.

A Helis spokeswoman said the company is readying an official response to the two letters.

“As a general matter, neither the questions posed by the Corps nor the matters raised by the EPA were unexpected and, for the most part, are similar to questions previously posed to us,” Virginia Miller said. “We believe our project as planned is consistent with the requirements of applicable law and regulations of the Corps.”

The current wetlands permit application is Helis’ second. Earlier this summer, the Corps asked the company to revise the original application, which sought permission to build a 10-acre drilling pad. The larger pad would have allowed Helis to drill a vertical well, test samples to see if they were promising for oil, then drill a horizontal shaft and employ a method of drilling known as hydraulic fracturing, or fracking, to extract the oil the company believes is buried 13,000 feet underground.

But after geologists consulting with the Corps questioned whether the area has enough oil to make the well commercially viable, Helis agreed to revise the application to seek a smaller drilling pad.

Helis spokeswoman Miller said the current steep fall in the price of oil — viewed by some as an attempt by world oil producers to put the squeeze on fracking, which is more expensive than conventional oil extraction — would have no effect on Helis’ plans for its St. Tammany well.

Helis’ plan to drill for oil has been controversial in St. Tammany since it became widely known in April. Protesters have packed public meetings and demanded that officials stop the plan. Those cries led the parish to hire a law firm to sue state Commissioner of Conservation James Welsh to prevent him from issuing a drilling permit, another permit that Helis needs.

The Office of Conservation hosted an eight-hour public hearing on that application Nov. 12. A decision on the drilling permit is expected by Dec. 19.

Follow Faimon A. Roberts III on Twitter, @faimon.