Water Industry News
Los Angeles Daily News
Nitrogen removal plan for
By Jim Skeen
Sunday, April 10, 2005 - PALMDALE -- Well water tainted with nitrates from Palmdale's sewage treatment plant could be pumped out of the ground and used to irrigate alfalfa fields.
Facing a cleanup order from state water regulators, Los Angeles County sanitation officials prefer the cheapest of five alternatives ranging in cost from $10.6 million to $158.5 million.
Sanitation officials are discussing the cleanup alternatives with the state's Lahontan Regional Water Quality Control Board.
"We will work with them to come up with a plan that is mutually agreeable to both parties," said Palmdale Mayor Jim Ledford, who sits on the Los Angeles County Sanitation District 20 board. "No one is arguing with the goals. We all want a clean aquifer."
In November 2003, the Lahontan board issued a cleanup and abatement order to the sanitation district and to Los Angeles World Airports, which owns the 2,680 acres the district uses for wastewater disposal east of Air Force Plant 42.
Nitrates are a nutrient for plants but can cause a condition known as "blue baby" syndrome among infants. Nitrates have leached into the underground water table from Sanitation District 20's practice of spreading treated sewage effluent on barren land to soak into the ground.
Nitrates in well water pulled from near the spreading grounds since 1990 have periodically tested above the state cleanup level of 10 milligrams per liter, and computer projections show that if things don't change by 2025, the level could reach 24 milligrams per liter. The natural or background level is 0.75 milligrams per liter, officials said.
No drinking-water wells draw from that area, officials said.
The sanitation district is favoring an alternative that involves the installation of five wells to pump out water with high nitrate concentrations. The water would be placed in storage ponds along 40th Street East until it is needed to water crops.
That alternative would remove 119 tons of nitrates and would cost about $10.6 million in construction costs and over 20 years of operations and maintenance.
Lahontan staff is concerned about the amount of groundwater that would be pumped out for that alternative, an estimated 24,600 acre-feet over 20 years.
"We know there is an overdraft problem in the Antelope Valley area," said Harold Singer, Lahontan's executive director. "We want to raise the issue to the board and say that is is something they should keep in mind."
Lahontan staff is suggesting what it calls a more aggressive approach that would remove 130 tons of nitrates and cost $13.6 million over 20 years.
That approach calls for eight extraction wells, six of which would be installed as soon as possible, to pump out 7,200 acre-feet of the most contaminated water. The wells would be positioned closer together than in the plan preferred by sanitation officials.
Two more wells would be installed near sewage oxidation ponds along 30th and 40th streets east after they are taken out of service in 2009.
Lahontan staff is recommending their board require the district to submit a long-term strategy by the fall of 2006. That plan should look at pumping and treating water, with it either going back into the aquifer or of using it to replace uses that draw upon groundwater, officials said.
"The two alternatives are not too far apart," said Dave Synder, head of the water quality and soil engineering for the county's sanitation districts. "Both say: let's focus on the areas with the highest concentration, clean it up, monitor it and see how it comes out over time."
Three other alternatives were looked and considered impractical -- taking no action; installing 15 wells at a cost of $26.3 million; and an option, priced at $158.5 million, calling for installing 25 wells, treating the water, and then allowing it to percolate back into the groundwater.
All the alternatives being looked at assume that there will be an expansion of the use of effluent for agriculture by 2009; that the treatment plant will be upgraded for nitrogen removal; and that there will be 500 acres of water storage ponds constructed by 2009.
Jim Skeen, (661) 267-5743 firstname.lastname@example.org