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Its healthy to drink but
Tightening water standards may cost millions
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Some residents complain about the taste of their tap water.

Others often express dissatisfaction with the hardness of city water.

But when it comes to being healthy to drink, Manteca’s municipal is OK.

However, tougher federal and state standards being mulled for a number of naturally occurring elements ranging from arsenic to uranium could force the city to spend $49.6 million in construction costs plus $6.6 million in annual operation and maintenance. That translates into a $540 bump in the annual cost of a customer’s municipal water bill.

That was the bottom line of a state-required Public Health Goal report made Tuesday to the Manteca City Council by senior water engineer Keith Conarroe.

The report is designed to establish water quality goals but isn’t enforceable. It takes into account maximum containment levels that should be allowed using current health and science considerations as well as calculating a theoretical health risk. The report is required by the state every three years.

There are six constituents found in various wells in Manteca that are above the public health goal in terms of ideal maximum levels in the water. They are nitrates, arsenic, ethylene dibromide, dibromochloropropane (DBCP), uranium and gross alpha.

There has been a one-time occurrence of nitrate levels exceeding the target goal in one well in Manteca in November of 2007. It is constantly being monitored for nitrates. It could pose an acute health risk to infants under six months.

The city has been addressing the other trace elements found with the biggest cost being arsenic.

New federal standards adopted in 2005 have reduced the acceptable level of arsenic.

The previous standard was 50 parts per billion in terms of volume. It has now been reduced to 10 parts per billion. The 12 Manteca wells that are impacted are barely over the new standards that call for an acceptable level of essentially one fifth the amount of arsenic.

Public Works Director Mark Houghton has termed the increased Environmental Protection Agency arsenic standard that is about 100 times higher than the previous acceptable level as “extreme” caution.

Arsenic is a semi-metal element that is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices based on a 2009 federal Environmental Protection Act report.

Manteca - due to its decision to secure treated surface water through the South San Joaquin Irrigation District and to use it primarily for peak demand times in the spring, summer and early fall - is in a better position than many valley cities such as Lodi and Stockton that rely primarily on well water. That water is now being blended with well water to reduce arsenic levels.

Experts noted that arsenic occurs naturally in all water but at much higher concentrations in underground sources.

The city has been installing pipeline to deliver surface treated water to well heads at five different locations in Manteca. In doing so, it will dilute arsenic found naturally in ground water sufficiently to meet tough new EPA standards for arsenic.

The blending solution that originated with the municipal public works staff avoids the cost of an expensive arsenic treatment plant at five municipal wells. The big saving is avoiding the need to replace extremely specialized media used to remove the arsenic that typically can last less than two years before having to be replaced. The media cost replacement is $100,000 per well.

Manteca will still have to do that with seven of its 17 wells. It won’t with five that have - or will have - surface water blending. There are five other wells that do not need to reduce arsenic levels.

It cost the city $1.9 million and $3.1 million respectively to install arsenic treatment systems on Wells 24 and 25.

As for the hardness, Conarroe noted that is from calcium and other minerals that water absorbs under ground as it passes through various strata and rock.

He noted underground water tends to be hard but it is getting better as the city is also using soft Sierra water from the surface treatment plant.