History and Updates About the Potable and Waste Water in La Cruz de Huanacaxtle Jennifer Brinckmann - Amigos de La Cruz
May 3, 2013

Hole in concrete storage tank now replaced by new steel frame cover.

The following report was written by Walt Mintkeski, professional Environmental Engineer from Portland, based on a tour of drinking water facilities February 8, 2012, by a maintenance supervisor of Carcamos (pump stations) and Plantas de Tratamiento de Aguas Residuales (sewage treatment plants) for OROMAPAS in Nayarit.

Potable water for the town of La Cruz and the Marina Riviera Nayarit de La Cruz is provided by two wells, both equipped with submersible pumps producing 15 to 20 liters per second (237 to 317 gallons per minute) of water. One is located in the Las Brisas Vallarta Condominium complex near the southwest corner of the Instituto Tecnologico complex. The second is located north of the OXXO store on the Punta De Mita Highway at the eastern entrance to La Cruz in an undeveloped residential area called El Tizate.

Both wells have liquid hypochlorite injection pumps to add chlorine into the well water for disinfection as it leaves the well site. However, the injection system at the Las Brisas Vallarta well was not working when visited on February 8.

Water from the wells enters a piping system, which distributes it throughout the town and to the concrete storage tank located on the northern portion of the Monte Calvario hill, north of the Punta De Mita Highway. The tank has a storage capacity of 400 cubic meters (105,668 gallons). The concrete roof of the tank has a large hole approximately 3 feet by 3 feet and appears to be slowly collapsing. This does not significantly impact the ability of the tank to supply water to the town. However, the hole does provide a possible entrance point for contamination of the stored water.

As a point of additional information, on the dirt road to Playa La Manzanilla below the Highway to Punta De Mita, there is a potable water pump station owned by the Punta Mita resort development. It boosts the pressure of water supplied to the Punta De Mita town and resort complex from two wells located in the Valle De Banderas area and owned by Punta Mita. The pump station has 5 pumps: one new 40 horsepower (HP) submersible to be installed soon, one 40 HP vertical turbine, and three 30 HP vertical turbines.

Update to February 8, 2012 Report

On Monday March 4, 2013, Walt Mintkeski visited the concrete storage tank located on the northern portion of the Monte Calvario hill. As shown in the photo below, the concrete roof has been removed and a new steel frame is under construction. No information was available as to the schedule for completion of the new roof. In the interim, the water system is being operated without any water storage. This means that if both wells stop pumping due to mechanical failure or loss of electricity, the water system will very quickly stop delivering water to the La Cruz community.

Updated Wastewater Treatment Report

The following report was written by Walt Mintkeski, professional Environmental Engineer from Portland, Oregon. The original report was completed February, 11, 2012, based on two tours of wastewater facilities given on January 25 and February 8, 2012, by a maintenance supervisor of Carcamos (pump stations) and Plantas de Tratamiento de Aguas Residuales (sewage treatment plants) for OROMAPAS in Nayarit. The report was updated on April 22, 2013, based on a tour given February 15, 2013 by the same maintenance supervisor.

Wastewater from the town of La Cruz, the Marina Riviera Nayarit de La Cruz, and a small (.5 liter per second) pump station (on the west side of Arroyo Seco near the entrance to Restaurant Miramar) is collected by a gravity pipe system which conveys it to the Carcamo de Bombeo (Pump Station) de La Cruz. The station is located in the inactive wastewater treatment plant site, which extends between Camaron and Tiburon Streets at the south end of Pez Vela Street. At the southwest corner of the intersection of Tiburon and Pez Vela Streets is the local office of OROMAPAS, which is the government agency responsible for the operation and maintenance of the Carcamo.

The site of the pump station and abandoned treatment plant is most commonly recognized by the concrete channel, which runs through the middle of the plant site, out the south side, across Tiburon Street, and into a larger concrete channel, which empties into the Marina. Water in the channel runs most of the year. During the dry season, the water comes entirely from a spring, which emerges from the ground under a large Huanacaxtle tree on the north side of the plant at the intersection of Pez Vela and Camaron Streets. During the rainy season, stormwater flows into the channel from the east along Camaron Street and from the north along Pez Vela Street.

Before the Marina existed, the plant provided treatment of La Cruz's wastewater. Initially, a small, extended aeration plant with raw sewage pumps, rectangular aeration tank, rectangular secondary clarifier, and chlorine contact chamber (for disinfection of the treated water) was built on the site on the east side of the concrete channel.

As the town's population grew, a second slightly larger plant was built immediately east of the original plant. It had its own raw sewage pumps, rectangular aeration tank, circular secondary clarifier, and, chlorine contact chamber. In addition, there was a rectangular aerobic digester tank to treat waste activated sludge solids, and a filter press in a small concrete building to dewater the digested solids before they were composted by earthworms in a small rectangular tank. Treated wastewater, disinfected with chlorine, was discharged from the two plants, operating in parallel, via a 10” diameter metal outfall pipe, into the Marina at a point just west of space 12 on Muelle #5 (Dock #5).

The two plants were abandoned at the request of the Marina, which was concerned about their discharge into the marina area. Consequently, the Marina paid for the construction of an 8" diameter pipe (force main), which runs about 3 kilometers from the Carcamo northwest along Tiburon Street, north on Atun, east on the dirt road on the north side of La Joya Condominiums, north on the asphalt road on the west side of Punta Pelicanos to the Punta de Mita Highway, east to Highway 200, and south to the high point on the Puerto Vallarta Highway near the Punto Esmeralda Condominiums.

La Cruz's wastewater is pumped from the Carcamo de La Cruz through this pressure pipe and then flows in a gravity pipe to the OROMAPAS pump station in Los Picos. From there sewage is pumped to the OROMAPAS Carcamo #1 in Bucerias, and from there to the existing OROMAPAS wastewater treatment plant east of Bucerias. The plant has a capacity of 60 liters per second (60 lps or 950 gallons per minute or 1.37 million gallons per day).

Approximately 30% of the flow from the Carcamo de La Cruz is diverted from the 8" diameter pressure pipe to an extended aeration treatment plant located in, and owned and operated by, Las Brisas Vallarta Condominiums. The plant has a capacity of 15 liters per second, but normally only treats about 5 to 8 lps. The treated effluent is used for irrigation of the Las Brisas Vallarta property.

When the two treatment plants at the La Cruz site were abandoned, the raw sewage pumps of the larger, newer plant became the Carcamo de Bombeo de La Cruz. The pump station has 3 submersible pumps (two 25 horsepower and one 35 horsepower) with a total capacity of 18 liters per second (285 gallons per minute or .41 million gallons per day) and producing a pressure of 45 to 50 pounds per square inch (as observed on the pump header pressure gage).

These three pumps are at the end of a long, open concrete channel, approximately 8' wide by 12' deep by 30' long. The channel carries raw sewage from the gravity pipe collection system on Tiburon Street through a bar screen that removes large debris, which could plug the pumps.

The channel also acts as a primary clarifier because small rocks, sand, and sewage solids settle out and have to be removed at least once per month by a vacuum (Vactor) truck. Because the sewage solids decompose before being removed by vacuum truck, this open channel is probably the source of occasional odors from the plant site, not the concrete channel, which carries spring water to the Marina.

During the monthly cleaning of the channel, the water level in the channel must be lowered to expose the settled solids so that the vacuum truck can remove them. This would normally be done by turning on more pumps in order to send more sewage through the 8" force main pipe. However, the impellers on the existing pumps cannot develop enough pressure to do that. Therefore, a portion of the flow is pumped through the larger of the two abandoned treatment plants to reduce pump pressure and increase flow. This sewage is chlorinated before being discharged through the old 10" outfall pipe into the Marina. Walt Mintkeski witnessed this discharge of partially treated sewage into the Marina on Friday, February 3, 2012 at 9:15 am while the OROMAPAS vacuum truck was cleaning the channel in the Carcamo.

OROMAPAS intention is to eliminate this discharge into the Marina during the cleaning process by installing larger capacity sewage pumps to replace the old pumps. However, as of February 8, 2012, electrical components had be ordered and installed first before the pumps could be installed.

On February 15, 2013, Walt Mintkeski was given a tour of the existing OROMAPAS wastewater treatment plant, located approximately 3 kilometers east of Bucerias, and a tour of the improvements made at Carcamo de Bombeo (Pump Station) in La Cruz during the past 12 months. The improvements consisted of:

1. Two 23 horsepower (17.2 kilowatt) submersible pumps.

2. Two new motor control panels with soft starts to slowly start and stop the two pumps.

3. A new emergency diesel generator to provide backup power to the pumps if municipal electricity is lost.

The two pumps have sufficient capacity for normal sewage flows, except during heavy rain storms. Because of the improved pumping capacity, it is no longer necessary to divert flow through the old wastewater treatment plant and into the Marina during the monthly channel cleaning operation.

Walt Mintkeski, professional Environmental Engineer from Portland, Oregon, can be contacted at mintkeski@juno.com.

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